Transitioning to LiFePO4 Batteries in my Campervan/ Class B RV: A Major Upgrade

After many years of reliable service, my AGM batteries have finally reached the end of their life. While they still work, their capacity has drastically decreased. So, I decided it was time for an upgrade and made the big leap to LiFePO4 (lithium iron phosphate) batteries. This was no small decision, as switching to lithium required significant rewiring of my RV. Lithium batteries can't withstand the extreme heat under the hood where the AGMs were located.

The biggest challenge was finding space for the new batteries, as there was technically no available room in the RV. I considered installing them in the generator’s spot but chose to keep the LP generator for emergency power, as I value redundancy. In the end, I opted to install the lithium batteries inside the RV to protect them from the elements and extreme temperatures.

Here’s the teaser video.

I decided to place the batteries inside the lower galley cabinets, just below the microwave. The next hurdle was choosing which lithium batteries to buy, with options like Battleborn, SOK, Epoch, LiTime, and more on the market. After some research, I decided on SFK 300-Ah batteries. I love that SFK batteries are assembled in the U.S., have a compact form factor (using EVE cells), and are packed with features like external switches for Bluetooth, heating, and balancing options. They also offer an optional RS485 data port for direct integration with Victron systems with the Venos OS compatible devices like the Cerbo GX (when using the SFK data cable). Another added bonus is that the case can be easily opened for future repairs.

Sun Fun Kits (SFK) also provides detailed information about each battery's assembly and testing. The battery label includes the cell manufacturer, Battery Management System (BMS) details, construction specs, and test results. There's even a QR code that links to the SFK serial check site, where you can find individual cell test results and certifications.

I went with higher-capacity lithium batteries so I could run the RV's air conditioning (A/C) for a few hours. This feature is incredibly useful for me, especially for brief stops for groceries or dining out, allowing the A/C to run quietly without the generator and keep the RV comfortable without attracting attention.

The 2kW A/C inverter, along with all the fuses and breakers, is housed in a fabricated enclosure mounted on the side of the galley cabinet, just behind the driver's seat. I kept the original 1kW inverter/charger under the driver’s seat for now, though I plan to replace it with a Victron unit. The solar charge controllers and DC-to-DC chargers will also eventually be upgraded to Victron components. If you’re considering a similar upgrade, a 2kW or even 3kW Victron Multiplus inverter/charger would fit perfectly where my DIY enclosure is mounted, with enough room left for fuses and breakers.
Transitioning to lithium has been a significant upgrade for my RV, providing more reliable, longer-lasting power and greater flexibility for off-grid adventures.

How it all started:

Fabricating the enclosure for the inverter, fuses, and breakers involved pre-fitting a box replica of the inverter and a 6-post 300-amp busbars. At the time, it was the only 6-post bus bar I could find. I added a dab of Loctite to each bus bar bolts to prevent them from loosening.

The enclosure prior to painting.

Both bussbars mounted in place.

I painted it black (since it was too large for my powder coating oven). The cover is made from 1/2" birch plywood, stained, and protected with a matte polyurethane coating.

View from the top. The inverter remote/monitor is mounted on the cover in the foreground.

Renogy 2000-watt inverter with Eco-mode bolted in place.

Aluminum plate for mounting a negative main disconnect switch.

Blue Sea Systems 3000 HD-Series Heavy Duty On-Off Battery Switch with 600-amps rating. Both negative cables from the two lithium batteries terminate at the switch, while the positive cables are directly connected to the (+) bus bar via an MRBF Fuse Block Terminal.

Mounting placement for the main negative disconnect switch.

Fabricating a bus bar connector for the battery shunt using a thick copper bar, which is then nickel-plated for corrosion resistance.

Most, if not all, of the mounting hardware was nickel-plated as well.

Battery shunt placement utilizes the fabricated bus bar connector, with the other post of the shunt connected to the Blue Sea HD switch using a large 4/0 cable. I use MRBF fuse terminals and fuses for the positive bus bar wire connections. The MRBF fuse terminal bolts directly onto the bus bar posts, but I had to stagger the fuse terminal connections in pairs, facing opposite sides, because they wouldn't fit side by side; the bussbar posts are just a millimeter or two too narrow.

Chassis ground point connection utilizing an unused bolting point on the driver’s side B-pillar. Since the ground point is covered by the B-pillar trim, I had to make a hole for wire access. Chassis ground cable is connected to the negative bussbar terminal.

Wiring the inverter's 120 VAC output to the A/C line involved using a Kisae 20-amp transfer relay to automatically switch the power source for the air conditioner, prioritizing shore power. The A/C line from the breaker was disconnected and rewired to the transfer relay's AC input 2 (Utility) connection. The wire going to the A/C was then rewired to the transfer relay's AC output (load), while the inverter's AC output was connected to the AC input 1 (inverter) of the transfer relay.

Kisae 20-amp transfer relay mounted behind the fuse/ breaker box using double sided VHB tape.

Some of the wire runs (solar, 120-vac wire, DC-DC charger cables) along the driver side B-pillar.

The opening on the driver seat base was enlarged to accommodate additional wiring from the primary inverter located under the seat and the LP generator at the rear of the coach. The positive wire to the LP generator passes through a hole created by RT beneath the seat base.

The expanded opening is lined with rubber trim to protect the wires from abrasion. The two Romex wires shown are the original ones installed by RT for the main inverter's AC input and output.

Additional wires are routed to the bus bar terminal connections.

A section of the foam-backed floor cover was carved out to accommodate the wirings.

With the plastic floor cover installed, the wires running beneath it are completely hidden.

Here, you can see the busy wiring. This project involved extensive rewiring, with the 1-kW inverter/charger located under the seat and the 2-kW inverter dedicated to the A/C positioned behind the driver’s seat.

I fabricated the battery tray, which will be secured to the floor inside the galley cabinet under the microwave using screws and adhesive. The batteries will be held in place by two threaded rods on each side, along with a long flat bar running across both batteries to secure them and prevent any movement.

Unboxing both SFK 300-Ah LiFePO4 batteries. These batteries were packed exceptionally well, and shipping was quick. I really appreciate this company; they respond to questions thoroughly and promptly. I’m not affiliated with them in any way; I just admire how they treat their customers.

Both batteries tested 13.17-volts from the box. 

Pre-fitting both batteries into the battery tray mount.

A close-up view of the battery holding mount.

Mounted inside the cabinet.

It's a perfect fit—perhaps a bit too tight, as there's barely enough room to tighten the bolt nuts.

The external switches are easily accessible at the front, and the battery terminals are protected with silicone terminal covers for safety.

Only half of the floor space under the microwave was utilized; when needed, you can fit four batteries in this location.

A small opening was created in the upper right corner of the cabinet where the batteries will be mounted. The battery connection wires will pass through this opening to the enclosure busbars/ switch. The enclosure will be secured against the cabinet's front-facing wall using T-nuts.

Here’s how it looks with all the wiring completed. The wooden cabinet door fascia at the battery location was replaced with an aluminum Venetian bronze Lincane decorative sheet for ventilation.

The inverter enclosure is sized just right, allowing the driver’s seat to be fully moved back or reclined without altering the original RT configuration.

My DIY inverter enclosure measures 30.25" (L) x 13" (W) x 5.25" (D). If you prefer, a 2000VA Victron Multiplus inverter/charger (20.5" (L) x 10" (W) x 5" (D)) or a Victron Multiplus 2000VA Compact (20.4" (L) x 8.8" (W) x 4.9" (D)) can easily fit in that space, with enough room left for fuses and breakers. Even a 3000VA Victron Multiplus could fit comfortably at the bottom.

View of the main negative disconnect switch. Future projects include upgrading our primary inverter, solar charge controller, and DC-DC charge controllers to Victron, along with the Erkano GX display and monitoring system. The SFK batteries will enable data communication through the GX monitors, allowing you to view all battery data on the Erkano display.

It wouldn’t be complete without the badging for that professional look :-).

The battery BMS data can be monitored through an app via Bluetooth connection, and BMS settings can also be adjusted through the app. I find it especially convenient to do this directly on my Android head unit, but you can also use your phone for monitoring and adjustments.

A virtual battery can be set up to monitor all connected batteries on a single screen, providing multi-view support by saving each battery configuration as a virtual battery. While you can access more detailed information and settings when connecting to each battery individually, the auto-connect virtual battery is convenient for general monitoring once the individual settings are configured. SFK batteries also feature a 5-amp active balancer, which you can switch between modes using the built-in switch or through the app.

The detail tab (pictured above) for the individual cells of both batteries is especially useful for ensuring that all cells are balanced, functioning properly, and maintaining voltage under load.