Battery bank merging question

System

I have a bank of 4 trojan 105's at 24V runing a small solar backup system.

They have been hooked up for about 6 months and they were built in May of 07.


I have used the back up system twice but never has the bank been below 24.4V and has a light trickle from ~600w of Evergreens through a MX-60


I am ready to up size (XW4024 or 6048 with 1.2-1.6 KW of Evergreens) and just got 8 more T105's that were built last month.

I will either run 24 V with 3 strings or get 4 more batts and run 2 strings of 48V.

Would I be OK to merge the batteries into the same bank being they have had so little use?

mike95490

Re: Battery bank merging question

SKYWLKR wrote: »

I will either run 24 V with 3 strings or get 4 more batts and run 2 strings of 48V.

Would I be OK to merge the batteries into the same bank being they have had so little use?

If I was going to do this, I would get 4 more and go with 48V. Series banks are less susceptible to current hogging than parallel. With 48V, and only 2 parallel strings the current (and the resistance imbalances) will be less.

I would equalize each battery individually, BEFORE placing it in the strings, so that everything is all fully charged (all those batteries, may take a day or two, running generator) before you wire them up. And be sure to switch the inverters & chargers to 48V before you connect them to the bank.

System2

Re: Battery bank merging question

I have a large auto motive charge I can charge pairs with or I have a smaller 10/20 amp charger that I can set to 6V for individual.

I have access to Household grid power

I am leaning towards adding another four but it will be a MAJOR Tight squeze for my batt box, as in no air space at all where the batts touch...

It gets a bit warm here in Souther Louisiana in the summer but the tightness would be great for winter...