Can I charge a Renogy lithium battery below freezing?

Discharging LiFePO4 in the cold is fine. Charging it below freezing is what causes damage — lithium plates onto the anode instead of intercalating into it, and the capacity you lose does not come back. This is a property of the chemistry, not a Renogy quirk, and it is the single most common way a first winter kills an otherwise healthy lithium bank.

There are two ways to deal with it, and which one applies depends entirely on the battery you own.

If your battery self-heats

The Renogy Pro Series handles this itself. The heater activates automatically once charge current exceeds 6A, warming the cells until they can safely accept the charge, then stepping out of the way. You do not switch it on, and there is no separate controller to wire.

The 6A threshold matters more than it first appears. A trickle from a small solar array on a dim winter afternoon may never reach 6A, so the heater never triggers and the BMS simply refuses the charge. If you are relying on the heater, make sure something in the system can actually deliver that current — shore power, an alternator through a DC-DC charger, or enough panel.

If your battery does not self-heat

Then the charge waits. The BMS in a well-built pack will refuse it for you, which protects the cells but leaves you with a bank that will not take a charge until the box warms up. Practical options are to move the battery somewhere heated, insulate the compartment so waste heat from discharging keeps it above freezing, or accept that in genuinely cold conditions the bank charges only during the warm part of the day.

Cell temperature is what counts, not air temperature. A battery in an insulated locker that has been discharging overnight can sit several degrees above the outside air, and a battery bolted to an uninsulated aluminium floor can sit below it.

Which Renogy batteries heat themselves

The Pro Series does. If you are specifying a bank for a four-season rig, that is the reason to choose it over a battery that fits the same tray for less. If your rig is stored or used in mild conditions, you are paying for a feature you will not use, and the Core Mini's shorter case may matter more to you than the heater does.