Off-Grid Solar Calculators

Battery storage

Trolling Motor Battery Calculator

Thrust in pounds is not a physics SI unit, but motor makers publish peak amp charts that track it closely. This tool uses those chart slopes, then scales current by throttle so you can size the trolling-motor battery.

Inputs

Units
lb

Nameplate thrust of the trolling motor.

h
Ah

Usable fraction of rated capacity.

Terms of Service

Results

Please tick the box above to display the Result.

Engineering methodology

Peak current is not derived from SI thrust. It follows published marine amp charts: about 1.0 A per pound of thrust at 12 V, 0.65 A/lb at 24 V, and 0.46 A/lb at 36 V (Minn Kota-style intermittent maxima). Average amps = peak × throttle fraction. Amp-hours used = average amps × hours. Runtime hours = (battery Ah × DoD) ÷ average amps. Throttle here is a share of peak current, not the dial position: with PWM speed control, current falls faster than the speed setting, so part-throttle results are conservative.

Frequently asked questions

Why isn’t trolling-motor current just watts divided by volts?

Thrust is a force, not a power, so it cannot simply be divided by volts. Motor makers publish max-amp charts versus thrust and voltage. This tool uses those slopes. Chart amps are intermittent; continuous draw at a given speed is usually lower.

Why does a 24 V motor draw fewer amps than 12 V at the same thrust?

Similar mechanical power at higher voltage means lower current (P ≈ V × I). The 24 V and 36 V factors (about 0.65 and 0.46 A/lb) reflect that chart behavior.

How should I size trolling-motor cables and fuses?

Use the motor manufacturer’s wiring chart and ABYC practice, not this runtime estimate. Fuse for the cable ampacity. Peak chart amps are intermittent and can exceed average throttle current.

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