Attempting to troubleshoot issue with DC to DC charger
I took my 2015 Challenger to my local RV repair shop to have them install my four new lithium batteries, a lithium compatible converter, and turns out the dreaded DC to DC charger. The technician has called me a couple time to update on issues he can't seem to solve. When the DC to DC charger runs, it trips a 60 amp breaker. The breaker that is tripping is between house bank and DC to DC charger. It is a 40 amp charger (Renogy). Tech said at first bad charger so I got an expedited replacement and guess what, same issue. Now he says somewhere on house side of DC system there is a short. I have a general understanding of how the chargers are installed and we discussed his install in decent detail. He has a breaker between chassis battery and charger and then another breaker between the charger and the house bank. He is insisting that he double and triple checked his wiring and it is correct. He thinks there was a short somewhere before I took it in, but everything worked fine. RV has a residential fridge, a Xantrex inverter/charger. I was led to believe I needed the DC to DC charger to protect the alternator from the lithiums, but is that true? I just asked tech again and he said the DC to DC charger was best option. Can I not just use the ORIGINAL wiring, absent the DC to DC charger, and rely on the inverter to prevent the lithiums from damaging the alternator? I realize my Xantrex doesn't have a true lithium profile, but maybe 13.8v is close enough considering the majority of the charging would be done either when on shore power, on portable panels, or with genie running. I can always "consider" getting an inverter/charger that has a lithium profile in the future if it is essential. Help!
I'm going to visit the shop tomorrow to discuss, and I can really use the crash course on potential solutions!