Is this homemade battery charger circuit dangerous?

[Kanon Kubose]

The other day I found plans for a $3 battery charger that was just a diode and light bulb in series with the battery, using mains electricity. I posted a question about modifying it with a dimmer switch here: https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should come to sci.electronics.basics before I kill myself.

Taking their advice to heart, I have not built this darwin battery charger, but I do still have batteries to charge, namely a 7.2v nicd battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by putting a 12v car heater/fan in series with the battery, I got the amps low enough to trickle charge it. However, I suspect the 8.7v isn't enough, and also, as the charge goes on, the current falls. After a few hours, I measured C/24, and overnight it was C/60. I've read that nicads need at least C/10 to fully charge (though another source says C/16 will work), so this wall wart seems to be insufficient. (Strangely, when the current reached C/24 and C/60, removing the heater didn't affect the amp rate at all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to remove reverse current, then put it in series with the battery and some current-limiting load. This is essentially the same $3 dangerous battery charger except using 24vac instead of 110 mains voltage. Is it still dangerous? People in the other group said even 25 mA is lethal if it crosses the heart, like would happen if you stupidly grabbed both leads of unshielded alligator clips, and it doesn't matter that the current is limited. It's not limited enough, especially when the lightbulb begins cold.

Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or will the 24v burn them out? Since it's attached to a 7.2v battery, the voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I could monitor it and increase it as it falls, keeping the C/10 rate.

Thanks,

Kanon

 

[Mark Storkamp]

In article <b1949b2f-0b8c-4a35-9fe6-f3c6bd3fc2e7@googlegroups.com>,
Kanon Kubose <kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode
and light bulb in series with the battery, using mains electricity. I posted
a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should
come to sci.electronics.basics before I kill myself.

Taking their advice to heart, I have not built this darwin battery charger,
but I do still have batteries to charge, namely a 7.2v nicd battery pack for
a jigsaw. I found an 8.7vdc 360mA wall wart, and by putting a 12v car
heater/fan in series with the battery, I got the amps low enough to trickle
charge it. However, I suspect the 8.7v isn't enough, and also, as the charge
goes on, the current falls. After a few hours, I measured C/24, and overnight
it was C/60. I've read that nicads need at least C/10 to fully charge (though
another source says C/16 will work), so this wall wart seems to be
insufficient. (Strangely, when the current reached C/24 and C/60, removing
the heater didn't affect the amp rate at all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to
remove reverse current, then put it in series with the battery and some
current-limiting load. This is essentially the same $3 dangerous battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it crosses
the heart, like would happen if you stupidly grabbed both leads of unshielded
alligator clips, and it doesn't matter that the current is limited. It's not
limited enough, especially when the lightbulb begins cold.

Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or will
the 24v burn them out? Since it's attached to a 7.2v battery, the voltage
will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I could
monitor it and increase it as it falls, keeping the C/10 rate.

Thanks,

Kanon

We purchased a number of cheap cordless drills at work. The chargers
that come with them are nothing more than a wall wart, diode and
resistor. They work for a while, but eventually the batteries all died,
some of them simply would not take a charge, others got hot and melted
while in the charger.

Save yourself a lot of grief and just purchase a proper charger.

 

[John Larkin]

On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
<kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode and light bulb in series with the battery, using mains electricity. I posted a question about modifying it with a dimmer switch here: https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should come to sci.electronics.basics before I kill myself.

You could do it if you were very careful.

Taking their advice to heart, I have not built this darwin battery charger, but I do still have batteries to charge, namely a 7.2v nicd battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by putting a 12v car heater/fan in series with the battery, I got the amps low enough to trickle charge it. However, I suspect the 8.7v isn't enough, and also, as the charge goes on, the current falls. After a few hours, I measured C/24, and overnight it was C/60. I've read that nicads need at least C/10 to fully charge (though another source says C/16 will work), so this wall wart seems to be insufficient. (Strangely, when the current reached C/24 and C/60, removing the heater didn't affect the amp rate at all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to remove reverse current, then put it in series with the battery and some current-limiting load. This is essentially the same $3 dangerous battery charger except using 24vac instead of 110 mains voltage. Is it still dangerous? People in the other group said even 25 mA is lethal if it crosses the heart, like would happen if you stupidly grabbed both leads of unshielded alligator clips, and it doesn't matter that the current is limited. It's not limited enough, especially when the lightbulb begins cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.

Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or will the 24v burn them out? Since it's attached to a 7.2v battery, the voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I could monitor it and increase it as it falls, keeping the C/10 rate.

My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

I found an old DSL modem supply in the junk bin, 18 volts AC. In
series with a diode, it put a couple of amps into the battery. It was
getting hot so I figured it would trip a thermal overload, so I
started testing various appliances as series resistors. A belt sander
got it down to about half an amp. Left overnight like that, the car
started.

I couldn't jump it because it was head-in to my garage, and the path
to the street is short and steep uphill.

I guess I could have run a long extension cord out to a car on the
street and paralleled the batteries. That wouldn't crank directly, but
it would have recharged the dead one.

Now I keep a DC bench supply at home. It's handy for all sorts of
things.




--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

 

[Robert Roland]

On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
<kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode and light bulb in series with the battery, using mains electricity. I posted a question about modifying it with a dimmer switch here: https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should come to sci.electronics.basics before I kill myself.

There is nothing wrong with the theory, but I agree with those that
say it is too dangerous.

When the battery is not connected, there will be full mains voltage on
the connector, since the light bulb has much lower resistance than
your body.

I've read that nicads need at least C/10 to fully charge

C/10 will charge it in about 14 hours. C/20 will charge it in about 28
hours, and so on.

(Strangely, when the current reached C/24 and C/60, removing the heater didn't affect the amp rate at all. I wonder why?)

A fully charged NiCd cell can easily reach 1.4V. In this case, there
simply is so little voltage difference between the battery and the
power supply, that, even if there is almost no resistance, only a very
small current flows.

My new idea is to take a 24vac wall wart that I have and add a diode to remove reverse current, then put it in series with the battery and some current-limiting load. This is essentially the same $3 dangerous battery charger except using 24vac instead of 110 mains voltage. Is it still dangerous?

24V is very safe. Most people won't even feel anything if they touch
the poles directly to the skin. On your tongue, it will sting a bit,
since your tongue is wet and has very thin skin.

People in the other group said even 25 mA is lethal if it crosses the heart, like would happen if you stupidly grabbed both leads of unshielded alligator clips, and it doesn't matter that the current is limited. It's not limited enough, especially when the lightbulb begins cold.

Ohm's law says current is determined by two factors, voltage and
resistance. More voltage gives more current, while less resistance
gives more current. Your body (the skin, mostly) has quite a high
resistance, so the 24V will not be able to drive a current that is
high enough to be dangerous.

1. Could I use 12v appliances or light bulbs as the current limiter or will the 24v burn them out? Since it's attached to a 7.2v battery, the voltage will be lower, right?

Appliances are not good. They will have a very unpredictable
resistance. A brushed motor, for example, may have a different
resistance depending on where in its commutation cycle it is parked.

Light bulbs, on the other hand, are excellent for this application.
They have a strong current regulating effect. If you increase the
voltage, the filament heats up and the resistance increases, so the
current will not increase as much as the voltage increase would have
caused in a linear resistor. Here's an illustration:
http://sub.allaboutcircuits.com/images/quiz/00091x02.png

In fact, I used to have a commercial battery charger that did use
light bulbs as the regulating element. 20-30 years ago, they were
quite common.

Since you are using a half wave rectifier, the 12V bulbs will probably
be OK. If you sprung for another three diodes and made a full bridge
rectifier, the 12V bulbs may be overstressed. When your battery is
fully discharged, it will probably be about 6V. That would leave 18V
for light bulb.

