reversed polarity in coach battery

[kendall]

What would cause one of my coach batteries to reverse its polarity? I have two 6 volt batteries wired in series which gives me 12 volts with incredible stamina, but one of them keeps reversing its polarity. Any ideas?

 

[Tom]

Kendall, are you saying that occasionally the combined 12V becomes 0V? That's what would happen if one of the two batteries reversed polarity. Have you confirmed with a voltmeter on that battery that it does in fact reverse polarity? Personally, I've never seen that.

 

[John From Detroit]

What would cause one of my coach batteries to reverse its polarity? I have two 6 volt batteries wired in series which gives me 12 volts with incredible stamina, but one of them keeps reversing its polarity. Any ideas?

Ok, if ONE and only ONE of the batteries is reversing it's polarity (And I will bet this only happens when the batteries are in a discharge state doesn't it) it clearly indicates one of two conditions

Condition one, Which is easily repaired:  For some reason that one battery lost charge when it's partner did not, The solution is to "Equalize" the batteries, This can be done two ways... And you should use both,,, First, discharge both batteries, seperately, do this by using a resistive load such as a headlamp (they will work on 6 volts, about =70% brillance) and then recharge, OVERCHARGE using the instructions in another thread in this forum. 

If this fixes it,  Lift your face to the heavens and give thanks to the God of good batteries.

If not, then you have condition 2: (Replacable)

IN condition 2 one of the batteries has reduced capacity, this may be due to age, or other factors.  The solution is to replace BOTH batteries, yes BOTH of them with brand new batteries..... Or, one of the new advanced AGM 12 volt super batteries, (Also discussed in other threads here in the forum)


There are advantages and disagvantages to 2 six volts in serries... You have the disadvantage

NOTE: Reverse polarity is not a good thing from a battery's point of view

 

[Karl]

Time out! A lead/acid battery cannot possibly reverse it's polarity. Positive plates are coated with lead dioxide paste and negative ones with spongey pure lead, and they can't magically transfer these materials from one to the other. I think we have a problem with terminology or measurement technique.

Kendall, Please explain exactly what is happening and how you are making your measurements. The only way to truly see what's happening is to eliminate back circuits by removing the battery cables; then do your measurements. I'm pretty sure you'll find one of the batteries is either a high resistance, or completely shorted. If the case appears bulged out, chances are very good that it's shorted. Let us know.