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so I charged a car battery backwards

[486]

[486]

smells things
Joined
May 19, 2020
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5,208
Loc
pine city MN
gots me a fresh neverstart, 2018 vintage, p. much brand new
ran it dead leaving it in one of my newer acquisitions for too long, or at least near enough to dead that leaving it on the battery tester with the carbon pile cranked up didn't get more than 20 amps outta it, left it there until it was stone dead

figured that I'd try something experimental, whenever you see pictures of batteries taken apart, there's always one of the electrodes that's eaten away to nothing while the other one is looking practically brand new

I'd heard somewhere that the battery plates are both lead sulphate when the battery is dead, the electrolyte is water
you charge it and one of them turns to plain lead, the other turns to lead oxide and the water turns to sulphuric acid
so, if you got a dead battery it logically follows that you can charge it backwards so that it'll start eating up the other set of plates in there

turns out that ain't the case, sat that thing on the 30 amp charger for a couple days, but it never got to where it'd hold a load when charged backwards, few amps and its instantly down on volts
Ran it dead and I'm charging it back up normal, we'll see if it will hold a load normal

You guys are smart, where's my logic failing me?
 
78bronco460 said:
After formation the positive plates are lead dioxide vs the negative regular lead and polarity is fixed.
This is what they tell me at the battery plant I do jobs at.
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ah dang, no trade backs

oh well, knew there had to be some reason everyone wasn't doing it heh
 
You would have had better luck, emphasis on luck, after the battery was discharged and do just what you did. Except you should have left the battery with reverse polarity and charged it that way. That's about the only chance of getting it back without dissembly and rebuild.
 
Temporary backward charging can shock the plates and remove some buildup, but at that point its hardly worthwhile
 
rugger said:
You would have had better luck, emphasis on luck, after the battery was discharged and do just what you did. Except you should have left the battery with reverse polarity and charged it that way. That's about the only chance of getting it back without dissembly and rebuild.
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dunno man, my process was
mostly dead battery -> totally dead battery -> backwards charged battery -> fails load test spectacularly -> totally dead battery

Charging it normal ways now, though if I went and made them both lead oxide I guess it won't ever come back to life?
We'll see!
 
M92PV4U said:
If you spin it backwards does it charge in reverse?
Click to expand...
nope, gotta flip the diodes in the rectifier and then the regulator would probably get real fucked up unless you're running an external reg, one of them would be easy enough to insulate the case and ground the positive...

ETA: I'd just be putting the cables on the "wrong" posts and running everything normal
 
Ebs said:
It's like how high pinion diffs need reverse cut gears, except for batteries.
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dammit, when nobody had an av it was easy
when only I didn't have an av it was also easy

fuck it may as well get with the times and lose some of the pbb charm
brb dusting off the old HDDs to get my old avi found
 
Telephone switchboards are -48VDC. You need to do 4 batteries and dust off an old PBX
 
dntsdad said:
send it to Australia
Itll work
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all the acid will fall out then

78bronco460 said:
Telephone switchboards are -48VDC. You need to do 4 batteries and dust off an old PBX
Click to expand...
heh
learned that one quick when stripping phone wires with my teeth at work
after the first one bit me I figured I'd be smart and just do them one wire at a time so there wouldn't be a complete circuit
nope, still bit me somehow hahaha
 
Battery in parallel (+ to + ….. - to -)
Doubles the amps … same volts

Battery in series you double the volts … same amps

You made a series circuit. You gave it a boost in volts
 
[486] said:
I found some old timey glass insulators. You'll be pleased to know that soon as I get around to finding one that doesn't have any chips in the glass and I get all the rat shit washed off of it it'll be a butt plug at least once.
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.
cringe-sour.gif
 
grumpy356 said:
Battery in parallel (+ to + ….. - to -)
Doubles the amps … same volts

Battery in series you double the volts … same amps

You made a series circuit. You have it a boost in volts
Click to expand...
what did I do?

I'm confused how my explanation and later further clarification of my process was unclear.
I'm not even certain how I can draw a picture of what I did.
 
At least you unhooked it from the car first!
I just worked on an 03 Thunderbird that was charged backwards. The only only module on the network that is NOT fried is the airbag module. Fuckin totaled!
 
[486] said:
BB397E90-EBFD-42F0-A0A2-63B8A1C5024F.jpeg
what did I do?

I'm confused how my explanation and later further clarification of my process was unclear.
I'm not even certain how I can draw a picture of what I did.
Click to expand...
Think about how a 24 volt system is wired on a diesel truck.

2…. 12 volt batteries wired in series. Wire goes from the - wire of battery 1 to the plus of battery 2 so you get 24 volts

You didn’t have 2 batteries, but the charger acted as a battery for theoretical purposes
 
grumpy356 said:
Think about how a 24 volt system is wired on a diesel truck.

2…. 12 volt batteries wired in series. Wire goes from the - wire of battery 1 to the plus of battery 2 so you get 24 volts

You didn’t have 2 batteries, but the charger acted as a battery for theoretical purposes
Click to expand...
it woulda been a dead shorted 24v system, except for the fact that the battery was 100% dead before the charger was attached

as an aside, connecting a battery charger backwards to a not-dead battery is a great way to instantly destroy the rectifier
this is why a lot of battery chargers got those circuit breakers inline with the output
 
[486] said:
you also misread

this was 100% intentional
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Yeah Im picking up what your puttin down. I was just sharing a recent story.
Have you ever charged a AAA battery at 30Am with a car charger?
 
[486] said:
it woulda been a dead shorted 24v system, except for the fact that the battery was 100% dead before the charger was attached

as an aside, connecting a battery charger backwards to a not-dead battery is a great way to instantly destroy the rectifier
this is why a lot of battery chargers got those circuit breakers inline with the output
Click to expand...
Ok… guess I misunderstood

Yeah… I see it now
 
gmcxt said:
Yeah Im picking up what your puttin down. I was just sharing a recent story.
Have you ever charged a AAA battery at 30Am with a car charger?
Click to expand...
I have charged alkaline batteries with a wall wart and a few components, many years ago
just looked at it and there's a transistor a couple diodes and a couple resistors in that dingus, don't remember why there's all that junk there, but it worked about 50% of the time, the other times they just started leaking so NBD
 
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