A LiFePO4 battery lasts for years only if its charge controller uses the right voltages. Many controllers ship with presets built for lead-acid batteries.
So which values should you enter, and which should you leave alone? This article covers the key settings, starting values and how to enter them on common controllers.
What the bulk, absorption and float voltages actually do
Bulk comes first: the controller sends as much current as the limit allows, and the voltage rises. Absorption holds the set voltage while the current falls, topping off the charge.
Float drops the voltage to keep the battery full. Victron’s 12.8V LiFePO4 batteries use 14.2V absorption for 2 hours and 13.5V float.
Battle Born’s 12V 100Ah battery runs 14.2–14.6V absorption and 13.4–13.8V float, with absorption about 30 minutes per 100Ah.
Set bulk equal to absorption. If your controller has both, enter the same voltage in each.
Keep absorption short. Two hours is the recommended time.
Typical starting values: 28.4V absorption and 27V float for 24V, or 56.8V and 54V for 48V.
To scale a value from a battery datasheet, multiply the 12V figure by two for 24V or by four for 48V, then check the result against that datasheet. For winter settings, see battery maintenance tips for off-grid systems.
LiFePO4, lead-acid or lithium: which preset should you pick
Pick the LiFePO4 preset when your controller offers one, because lead-acid presets use higher voltages. New to controllers? For the basics, see the off-grid solar beginner guide.
| Setting | Lead-acid preset (EPEVER Tracer BP) | LiFePO4 preset (Victron SmartSolar) |
|---|---|---|
| Absorption (boost) voltage | Sealed 14.4 V, Gel 14.2 V, Flooded 14.6 V | 14.2 V |
| Float voltage | Sealed 13.8 V, Flooded 13.8 V | 13.2 V |
| Equalization | Flooded 14.8 V, Gel none | None |
Check the preset against your battery
What works
Treat the preset as a starting point, and compare each value with your battery’s datasheet.
What to avoid
Trust the preset name alone, because preset values vary between controller models.
What works
Check that equalization is off, unless the battery maker specifically requires it.
What to avoid
Leave equalization on because the preset enabled it. A lithium battery can be damaged by an unsuitable equalization charge.
What works
Set temperature compensation to zero for lithium.
What to avoid
Keep the lead-acid temperature compensation, which changes the charge voltage with temperature.
Why the generic lithium label can be the wrong chemistry
A menu entry that just says “lithium” can hide two different chemistries. EPEVER Tracer BP lists LiFePO4 and Li-NiCoMn as separate types, and their 12V defaults differ: 14.5V boost for LiFePO4 against 12.5V for Li-NiCoMn.
Pick the wrong one and your charge voltage is off for your battery.
Renogy’s Rover labels its lithium choice “Li (LFP),” with a 14.4V boost default. So check the chemistry name first, not just the word lithium.
Check the label for “LiFePO4” or “LFP” before you pick a preset, because “lithium” alone does not name the chemistry. On an EPEVER Tracer AN-G3, you must select the User type to change battery parameters on the LCD, and a wrong preset gives the wrong charge voltage.
Never charge a LiFePO4 battery below freezing (0°C/32°F), or it takes permanent damage. For a garage or shed setup, see how to keep the battery box above freezing.
How much charge current is safe for your battery
The battery’s maximum charge current is your ceiling. For a 12V 100Ah battery, that’s 50A, or 0.5C, half its capacity. Set the controller at or below that figure. Still choosing a battery? See making the right battery choice.
Count every charger. Solar, an alternator and a shore charger feed the same battery, so add their currents and keep the total under that limit. To size the controller to your array, see truck camper setups.
Charging a LiFePO4 battery below 0°C (32°F) can plate lithium onto the cells, and that capacity loss is permanent. The Battle Born 100Ah BMS blocks charging below that point, but the battery can still discharge down to -20°C (-4°F). Enable the low-temperature cutoff on your controller if it has one, and set it above 0°C. Victron’s lithium profile uses 5°C, so the controller stops charging before the BMS has to.
What the cutoffs cannot protect your battery from
Before you change any threshold, follow this order, and for the cycle and depth-of-discharge numbers behind these limits, see lithium vs lead-acid storage:
- Set the overvoltage disconnect above your bulk, absorption and float voltages on EPEVER controllers.
- Low-voltage reconnect goes above low-voltage disconnect: EPEVER defaults are 11.1V and 12.8V on 12V.
- Renogy Rover sets overvoltage shutdown 2V above boost: 16.0V against a 14.4V default.
- Low-voltage and overvoltage settings are protection limits, not charge targets.
Before you enter any value
- Find the charging voltage range in your battery’s datasheet.
- Set your absorption target inside that range. On a Battle Born 100Ah, that range is 14.2–14.6V.
- Check that the target stays below the BMS high-voltage cutoff. On the same battery, that cutoff is 14.7V.
- Set the controller to the maker’s charging limits, not to the BMS cutoff.
- Keep the BMS shutdown as a last line of protection, never as your charge target.
How to enter the settings in your controller, step by step
Follow these steps on each controller, in this order:
- In VictronConnect, connect to the SmartSolar controller and open its settings.
- Select the battery preset that matches your battery, or create or edit a user-defined preset if none fits.
- Change the charge voltages and limits to the values in your battery maker’s datasheet.
- On an EPEVER Tracer AN-G3, press SELECT until you reach the battery-voltage screen.
- Hold ENTER until the battery-type screen flashes, press SELECT to choose LiFePO4, then press ENTER to confirm.
- To set your own values, select User on the LCD. Press SELECT to change each value and ENTER to confirm it.
Set up a Renogy Rover
-
Select Li (LFP)
Use the battery-type controls. Li (LFP) shows on screen.
-
Add the controller in DC Home
Connect the BT-2 and add the Rover in the app.
-
Enter the battery parameters
Enter voltages, cutoffs and current limit from your datasheet.
-
Run the charging test
In sun, the app shows charging current. No charging? Recheck the settings. For low-sun months, see battery cycle guidance.
Your battery’s datasheet sets the charge voltages, not a generic preset. Pick the LiFePO4 or LFP preset, turn off equalization, and enable the low-temperature cutoff.
Next, open your battery’s datasheet and note its charging voltage range and maximum charge current. Enter those values, then run a charging test in sunlight.
Frequently asked questions
What charge voltages apply to a 24V LiFePO4 system?
For a 24V LiFePO4 system, Victron’s settings are 28.4V absorption and 27V float, with absorption held for 2 hours. Check these against your own battery’s datasheet before you enter them, since other controllers and batteries use different values.
Can a LiFePO4 battery be charged when the temperature is below freezing?
No, not when the temperature is below freezing. A Battle Born 100Ah battery blocks charging below 32°F (0°C), and other batteries set their own limit. Check your battery’s low-temperature charging limit before you set the controller.
Does a LiFePO4 battery need a storage mode on the charger?
No, a LiFePO4 battery does not need a storage mode. Its float voltage already keeps it full while it sits idle. If your charger has one anyway, set it to the same voltage as float.
Can I use the same settings on a Victron controller and a Renogy controller?
No. Victron and Renogy use different default values, so one controller’s settings don’t carry over.
Victron uses 14.2V absorption and 13.5V float, while the Renogy Rover’s lithium boost default is 14.4V. Set each controller from your battery’s datasheet.