Attempting to troubleshoot issue with DC to DC charger

[Tinman2111]

Hello all:

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!

Thanks

Mark

[HarryS]

I would think, if you have a 'short' on the house battery side, you would see it popping breakers on the DC circuits. To answer your question about the alternator and the inverter/charger, the DC from the alternator to the house batteries doesn't go thru the inverter at all. That only comes into play when on shore or generator power. The inverter/charger takes 120VAC and turns(converts) into 12VDC to charge the batteries. Unfortunately, it sounds like you are at the mercy of the guy doing the install at this point.

[Bob Denman]

Have you tried calling the folks at Renogy?

[Tinman2111]

Thank you Bob, I ultimately figured out the inverter cannot be both a charger and inverter at the same time, oops. Yes, the tech called Renogy (according to tech multiple times) and Renogy insisted issue with wiring. I understand, mostly anyway, the need to protect the alternator from the lithium, so I'm trying to explore other ways of protecting the alternator. Maybe the lithium BIM from Battleborn is the solution, and just go back to "original" by taking out the damn DC to DC charger from the equation. You're likely right, at the mercy of the tech...... Damn I wish I knew more about my RV and EVERYTHING in it! Leaned a boatload since getting it.....oh the embarrassing stories I could tell.....Thank goodness for the forum, it has "educated" me many times on how to fix my SNAFU's.

[Bob Denman]

Don't be embarrassed for not knowing enough: it's how we ALL learn this stuff.
Good luck with this project

[Tinman2111]

Well, I guess I can call off the posse. The tech called me (working late to fix my RV) and said he located the issue. He found a 2/0 cable in the battery compartment that was sharing a common positive post with three other positive cables. He said it was intermittently shorting. Fixed it and he said everything is great now! I asked him what the shorting cable was used for and he said he didn't even know, but said it was capable of carrying greater than 60 amps and being that he shared its circuit when he did the install, it tripped the breaker for the DC to DC charger.

And Bob, I not embarrassed for being RV illiterate, I'm only embarrassed by the stupid crap I've done because of my illiteracy!! I wear my my noob RV badge with pride!!