Solar & battery
Solar Battery Bank Calculator
Wire a battery bank in series and parallel to reach a target voltage and capacity.
Result
Series raises voltage, parallel raises capacity. Every battery in a bank should be the same make, model, age and state of charge, because the weakest one sets the behaviour of the whole string. More than three or four parallel strings of lead acid is generally discouraged, since current shares unevenly between them.
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About this calculator
Series or parallel?
Series adds voltage and keeps amp hours the same. Parallel adds amp hours and keeps voltage the same. Energy in kWh is the same either way; the wiring and current are not.
Can I mix old and new batteries?
No. The bank performs like its worst cell, so a new battery added to an aged string is dragged down to match and both wear out sooner.
The formula
series = target volts / battery volts; strings = target kWh / capacity per string
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