Dual 12V Systems - Is it possible with aux battery

45Kevin

Well-known member
My van came with the aux battery located in the engine compartment and has the EK1 and F150 terminals under the drivers seat.

I would like to have two separate 12V systems.

One would run off the aux battery and power the fan and my cheap Chinese diesel furnace.
Those two devices would probably not get used a lot together. The aux battery could probably run the furnace for two straight days before it got down to 50% SOC.

The reason for two systems is that the aux battery will discharge at a lot colder temps than my lithium batteries. So on cold days when I enter the cold van I can run the furnace before the inside temp is warm enough to let the lithium batteries work.

I will be using a Renogy DCDC 50A charger for the lithium batteries, as well as solar and shore power through my Renogy invertor.

The DCDC will draw from EK1 (I think) and the furnace power will come from the F150 (I think). I'm still trying to wrap my head around this.

My question is, can I get two independent 12V systems, or will they be connected through the connection of the charger to the vehicle system?

The Renogy DCDC Operation booklet states that if the solar controller part of the DCDC senses a fully charged house bank it will divert power to the starter battery, which in this case would be the aux. So it seems the connection is a two way street.
I could use a separate controller if needed.

My head is going to explode.
 

kcshoots

VanTripping.com
You can certainly have separate 12vdc systems. They can each be charged by alternator an even the same solar generation yet have different and separated loads on each. I do this using the factory Aux battery that supplies power to fuse panels for my stereo, air compressor and auxiliary driving lighting, and a few small charging ports and area lighting in the cab, but keep all of my "house" loads on my House battery system (camper lighting, cooking, heating, fridge/freezer, etc). Just supply a separate power lead from each battery to its load center/fuse panel. Grounding systems can be separate or combined, as they are eventually combined at the chassis anyways. I charge each separate system from alternator and use an auxiliary lower amperage shore power charging output to the Aux battery to keep it maintained--helpful when using those auxiliary loads too. BlueSeas actually makes a 12vdc fuse panel with two separated inputs/sources and output groups so that you can use one fuse panel for two different power sources and systems. I see the benefit of this in that my starter battery only does starting so preserved for that function, while the Aux battery provides power for auxiliary driving/cab loads, and the House battery for all of the camper/cabin loads so that neither of the other loads can use up available capacity on the other batteries, meanwhile, they auto connect to alternator for charging and auto disconnect to keep separated and with battery switches, any combination of the three batteries can be manually interconnected for emergency use.

The auxiliary output from your solar controller makes the connection for charging only when conditions warrant, but loads will be separated.
 

autostaretx

Erratic Member
The EK1 can only supply (squints at photo ... hmmm ... an NCV3) about 20 amps continuous on the "always on", and i wouldn't exceed 12 amps on the "ignition switched"

--dick
 

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