My Renogy Lithium battery bank depleted last spring due to 6 months of inactivity and I had turned off my solar panels during those six months due to freezing winter weather. In my case the draw from the CO and LPG detectors over six months were enough to deplete my batteries. In addition to the above suggestions here are some random suggestions:
-Use a voltmeter to read the voltage at the Lithium battery terminals.
-If you can, using a multimeter and with the solar panels disabled (or at night), read the amount of current, in amps, your system is drawing from the battery bank.
-Is your 12v fridge running at night when solar panels are inactive.
-Check your suspect fuses again to confirm they haven’t blown again.
-if not already check with the SMB facility where you purchased your Sprinter for their suggestions.
Even if you’re able to revive our Lithium batteries, you’re going to want to find out what caused the incident in the first place to avoid it happening again.
2006 E350 SMB RB50 6.0 PSD