Thread: 6v batteries in series mystery

Originally Posted by brettw

I used a different, much less powerful charger after my fishing trip yesterday. Results were the same.
Battery 1bubbled vigorously. Batt 2 didn't.
Battery 1 is charged into upper : high " range, Battery 2 is in fair range

I now have a 6 v charger so ill try them separately tomorrow.

Thanks

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When in series, the batteries will charge according to their internal resistance. If you have one with lower resistance, it will get most of the current.

With two good batteries, they charge close to equally, if one is bad, you end up with a situation like yours.

May want to look into the warranty coverage on that battery with as little delay as you can.
Get the paperwork in order and give 'em a call.
An older friend who owned a battery store, now retired, told me once that the battery industry standard at that time was that about 10% of new batteries fail during the warranty period. It does happen.

Originally Posted by Atimm693

When in series, the batteries will charge according to their internal resistance. If you have one with lower resistance, it will get most of the current.

With two good batteries, they charge close to equally, if one is bad, you end up with a situation like yours.

Worked the problem again today.
Charged the weaker one by itself.
Wouldn't completely charge according to the charger display.
Last try tomorrow by reversing the order of connections.
Weaker battery gets positive charging lead, stronger gets negative lead
.

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Keep in mind....When running batterys in series...the weaker battery will eventually pull the other one down to its level. This is why it is recommended to replace all of the batterys in a series when one goes bad. They need to be same brand, same type, same group size, and same age. So if you determine that one battery is going bad....you need to replace both.

Originally Posted by "G"

Keep in mind....When running batterys in series...the weaker battery will eventually pull the other one down to its level. This is why it is recommended to replace all of the batterys in a series when one goes bad. They need to be same brand, same type, same group size, and same age. So if you determine that one battery is going bad....you need to replace both.

Please help me fully understand :

Two 6v batteries charged together in series.
Take off charger
Wait at least one day for surface charge to dissolve
Talk a reading of voltage of both
They should be very close to each other.
Say 6.36. 6.48 ?

If not, then i have a problem?

What about the cells individually?
I have a good hydrometer.
All should be solidly in the "good " range.
Again similar on both batteries?


Thanks again

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Originally Posted by brettw

Please help me fully understand :

Two 6v batteries charged together in series.
Take off charger
Wait at least one day for surface charge to dissolve
Talk a reading of voltage of both
They should be very close to each other.
Say 6.36. 6.48 ?

If not, then i have a problem?

What about the cells individually?
I have a good hydrometer.
All should be solidly in the "good " range.
Again similar on both batteries?


Thanks again

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You should really charge them individually. When charging in series, there is nothing to limit the current each battery is getting, no equalizer, so to speak. One battery can be soaking up all of it and leaving nothing for the other. If you have good batteries it is not an issue, but that is not the case here.

To me it seems like you have a bad battery, no question about it.

Originally Posted by "G"

Keep in mind....When running batterys in series...the weaker battery will eventually pull the other one down to its level. This is why it is recommended to replace all of the batterys in a series when one goes bad. They need to be same brand, same type, same group size, and same age. So if you determine that one battery is going bad....you need to replace both.

This is not strictly true for batteries in series. In parallel, yes, if two batteries are hooked together then they will essentially self-level. If one is dead or dying, it will kill the other as well, with no load applied.

In series, the batteries are still isolated and will not draw from each other. However, if one is weaker than the other, it will discharge sooner when a load is applied. You are only as strong as your weakest battery.

Thanks
I read that a new deep cycle battery takes many cycles to get up to full charge capacity.
Could this be why battery 2 is not charging fully?
Battery 1 has probably 30 cycles on it.
I consider them both new, which may be wrong.
When are 2 batteries incompatible?

Battery 1 was bought in April
Just got battery 2 a few days ago.

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Originally Posted by Atimm693

You should really charge them individually. When charging in series, there is nothing to limit the current each battery is getting, no equalizer, so to speak. One battery can be soaking up all of it and leaving nothing for the other. If you have good batteries it is not an issue, but that is not the case here.

To me it seems like you have a bad battery, no question about it.



This is not strictly true for batteries in series. In parallel, yes, if two batteries are hooked together then they will essentially self-level. If one is dead or dying, it will kill the other as well, with no load applied.

In series, the batteries are still isolated and will not draw from each other. However, if one is weaker than the other, it will discharge sooner when a load is applied. You are only as strong as your weakest battery.

Ok
I can charge in parallel andmove back to series for fishing?
Good idea?
Bad idea,?

Thanks

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