Recovering a Discharged Valence U27-12XP LiFePO4 Battery

The Problem

The Valence battery had discharged below the recommended minimum, dropping to 10.5V instead of being recharged above 11V, leaving it in a deeply depleted state. The owner had been charging for a year using solar with an MPPT controller but without a dedicated lithium charger profile, and had no experience using the Valence BMS software.

Solution

Before you start, obtain the Valence BMS software, which is not freely downloadable from a public site. It is supplied by Valence/Lithium Werks and is typically provided to dealers and OEM integrators; you will usually need to request it (and the matching BMS interface cable) from a Valence battery supplier or distributor, and confirm you have the correct version for the U-Charge XP range before beginning (verify the exact software version and supplier before ordering).

1. Connect a laptop to the Valence battery via the BMS cable and open the Valence BMS software; configure the laptop power settings so the screen and sleep never activate during charging.
   • If the software will not connect, check that you are running it as Administrator.
2. Fit a fuse to the positive cable at the battery terminal before attaching the charger.
3. Connect the Victron 30A Bluetooth charger to the battery, then open the Victron Connect app on your phone and set the charger to lithium profile mode.
4. Start a charge cycle and monitor both the BMS software on the laptop and the Victron app; when the charger drops into float or storage mode, restart the charge cycle manually from the app.
   • The BMS software will show the cell balancer activate once cells reach around 90% — this is normal and expected.
5. Continue restarting charge cycles until the charger shows the battery pulling less than 1A; for a complete top-up, continue until current is below 0.2A.
6. Disconnect the charger; the resting voltage should settle to around 13.2–13.5V and the green LED on the battery should flash approximately every 20 seconds to confirm full recovery.