2. Would a dimmer switch work to make it finely tuneable? That way I could monitor it and increase it as it falls, keeping the C/10 rate.

Yes, a dimmer should work. However, if you can find the right bulb,
you will not need to adjust the current during a charge cycle. It will
remain plenty constant enough.

Note, however, that this type if charger is fully manual. It will keep
charging the battery until you disconnect it. In order to know how
long to charge, you must know the battery's initial charge state,
which in practice means that you must fully discharge the battery
before you can charge it.

Personally, I'd consider buying an automatic charger. It is
tremendously convenient:

- You can charge the battery without knowing its charge state in
advance.

- You do not need to remember to stop the charging at the correct
time.

Such a charger does not have to be expensive. Look for the term "delta
peak". That indicates the automatic charge state detection. Here's an
example:

http://www.ebay.com/itm/Orion-Advantage-IQ801-1A-Delta-Peak-Charger-ORI30198-/370841082084?pt=UK_ToysGames_RadioControlled_JN&hash=item5657d9d8e4

You must, of course, pick one that is suitable for your specific
battery.
--
RoRo

 

[ehsjr]

On 7/17/2013 2:40 PM, Kanon Kubose wrote:

<snip>

I do still have batteries to charge, namely a 7.2v nicd battery pack
for a jigsaw.

I found an 8.7vdc 360mA wall wart, and by putting a 12v car heater/fan
inseries with the battery, I got the amps low enough to trickle charge
it. However, I suspect the 8.7v isn't enough, and also, as the charge
goes on, the current falls.

After a few hours, I measured C/24, and overnight it was C/60.
I've read that nicads need at least C/10 to fully charge (though
anothersource says C/16 will work), so this wall wart seems to be
insufficient.
(Strangely, when the current reached C/24 and C/60, removing the
heaterdidn't affect the amp rate at all. I wonder why?)

Because the closer to fully charged, the lower the current
the battery will draw, as you observed. The lower the current
drawn through your heater, the lower the affect the heater
will have on the circuit. The effect the heater has can be
computed by V = I * R where V is the voltage dropped in the
heater, I is the current drawn through it, and R is the
resistance of the heater.

Your circuit looks like this:

8.7 Vin----[Heater]---+
|
[NiCd]
|
Gnd --------------+

As the charge continues, the NiCd voltage rises, so the voltage
drop across the heater decreases. If the pack voltage reaches 8.7 volts,
there is no current drawn, and no voltage drop across the heater. It
would make no difference if the heater was in the circuit
or not.

Also, measuring small currents presents a challenge, even to
expensive multimeters. When used in series with the circuit
to measure current, they cause a voltage drop that affects
circuit performance. That can sometimes cause a significant
error in the measurement.

Ed

Kanon

 

[Ian Field]

"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...

On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the amps
low enough to trickle charge it. However, I suspect the 8.7v isn't enough,
and also, as the charge goes on, the current falls. After a few hours, I
measured C/24, and overnight it was C/60. I've read that nicads need at
least C/10 to fully charge (though another source says C/16 will work), so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to
remove reverse current, then put it in series with the battery and some
current-limiting load. This is essentially the same $3 dangerous battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both leads of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

 

[Ian Field]

"Robert Roland" <fake@ddress.no> wrote in message
news:jjpfu816pal6ut8eu64qngp3d8d1vbkcaa@4ax.com...

On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should
come to sci.electronics.basics before I kill myself.

There is nothing wrong with the theory, but I agree with those that
say it is too dangerous.

When the battery is not connected, there will be full mains voltage on
the connector, since the light bulb has much lower resistance than
your body.

Seems I missed the original thread - but it sounds like the old "bridge
rectifier spliced into a lamp circuit" trick.

The first and most obvious trick is to splice the bridge into the neutral
lead so in normal use the rectifier and load isn't on the live side. There's
various ways of limiting the voltage, like a hefty zener or a crowbar
thyristor.

Not the safest way to charge batteries - but the dangers can be managed.

Its handy for emergency desulphating lead acid batteries - but if they've
got that bad they'll never be 100% again.

