How long to recharge your bank — capped at what the battery can actually accept, with the LiFePO4 absorption taper built in, so the number is one you can trust.
The designer adds up your real charge sources — solar, alternator/DC-DC, shore — and shows the combined recharge time for your actual bank, capped at its acceptance.
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Charge time is more than energy ÷ power. Two things most calculators miss: the battery only accepts so much current (its C-rate), so piling on more charger power past that limit does nothing; and LiFePO4 tapers near full — it charges fast and near-linear to about 90%, then the BMS rolls the current off through absorption, so the last 10% takes disproportionately longer.
This calculator caps the charge current at what the bank accepts and models the taper, so the time is achievable. Cold also reduces acceptance — charge times stretch in winter.
Because the battery has a maximum charge rate (its C-rate). Once your combined charger current hits that limit, extra power can't go in any faster — it only helps reach full a little sooner as the bank tapers near the top.
LiFePO4 charges near-linearly in bulk, then enters absorption: the BMS reduces current as cells approach full, so the final stretch is slower than the bulk phase. We model that taper rather than assuming a flat rate.
LiFePO4 commonly accepts up to about 0.5C continuously (some support 1C); AGM/gel are happier around 0.2–0.3C. Check your battery datasheet — the calculator uses it to cap the current.
Wattonomy applies these standards in its calculations. It is not certified, sponsored or endorsed by ABYC, ISO, NFPA or Victron. Last reviewed June 2026 — see the methodology.
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