Electric Bike / Onewheel Solar Charging Sizer

A 500 Wh e-bike pack needs more than 500 Wh from solar because the charger and inverter waste energy. Divide pack watt-hours by charger efficiency, then by peak sun hours and array derate.

Inputs

Results

Energy drawn from solar: 588Wh
Array size for one recharge: 157W

Recommended gear

200 W 12 V solar panel
A common van and cabin module. Parallel or series as your controller allows.
Typical range: $90–$180
40 A MPPT charge controller
Size the current rating above array watts divided by battery volts, plus 20%.
Typical range: $120–$250

Engineering methodology

Energy drawn from solar = pack watt-hours ÷ charger (and inverter) efficiency. Array watts for one recharge in the entered sun window = that energy ÷ (peak sun hours × array derate). Direct DC MPPT e-bike chargers can skip the inverter; use a higher efficiency in that case.

Frequently asked questions

How much solar do I need to recharge a 500 Wh e-bike battery?

At 85% charger efficiency you need about 588 Wh from the array. With 5 peak sun hours and a 0.75 derate, array size ≈ 588 / (5 × 0.75) ≈ 157 W of nameplate panel for one full charge in that window.

Why isn’t array size just pack Wh divided by peak sun hours?

Charger and inverter waste energy, and panels do not deliver STC watts all day. Divide by efficiency, then by PSH × derate.

Can I charge an e-bike BMS faster by oversizing the array?

The bike charger and BMS cap current. Extra panel watts beyond what the charger will accept do not shorten charge time. Do not exceed the charger’s input rating.

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Disclaimer — no professional advice, no liability

Do not exceed the charger’s input rating or the bike BMS limits. This is energy planning, not a charging-protocol spec.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a system design, and they do not constitute engineering, electrical, fire-safety, building-code or other professional advice.

Results can be wrong, incomplete or inapplicable to your equipment, wiring, climate, codes or use case. You must independently verify every figure, assume all risk, and have a licensed electrician or qualified solar installer review any purchase, wiring or installation before you act on it.

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Electric Bike / Onewheel Solar Charging Sizer

Inputs

Results

Recommended gear

Engineering methodology

Frequently asked questions

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