 

[John Larkin]

On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the amps
low enough to trickle charge it. However, I suspect the 8.7v isn't enough,
and also, as the charge goes on, the current falls. After a few hours, I
measured C/24, and overnight it was C/60. I've read that nicads need at
least C/10 to fully charge (though another source says C/16 will work), so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to
remove reverse current, then put it in series with the battery and some
current-limiting load. This is essentially the same $3 dangerous battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both leads of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

 

[Ian Field]

"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...

On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few hours, I
measured C/24, and overnight it was C/60. I've read that nicads need at
least C/10 to fully charge (though another source says C/16 will work),
so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to
remove reverse current, then put it in series with the battery and some
current-limiting load. This is essentially the same $3 dangerous battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both leads
of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the rectifier
sticking the battery on wrong way round.

 

[John Larkin]

On Fri, 19 Jul 2013 16:02:48 +0100, "Ian Field" <gangprobing.alien@ntlworld.com>
wrote:

"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...
On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few hours, I
measured C/24, and overnight it was C/60. I've read that nicads need at
least C/10 to fully charge (though another source says C/16 will work),
so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode to
remove reverse current, then put it in series with the battery and some
current-limiting load. This is essentially the same $3 dangerous battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both leads
of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the rectifier
sticking the battery on wrong way round.

I think it was deliberate to sell batteries. It would be trivial to shut off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Ian Field]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:23niu8hkvbj66qrk6gu3qifiili5dc7ha2@4ax.com...

On Fri, 19 Jul 2013 16:02:48 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...
On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the
amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few hours,
I
measured C/24, and overnight it was C/60. I've read that nicads need
at
least C/10 to fully charge (though another source says C/16 will
work),
so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate
at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode
to
remove reverse current, then put it in series with the battery and
some
current-limiting load. This is essentially the same $3 dangerous
battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both
leads
of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get
things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the
rectifier
sticking the battery on wrong way round.

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.

A bit inconvenient perhaps - and very rarely at that, its not a good idea to
discharge a lead acid battery so low it won't activate the polarity detect,
that inconvenience is a good reminder of that. If a battery has got that
dead in storage - it probably *IS* scrap.

You don't need a fully fledged old style charger, pretty much any DC output
wall-wart can jump start the polarity detect.

 

[John Larkin]

On Fri, 19 Jul 2013 16:57:11 +0100, "Ian Field" <gangprobing.alien@ntlworld.com>
wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:23niu8hkvbj66qrk6gu3qifiili5dc7ha2@4ax.com...
On Fri, 19 Jul 2013 16:02:48 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...
On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity. I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the
amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few hours,
I
measured C/24, and overnight it was C/60. I've read that nicads need
at
least C/10 to fully charge (though another source says C/16 will
work),
so
this wall wart seems to be insufficient. (Strangely, when the current
reached C/24 and C/60, removing the heater didn't affect the amp rate
at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode
to
remove reverse current, then put it in series with the battery and
some
current-limiting load. This is essentially the same $3 dangerous
battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both
leads
of
unshielded alligator clips, and it doesn't matter that the current is
limited. It's not limited enough, especially when the lightbulb begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter or
will the 24v burn them out? Since it's attached to a 7.2v battery, the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger won't
operate.

I keep an old fashioned charger with iron cored transformer to get
things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the
rectifier
sticking the battery on wrong way round.

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.

A bit inconvenient perhaps - and very rarely at that,

A light left on, even a door not fully closed, can drain a battery to zero.
That's not all that rare.

its not a good idea to

discharge a lead acid battery so low it won't activate the polarity detect,
that inconvenience is a good reminder of that. If a battery has got that
dead in storage - it probably *IS* scrap.

That's what the battery sellers say. After I recharged my zero-volt VW battery,
it worked fine.

You don't need a fully fledged old style charger, pretty much any DC output
wall-wart can jump start the polarity detect.

