Capacity vs Charge Rate Trade-offs

Why a bigger pack charges slower, and how to size the charger to match.

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Why a bigger pack charges slower, and how to size the charger to match.

Charger current versus pack size

Charge time is capacity divided by charger current; doubling the bank doubles the wait unless the charger grows too.

Where the limits really are

The cell rating and the BMS set the ceiling; heat decides how long you can hold it.

Voltage & sizing questions

Short answers to the ones that come up most.

How do I choose a battery voltage?

It is set by the equipment: 12V for small loads, 24V for light traction, 48V for storage and most traction, higher for industrial systems.

How do I work out runtime?

Multiply amp-hours by nominal voltage for watt-hours, then divide by the real load — and discount 10–15% for conversion losses.

Why is a 12V lithium battery labelled 12.8V?

LiFePO4 cells are 3.2V nominal, so four in series give 12.8V, which 12V equipment accepts.

What does C-rate mean?

Current relative to capacity: 1C on a 100Ah battery is 100A.

Can I series-connect different batteries?

No — same model, capacity and age, or the strings unbalance.

Back to Charging & BMS · All Redway guides

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