Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old July 16th 05, 08:06 AM
mike
 
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Default Can you fix a lead-acid battery that's charged backwards?

I bought a pair of electric scooters. They'd "fixed" the charger
and managed to get the batteries charged backwards. Can I discharge
them and charge 'em up forwards? Any special techniques? Fast/slow/
charging?
May be a moot point as I expect the speed controller box is fried too.
mike

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Old July 16th 05, 08:31 AM
James Sweet
 
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"mike" wrote in message
...
I bought a pair of electric scooters. They'd "fixed" the charger
and managed to get the batteries charged backwards. Can I discharge
them and charge 'em up forwards? Any special techniques? Fast/slow/
charging?
May be a moot point as I expect the speed controller box is fried too.
mike


Generally no, since you can't access the individual cells inside the battery
separately you'll normally end up with some cells charging ok and others
reversed, it's easier to just buy new batteries.

The speed controller is probably pretty simple, crack it open and have a
look.


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Old July 16th 05, 12:38 PM
Just Another Theremin Fan
 
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Can I discharge them and charge 'em up forwards?

ROTFPML!!!!! Is this post serious?

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Old July 16th 05, 09:28 PM
satellite_jim
 
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I actually have some experience with backwards batteries. I grew up in my
fathers auto repair shop in the sixties. Back then if you hooked up the
jumper cables to a generator equipped car you could start the car and the
generator would reverse polarity and you could go on your merry way with a
positive ground American car. We would just leave the lights on over night
and then charge the battery the correct way and polarize the generator (jump
the positive to the generator output lead for a second) in the morning. If
the battery was good to start with it would recover fine.

Jim.........


"mike" wrote in message
...
I bought a pair of electric scooters. They'd "fixed" the charger
and managed to get the batteries charged backwards. Can I discharge them
and charge 'em up forwards? Any special techniques? Fast/slow/
charging?
May be a moot point as I expect the speed controller box is fried too.
mike

--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
.
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted 12" LCD for Compaq Armada 7770MT.
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/



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Old July 16th 05, 10:10 PM
Dave Plowman (News)
 
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Default

In article ,
satellite_jim wrote:
I actually have some experience with backwards batteries. I grew up in
my fathers auto repair shop in the sixties. Back then if you hooked up
the jumper cables to a generator equipped car you could start the car
and the generator would reverse polarity and you could go on your merry
way with a positive ground American car.


I don't see how, as the cutout wouldn't pull in. That only happened when
the generator started producing more than battery volts which it couldn't
when reverse connected.

One way to instantly polarize the dynamo was to flick the cutout in
manually.

--
*Do infants enjoy infancy as much as adults enjoy adultery? *

Dave Plowman London SW
To e-mail, change noise into sound.


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Old July 17th 05, 05:02 PM
Jim Adney
 
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On Sat, 16 Jul 2005 00:06:10 -0700 mike wrote:

I bought a pair of electric scooters. They'd "fixed" the charger
and managed to get the batteries charged backwards. Can I discharge
them and charge 'em up forwards? Any special techniques? Fast/slow/
charging?


I think you should have a good shot at this. Try just discharging them
first, use a light bulb that lights normally across the battery to
discharge them, and let it go a couple days past the time when the
bulb is no longer glowing.

Then connect the charger properly and try to charge them, slowly. If
they take too much current, insert the light bulb again as a current
limiter, but you should be able to take the bulb out of the circuit
after a day or 2.

Let us know how this progresses.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------
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Old July 17th 05, 05:37 PM
Jim Adney
 
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On Sat, 16 Jul 2005 22:10:12 +0100 "Dave Plowman (News)"
wrote:

In article ,
satellite_jim wrote:
I actually have some experience with backwards batteries. I grew up in
my fathers auto repair shop in the sixties. Back then if you hooked up
the jumper cables to a generator equipped car you could start the car
and the generator would reverse polarity and you could go on your merry
way with a positive ground American car.


I don't see how, as the cutout wouldn't pull in. That only happened when
the generator started producing more than battery volts which it couldn't
when reverse connected.


I guess I'll have to think about the WHY of this, but I've seen it
happen. I agree that it's odd. The time I saw it, the owner had
installed the battery backwards, then realized his mistake and put it
in correctly. When I got to it the battery was correct, but I
eventually determined that the generator was polarized backwards.

Now I have to admit that it never occurred to me to wonder why putting
the battery in backwards would reverse polarize the generator while
putting the generator in forwards wouldn't correct it.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------
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Old July 18th 05, 04:59 AM
Bill Janssen
 
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Default

Jim Adney wrote:

On Sat, 16 Jul 2005 22:10:12 +0100 "Dave Plowman (News)"
wrote:



In article ,
satellite_jim wrote:


I actually have some experience with backwards batteries. I grew up in
my fathers auto repair shop in the sixties. Back then if you hooked up
the jumper cables to a generator equipped car you could start the car
and the generator would reverse polarity and you could go on your merry
way with a positive ground American car.


I don't see how, as the cutout wouldn't pull in. That only happened when
the generator started producing more than battery volts which it couldn't
when reverse connected.



I guess I'll have to think about the WHY of this, but I've seen it
happen. I agree that it's odd. The time I saw it, the owner had
installed the battery backwards, then realized his mistake and put it
in correctly. When I got to it the battery was correct, but I
eventually determined that the generator was polarized backwards.

Now I have to admit that it never occurred to me to wonder why putting
the battery in backwards would reverse polarize the generator while
putting the generator in forwards wouldn't correct it.



I think the key to an explanation is that the cut out relay senses
current direction as determined
by referencing the magnetic field of the current to the magnetic field
of a voltage fed electromagnet.

Since both were reversed the cut out relay didn't have a clue as to the
polarity.

I hope I explained my thinking clear enough.

Bill K7NOM

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Old July 18th 05, 01:14 PM
Dave Plowman (News)
 
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In article ,
Bill Janssen wrote:
I think the key to an explanation is that the cut out relay senses
current direction as determined by referencing the magnetic field of
the current to the magnetic field of a voltage fed electromagnet.


Since both were reversed the cut out relay didn't have a clue as to the
polarity.


I hope I explained my thinking clear enough.


In the UK, when I were a lad, most cars were positive ground. This of
course made no sense to the average punter, and it was very common for the
clueless to fit a new battery the wrong way round. And the symptoms were
the battery didn't charge.
As electronics became more popular, the change was made back to negative
ground for new vehicles. And if the owner of an older vehicle wanted to
fit a modern stereo, the easy answer was to convert it to negative earth,
and I've done dozens. And always had to re-polarise the dynamo before it
would cut in and charge. If the cut in had operated with the battery the
'wrong' way round, that would have re-polarised the dynamo and made this
unnecessary.

Of course, this was with the infamous Lucas electrics. Could be that other
makes work differently.

--
*Sometimes I wake up grumpy; Other times I let him sleep.

Dave Plowman London SW
To e-mail, change noise into sound.
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Old July 18th 05, 11:47 PM
jakdedert
 
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"Dave Plowman (News)" wrote in message
...
snip
Of course, this was with the infamous Lucas electrics.


....the Prince of Darkness....

jak






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