Trickle charger chassis battery from house battery and solar

[susswein]

The chassis battery on my 2001 e350 has developed a parasitic load that drains the battery in about a week. I've disconnected the solenoid between the house and chassis batteries, so I know that's not the problem.

Can anyone suggest a scheme or device to trickle charge the chassis battery from my house battery system, which includes? I know that some solar controllers have this option, but I'm perfectly happy with my morningstar moot controller and would prefer not to replace it.

 

[Herbie]

How is the solenoid for the house/starter battery controlled?

There are a number of systems that sense both battery voltages and will automatically close the solenoid when it detects a charging voltage on either end. That's what I use (specifically, this system: https://images.carid.com/t-max/items/pdf/47-3800-installation-manual.pdf)

So when the alternator is running, it senses charging voltage from the chassis side and connects the house battery. Similarly, when I'm on shore power or solar (which connect to the house battery) then the system sees the charging voltage from the other end and also closes the solenoid. I have manual breakers at both ends of the house-chassis link so I can sever the connection if needed. The T-Max controller also lets me manually close the solenoid with a button in case I need to "self jump" or want to have extra juice for running a heavy load. In practice, this means that in my driveway, the solar panel on the van ends up doing maintenance charge on both batteries throughout the day. I very quickly got used to hearing the "clack" on the contactor opening and closing as the voltages go up/down.

The downside of this is that the house and starter batteries need to be "compatible" from a charge voltage standpoint. I couldn't run a LiFePo4 house battery with this setup as it would directly connect the alternator whenever the engine was running. It would be easy to insert a DC-DC charger into the mix but that doesn't do the same job of feeding charge back to the starter battery, and I'd lose the self-jump capability unless I added a provision for it.

 

[pugslyyy]

The chassis battery on my 2001 e350 has developed a parasitic load that drains the battery in about a week. I've disconnected the solenoid between the house and chassis batteries, so I know that's not the problem.

Can anyone suggest a scheme or device to trickle charge the chassis battery from my house battery system, which includes? I know that some solar controllers have this option, but I'm perfectly happy with my morningstar moot controller and would prefer not to replace it.

Are your start and house batteries set to combine when the engine is running? (Blue Sea ACR or similar?)

If so, you can always just manually combine the batteries when parked...

 

[susswein]

Yes, I could put in a manual combiner switch, but I don't trust myself to remember to connect and disconnect. It would nice to have it automatic and mindless.

Has anyone used a trick-l-charge unit? It seems to do what I need.

 

[pugslyyy]

Yes, I could put in a manual combiner switch, but I don't trust myself to remember to connect and disconnect. It would nice to have it automatic and mindless.

Has anyone used a trick-l-charge unit? It seems to do what I need.

It's possible to wire the REDARC SBI to work this way. (It's the way I have it set up on my van.) Takes a couple of extra relays to get it to work "backwards".

 

[susswein]

Ooops... It's actually called a trick-l-start or ampl-start.

 

[1stDeuce]

If you have a "load" output on your charge controller that is active when the controller is actively charging, you could use this, connected to the chassis battery to also charge the chassis battery... It would automatically disconnect when the panels aren't charging...

 

[susswein]

Thanks 1stdeuce, but no such luck.