Battery mixing question...again

lazza

HI Forum

If adding a new 250Ah 12V battery to an existing 2-year-old 250Ah 12V battery, which of the following would be worse:

a. putting them in series at 24V?
b. putting them in parallel and maintaining the 12V system?

I know that mixing new batteries with old ones is bad practice , but in this case there may be no choice....

Many thanks
Larry

BB.

Re: Battery mixing question...again

I don't know which is worse, or better... In series, the cells should be matched so that you can avoid excessive equalization--plus your string AH capacity is limited by the weakest cell (first cell to go under 0% state of charge will die).

In parallel, the batteries may not equally share current (an inexpensiive DC current clamp meter on-site for monitoring parallel connected strings highly recommended).

In the end--I would look at the size of your loads and/or available charging energy... If they are >~1,200 watts max continuous, I would look at going to 24 volt inverter/chargers/rewiring panels/etc. And, the needs of your loads (12 vs 24 volt loads, length of wire runs, etc.).

I probably would not make the 12/24 volt decision on the mixing of old/new batteries.

-Bill

lazza

Re: Battery mixing question...again

Ok, thanks Bill... will do as you suggest