The question was,
I want to build a battery monitor as im having problems with the two strings balancing.
The answers were,
Change the batteries that are faulty.
Your wireing is wrong.
Rewire this way.
Good advice but not an answer to the question folks, especially based on the small amount of info available about the battery problem.
If we were working on the actual battery problem then here are some questions that should be asked.
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Which string of batteries is it that are low the 0 to 12v or the 12 to 24v?
Is it the same string that goes low all the time?
Is anything else hooked on the batteries at any point?
Have you disconnected the posatives from all the batteries, waited several hours and checked the 'At Rest' voltage of each? How many were low?
Are you able to check the cells with a hydrometer? Are they all the same?
Have you followed the charging instructions on the batteries?
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The only way to really know what is going on with the batteries is to treat each battery individualy, running a charge and discharge on each to find its capacity then checking all your connections for good conductivity if you find all batteries are OK.
Daz