| Configuration | Voltage | Capacity | Energy |
|---|
Series vs Parallel
Two wiring choices shape a battery bank. Series connections stack voltage — two 12V batteries in series make 24V at the same amp-hours. Parallel connections stack capacity — two 12V batteries in parallel stay 12V but double the amp-hours. Many large banks combine both to hit a target voltage and capacity at once.
Amp-Hours, Watt-Hours, and Usable Energy
Amp-hours only tell the full story alongside voltage. Multiply the two for watt-hours, the true measure of stored energy that lets you compare a 12V and a 24V bank fairly. Then apply your depth of discharge to find what you can actually use without harming the batteries.
Sizing a Bank
Start from the energy you need in watt-hours, divide by the energy in one battery, and round up to get a battery count. The helper above does this, giving a quick target before you refine the series and parallel layout for your system voltage.
Frequently Asked Questions
Can I mix battery sizes or ages?
Avoid it. Mismatched batteries in a bank share current unevenly, age faster, and can undercut the whole pack. Use identical batteries.
Does parallel wiring change voltage?
No. Parallel keeps voltage the same and adds capacity. Only series wiring raises voltage.
Why is usable energy lower than total?
Most chemistries should not be fully drained. Lead-acid likes a 50 percent floor; lithium can go to 80 to 100 percent.