"Fixing" crap Harbor Freight battery charger

[Cydrome Leader]

Leif Neland <leif@neland.dk> wrote:

Cydrome Leader formulerede sp?rgsm?let:


I just gave this a few minutes of though and drew a blank. How do you
directly test to make sure nobody stole your ground?

The only thing I could come up with was run a thin wire along your ground
system in a loop and assume scrappers will steal that too. If that guard
wire of whatever you'd call it opens or goes missing you've triggered an
alarm?

Measure the resistance between the tower and a separate ground
connection.

Leif

That still sounds tricky as there may be multiple grounds all connected to
your ground busbar. I just took a peek at the telecom room on this floor
and the plate on the wall had nearly a dozen connections, of which 3
seemed to be going back to the electrical riser for the floor. You could
remove most of those connections and everything would still be grounded,
enough that nobody dies from a frayed power cord, but just not able to
take a lightning strike or some major electrical contractor screw up.

I'd love to see the AT&T manual not on how to sweep floors, but on
grounding everything.

 

[Jeff Liebermann]

On Mon, 12 Aug 2013 20:31:38 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote:
On Mon, 12 Aug 2013 16:37:05 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

It's pretty sad lead acide battery chargers were the most sensitive
devices out of that mix of hardware.

I still don't know exactly what killed all the chargers. I would
expect such high power devices to be built rather rugged, but
apparently, that's not the case.

Very odd. Some sort of fatal design flaw with the regulation parts is what
it sounded like.

Some kind of design error might be a possibility, but why would
charger from various vendors all have the same problem? I wish I had
spent some time doing a post mortem, but I just wanted to get rid of
them and replace them with something that works.

I just gave this a few minutes of though and drew a blank. How do you
directly test to make sure nobody stole your ground?

The only thing I could come up with was run a thin wire along your ground
system in a loop and assume scrappers will steal that too. If that guard
wire of whatever you'd call it opens or goes missing you've triggered an
alarm?

That's exactly what I was thinking and probably the best way.

I could also measure the ground resistance to another nearby ground
rod, and trigger an alarm on any abrupt change in resistance. The
trick will be to design it so that it will survive a lightning strike.

I vaguely recall this being discussed in an article in Above Ground
Level magazine, but don't recall the issue or method.
<http://agl-mag.com>



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Shaun]

"Roger Blake" wrote in message
news:20130805104023@news.eternal-september.org...

Given the less-than-steller reviews and HF's reputation for electronics,
I should not have bought this thing, a 12 Volt 6 or 2 amp (switch
selectable) charger for car batteries. The problem is that instead of
providing the tapering charge and switch to trickle it is supposedly
designed for, this "charger" discharges and kills batteries instead. (In
contrast, I have a 4 amp Schauer charger that is about 40 years old
which still works just fine.)

Instead of throwing out the HF unit, I was thinking that it has a perfectly
usable case, transformer, ammeter, and wires with alligator clips. Just the
crapulent Chinese electronics are bad so I'd like to trash that stuff
and turn this into an "old school" type charger like my Schauer.

The transformer secondary is center tapped and reads about 28 volts AC
across the ends, 14 volts on each leg from the center. The original
electronics are on a small board with 7 transistors, 2 SCRs, a couple
of diodes, and numerous resistors. (That's a lot of stuff just to
kill batteries!) Searching online I'm finding a bewildering array of
home-brew battery charger circuits, everything from simply using a bridge
rectifier on the transformer secondary to more complex circuits to taper
the charge and either switch off or go to trickle when the battery is
fully charged.

The behaviour of my old Schauer is to gradually reduces current until
the battery is fully charged, where it will stay at a low level and not
hurt the battery if left on overnight or even for a few days. I have
not opened it up yet to see what's inside, but being an early 1970s unit
I'd be surprised if there is much aside from a transformer and rectifier.

Anyone have a simple circuit handy that works well for this? I've seen
a few plans online that just say to use a bridge rectifier of suitable
capacity, but I want to be reasonably sure that this thing won't kill
any more batteries.

--
Roger Blake
Change "invalid" to "com" for email.
Google Groups killfiled.

Harbour Frieght products are crap! You get what you pay for! Why don't you
just go out a buy a new one from a reputable store. The rest of the parts
in your dead battery charger are probably crap too.

 

[Shaun]

"Michael A. Terrell" wrote in message
news:6O6dnTJo4Z7B0pfPnZ2dnUVZ_vGdnZ2d@earthlink.com...


Shaun wrote:

Harbour Frieght products are crap! You get what you pay for! Why don't
you
just go out a buy a new one from a reputable store. The rest of the parts
in your dead battery charger are probably crap too.

WTH is 'Harbour Frieght'? Another of your drug induced nightmares?


If your so fucking stupid that you can't figure that out, you shouldn't be
posting. "Harbour" is the Canadian way of spelling that word, and Frieght
is just a typo, nobody is perfect, we all make mistakes - look at your
parents; they had you ASSHOLE. What do you get out of critiquing someone
else's spelling? Does it make you feel superior to other people, do you
need to do that for your low self esteem. You are a pathetic excuse for a
Human being!