Fine if you're an EE and have the means to do that, like I did. Ordinary mortals
buy a garbage charger and then a new battery that they don't need.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Ian Field]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:nqpiu89qgfoeglm4ufs2jkqk7g46f7taeu@4ax.com...

On Fri, 19 Jul 2013 16:57:11 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
news:23niu8hkvbj66qrk6gu3qifiili5dc7ha2@4ax.com...
On Fri, 19 Jul 2013 16:02:48 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...
On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity.
I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the
amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few
hours,
I
measured C/24, and overnight it was C/60. I've read that nicads need
at
least C/10 to fully charge (though another source says C/16 will
work),
so
this wall wart seems to be insufficient. (Strangely, when the
current
reached C/24 and C/60, removing the heater didn't affect the amp
rate
at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode
to
remove reverse current, then put it in series with the battery and
some
current-limiting load. This is essentially the same $3 dangerous
battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both
leads
of
unshielded alligator clips, and it doesn't matter that the current
is
limited. It's not limited enough, especially when the lightbulb
begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter
or
will the 24v burn them out? Since it's attached to a 7.2v battery,
the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger
won't
operate.

I keep an old fashioned charger with iron cored transformer to get
things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the
automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the
rectifier
sticking the battery on wrong way round.

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at
best.

A bit inconvenient perhaps - and very rarely at that,

A light left on, even a door not fully closed, can drain a battery to
zero.
That's not all that rare.

Probably quite common if you're careless.

its not a good idea to
discharge a lead acid battery so low it won't activate the polarity
detect,
that inconvenience is a good reminder of that. If a battery has got that
dead in storage - it probably *IS* scrap.


That's what the battery sellers say. After I recharged my zero-volt VW
battery,
it worked fine.

It wouldn't have been if you'd left it in that state even as much as only a
week - they sulphate PDQ when discharged dead flat.

 

[John Fields]

On Fri, 19 Jul 2013 17:38:27 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:nqpiu89qgfoeglm4ufs2jkqk7g46f7taeu@4ax.com...
On Fri, 19 Jul 2013 16:57:11 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
news:23niu8hkvbj66qrk6gu3qifiili5dc7ha2@4ax.com...
On Fri, 19 Jul 2013 16:02:48 +0100, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:nkqgu8p4tb92g77c6amapr895lddnfi1pj@4ax.com...
On Thu, 18 Jul 2013 22:16:13 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:ce7eu8t36r1jjt34cg3cu30c90oqluub15@4ax.com...
On Wed, 17 Jul 2013 11:40:44 -0700 (PDT), Kanon Kubose
kanon11@gmail.com> wrote:

The other day I found plans for a $3 battery charger that was just a
diode
and light bulb in series with the battery, using mains electricity.
I
posted a question about modifying it with a dimmer switch here:
https://groups.google.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE

Everyone there said I was a candidate for a darwin award and that I
should
come to sci.electronics.basics before I kill myself.


You could do it if you were very careful.


Taking their advice to heart, I have not built this darwin battery
charger, but I do still have batteries to charge, namely a 7.2v nicd
battery pack for a jigsaw. I found an 8.7vdc 360mA wall wart, and by
putting a 12v car heater/fan in series with the battery, I got the
amps
low enough to trickle charge it. However, I suspect the 8.7v isn't
enough,
and also, as the charge goes on, the current falls. After a few
hours,
I
measured C/24, and overnight it was C/60. I've read that nicads need
at
least C/10 to fully charge (though another source says C/16 will
work),
so
this wall wart seems to be insufficient. (Strangely, when the
current
reached C/24 and C/60, removing the heater didn't affect the amp
rate
at
all. I wonder why?)

My new idea is to take a 24vac wall wart that I have and add a diode
to
remove reverse current, then put it in series with the battery and
some
current-limiting load. This is essentially the same $3 dangerous
battery
charger except using 24vac instead of 110 mains voltage. Is it still
dangerous? People in the other group said even 25 mA is lethal if it
crosses the heart, like would happen if you stupidly grabbed both
leads
of
unshielded alligator clips, and it doesn't matter that the current
is
limited. It's not limited enough, especially when the lightbulb
begins
cold.

