I built two 12 V, 7.2 A, 125 W solar panels from eBay Everbright Solar cells, planing to produse 18 V, 14.4 A, 250 W and to store in 5 X 12 V 200 AH batteries.Each 12 V battery is made from 6 X 4 OPzS 200 AH .When I put the first panel on the roof, the open circuit was 19.5 V and when I connected the first battery, the current was 3.75 A .The temperature was 30 C (86 F) fully sunny day and the panel was on 30 degrees S SW.
The connecting wire is 8 AWG 10 m (30')
I decided that the battery was weak and I left it for 2 days to charge. Finally the current fell down to 1.2 A.Then I swiched to the next battery and the current rised to 2.6 A.
I continued to change the bateries untill yesterday when I connected the 5 batteries in parallel 12 V 1000 AH.Then I checked the voltage It was 12.66 V. I left the panel to charge - the voltage was 13.5 V and the current 1.3 A .
I desided to leave the batteries for 3-4 days to charge and then to check the density of the electrolite with a density meter. I put a 20 A fuse for security.
At the moment I havn't got a charge controller (my son is working on an 12 V 20 A controller).
I made some mistakes during the building - First the measures of the panels are too big - 1.75 m X 0.75 m (5.7' X2.5') Second, I put the cells on a glass and cover with Lexan.Finally when the Lexan expanded from the heat and broke the glass bottom and now I'm planing to change the second panel's Lexan with normal glass.
This is the begining, as I'm planing to double the panels till the end of the summer.
I will use the batteries for lighting during the weekends and mainly for a refrigerator for the hot summer.
I will not use the batteries untill they are not fully charged.
Here are the stupid questions
Is the current drop normal for this moment and this wire connection?
What can I do to rise the current of the panel to his optimum current of 7.2 A?