Nominal battery energy in watt-hours (Wh) equals nominal voltage (V) multiplied by capacity in amp-hours (Ah). Compare batteries in Wh when voltages differ; then allow for usable capacity, losses and the actual lighting schedule before estimating runtime.
Energy = nominal voltage × amp-hours
For illustration, a 12.8 V, 50 Ah battery has a nominal energy of 640 Wh. A 3.2 V, 100 Ah battery has 320 Wh. These are calculation examples, not HPPOWER product specifications.
Nominal is not fully usable
Usable energy depends on depth of discharge, temperature, ageing, controller limits and system losses. A configuration should include a practical reserve rather than assume every nominal watt-hour is available.
The lighting schedule changes the load
Daily demand depends on the actual electrical input at each brightness level and the time spent at that level. Motion detection and scheduled dimming should be specified, not hidden inside a runtime claim.
Ask for the complete energy balance
Review panel production, usable battery energy and the night-time schedule together. Check the less sunny season as well as typical conditions before deciding on the battery size.
Product reference: HPPOWER manufacturer catalogue (PDF, English). This guide explains selection principles; the agreed configuration sheet defines the supplied product.
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