Engineering calculator

DC-DC charger and alternator sizing

Estimate alternator input current, daily driving charge and cable/fuse guidance without assuming the alternator’s full rated output is available.

DC-DC charger presetView manufacturer dataCharger output current (A)Charger efficiency (%)Battery voltageAlternator voltage (V)Alternator rated output (A)Vehicle base load (A)Alternator reserve allowedDriving/charging hours per dayCable length, one way (m)Maximum voltage dropCable ampacity (A)Planning input used for both cables; verify input and output cable ampacity separately.Existing input fuse (A)

Charging estimate

Alternator input current

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Safe max charger output

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Daily charge gain

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Daily charge energy

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Input / output cable

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Input / output fuse guide

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Checks: —

Safety and limitations

This tool provides planning estimates only. It is not a substitute for a qualified design, inspection or local code compliance.
Use the exact manufacturer documentation for the equipment, materials, limits and installation method you intend to use. Do not select hardware from the result alone.
Verify every input, unit, operating condition, environmental limit and installation derating before relying on the result.
Protection devices, emergency controls and final commissioning must follow the manufacturer’s instructions and applicable local standards.
Electrical, gas, fuel, towing, structural and fire-safety work must be reviewed or completed by a suitably qualified professional where required.
This result does not include local approval, exact product compatibility, site-specific conditions, fault studies or commissioning measurements.

If any input is unknown, stop and obtain the datasheet or professional verification before purchasing or wiring components.