I've been wanting to increase the storage of my small system (7x100W Panels) for a while now, but finally did so today. I've doubled the capacity to 416 amp hours.
Battery Bank
The battery bank now consists of four 6V golf cart batteries that I purchased at Costco. They are rated at 208 amp hours each. The bank is composed of two parallel banks of two batteries in series : where the two batteries in series doubles the voltage (6 to 12) and the parallel battery banks doubles the capacity (208 AH to 416 AH).
Cable Upgrade
Last night I changed out the 10 AWG wire from the controller to the battery bank with a 6 AWG wire. I was surprised to see the voltage drop at 40A with the 10 AWG over 6' of wire was 0.48 V. The 6 AWG wire will be 0.19 V now: a loss of 4% down 1.6%.
Future Upgrade
Now that winter is picking up it's stride, I don't want to loose energy when I can make simple changes. The next will be to change the 4 AWG cable from the battery bank to the inverter and replace it with 2/0. That will lower the voltage drop @ 100 Amps from 0.3 to 0.09: very significant : less than 1/3 of the loss. I should have done this earlier, but in the summer there was sunlight to spare. Not so anymore...
COST:
208 AH 6V Battery: approximately $83 each ==> result: storage of 416 AH
6' of 6 AWG cable: approximately $3.50 ==> result: less voltage drop from controller to battery bank
(I will upload the photo when I get data back up...)
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