How long to charge a 200Ah battery with 200W of solar?
Putting back 80% of a 12.8 V 200Ah LiFePO4 bank takes about 2,226 Wh — 2.9 days of sun on 200 W of panels at 4.5 peak sun hours, or one day on about 575 W of panels.
How to work it out
- 200 Ah × 12.8 V × 80% = 2,048 Wh ÷ 92% charging efficiency = 2,226 Wh
- 200 W × (1 − 14% losses) = 172 W per peak sun hour × 4.5 h = 774 Wh a day
- 2,226 Wh ÷ 774 Wh = 2.9 days (12.9 hours of full sun)
Doubling both the battery and the panels leaves the time where it was for one 100 W panel and a 100 Ah battery. What a 200 Ah bank really needs is enough panel to refill a day’s use in a day.
Adjust for your project
More options: Refill · Charge controller · Losses
- Peak sun hours needed
- 12.9 hours
- Energy to put back (with charging losses)
- 2,226 Wh
- Panel output per day
- 774 Wh
- Peak charging current (MPPT, full sun)
- 15.6 A
- Panel watts to refill it in one day
- 575 W
Recharge time with other panel sizes
| Solar panel watts (total) | Sunny days to recharge | Peak sun hours needed | Peak charging current (MPPT, full sun) |
|---|---|---|---|
| 50 | 11.5 days | 51.8 hours | 3.9 A |
| 100 | 5.8 days | 25.9 hours | 7.8 A |
| 200 | 2.9 days | 12.9 hours | 15.6 A |
| 300 | 1.9 days | 8.6 hours | 23.4 A |
| 400 | 1.4 days | 6.5 hours | 31.3 A |
| 600 | 1 day | 4.3 hours | 46.9 A |
What to know about recharging a 200 Ah bank
- About 575 W refills it in a day. With 4.5 peak sun hours and 14% losses, each watt of panel puts back about 3.9 Wh a day; 2,226 Wh ÷ 3.9 is about 575 W.
- Peak current grows with panels. 575 W of panels into 12.8 V is up to about 45 A at midday through an MPPT controller — a 50 A controller, or move to 24 V.
- From a generator or charger. A 40 A mains charger puts back 2,048 Wh in a bit over four hours of bulk charging — the fastest fix after a cloudy week.
- Lead-acid of the same size holds half as much usable energy (1,200 Wh at 12 V and 50%) and needs a full absorption charge regularly.
The energy in the bank is on how many watt-hours in a 200Ah battery, and the controller size on what size charge controller for a 400 watt solar panel. The single-battery case is how long a 100W solar panel takes to charge a 100Ah battery.
Different size? Use the full Solar Battery Charge Time Calculator.
What you’ll need
- 100 W solar panelMid-range price
The building block of most van, boat and RV systems. Check the data-sheet Voc and Isc before you decide how to wire several of them.
See options on Amazon (opens in a new tab) - MPPT solar charge controllerMid-range price
Converts a higher panel voltage into charging current, so you can wire panels in series and lose less in the cables. Size it on output amps and maximum PV voltage.
See options on Amazon (opens in a new tab) - Smart battery charger (lithium-compatible)Mid-range price
A mains or generator-powered charger with a LiFePO4 profile tops up a bank when the sun doesn’t. Match its charge voltage to the battery data sheet.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How long to charge a 200Ah battery with 400W of solar?
About 1.4 days at 4.5 peak sun hours.
How long to charge a 200Ah lead-acid battery from 50% with 200W?
About 1.8 days of sun for the energy, plus the slow absorption stage.
Other common sizes
- How long a 100W solar panel takes to charge a 100Ah battery — 2.9 sunny days (12.9 hours of full sun)
Sources
- Victron Energy — Energy Unlimited (book) (opens in a new tab) — Lead-acid charge efficiency 80–95% (85% suggested as a starting value); battery energy efficiency about 75% for full cycles, about 89% in partial state of charge; inverter efficiencies above 90%.
- Victron Energy — Lithium Battery Smart manual, technical data (opens in a new tab) — LiFePO4 12.8 V: cycle life 2,500 at 80% DoD, 3,000 at 70%, 5,000 at 50% (to 80% of capacity); 92% round-trip efficiency; 12.8 V 100 Ah: recommended continuous discharge ≤100 A (1C), maximum 200 A; capacity about 20% lower at 0 °C; charge only between +5 °C and +50 °C.
- Victron Energy — Which solar charge controller: PWM or MPPT? (2020) (opens in a new tab) — MPPT output current = panel watts ÷ battery voltage (100 W ÷ 13 V = 7.7 A); a PWM controller pulls the panel down to battery voltage (81 W from a 100 W panel at 25 °C, about the same as MPPT at 75 °C); temperature-coefficient method; example panel Voc 21.6 V, −0.35 %/°C.
- National Laboratory of the Rockies (formerly NREL) — PVWatts® Calculator (opens in a new tab) — Look up the solar resource (peak sun hours) and yearly output for your own address; default system losses 14%.
- NLR (formerly NREL) — PVWatts® v8 API, NSRDB PSM V3 TMY data (opens in a new tab) — City figures on this site: fixed open-rack array facing due south, tilted at the site’s latitude, 14% system losses, queried October 2026.