Lithium battery upgrade. Charging circuits

[kpeggleston]

I just had a DC2DC charger installed. The RV repair guy told me the batteries are all still interconnected but now the coach batteries only draw 30 amps max from the alternator. All other functions remain the same as the battery boost is still connected through the solenoid.

[dvspl]

Originally Posted by bluztoo

aaurbane - Really helpful idea on the lithium to chassis battery connection with your breaker and switch. I am just now making the move to lithium and I am concerned about not being able to start the rig with the coach battery backup as it will hurt the lithium. I thought the dc-to-dc isolated charger would be enough to couple the two systems, but I guess not. Just seemed to me there should be a simple way to do it and I think you hit on it.

I used the existing line from the charge solenoid to connect to the DC to DC charger. This gave me an easy way to charge the lithium batteries safely, but no way to use the house batteries to start the engine in an emergency. I decided to carry one of those little jump start battery packs instead. I just recharge it occasionally and it sometimes comes in handy for charging other things (e.g. cell phones).

[907-Jayco]

Originally Posted by aaurbane

I'm installing 3 battleborn, victron multiplus, DC to DC charger and solar mppt. In my 2021 30z there's 4 gauge wire from the eng bat to the emergency connect solenoid and then to the house battery. I removed the wires from the solenoid and connected them, which gives me 4 gauge back to the house battery. Just before the house battery I put an off/1/2 rotary switch. 1 goes to the victron 30 amp DC to DC charger. 2 goes to a breaker and then the house battery. 2 gives me the option to connect the house and engine batteries for emergency start but normally I'll use 1 so that the lithium batteries don't damage the alternator. Battleborn told me the li bim 225 won't limit the flow of amps. I've got a 60 amp breaker/switch at the eng bat and the same after the rotary switch. I also had to run a 10 gauge wire from the solenoid back to the eng bat to keep the step working.

This looks very close to what I'd like to do on our 2021 27U. Did you happen to make a line diagram I could steal? I'm just savvy enough about this stuff to be dangerous and don't want to make any expensive mistakes.

Thanks!

[2014Greyhawk31F]

Just found your post, sounds like good sense to me, putting the circuit breaker in the emergency start circuit. Any chance you could post a 1-line diagram of your set-up?
Thx for the post!

[TnK]

Interesting discussion and I wish I knew more and could help.
But you guys keep talking and I’ll keep listening…and learning!
Thanks!

[TLF]

Originally Posted by kpeggleston

I just had a DC2DC charger installed. The RV repair guy told me the batteries are all still interconnected but now the coach batteries only draw 30 amps max from the alternator. All other functions remain the same as the battery boost is still connected through the solenoid.

I'm curious how they wired this up to keep the battery boost working. Was a diagram provided or was it explained to you? I replaced my 1 LA battery with a Lithium battery and I need to figure out the best way to wire in a Victron Orion DC to DC charger in my Melbourne.

I suppose wiring power to the Victron parallel to the solenoid (which I believe bridges house and chassis batteries when that button is pushed) while moving the ignition wire from the solenoid to the Victron would do it. Then the solenoid circuit would only be closed by pressing the battery boost button under the dash while the Victron DC to DC charger would be triggered by the ignition, but I'd love confirmation.