24VAC is safe. In the US, 48 volts AC is generally considered safe.



Other questions, assuming this circuit isn't dangerous:

1. Could I use 12v appliances or light bulbs as the current limiter
or
will the 24v burn them out? Since it's attached to a 7.2v battery,
the
voltage will be lower, right?

2. Would a dimmer switch work to make it finely tuneable? That way I
could
monitor it and increase it as it falls, keeping the C/10 rate.


My car was dead one day, some light left on. The battery was zero
volts. I bought a battery charger at Kragen, and it wouldn't charge
the battery. These modern switchmode chargers will not push current
into zero volts. Personally, I think it's a scam to sell more
batteries. "It won't take a charge" the guy said "you need a new
battery." So I got my money back on the stupid charger.

Most modern battery chargers have polarity detect - if the battery is
totally dead flat, there's no polarity *TO* detect and the charger
won't
operate.

I keep an old fashioned charger with iron cored transformer to get
things
started on a *DEAD* dead battery.

Once the battery can sustain a few volts on the terminals, the
automatic
charger can detect polarity and work as the designer intended.

The designer was an idiot, or designed it specifically so Kragen can
sell more batteries.

You might find it was designed that way to stop people killing the
rectifier
sticking the battery on wrong way round.

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at
best.

A bit inconvenient perhaps - and very rarely at that,

A light left on, even a door not fully closed, can drain a battery to
zero.
That's not all that rare.

Probably quite common if you're careless.


its not a good idea to
discharge a lead acid battery so low it won't activate the polarity
detect,
that inconvenience is a good reminder of that. If a battery has got that
dead in storage - it probably *IS* scrap.


That's what the battery sellers say. After I recharged my zero-volt VW
battery,
it worked fine.

It wouldn't have been if you'd left it in that state even as much as only a
week - they sulphate PDQ when discharged dead flat.

---
Sounds like hearsay to me, and where's the quantitative evidence that
supports your assumption?

--
JF

 

[Michael A. Terrell]

John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.

Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

Who cares about lawsuits, or killing their customers?

Other than the roll around garage chargers, I haven't seen anything
other than a float charger that will try to charger a dead battery.

My charger was built from a motorhome battery eliminator and a
Variac. I can set the initial charge rate from a few mA, to 30 amps and
see how the battery is charging. I built it over 40 years ago. I have
used it to start a car with a 'dead' battery more than once.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[Ian Field]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:Jf-dnVU_w5YhhHfMnZ2dnUVZ_rCdnZ2d@earthlink.com...

John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at
best.


Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

Who cares about lawsuits, or killing their customers?

Other than the roll around garage chargers, I haven't seen anything
other than a float charger that will try to charger a dead battery.

I have a couple of optimates that have desulphate pulse modes, but they
won't start without at least 2V on the terminals to detect correct polarity,
so if the battery is dead flat it needs an external DC source to get it
started.

Generally battery recovery is satisfactory unless its stood any length of
time dead flat.

Maybe they should include a start button, perhaps current limited at the
desulphate pulse voltage.

 

[John Larkin]

On Sat, 20 Jul 2013 01:01:38 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.


Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

What's going to catch fire? The battery? Some idiotic Chinese electronic charger
that doesn't current limit?

Who cares about lawsuits, or killing their customers?

Why kill them when it's more profitable to rip them off?

Other than the roll around garage chargers, I haven't seen anything
other than a float charger that will try to charger a dead battery.

Old fashioned cheap transformer-rectifier chargers worked fine on a dead
battery. The new electronic chargers are too smart to do that.

My charger was built from a motorhome battery eliminator and a
Variac. I can set the initial charge rate from a few mA, to 30 amps and
see how the battery is charging. I built it over 40 years ago. I have
used it to start a car with a 'dead' battery more than once.

