While it is technically possible to charge a LiFePO4 battery with a lead-acid charger, it is generally not recommended. Here’s why:

1. Voltage Mismatch: A 12V LiFePO4 battery voltage remains around 13.3 to 13.4 volts at 100% state of charge, while a lead-acid battery voltage remains between 12.6 to 12.7 volts. This mismatch can lead to undercharging or overcharging, which can decrease performance or cause irreversible damage to the LiFePO4 battery.

2. Charging Stages: LFP batteries have two charging stages and do not require float charging, a requirement for SLA batteries. If you use an SLA charger to charge your LiFePO4 battery, you must switch off the float charging option. If you cannot switch off the float charging option, it will overcharge your LiFePO4 battery.

3. Equalization Mode: You should also turn off the equalization option from your lead-acid charger.

4. Reviving a Sleeping Battery: The lead-acid charger cannot revive a sleeping or disconnected LiFePO4 battery.

Therefore, using a lead-acid charger may result in suboptimal charging efficiency and could potentially lead to damage or reduced lifespan of the LiFePO4 battery. It’s always best to use a charger specifically designed for lithium LiFePO4 batteries.