[badA31]

Even at 59 years old I guess I don't know everything! This is a new one on me. A friend with a chevy powered T-bucket had a starting problem today. He told me that the car was running and he shut it down briefly. He said that when he re-started that everything was dead, like with a dead short. He said the battery started to boil. After trying a few common checks he hooked a battery charger to it and heard a loud CLICK. The car started and all systems worked fine. He said that the 12 volt system had reversed it's polarity. WHAT??? Have you guys heard of this? Am I just that dumb?

 

[poncho62]

Never heard of it................and I am old too.

I think he has a bad connection and is going to have the same problem again.

Our resident electrical expert, Docvette will probably have some more to say about this.

 

[Kevin45]

It happens. When I first bought my '62 Impala, I drove it home about 40 miles. Pulled it in the drive and it would not start. I jumped it and the wires started smoking. I hooked the jumper cables up right, but the battery was in backwards. Positive to ground and negative to starter. Luckily the wires started frying before the battery blew. So to say the car went back for some major rewiring. Everything under the dash was good but the harness under the hood was cooked pretty good. The only explanation the guy could come up with was the battery was dead when put in and then charged up. What surprised me was that it was a new battery and most new batteries are charged before they leave the store or already have a charge in them. I'm surprised it didn't burn up before that because I tried th car out a week before that.

 

[docvette]

Loud Click...

Doc here:imp:

HAPPY THANKSGIVING!

Reversed on it's own? I think not...Never heard of it..

What it sounds LIKE happened was the solenoid developed a short internally to a ground source,or even power...holding the drive unit in while doing so.(The loud "Click")

At any rate, I'd check that harness and the starter first..

Then the alternator circuits for shorting, The regulator, if it went bad will load up the power and drain the battery also..

A blown set of diodes can crowbar to ground (making a short) and boil a battery.The click could have been the substrate blowing apart...Anyway he'll know, right off..It won't charge!

A boiled Battery is a MASSIVE short. If it is other than an internal solenoid short Main terminal (any other System) It should have blown a fusible link, If he has one. If not I'd advise him to install one It might save his Rod in the future.

One other rare case is a plain shorted battery, Internal short boiling it over from whisker growth in the sluff box, may have cleared with the "Hit" from the jump, but will occur again..as the battery sloshes around. But usually it just blows the battery up, or charge never returns after the short melts away..

Let us know what he finds!

HAPPY HOLIDAYS!

Doc imp:

 

[Forkliftguy]

If you discharge a battery right down to 0V (well, as close to zero as possible) and then charge it "backwards" (charger + to batt. -, charger - to batt. +) you can in effect reverse the polarity of the battery.

Here is the reason: In order for a battery to delivery any charge, the lead plates on the anode side have to be chemically different then the lead of the positive side (FYI the positive plate are usually "lead peroxide", negative is pure lead). The electrical charge gets created when the the lead plates are in the process of transforming in to Lead Sulfate. Once all of the plates have become lead sulfate there is no longer any chemical reaction and the battery is "dead". Since all of the lead plates are now identical in chemical make up, If you send current through the battery in the wrong direction you will cause the negative plates to turn into lead proxide, and the positive plates will turn into pure lead.

The reason this is bad is for one thing the terminals will now be marked incorrectly, and second there is always one more negative lead plate than positive plates. The reason for this is so that both sides of the positive plates get reacted upon evenly since they expand and contracted during charge/discharge cycles. (a battery is composed of a lead plate sandwich: neg plate, pos plate, neg plate, etc.) If that extra neg plate was not there, the last positive plate would only be reacted upon from one side which would cause it to warp. If you charged the battery backwards you now end up with two positive plates on the extremes of the "Lead Sandwich" which will warp the battery case and possibly short the battery internally.

Correct me if needed DOC.


Marc

 

[Old School Nut]

Reversal

my training has only been with aircraft batterys, and aircraft baterys use spongy lead (Pb) for the negative and lead dioxide (PbO2) for the positive... i never heard of a lead acid battery reversing like that, but i do know that aircraft nickel-cadmium can reverse ON ITS OWN when extreamly discharged. this is called simply, reversal, and this is what my Marathon service manual has to say on the subject...

Reversal: in a rechargeable battery, this refers to a change in the normal polarity of the cell or a battery to the opposite polarity as when a cell is driven into reverse during a deep discharge, or,when a cell or battery is inadvertently charged in reverse.

Source, Page 38, 2nd paragraph, section 13.0 definitions of commonly used battery terms of the marathon battery instruction manual (care and maintenance of nickle-cadmium batterys)

this is obviously not a lead acid battery, however this is the only thing we were taught about reversal. i hope this helps.

 

[julmer]

I'll go with Docvette on this one. Sounds like a huge short and most likely in the starter solonoid itself. I would pull the starter and examine the guts of the solonoid for dirt or loose pieces and I'd do it soon. That kind of a short can be very dangerous - like the battery exploding in your face or the car burning down.

 

[badA31]

Thanks for the replies guys ! At least now I know I'm not as dumb as I thought!!:thumbup:

 

[Old School Nut]

yeah i agree, it does look like a short in the relay.... however reversal does happen, it wont just happen then flip back around..

 

[Forkliftguy]

yeah i agree, it does look like a short in the relay.... however reversal does happen, it wont just happen then flip back around..

Yeah, it would have to have been charged backwards while being completly dead or close to it.

 

[docvette]

reversal

Doc here:imp:

HAPPY THANKSGIVING!

Yeah, my thoughts too...It would have needed "Outside" help to reverse itself.

Unless the guy Charged it backwards from dead ... and isn't telling all he knows..Once he realized what happened..:smash:

AND there would have been residual Damage...Like semiconductors Don't like reverse polarity...Cd players, Tach's, Amps, Digital clocks, Engine modules..Ect...

Sounds like an internal short at the solenoid..

HAPPY HOLIDAYS!

Doc imp: