Dual charging system issue

[jimbob78cj]

I am building a vehicle for overlanding. I am running a standard lead acid dual battery system where one battery is designated as the starting battery and the other as an accessory battery. The batteries are connected together and charged by the alternator while vehicle is running and the two batteries are disconnected from each other when the vehicle is off to prevent accessories from draining the starting battery. Since I have a few accessories that could drain the accessory battery too fast, I decided to add a 200W solar array to the roof and bought a Renogy Wanderer 30 amp PWM charge controller that is connected to the accessory battery to charge it while the vehicle is not running.

My problem is that when I crank the vehicle and the alternator starts charging both batteries, the Renogy controller will disable itself (all lights go off) and I have to disconnect and reconnect the panels and battery momentarily to get it back working once the vehicle is off again. If I disconnect the panels prior to starting the vehicle, all is good. Is this a design issue or a charge controller issue?

 

[Rednecktek]

The alternator is sending a much higher voltage to the batteries than they can take for that brief moment when the truck starts sending a really high voltage spike (14+v) to the batteries. This doesn't bother the batteries at all but your SCC is seeing it as an over voltage and tripping its safety. That's why disconnecting and reconnecting solves the problem, it's resetting the over voltage trip.

DC-DC converters for LFP and accessory batteries are designed to ignore that and just keep trucking along.

 

[jimbob78cj]

The alternator is sending a much higher voltage to the batteries than they can take for that brief moment when the truck starts sending a really high voltage spike (14+v) to the batteries. This doesn't bother the batteries at all but your SCC is seeing it as an over voltage and tripping its safety. That's why disconnecting and reconnecting solves the problem, it's resetting the over voltage trip.

DC-DC converters for LFP and accessory batteries are designed to ignore that and just keep trucking along.

Interesting. If I reset the SCC while the engine is running, it will disable again after a few minutes. It's not instantaneous. And if I leave the SCC connected to the battery, but disconnect only the panels when cranking/running, there are no issues.

 

[Rednecktek]

I suspect your PWM is still tripping out trying to argue Battery Voltage VS Alternator Voltage VS Panel Voltage. When the panels aren't doing anything (not connected) the controller isn't doing anything and doesn't care what you do with it.

A proper DC-DC charger should alleviate that issue, I think your PWM is a lost cause though.