Repairing a LiFePO4 battery can be a complex process and should be done with caution. Here are some general steps you might follow:

1. Identify the Problem: The first step is to identify the issue with your lithium LiFePO4 battery. This could be anything from a stripped terminal to an over-discharged battery.

2. Stripped Terminal: If you’ve stripped one of the threads in a terminal on your lithium LiFePO4 battery cell, you might be able to fix it without too much effort.

3. Over-Discharged Battery: If you have an over-discharged 12V LiFePO4 battery that won’t charge above 10.2V using its included charger, you could potentially use a bench power supply to revive it. Set the power supply to 13.8V, attach the leads to the battery, and slowly increase the current to 1% of the LiFePO4 battery pack’s capacity (e.g., if you have a 100Ah battery, set it to 1A). Let it run for 60 minutes.

4. BMS Issues: If the Battery Management System (BMS) is malfunctioning, opening up the case (note: within the warranty term, you were not eligible for a warranty.) and checking on the LiFePO4 cells might be an option. A broken BMS can be replaced with a new one.

Please note that these are general guidelines and may not apply to all situations or types of LiFePO4 lithium batteries. Always refer to your manufacturer’s instructions and safety guidelines when attempting any kind of repair. If you’re not comfortable doing this yourself, consider seeking help from a professional.

Remember, working with any type of batteries can be dangerous if not done properly. Always take necessary precautions and safety measures when handling batteries.