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LiFePO4 charging basics
Lithium iron phosphate (LiFePO4) batteries are forgiving, but they do need the right charger settings and they must not be charged when they are too cold. Here is what manufacturers say.
Your battery's manual comes first. Settings differ between brands and models. The numbers below are examples quoted from specific manufacturers' documents, not universal values.
How a charge works: the stages
Most chargers use stages. Battle Born Batteries explains them like this:
- Bulk: the charger pushes its maximum current until the battery reaches the set voltage.
- Absorption: the charger holds a constant voltage while the current falls as the battery fills.
- Float: a lower holding voltage. It exists for lead-acid batteries, which lose charge on their own. Battle Born says float charging is not necessary for its LiFePO4 batteries.
Example charge settings for a 12V LiFePO4 battery
| Setting | Battle Born BB10012 (100Ah) | Victron Lithium Battery Smart (12.8V) |
|---|---|---|
| Absorption (charge) voltage | 14.2V to 14.6V (14.4V recommended in Battle Born's charging guide) | 14.0V to 14.4V; 14.2V recommended |
| Absorption time | 30 minutes per 100Ah battery bank | 2 hours recommended |
| Float voltage | 13.4V to 13.8V (not required) | 13.5V |
| Temperature compensation | Disable | Disable (or set to 0 mV/°C) |
| Recommended charge current | 0.5C (50A max for this model) | Up to 30A for the smallest model (varies by size) |
| Charging temperature range | Low-temperature charge protection built into the BMS, per Battle Born's charger setup guide | 5°C to 50°C (41°F to 122°F) |
Values quoted from each maker's datasheet or manual (linked below). Other batteries may differ; use your own battery's documents.
What this means when you set up a charger
- Pick the charger's LiFePO4 or lithium profile, or a user-defined profile matching your battery's numbers. Victron recommends a charger with a profile that matches the chemistry.
- Turn off temperature compensation and equalization. Victron says temperature-compensated charging is not required for lithium batteries; Battle Born lists temperature compensation as "No/Disable."
- If the charger has a "storage" mode, Victron says to set it to the same value as the float voltage.
- Do the same on every charger feeding the battery: solar controller, DC-DC charger and shore charger. Mismatched settings are a common cause of problems.
- 24V and 48V systems use proportionally higher settings. Victron lists 28.4V and 56.8V absorption for its 24V and 48V setups; check your own battery's manual.
Cold weather: the big rule
Battery University explains that lithium-ion batteries should not be charged below freezing (0°C, 32°F) because metallic lithium can plate on the anode, which permanently harms performance and safety. Some makers set the limit higher: Victron allows charging its Lithium Battery Smart only from 5°C (41°F), says cells can be permanently damaged if charged below that, and says setting its BMS to allow charging below 5°C voids the warranty.
- Discharging is different. Victron allows discharge from -20°C to 50°C (-4°F to 122°F). You can usually run loads in the cold; the issue is charging.
- Options in cold climates: a battery with built-in heating, keeping the battery inside the heated living space, or a BMS that blocks charging when too cold. Battle Born offers a heated model (BB10012H) whose heater draws 28W when enabled, per its datasheet.
- Solar in winter: a cold morning plus sun means your solar controller may try to charge a frozen battery. Make sure something, usually the BMS, prevents it.
What the BMS does (and does not do)
A battery management system (BMS) watches the cells and disconnects charging or discharging when something goes out of range, such as voltage too high or low, current too high, or temperature too low or high. Battle Born's datasheet lists a high-voltage BMS protection point of 14.7V. Victron's Lithium Battery Smart instead uses an external BMS, and its manual says to use it only with a Victron-approved BMS.
The BMS also balances cells, keeping them at similar charge levels. That usually happens near full charge. Battle Born lists a cell balancing range of 14.2V to 14.6V, and Victron recommends a longer absorption periodically (at least 2 hours a month for lightly used systems, 4 to 8 hours a month for heavily cycled ones) so balancing can finish.
A BMS is a safety net, not a charger. Relying on it to cut off a badly set charger every day is not good practice; set the charger correctly so the BMS rarely has to act.
Storage charge
- Battery University recommends storing lithium-ion at about 40% to 50% charge in a cool place. Some LiFePO4 makers give their own storage advice; follow it.
- Do not store it empty. A very low battery can be damaged by its own self-discharge or by small loads.
- Disconnect loads, including small ones like monitors and detectors, unless the maker says otherwise.
- Check the voltage every month or two during storage.
For full off-season steps, see How to store a battery over winter.
Quick checklist
- Find your battery's absorption voltage, float voltage, absorption time and maximum charge current.
- Set every charger to match.
- Disable temperature compensation and equalization.
- Make sure charging stops below the battery's minimum charge temperature.
- Let it reach full charge regularly so the BMS can balance the cells.
- Store partly charged, cool and disconnected.
Charging from the alternator? See Alternator charging explained. Comparing chemistries? See Battery types explained.
Common questions
Can I use my old lead-acid charger?
Only if it has a lithium or LiFePO4 setting, or settings you can adjust to match your battery's manual. Some lead-acid chargers use equalization or desulfation modes that apply higher voltages, which a LiFePO4 battery does not need. Check both manuals before connecting.
Do I need to fully charge it every time?
No. LiFePO4 batteries do not need regular full charges the way lead-acid batteries do. Follow the battery maker's guidance on occasional full charges for cell balancing.
What happens if the BMS shuts the battery off?
The battery stops charging or discharging to protect itself. Find out why first: too cold, too hot, voltage too high or low, or too much current. Fix the cause, then follow the manual to recover it.
Quick checklist
- Set every charger (shore, solar, alternator) to the battery maker's settings.
- Know your battery's charging temperature limit and whether it has low-temperature protection.
- Use correctly sized wire and fuses.
- Store it per the manual if it will sit unused. See winter battery storage.
General information. Always follow your battery and charger manuals.
Sources
- Battle Born Batteries, BB10012 100Ah 12V datasheet (PDF)
- Battle Born Batteries, The Basics of Charging LiFePO4 Batteries
- Battle Born Batteries, Guide to Programming a Victron SmartSolar Charge Controller
- Victron Energy, Lithium Battery Smart manual (PDF)
- Victron Energy, Lithium Battery Smart technical data
- Battery University, BU-410: Charging at High and Low Temperatures
- Battery University, BU-702: How to Store Batteries