Your engine is already a generator
Two hours of driving ≈ a good solar day.
Two hours of driving ≈ a good solar day.
If your rig has an engine, you own a generator you're probably not using.
A DC-DC charger takes power from your alternator and charges the house bank properly while you drive. For anyone who moves regularly, this is often the highest-value charging upgrade available.
Why not just run a wire? Because connecting a lithium house bank directly to an alternator is a genuine way to destroy an expensive alternator. Lithium accepts current so aggressively it can pull the alternator far past its continuous rating until it overheats and fails. A DC-DC charger: - Limits current to a level your alternator can sustain - Isolates the starter battery so you can never strand yourself - Applies a correct lithium charge profile
Sizing: stay well under half your alternator's rating for continuous draw. Check whether yours is a smart or variable-voltage alternator — those need a charger that handles variable input, and it's a common gotcha.
The Power Sizer turns your real appliance loads into a full spec — battery bank, solar array, controller, inverter and roof space — then matches it to gear that actually fits the number.
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