Battery Charge Time Calculator

Hours = energy to replace ÷ charging power. A 5 kWh battery discharged to 80% needs 4 kWh back; at 95% charge efficiency that is about 4.2 kWh, so a 1,000 W charger takes roughly 4 hours 12 minutes. Lead-acid adds more on top for the slow absorption phase at the end.

About 95% for lithium (LiFePO₄) and 80–85% for lead-acid and AGM — the difference is energy lost as heat and gassing during the charge. It is one of the quiet reasons lithium systems need less solar for the same daily cycle.

Lead-acid batteries only accept full current up to about 80% charge; after that the charger drops into a low-current absorption phase that can add 2–4 hours. Skipping it repeatedly causes sulfation and kills the bank early. Lithium takes near-full current almost to the top, which is why it recharges so much faster in practice.

Use a realistic average, not the array’s nameplate: panels deliver their best for only a few midday hours. As a rough rule, an array yields its rated power × your peak sun hours spread across the day — a 1,600 W array in a 4.5-sun-hour location averages well under 1,000 W. For a quick estimate, use about 70% of array rating for the main charging window.

Within limits. Batteries have a maximum charge rate — often written as a C-rate: 0.5C means a 100 Ah battery accepts at most 50 A. Lithium commonly takes 0.5–1C, lead-acid more like 0.1–0.2C. Exceeding it heats the battery and shortens its life, so check the datasheet before upsizing the charger.