How to Charge LiFePO4 Batteries with Solar Panels
Built by Jeremy Panasuk. Published October 3, 2026.
Charge voltages and current limits are from the Battle Born BB10012i / BB10012iH manual. The array current is this site's charge-controller function. Match them before you turn a controller up to "lithium."
What to program
The charging section says to verify that the converter, inverter-charger, solar charge controller, or DC-to-DC charger can be programmed to that profile. If the charger cannot do multi-stage charging, the manual says to program bulk/absorption and to disable equalization and temperature compensation. Absorption time in the specifications table is 30 minutes per 100 Ah of battery bank. High BMS voltage protection is 14.7 VDC. The cover warning says: risk of fire and burns; do not open, crush, heat above 150°F, or incinerate; follow the manufacturer's instructions.
Two of these batteries in series make a 24 V 100 Ah bank. The manual says to charge that series pair at a bulk and absorption voltage of 28.8 V and a float voltage of 27.2 V. Series may go up to 48 V. The manual says not to exceed a 48 V setup, or the warranty is void. Four in series are the 48 V 100 Ah example it prints. Before any series connection, charge each battery to 14.2 V–14.6 V so they are at the same state of charge. In parallel, the manual says voltage stays the same and capacity and current limits are additive. Its example is two batteries making a 12 V 200 Ah bank that can deliver 200 A continuously. It says every cable has to carry the maximum current the batteries can deliver, and that appropriate fuses and circuit breakers are highly recommended.
The manual says not to operate the battery in series or in parallel with any other type of battery. Terminal torque is 9 to 11 ft-lb. Finger-tight hardware, it says, can cause severe damage and void the warranty.
The solar current has to fit under 50 A per battery
Battle Born's sizing article uses 2,400 Wh as a 12 V example. Put that day into the solar size calculator with sun hours 4, autonomy 2, and depth of discharge 80%. sizeSystem returns 2,400 ÷ 4 ÷ 0.75 = 800 W of array, and a bank of 2,400 × 2 ÷ 0.8 = 6,000 Wh, which is 500 Ah at 12 V. sizeController then does 800 ÷ 12 ÷ 0.85 = 78.4 A and lists an 80 A controller.
Eighty amps is above the 50 A maximum charge current of one BB10012i. The manual's parallel rule is that current limits are additive, illustrated by two batteries delivering 200 A continuously, which is two times the 100 A maximum discharge of one battery. Five of these 100 Ah batteries are the 500 Ah bank the calculator printed. If that 80 A split evenly, each battery would see 80 ÷ 5 = 16 A, and 16 A is under both the 50 A maximum and a 0.5C rate on a 100 Ah battery (0.5 × 100 A = 50 A). Even splitting is arithmetic from the manual's "additive" statement. It is not a balance guarantee. The manual still wants fuses or breakers on the battery cables.
At the form's default 24 V, the same 800 W array produces 800 ÷ 24 ÷ 0.85 = 39.2 A, and the listed controller is 40 A. A single series pair is only 100 Ah at 24 V, and the calculator's bank at 24 V is 250 Ah, so one pair is not the whole bank. Charge voltage for each series pair remains the manual's 28.8 V bulk/absorption and 27.2 V float.
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One common mistake
Leaving an AGM equalization or a temperature-compensation slope turned on. The manual's lithium profile lists equalization as 14.4 V / disabled and temperature compensation as disabled. The other mistake is landing an 80 A controller on a single 100 Ah battery: 80 A is greater than the 50 A maximum charge current on this model. Chemistry notes that sit beside AGM are on AGM vs lithium. Recharge wattage from the battery's amp-hours, rather than from the daily load, is on panels to charge a battery.
Limits
Do not charge this battery under 32°F (0°C). The BMS blocks charging current there. Do not series past 48 V. Do not mix it with another battery type. Do not open the case. Solar wiring and overcurrent protection on the array are a licensed electrician's job; the array fuse case is on how to fuse a solar panel array. Heat-enabled BB10012iH models have a separate heating guide that this page does not reproduce.
FAQ
What charge voltages does the BB10012i manual publish?
Absorption 14.2 V to 14.6 V, float 13.4 V to 13.8 V, equalization 14.4 V / disabled, temperature compensation disabled. Two batteries in series are charged at 28.8 V bulk/absorption and 27.2 V float. High BMS voltage protection is 14.7 VDC. Maximum charge current is 50 A, and the recommended charge current is 0.5C.
Why does an 800 W array at 12 V collide with a 50 A limit?
800 ÷ 12 ÷ 0.85 = 78.4 A, so the calculator lists an 80 A controller. The manual's maximum charge current for one BB10012i is 50 A. Five paralleled 100 Ah batteries are the 500 Ah bank from 2,400 Wh, 2 days, and 80% depth of discharge. 80 ÷ 5 = 16 A if the current splits evenly.
When will the BMS refuse a charge?
The manual says the BMS will not allow a charging current under 32°F (0°C). It will continue to discharge down to −4°F (−20°C). The battery charge temperature range on the charging page is 32°F to 131°F (0°C to 55°C).
Compiled with AI assistance from the sources below. Spot an error? Email [email protected].
Sources
- Battle Born / Dragonfly Energy, BB10012i and BB10012iH manual, PMI_BB10012i Rev 015, 8/12/2026 — accessed Oct 3, 2026.
- Battle Born Batteries, How to Size a Deep Cycle Battery Bank, May 22, 2026 — accessed Oct 3, 2026.
- SolarSizer calculator, assets/app.js (sizeSystem and sizeController) — accessed Oct 3, 2026.