Would never try this but...

[force9BOAT]

Just out of curiosity I'm wondering if a lead-acid battery were 100% discharged then would it be possible to reverse the +/- cables and recharge it backwards thus reversing the polarity?  In other words, internal to the battery is its polarity just a matter of the direction it was charged in?

Rob

[Flux]

Batteries are always made with one more positive plate than negative. Normally the plates are made in a different way so they shouldn't work as well if reversed.

Early Plante plates were formed in the same way and the negative reversed at the end of the forming process. These wouldn't object much but you would still have the wrong number of Plates. No modern plates are made this way.

Many years ago I came across some starter batteries on a large Cummins generator that were working with reversed polarity and they started that Diesel ok. No one knew when they had been reversed.

There were at one time backyard empires that built reconditioned batteries using old negative plates as they usually live longer than the positives, I suspect they were pretty useless.

The basic process is reversible but for modern plates they are pasted with different compounds and formed specially. The positive material is lead dioxide and the negative is spongey lead in the final formed state. I don't think all manufacturers  use the same materials for pasting, but now the number of manufacturers is so limited that that may no longer be true.

Flux

[boB]

Over-discharge of a multi-cell battery can reverse the polarity of a single

cell but I don't think it's a good thing.  I know that Nicd and NiH batteries

can recover from reversal (and it's still reduces their life) but I'm not sure

about regular flooded lead acid Antimony/calcium batteries.  I ~think~ that

their resistance goes up in this case.

I know that the composition of the plates of Lead Acid batteries are such that

they will work best and last longer when used with the normal polarity.

I might ask my friend who works for a local battery manufacturer this

question.

boB

[badmoonryzn]

One of the things that happens to a battery in normal use is the plate oxidizes and eventually there is so much crap on the plate it does not conduct electricity well. Many things can go wrong, but the most common is plate oxidation in a normal situation. Heat is the cause of most battery failures. I have run in to reversed battery hook-ups with 8Ds in trucks and buses at least once or twice a year. I suppose it is because of how the battery looks was my best guess. Often the tiny little plus and minus are hard to see on the 8Ds. Mind you this is just a guess as I can't see how one could make that mistake, but I suppose it could happen if one was having an LSD flashback. I have charged batteries backwards to remove this deposit. It works on some batteries, some blow up because of an internal short. Oh well, I still think it is worth a try if one has an area that will not screw up in case of the latter. How about running a couple of hundred volts AC in to bad nicad packs for just a second to blow the crap off of the plate. It works too, but sometimes the results are the same as the lead acid. BOOM! Just remember, don't try this at home! The newer sealed batteries loose their electrolytes after a while and go south pretty fast.

Regards,

badmoon

[Seaspray0]

Absolutely NOT!  The battery works off the principle that the electrostatic potential between two metals (lead and zinc) is near 2 volts.  Anything lower and the zinc dissolve into the acid.  Anything higher and the zinc is replated from the acid.  You technically can't discharge a battery to even zero volts without ruining the cathode and anode plates (which is why there are cutoff's on good circuits to protect the battery from damage when the voltage gets low).