Charging a LiFePO4 lithium battery from an alternator involves several considerations to ensure the longevity and safety of the battery. As a last resort, here are some general steps and guidelines:

1. Connection: Connect the LiFePO4 lithium battery to the alternator.
2. Voltage and Amperage: Set the voltage and amperage to the required levels. LiFePO4 lithium batteries should be charged using a 14.6-volt charger with a maximum amperage of around 30% of the battery capacity.
3. Start Charging: Start charging the battery. When the battery is fully charged, turn off the alternator.
4. Battery Combiner: Consider using a Victron Cyrix Li-Charge or Li-CT intelligent battery combiner. These devices are designed to manage the charging process and protect both the battery and the alternator.
5. Battery Management System (BMS): Ensure your lithium LiFePO4 battery has a BMS. This system manages the charging process to prevent overcharging and undercharging, which can damage the battery.

But always remember, as a rules of thumb, always charging a lithium iron phosphate battery with a lithium iron phosphate battery charger.

Can You Charge a LiFePO4 Battery with a Car Alternator?

Charging a LiFePO4 lithium battery directly from a car alternator is technically possible, but it’s generally not recommended. This is because alternators are designed to charge lead-acid batteries, which have a different charging profile than lithium batteries. A direct connection could cause overcharging and damage to the LiFePO4 lithium battery.

LiFePO4 lithium batteries have very low internal resistance, and an alternator tends to deliver as much current as possible. If you charge a lithium LiFePO4 battery with a car alternator, the alternator could start to burn out or even catch fire.

However, there are ways to safely charge a LiFePO4 lithium battery with an alternator. One method is to use a Victron Cyrix Li-Charge or Li-CT intelligent battery combiner. These devices manage the charging process and protect both the battery and the alternator.

Another important component is a Battery Management System (BMS), which manages the charging process to prevent overcharging and undercharging. A good BMS can also prevent the battery from drawing too much current from the alternator.

These are general guidelines and the exact process can vary based on the specific type of Lithium LiFePO4 battery and its usage conditions. As a rules of thumb, to ensure the long-term health and safety of the battery, always charging a lithium iron phosphate battery with a lithium iron phosphate battery charger.