differing batteries

[electrak]

I have a question for persons more knowlageable then me, I have 7 deep cycles batterys of 450 AH and some golf cart batteries(200 AH), would it be better to sieres them 7+2 and have the smaller batteries work harder or 7+3 and have the brutes do the heavy work. I want 48 volts they are all 6 volts.

Thanks for your help

Dave

[commanda]

Series the 7 x 450AH. Parallel 2 of the 200AH (= 400AH) and series this with the other 7.

Amanda

[dnix71]

Amanda's answer is what I would give. You want all the batteries to do equal work, if possible. The down side of having that many batteries in series is that if one fails, you don't get much out of the bank.

If you could run 24 volts the system would be more fault tolerant.

[electrak]

thanks, I wasn't sure if it would be better to use two of three

[Flux]

It's a bad situation, but the answers the others give is the best compromise. The thing will most likely get out of balance and occasionally you will need to deal with it.

When one part of the string starts to show lower sg you will need to divert more charging current to it by putting a shunt load across the over charged bit until the low bit equalises. Most likely the string of 7 will need equalising and a lamp across the odd pair will reduce its charging current in relation to the others. Do it when you have good charging conditions.

Flux

[electrak]

Thanks for the advice, I have grid at the moment, looking to go to a time of use plan that can/will shut off power at times thoughout the day ( 14 hours minimum ) for 1/5 the rate.