Dual battery to lithium battery setup

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OffRoadScott

OffRoadScott

10 Year
Joined
Sep 25, 2014
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102
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3,226
Location
Gilbert, AZ
Currently I am running 2 group 31 Optima batteries for starting. I was going to use the 2nd 31 as the house battery but was wondering if there is a way I can wire in my lithium batteries? Can I wire in a Victron DCDC charger after the Blue Sea ML-ACR? If so can someone explain it in both writing and a schematic?

The setup would be 2 group 31 batteries in the engine bay for starting/winching/jumping and in the back behind a custom 8020 aluminum drawer system would be 3 12V 100Ah Battleborn Lithium batteries in parallel.
 
I run a victron orion xs 50A DC DC charger. Input is to the main battery and output to a 100ah lifepo4. It's all automatic and essentially idiot proof and easily configured via their app via BLE.

There's really nothing to it - victron has plenty detailed wiring info.

Just make sure you have a good earth connection to ensure minimal voltage drop from the engine bay to your lifepo4 batteries. I'd put the orion close to the batteries so it better senses their charge voltage. The orion is also ip65 - not an issue if you have it all in the back of your 80.

cheers,
george.
 
This is the model I'm using. It's their newer one and very efficient, so minimal heatsink size on it. Since my lifepo4 is in the 2nd battery tray, it's all mounted here. This was during installation.

cheers,
george.

PXL_20260212_180344127.webp
 
I would think you want the DCDC charger connected to the same battery that is connected to the alternator.

I use a LiTime DCDC charger (sans overland tax) and I mounted in the cabin near the house battery. A DCDC charger must be rated for the engine bay if mounted there.

DCDC charger installation is just a single fused wire from the DCDC charger to the battery. Fused at the battery and also fused at the DCDC charger if it can send current back. The wire has to be large enough gauge to support the current over the given run length.

The DCDC Charger installation is independent of the Blue Sea ML-ACR and how it is installed.

I personally would not install Battleborn Batteries due to their flawed design.
 
peesalot said:
OP, just curious, whats the load expected ? Thats ALOT of battery.
Click to expand...
My biggest draw is going to be the ARB compressor. I was going to wire that into the AGM 2nd battery but now that I have 300Ah I will have it wired in with everything else.

ARB compressor
Fridge
Inverter
CPAP machines x 2
USB chargers
Battery chargers for tools
 
george_tlc said:
I run a victron orion xs 50A DC DC charger. Input is to the main battery and output to a 100ah lifepo4. It's all automatic and essentially idiot proof and easily configured via their app via BLE.

There's really nothing to it - victron has plenty detailed wiring info.

Just make sure you have a good earth connection to ensure minimal voltage drop from the engine bay to your lifepo4 batteries. I'd put the orion close to the batteries so it better senses their charge voltage. The orion is also ip65 - not an issue if you have it all in the back of your 80.

cheers,
george.W
Click to expand...
When you say close to the batteries are you referring to the AGM or the lithium? I plan on running 1/0 to the back and they will be wired in parallel with 1/0 as well.
 
Last edited:
george_tlc said:
^ You want the victron close to the lifepo4 batteries since it has to sense the voltage to determine the state of charge. i.e. short wires from the victron to the lifepo4 batteries.

The input to the victron should be from your main battery, the one that the alternator is directly charging.


cheers,
george.
Click to expand...
Okay but with the Blue Sea ML ACR isn't the alternator charging both, or should I connect it to the starting battery?
 
The alternator charges the main battery directly - connect cable to victron to the main +ve. Your ACR then activates to charge your 2nd AGM when the alternator is running.

Victron will automatically sense alternator is charging and then activate (as needed) charging of the lifepo4 batteries.

No point feeding the victron from the output of the ACR...

cheers,
george.
 
You can definitely run a 3 battery system (dual engine bay batteries with cabin lithium). In most scenarios the 2nd engine bay lead battery acts solely as a backup cranking battery since you have your house needs now redirected to the rear lithium power. What do you have wired to your second agm?

You can keep the dual agm setup relatively untouched and just expand by running a positive lead off the start battery to the cargo area where you would mount the DC to DC charger, reiterating what everyone above said (DC to DC closest to the charging battery). The DC to DC needs a common ground, and the best way to do that is to connect the DC-DC ground to a negative bus bar near the DC-DC, then making direct connections from each battery (start and lithium) negative to that bus bar.

Theres no real need to run 1/0awg cable to the rear. If you have a 50amp charger, you want 4awg or 2awg max running from start + to DC-DC input.
 
george_tlc said:
This is the model I'm using. It's their newer one and very efficient, so minimal heatsink size on it. Since my lifepo4 is in the 2nd battery tray, it's all mounted here. This was during installation.

cheers,
george.

View attachment 4196223
Click to expand...
George-- that looks very good. A few questions --

Where did you get that orange mount?

What type of lifepo4 battery did you get?

Does the lifepo4 battery reside in the second battery tray? No problems with it in the engine compartment?
 
^ I designed the orange mount and 3d printed in petg. I have a 100ah ecoworthy (new version with the bluetooth monitoring). No issue with heat. Lifepo4 are not li-ion... Been installed for at least a year now and all behaving very happily.

cheers,
george.
 
sjpitts said:
George-- that looks very good. A few questions --

Where did you get that orange mount?

What type of lifepo4 battery did you get?

Does the lifepo4 battery reside in the second battery tray? No problems with it in the engine compartment?
Click to expand...
I don't think George @george_tlc doesn't have to worry about high temps like we do here in AZ, Sunnyvale is in a nice cooler climate.
 
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