DC-to-DC Calculator
DC-DC & Alternator Charge Calculator
Estimate real charging current, voltage drop, time to charge, and alternator belt load. Orion presets included.
Vehicle & Alternator
Tip: warm engine bays reduce effective alternator output. Adjust “Thermal derate.”
50%
80%
Electrical out / mechanical in. Typical 50–60.
Fraction of rating at your common cruise/idle.
DC-DC Charger
Typical LiFePO₄ 14.2; AGM 14.4.
Cabling & Voltage Drop
Enter one-way length. Calculator uses copper AWG resistances at 20°C.
Lugs, breakers, disconnects, etc.
Top-line Results
Charging current
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Battery power
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Time to target
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Belt load
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Charging current is limited by the smallest of: alternator available, DC-DC max, and voltage-drop constraints.
Alternator & Belt Mechanics
| Alt available (A) | — |
|---|---|
| Electrical power out (W) | — |
| Mechanical power in (W) | — |
| Belt load (HP) | — |
Voltage Drop Detail
| Alt → DC-DC drop (V) | — |
|---|---|
| DC-DC → Battery drop (V) | — |
| Total path drop (V) | — |
| Percent of system voltage | — |
Assumptions & Notes
- LiFePO₄ modeled as near-constant current until ~90–95% SOC, then taper overhead added.
- AGM modeled with earlier taper; extra time added above ~80% SOC.
- Wire resistances use copper at 20°C. Real-world temps raise resistance slightly.
- Verify alternator belt condition and pulley alignment when adding large DC-DC loads.