Sizing Methods & Load Audits

How to build a load list, and why the audit beats the calculator.

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How to build a load list, and why the audit beats the calculator.

Building a load audit

List every load with its hours; the audit usually shows the inverter idling draw as a surprise.

From load to pack size

Convert to kWh, add autonomy days and losses, then round up to the next standard pack.

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.

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