My LiFePO4 Battery setup

I just finished this project and thought it might be useful to generate ideas for others. My parameters were:

- I didn't want the LiFePO4 battery in the engine compartment
- I needed to be able to convert back to a (mostly) stock 5-seat vehicle when needed
- I sleep in the vehicle (comfortably too!)
- I use the vehicle for Sheriff Search and Rescue, camping and fly fishing trips. I may be parked in one spot several days.
- I run a Dometic CFX 35 fridge, and recharge various SAR tools, radios, computers, lighting, etc at times
- I wanted "always on" power in the rear of the vehicle, but wanted to have that be Lithium or AGM starter as desired.
- I wanted to be able to charge the LiFePO4 at ~20A from my alternator or from my 100W portable solar panels

So...here's where I ended up:

- I have an X2 AGM starter battery with battery boost diode. This can feed my "always on" power panel in the rear (when desired) and be charged by solar.
- I have a Renogy 100Ah bluetooth LiFePO4 battery mounted/anchored in a cheap battery case behind the driver seat. This can feed the "always on" power panel when needed. It can also be charged by alternator or portable solar. I can monitor battery charge state with their bluetooth app.
- Fridge and LiFePO4 can be removed from the vehicle and run at a campsite if desired.

I made a representation of the wiring diagram below. Essentially, I ran fused 6awg welding cable from the AGM starter battery along the driver side back to the "breakaway" rear tray. I mounted a Blue Sea busbar to the underside of the tray. From there I ran a 10awg cable that pops out with an Anderson powerpole connector at the rear of the driver-side passenger door. From there, another short Anderson cable allows me to connect it to the input of the LiFePO4 Victron 12-12 18A DC-DC smart charger. This gives ~20A of DC alternator charging for the LiFePO4 battery.

Next, I ran 10awg cable from the busbar to the rear "jack compartment". That is terminated with another Anderson connector. I installed a Blue Sea 6-circuit fuse panel in there. Note - the vehicle jack can still be removed without issue. The input to the fuse panel is an Anderson connector. So, there are three Anderson-terminated cables here - one is on the fuse panel, one is an AGM starter battery cable, and the third is the LiFePO4 battery cable. I will normally leave the LiFePO4 connected to the fuse panel. In "stock" mode, I can connect the AGM cable to the fuse panel and remove all the LiFePO4 battery gear. NOTE: THE AGM and Lithium batteries can NEVER be connected to the fuse panel at the same time or all the fuses will blow (and the wires may melt)!

The fuse panel feeds the rear "always on" power panel. This is also Blue Sea. It contains a power switch with an integrated 15A breaker. Next are 2x30A Anderson powerpole outlets, which can also be used as inputs from an MPPT portable solar charger. They are wired directly to the fuse panel and are not switched. Almost all of my 12V devices have Anderson connectors so this works great. The next outlets are a USB-A and USB-C PD charger with an integrated voltmeter (Powerwerx). The final outlet is an Engel/ARB/Dometic 2-pin 12V power connector. Both of those panel-mounted devices are controlled by the panel switch. I skipped the unreliable 12V cigarette lighter outlet.

I could have saved one wire run by using a fancy all-in-one MPPT/DC-DC device that might fail over from LiFePO4 to AGM when needed, but most of those had issues including very low open circuit solar panel input voltage limits. I use a Victron MPPT charger for my 100w Rockpals panel, and that puts out a solid 95W or so in full sun.

 

Great write-up, and nice installation. Thanks also for telling me what those plug-in connectors are called!

 

Bread rack shelf is a great idea.

 

Nice write-up. Thanks for posting

 

It's pretty handy, and a lot cheaper than a drawer... You can order custom sizes at www.TheShelvingStore.com . I have the OEM sliding tray (with some added tie-downs), so the fridge & shelf slide out as needed.

 

That’s awesome! Very well planned set up. I wouldn’t mind seeing your solar panel set up too if you don’t mind.

 

My solar is just a Rockpals portable folding panel. I connect it to a Victron MPPT charger with Anderson connectors, then plug it into the Anderson outlets in the power panel. I have a long extension cable so I can park in the shade while the panel is in the sun...

 

Love what you did here. Exactly what I am trying to do. Want to build rear power system into back of 4runner and try to utilize that rear cubby area. Want to be able to remove components like you did. Really well thought out.

 

Hi @shelt, great write up! can you please help me understand one thing about the wiring. The blue sea fuse panel has two anderson connectors going into it: one black and one red. The red wire is from either the LiFeP04 battery or the Bus Bar correct? If you're using the Lifep04 then the red wire from that connects to the fuse panel. If not, then you just have the red wire from the bus bar (pulling from the stock starter battery). Is that correct? So you can connect it either way and remove the battery when you need the back seat space.

The same would go for the black wire. Either from starter battery bus bar or from victron. Correct?

 

We discussed this in detail via PM. Actually there are two pairs of Anderson-terminated cables (red+black in each pair) that are available for the blue sea fuse box and either pair can connect to the third Anderson pair on the fuse box. One pair comes from the lithium and the other comes from the starter/AGM busbar. Normally I would have the pair from the lithium plugged in. If I remove the lithium, I can use the pair from the AGM busbar.

Note I have a new variation of this setup including a permanent roof solar panel and a Redarc all-in-one charge controller. I'll try to write that up soon...