I keep a Lascar bench supply around now. It current limits.




--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Ian Field]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:5t4mu8tlokmpetceti9de8g1ivua3fbnqq@4ax.com...

On Sat, 20 Jul 2013 01:01:38 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut
off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at
best.


Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

What's going to catch fire? The battery? Some idiotic Chinese electronic
charger
that doesn't current limit?



Who cares about lawsuits, or killing their customers?

Why kill them when it's more profitable to rip them off?


Other than the roll around garage chargers, I haven't seen anything
other than a float charger that will try to charger a dead battery.

Old fashioned cheap transformer-rectifier chargers worked fine on a dead
battery. The new electronic chargers are too smart to do that.


My charger was built from a motorhome battery eliminator and a
Variac. I can set the initial charge rate from a few mA, to 30 amps and
see how the battery is charging. I built it over 40 years ago. I have
used it to start a car with a 'dead' battery more than once.

I keep a Lascar bench supply around now. It current limits.

The bulk charge phase is usually constant voltage, there may not be much in
the way of current limiting until it gets to the float charge phase.

 

[Michael A. Terrell]

John Larkin wrote:

On Sat, 20 Jul 2013 01:01:38 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.


Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

What's going to catch fire? The battery? Some idiotic Chinese electronic charger
that doesn't current limit?

A car battery with a shorted cell can boil over and rupture. Not that
you give a damn.

Who cares about lawsuits, or killing their customers?

Why kill them when it's more profitable to rip them off?

Sigh. They have to be idiot proof for the uneducated masses. No one
who builds battery chargers gives a damn about your problem.

Other than the roll around garage chargers, I haven't seen anything
other than a float charger that will try to charger a dead battery.

Old fashioned cheap transformer-rectifier chargers worked fine on a dead
battery. The new electronic chargers are too smart to do that.

Complain to their company lawyers, who don't want more lawsuits.

My charger was built from a motorhome battery eliminator and a
Variac. I can set the initial charge rate from a few mA, to 30 amps and
see how the battery is charging. I built it over 40 years ago. I have
used it to start a car with a 'dead' battery more than once.

I keep a Lascar bench supply around now. It current limits.

Good for you. I haven't had a completely dead battery since 1997,
when a #8 AWG wire shorted to the frame and pulled the battery to zero
volts. With the hot summers in Florida batteries die without warning. I
pulled into an electronics supplier in Destin one day. When I went to
leave, the car wouldn't even click the solenoid. Like several other
failed batteries, a cell had opened.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[John Larkin]

On Tue, 23 Jul 2013 04:54:43 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

John Larkin wrote:

On Sat, 20 Jul 2013 01:01:38 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


John Larkin wrote:

I think it was deliberate to sell batteries. It would be trivial to shut off the
charger if it saw, say, -0.6 volts at its terminals.

A car battery charger that won't charge a dead battery is idiotic at best.


Sure it is. Who wants to make sure someone doesn't try to charge a
battery with a shorted cell and start a fire?

What's going to catch fire? The battery? Some idiotic Chinese electronic charger
that doesn't current limit?


A car battery with a shorted cell can boil over and rupture. Not that
you give a damn.

If it shorts while it's fully charged, yes, but that's very rare. Car batteries
are amazingly rugged. But that's not the situation we're talking about here.

If it's already shorted and stable that way, charging current will apply zero
power to a shorted cell, so it won't "boil and rupture." I^2 * R = 0 when R = 0.
Dinky chargers don't have enough power to boil a battery anyhow.

Beside, the cheap electronic chargers would still pump current into a battery
with one zero-volt cell. They just won't put current into a battery with all
zero volt cells.

Who cares about lawsuits, or killing their customers?

Why kill them when it's more profitable to rip them off?


Sigh. They have to be idiot proof for the uneducated masses. No one
who builds battery chargers gives a damn about your problem.

They design them that way to sell to parts stores, who sell the chargers and
then sell batteries to replace the ones that "won't take a charge."


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators