I found this film. It might be interesting for some of us who have a camper truck equipped with lithium batteries.

https://www.youtube.com/watch?v=jgoI...ature=youtu.be

 

Are there systems that hook a lithium battery system directly to the alternator? I thought most camper systems have a "traffic cop" or a piece of equipment that was a invertor/charger/power supply all built together. Don't these systems monitor the charging current, whether from shore power, solar panels, or the vehicles charging system?

 

The "typical" lithium battery has a protection board which acts like a circuit breaker to prevent overcharging or over-discharging or short-circuits, but it doesn't do anything to manage normal charging. I'd assume most big lithium iron phosphate batteries get used with solar power systems that include a charge controller, which limits the charging voltage and current as necessary.

Overloading the alternator seems to be a risk anytime you ask it to charge a large deep-cycle battery, regardless of battery chemistry. I'd consider adding a 0.1 ohm resistor between the battery isolator and the camper battery; that would limit charging current to about 24 amps maximum, but dissipate as much as 58 watts, so it would need to be a big wire-wound resistor (100 to 200 watts to be safe). Maybe nobody ever does that, for a reason I haven't thought of.
This page suggests either an isolator from Battlebornbatteries that limits charging time (15 minutes on, 20 minutes off) or a Renogy DC to DC charger (available in 20 to 60A sizes) which has the additional benefit of settings for different battery chemistries.
https://www.mobile-solarpower.com/ba...isolators.html
Other DC-DC charger brands: Victron, Sterling Power, Votronic (German)
CTEK has combination solar charge controllers and DC-DC charger:
https://smartercharger.com/collectio...s/20a-off-grid
https://smartercharger.com/pages/ctek-d250sa

 

That's why I recommend people with the simple contactor or relay isolator systems for charging their campers and rv's use a smaller 10 gauge charge wire running all the way from the engine compartment to the camper, and installing a 30 amp circuit breaker along with it near the contactor/relay. My theory is the same as yours, a fully charged starting battery and a spinning alternator both are sometimes presented with a deeply discharged camper/rv battery via this isolator relay, and if the starting system has the capability, it's going to throw all it's got to the camper battery all at once. My theory was like yours, the smaller wire would be a resistance, and the circuit breaker would trip and then self reset if things got a little to much for the circuit. It would trip and reset till the camper battery finally built up enough to not take a unreasonable amount of charge current.