Yeah yeah, I know there are lots of other discussions about battery isolators out there, and I've read a ton, but can't figure out how to solve my problem: my battery won't properly charge from my truck's alternator.
I have a 2015 Fleet Shell model (no shore power), so I rely heavily on the battery charging from my truck's alternator. When I bought the camper, I noticed that the isolator would "click" on and off, and I wasn't getting much charge. Turns out the house battery was old and needed to be replaced. No biggie. I replaced the battery, and it appears that the same thing is happening. So, maybe my truck's battery is bad? Not the case, I tested it with a multimeter, and double checked by having it checked at an auto parts store. Maybe the 10AWG wire isn't big enough and the voltage drop is too high? Possibly... but FWC has repeatedly sworn by it. Bad battery isolator? I don't think so. The true culprit (so far as I can ascertain): Low voltage in the house battery.
For context, I'm running a two battery system in the camper with a Goal Zero Yeti 400 (https://www.goalzero...-power-station/) chained to a 12v deep cycle lead acid battery of the same size (https://www.goalzero...cement-battery/). Using this system, I can plug a solar panel into the Yeti 400 when the car is parked, and the chained battery is attached the the camper's ring terminal connectors. I run a domestic CFX3 50 IM fridge, which has pretty descent power draw. Currently, the goal zero battery is indicating that my batteries are 80% charged. Using a multimeter, I measured the chained battery at 12.4 volts (12.3 when the fridge is running).
The stock Sure Power isolator says in the manual that it will detach the system (i.e. not charge) if the camper battery drops below 12.4-12.9 volts. This explains why it clicks on and off. It is trying to charge the camper battery, but the voltage is too low, so it cuts out. I saw a post where someone replaced their Sure Power isolator with a Blue Sea ML-ACR, which many people consider a superior product. However, the Blue Sea product STILL shuts off when the camper battery drops below 12.5V. The only reason this fix worked is because the ML-ACR includes an override switch to bypass the separator.
So yes, for an additional cost and a bunch of frustrating installation labor, I could switch to the Blue Sea separator and have a fancy switch to force the batteries to charge while driving, but that seems pretty silly. I'm having a hard time understanding why the cutoff voltage is so high on all of these products. Based on voltage diagrams I've seen for typical 12V batteries, both of these isolators are only able to charge the camper batteries from 90 to 100 percent, but will not work if the battery drops below 90%. That seems absurd. Aren't these supposed to be deep cycle batteries after all? Shouldn't there be a product that can charge them up when they are more drained as long as the alternator is firing? Is there something I'm missing here? Thanks for your help!