Hello All,

I was wondering if there are advasntages of useing two six volt batteries in series rather than one 12 volt. Would I get longer run times on equipemnt or does it all equate to the same thing (assuming a/h is the same).

Thanks for any comments

The advantage is more capacity.

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Dereck, PE, MSEE
Moderator

And in his next post Sunking will explain to you the different capacity between using 2x6v 200ahr batteries compared to using a 12v 200 ahr battery

I will still use my 12 volt charger for two 6v's conected in series right?


Additionaly, if two 6v's are better, would 3x4v be even better?

Dave it all depends on what capacity you need. Typically you do not want to parallel batteries to achieve a set capacity at a given voltage. 12 volt batteries capacity is usually on the range of 20 to 100 AH. There are some larger ones, but not many.

So if you want a 2000 AH stack, you will likely use 2 volt cells rated at 2000 AH.

Yes you can use your 12 volt charger, but you need to be careful with it. Is this charger made for a auto battery?

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Dereck, PE, MSEE
Moderator

No, this is the charger that cme with that sump pump I spoke with you earlier about. I believe it is a three stage charger. Looks like I will follow your sugestion and go with the T105's rather than the Lifeline AGM.

One person I spoke to said they got nine years out of the T105's used in an RV. Is nine year life span possible?

It is possible but very rare. It all depends on a lot of factors. One is Depth of Discharge to never go beyond 10 to 20% and immediately recharging.

I would guess to say the person claiming 9 years used the battery until it completely failed. However I would bet after 5 years the battery lost 50% of its capacity.

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Dereck, PE, MSEE
Moderator

To answer it more simply, calculate what AH capacity you need, then do it with the least number of parallel batteries. A battery is easier to keep a balanced charge thruout the bank if they are in series. With parallel wiring one stronger or weaker battery can affect how the bank charges, and an imbalance in the charge can occure. This may require you to separate and equalize to regain balance in the system more often than is in series. If you can get the AH needed in one series the charge current MUST go thru each battery equally. The battery bank will be happier for it. Sometimes this is not feasable but have the fewest parallel strings you can. There are big 2V batteries if you need them with big AH ratings. The best is one series string with the AH needed. You should never add to a string, older batteries with new. If you need to grow add a parallel string and design the option to charge independently of each other when needed.