 

[Michael A. Terrell]

Shaun wrote:

"Michael A. Terrell" wrote in message
news:6O6dnTJo4Z7B0pfPnZ2dnUVZ_vGdnZ2d@earthlink.com...

Shaun wrote:

Harbour Frieght products are crap! You get what you pay for! Why don't
you
just go out a buy a new one from a reputable store. The rest of the parts
in your dead battery charger are probably crap too.

WTH is 'Harbour Frieght'? Another of your drug induced nightmares?

If your so fucking stupid that you can't figure that out, you shouldn't be
posting. "Harbour" is the Canadian way of spelling that word, and Frieght
is just a typo, nobody is perfect, we all make mistakes - look at your
parents; they had you ASSHOLE. What do you get out of critiquing someone
else's spelling? Does it make you feel superior to other people, do you
need to do that for your low self esteem. You are a pathetic excuse for a
Human being!

Your the one who is brain fucked. There is no US company named
Harbour Frieght, so go fuck yourself.
..

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

 

[Shaun]

"Michael A. Terrell" wrote in message
news:CIWdnYMQnohKuZDPnZ2dnUVZ_judnZ2d@earthlink.com...


Shaun wrote:

"Michael A. Terrell" wrote in message
news:6O6dnTJo4Z7B0pfPnZ2dnUVZ_vGdnZ2d@earthlink.com...

Shaun wrote:

Harbour Frieght products are crap! You get what you pay for! Why don't
you
just go out a buy a new one from a reputable store. The rest of the
parts
in your dead battery charger are probably crap too.

WTH is 'Harbour Frieght'? Another of your drug induced nightmares?

If your so fucking stupid that you can't figure that out, you shouldn't be
posting. "Harbour" is the Canadian way of spelling that word, and Frieght
is just a typo, nobody is perfect, we all make mistakes - look at your
parents; they had you ASSHOLE. What do you get out of critiquing someone
else's spelling? Does it make you feel superior to other people, do you
need to do that for your low self esteem. You are a pathetic excuse for a
Human being!

Your the one who is brain fucked. There is no US company named
Harbour Frieght, so go fuck yourself.

Splitting hairs proves nothing. I think the content and general idea of a
message to be important unlike some anal retentive prick like you that looks
for problems.


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

 

[Roger Blake]

Just as a followup here, for the moment I've solved my need for a
second automotive battery charger by picking up another 35-40
year old charger at a flea market. It works great! There's something
to be said for simplicity.

I'll play around with the Harbor Freight unit when I have a chance,
there are a lot of possible circuits out there to play around with.

--
Roger Blake
Change "invalid" to "com" for email.
Google Groups killfiled.

 

The following link is a rough schematic of the 12V 6A-2A / 6V charger:
https://photos.google.com/search/_tra_/photo/AF1QipNXWaVaaAFuiiNUne5LutYuxNwdPGT03vcmpefG

Please note: All resistor values are measured and approximate!
Theory of Operation:
The input transformer has some primary side switching to change the secondary voltage for 12V 2a, 6a and 6V.
SCR's AC1 and AC2 are triggered on alternate half cycles of the ac input to charge the battery. Triggering is done by P1 turning on via N1 turning on, N2 and P2 turning off. The voltage divider of 23K and the parallel 9.4k resistors sets VREF as a percentage of battery voltage. The TL431 has a nominal reference level of 2.495 volts. Therefore, V_BATTERY must be > 2.495/(4.7/(23+4.7)) or about 14.7 volts to turn on VR which disables charging by turning on P2 - N2 turning off N1,P1, AC1, AC2. P3 provides hysteresis to hold VR conducting by raising VREF when VR turns on. P4 turns on when P1 is on and V_BATTERY exceeds the rectified AC from D1 D2 via P1. P4 on turns on N3 which clamps VREF low turning VR off and continuing to enable triggering. The sensing process repeats on each AC half cycle. AC1 and AC2 will turn off at the end of their positive cycle if there is no gate drive from P1.
Design Notes:
V_BATTERY is required to power N1,N2,P2,VR,P3,N3. Without battery voltage, N1 will not conduct and P1 will not trigger AC1 and AC2 => No battery charging.
The reference voltage divider is fixed for a 12 Volt lead acid battery. Hence the note on the charger stating that 6Volt battery charging must be manually terminated.
N2, N3 have no base emitter bypass resistors. Collector - base leakage current could turn them on.
There is no protection for reversing the battery leads. It May be OK as is but I have not tried it.
Possible failure modes:
AC1 and/or AC2. would be likely candidates. BT151's are about $0.75 each in low quantities. AC1/AC2 triggering problems require chasing through the entire PC board to see where the signal is lost.

Overall, the HF unit is well constructed for the price. I could envision scenarios where it would fail. YMMV ;-)

AJG