Lead Acid Battery Charging

[Ian Field]

"Fred Abse" wrote in message
newsan.2012.07.21.08.39.22.870208@invalid.invalid...

On Fri, 20 Jul 2012 14:48:41 +0100, Ian Field wrote:

***I'd delete the forward conducting diode (D1)

Many (most) integrated regulators don't like being backdriven.

***the reverse protection diode would take care of that - but only if each
regulator had its own diode, and in any case I agreed with whoever said a
single 5V reg would do.

***Phil already pointed out the forward conduction diode knocks 0.6V off the
output - If the OP really does feel the need to include that diode, then the
correct output can be restored by grounding the reference pin via a
compensating diode with a bias resistor to force a forward volt drop.

 

[krw@att.bizzzzzzzzzzzz]

On Sat, 21 Jul 2012 02:01:09 -0700, Fred Abse <excretatauris@invalid.invalid>
wrote:

On Thu, 19 Jul 2012 12:43:43 -0700, jsscshaw88 wrote:

My concerns are

1. Will the charger not affect the 7805 in any way, if I connect it to the
output of the 7805? The diode D1 is protecting the output of the 7805 from
charger. Am I right?

2. If I do not use the D2 than the output of the 7805 will be connected to
+12 V out put of the battery. And the load will get 12 V instead of 5
volts.

I can only use one ( same) connector to provide power to the load and for
getting the battery charged via battery charger.

You still haven't answered the burning question:

Why the string of three regulators, when one will do the job?

The question wasn't answered but it looked to me that the intermediate
voltages were being used.

>Phil Allison's comment is correct. You won't get 5 volts out.

 

[Fred Abse]

On Sat, 21 Jul 2012 15:27:23 +0100, Ian Field wrote:

in any case I agreed with whoever said a
single 5V reg would do.

I think that might have been me ;-)

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Sat, 21 Jul 2012 11:48:20 -0400, krw@att.bizzzzzzzzzzzz wrote:

The question wasn't answered but it looked to me that the intermediate
voltages were being used.

That wasn't what she drew.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[krw@att.bizzzzzzzzzzzz]

On Sat, 21 Jul 2012 09:46:54 -0700, Fred Abse <excretatauris@invalid.invalid>
wrote:

On Sat, 21 Jul 2012 11:48:20 -0400, krw@att.bizzzzzzzzzzzz wrote:

The question wasn't answered but it looked to me that the intermediate
voltages were being used.

That wasn't what she drew.

You're right. I was remembering that the arrows form the regulators were just
that, not grounds.

 

[David Eather]

On Saturday, 21 July 2012 08:24:32 UTC+10, David Eather wrote:

On Saturday, 21 July 2012 01:39:14 UTC+10, (unknown) wrote:
Hi,

The Load and the battery has following female connector on it

http://www.digikey.com/product-search/en?lang=en&site=us&KeyWords=CP-040DH

The battery has the following male connector on it

http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=CP-2211-ND

This connector has two different connector on each end. I cut the connector on one end and solder it to the output of the 7805 ( positive terminal) and the ground of the battery.

I do not know whether this connector has an internal switch or not ...

jess

It doesn't matter - on further reflection a plugable switch won't solve the problem.

The 'real' solution is to design a custom battery charger - because that diode stuffs it up for off the self chargers. Normally the state of voltage tells a lot about the amount of charge but in this case there is an extra .7 that isn't taken into account.

As a suggestion you could replace it (IIRC D2) with a 1 amp 30 volt schottky diode (1N5818 or 1N5818 would be OK) - this will *reduce* the problem introduced by the diode.

But the best solution is to customize the charger (there is an ugly hack that might be possible - similar to using the diode to jack up the output voltage of the 7805)

 

[Ian Field]

wrote in message
news:68cae7f7-0ac5-4ce6-b614-543f55a8038a@googlegroups.com...

Hi,

Will 1N5819R will work instead of 1N5818. The digikey link is given below

http://www.digikey.com/product-detail/en/1N5819/1N5819IR-ND/446794

I have few 1N5819 already in stock. I have to place order for 1N5818.


***1N5817=20V, 1N5818=30V & 1N5819=40V.

Apart from those differences; all 3 are pretty much the same - The "R"
suffix may be an artefact of their stock number, or posibly an encapsulation
variant.

 

[Fred Abse]

On Sun, 22 Jul 2012 10:53:19 -0700, jsscshaw88 wrote:

I am unable to understand that why a zener will work better than a diode

1N5818, etc are not zener, they are schottky.

Lower forward voltage than a junction diode, at the expense of (usually)
higher leakage.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Ian Field]

wrote in message
news:61ac63bc-0f85-4e21-8500-9823b12a36dd@googlegroups.com...

I am unable to understand that why a zener will work better than a diode

***A zener is a diode with the difference that its doped in such a way as to
have a closely defined by voltage, reverse leakage and a sharp knee curve in
the reverse current - strictly speaking; anything less than 7V is a zener
and anything over 7V is an avalanch diode.

***I've found by experiment that I can usually identify zeners with a DMM
diode check range because they read almost exactly 0.7V, regular (for mains
frequency) diodes usually come in between 0.55 & 0.65V, fast diodes usually
have Vf down to about 0.4V. SB diodes are quite variable from as much as
0.4V for a small signal type, to as low as 0.1V for a thumping great metal
stud rectifier.

***SB diodes with your application will give the lowest Vf loss, with a 12V
SLA battery; any common SB diode will have adequate reverse voltage rating -
provided there's no large inductors to produce back emf. SB diodes do have
measurable reverse leakage, but that shouldn't be a problem.

 

Hi,

Will 1N5819R will work instead of 1N5818. The digikey link is given below

http://www.digikey.com/product-detail/en/1N5819/1N5819IR-ND/446794

I have few 1N5819 already in stock. I have to place order for 1N5818.


Thanks

jess

 

[Ian Field]

"Fred Abse" wrote in message
newsan.2012.07.22.18.21.28.798630@invalid.invalid...

On Sun, 22 Jul 2012 10:53:19 -0700, jsscshaw88 wrote:

I am unable to understand that why a zener will work better than a diode

1N5818, etc are not zener, they are schottky.

***Back in the days when I repaired monitors for a living, I found that some
manufacturers used either a 1N5817 or a BYV10 20 SB diode to clamp the
connection between the UC3842 & the MOSFET gate, it was fairly usual for the
source current sensing resistor to fail O/C if the MOSFET punched through.
The SB diodes were much better at failing S/C under such extreme conditions
than a zener - sometimes they even protected the UC3842!

 

I am unable to understand that why a zener will work better than a diode