Where This Guide Comes From
This guide follows the Camping with the Coles conversion — a couple who swapped their RV's single lead-acid battery for a two-battery lithium bank, and filmed every part of the decision, from the parts list to the bench test. It's aimed squarely at beginners, and it covers the parts you need before you touch a wrench. The video is right here:
The reason this guide works as a checklist: the Coles had already hit the limits of their lead-acid system on real trips — a couple of days of boondocking with very small power usage. Their goal was a week or longer, and the parts below are exactly what got them there.
Step 1: Do the Math First
Before buying anything, figure out what capacity you need. The Coles' method is the same one we recommend to every customer:
- List all the appliances you want to run.
- Note each one's wattage and how many hours a day you'll run it.
- Multiply: watts × hours = watt-hours. Then divide by 12V to get amp-hours — the unit batteries are rated in.
Their example: a 150W laptop for 4 hours a day = 600Wh ÷ 12V = 50Ah per day. A 100Ah lithium battery gets you about two days on that single load. The exact number is hard to pin down until you actually measure your usage, but this rough list method gets you in the right class — and the right class is what matters when you're choosing between a 100Ah and 200Ah bank.
The Battery: What a "Smart" Lithium Battery Is
The heart of the system: two 100Ah smart lithium batteries, in their case Renogy. Two things to know before you buy:
- BMS built in: every quality lithium battery has a battery management system — a small computer inside that controls charging and discharging, balances cells, and cuts off protection in extreme conditions. That's non-negotiable, and it's what makes "just drop it in" safe.
- Shelf mode: many lithium batteries ship in "shelf mode" — completely shut down with no voltage at the terminals. You activate them by plugging in the activation key and holding the button until the light goes bright. Press and hold again to return to shelf mode for storage. This is a safety feature, not a defect — the battery is inert until you wake it up.
The Charger: Why Your Old Converter Won't Cut It
Different batteries need to be charged differently. You can theoretically drop a lithium battery onto an old lead-acid charger, but it won't use its full capacity — and in some cases it'll undercharge or damage the bank over time.
The Coles' 2016 converter did not support lithium, so instead of replacing it, they added a separate Renogy 50A DC-DC battery charger with built-in MPPT solar charging. Two devices in one box: it takes power from shore, the truck's alternator, or solar, and figures out the right voltage and amperage to charge the battery optimally. It's effectively the brain of the whole system — and it also has a port for smart monitoring via Bluetooth, so you can check charging from the truck while you drive.
That DC-DC path matters for another reason we've covered before: charging a lithium bank directly from an alternator can overload it. A DC-DC charger regulates the flow and protects both the battery and the alternator.
The Battery Monitor: Because Voltage Lies
This is the part beginners skip, and it's the part you'll miss most. Lithium batteries don't indicate their charge state through voltage like lead-acid — the discharge curve is too flat. So you need a battery monitor with a shunt: the shunt sits in between the battery and the charger, counts what you use versus what you put back in, and shows you actual state of charge, current usage and how much power you have left.
Without one, you're guessing — and guessing wrong on a lithium bank means "oops, it's flat" with no warning. The Coles installed one to monitor both batteries in real time. On our batteries, the same function is built into the BMS communication (CAN/RS485/Bluetooth), so if your battery supports monitoring, the shunt can sometimes be optional — but for a mixed-brand build, a shunt monitor is the safe default.
Fuses, Wire and Switches: The Safety Layer
Three things that don't feel like upgrades but absolutely are:
- Fuses: your battery bank should have a fuse connected to the positive terminal (an ANL fuse in their case), and high-current devices like inverters should be fused too. In a short, the fuse blows and cuts everything off instead of cooking the equipment and wires.
- Proper gauge wire: assess your rig for wire length, then look up the right gauge for that length and expected current. Undersized wire is a fire risk, not a savings.
- A battery cut-off switch: not strictly required, but very useful — flip it off when troubleshooting or reconfiguring. If something's going wrong, "off then on" solves most problems safely.
The Inverter: Pure Sine Wave Only
If you want to run household 110V devices, you need an inverter — and the video's advice is specific: get a pure sine wave inverter if you plan to run electronics. Modified sine wave inverters are cheaper, but they can damage things like laptop adapters and battery chargers over time.
To size it: add up the wattage of everything you'll run at the same time, then add a safety factor of 10–20%. The Coles chose a 700W pure sine inverter — enough to charge both laptops at once, not enough for a microwave. That's the correct way to think: size the inverter to what you actually run, not to "what if I want everything."
Where to Put Everything
Space planning matters more than it seems. Their logic, which is worth copying:
- Put the charger and batteries as close to the main converter as possible — that minimizes current loss and shortens wiring runs.
- Check the space's downsides: their candidate spot was next to the hot water heater and under the sink, so they committed to mounting everything up off the floor, not on it.
- Measure vertical and horizontal clearance (they had a gas line with only ~10 inches to spare) before committing.
- Add a fan — electronics are heat-sensitive, and a small fan in an enclosed space keeps everything alive much longer.
Bench-Test Before You Install (This Is the Pro Move)
The best habit in the video: they set up every component on a desk before installing it in the trailer. Activate the batteries, check voltage with a multimeter (13.29V — alive), test the inverter (hair clippers, naturally), and verify the charger actually charges.
That bench test caught a real problem: the charger wouldn't start charging — because the alternator threshold is at least 13.2V, and their little test charger only put out 12.6V. Swapping to an adjustable AC adapter set to 13.5V got the batteries charging immediately. Found on the desk, that's a five-minute fix. Found in the trailer, that's a frustrating afternoon ripping out wiring.
The final checklist before install: turn off AC power, make sure the trailer is completely unplugged, and disconnect all 12V power at the battery disconnect.
Bottom Line: The Beginner's Parts Checklist
- Batteries with BMS — sized by your load list, activated out of shelf mode.
- A lithium-compatible charger — DC-DC charger with MPPT if you want shore + solar + alternator in one box.
- A battery monitor with shunt — because lithium voltage lies.
- Fuses, correctly sized wire, and a cut-off switch — the safety layer.
- A pure sine wave inverter — sized to your actual simultaneous load plus 10–20%.
- A heated, ventilated, accessible location — off the floor, with a fan.
- A bench test before install — the step that turns a weekend job into an afternoon.
With that list, the conversion goes from "two or three days of careful boondocking" to "a week or longer without thinking about power." Not bad for an afternoon of wiring.
And if you're not hunting for a consumer brand but need the lithium RV battery or the battery core for your own system — a custom LiFePO4 pack at a specific voltage and capacity, an OEM or ODM project, or wholesale supply for your own battery line — that's what we do. Dajiu Energy is a Chinese manufacturer building LiFePO4 batteries for RVs, homes, golf carts and portable applications since 2017. Our product range covers LiFePO4 drop-in replacement batteries, EV and golf cart batteries, wall-mounted home storage, portable power stations, commercial energy storage and battery swap cabinets — explore the full lineup in our product center, or browse more buying guides. Tell us your voltage, capacity and size, and we'll engineer the pack to hit it.
What Our Readers Asked (Top Comments on the Video)
These are the most-liked comments on the source video, with our practical answers. The original creators did not reply to most of these threads, so the answers below are ours — written the way we'd answer a customer on the shop floor.
Source video: Camping with the Coles — "RV Lithium Battery Upgrade / Conversion for Newbies! | Renogy LiFePO4" (youtube.com/watch?v=zdyN71u7U_c). Comment excerpts are quoted verbatim from the video's top comments; the original creators did not reply to most of these threads, so all answers are Dajiu Energy's own.