Switching an RV to lithium (LiFePO4) batteries often goes hand in hand with a new inverter charger, because the unit that charges the batteries from shore power also has to match lithium’s voltage needs. Two widely installed 12V, 3kW-class options show what to look for. Victron’s datasheet for the MultiPlus-II 2x120V 12/3000 lists 2,400W continuous at 25°C, a 120A charger and a 50A-per-leg transfer switch. Xantrex’s Freedom XC PRO 3000 datasheet lists 3,000W continuous at 40°C and a 150A charger. This guide covers the lithium settings that matter, how to size the inverter, the charger and the battery bank together, and worked recharge and shore-power math.
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The models referenced here are the Victron MultiPlus-II 2x120V (on Amazon) and the Xantrex Freedom XC PRO 3000 (on Amazon). Specs come from each maker’s datasheet and manual. Sizing figures are my estimates, worked out step by step below.
Electrical safety: this is general information, not electrical advice. AC wiring between shore power and an RV panel is regulated by code, and DC battery circuits can deliver enough current to start fires. Follow the manufacturer’s manual and have a qualified technician install or inspect the work.
What makes an inverter charger “lithium-ready”
| Feature | Why it matters for LiFePO4 | What to look for |
|---|---|---|
| Adjustable absorption voltage | LiFePO4 makers specify a narrow charge voltage | User-set voltage covering about 14.2–14.6V on 12V systems |
| Float control | LiFePO4 doesn’t need a high float | Float you can set low (around 13.5V) or skip |
| Equalization off | Equalize is a lead-acid process | Ability to disable it entirely |
| Temperature compensation off | Lead-acid compensation raises voltage in the cold | Option to disable, or a lithium preset that does |
| Charge current limit | Keeps charging within the battery’s recommended rate | Adjustable maximum charge amps |
| Recovery from a BMS shutdown | A lithium battery can disconnect itself at low voltage | Charging that starts on a 0V or disconnected battery (Xantrex lists 0V charging) |
| Communication | Lets the battery steer charging | Network support (Victron VE.Bus/GX; Xantrex RV-C, NMEA 2000, J1939) |
Two common 3kW-class choices
| Spec (datasheet) | Victron MultiPlus-II 2x120V 12/3000 | Xantrex Freedom XC PRO 3000 |
|---|---|---|
| Continuous output | 2,400W at 25°C; 2,200W at 40°C | 3,000W at 40°C |
| Surge | 5,500W peak | 6,000W for up to 5 s |
| Max charge current | 120A | 150A |
| AC pass-through | 50A per leg, 120/240V split-phase or 120V input | 40A continuous, 50A surge relay |
| Transfer time | Under 18 ms on L1, about 40 ms on L2 | See the owner’s guide |
| Idle draw | 15W (4W search mode) | Not stated on datasheet |
| Shore assist | PowerAssist on L1 | Not a listed feature |
| Recommended DC fuse and cable | 400A; 2 × AWG 1/0 under 5 m | 350A max; 4/0 AWG under 5 ft |
For lithium owners, the practical takeaways are that the Xantrex charges harder and accepts a 0V battery, while the Victron draws less at idle and can assist a weak pedestal. My Victron vs Xantrex comparison covers the rest.
Step 1: size the inverter from your RV loads
List what you want to run at the same time on battery. Typical figures (estimates; check your appliance labels):
| Load | Typical draw |
|---|---|
| Microwave (1,000W cooking power) | About 1,500W from the outlet |
| Coffee maker | About 900–1,200W |
| Residential refrigerator | About 150W running, higher at compressor start |
| TV and streaming box | About 100W |
| Laptop and phone charging | About 100W |
| 13,500 BTU rooftop AC | Often 1,300W+ running, with a large startup surge |
Example: microwave + fridge + TV = about 1,750W. Add about 25% headroom and you get roughly 2,200W, which fits a 2,400W-class or 3,000W unit. Running a rooftop AC on battery is a separate project; see my guide on running an RV AC from a MultiPlus.
Step 2: make sure the battery bank can supply it
At 12V, high wattage means very high DC current. Battery current ≈ AC watts ÷ (12V × about 90% efficiency):
| AC load | DC current at 12V (estimate) | 12V 100Ah batteries needed at 100A BMS each |
|---|---|---|
| 1,000W | About 93A | 1 (at its limit), 2 for headroom |
| 2,000W | About 185A | 2 |
| 2,400W | About 222A | 3 |
| 3,000W | About 278A | 3 |
Many 12V 100Ah LiFePO4 batteries list a 100A continuous BMS limit; LiTime and Redodo both do for their 100Ah models. So a 3kW inverter at full output needs about three in parallel. My 100Ah battery runtime guide shows how far each battery goes.
Step 3: match the charger to the bank
A powerful charger is only useful if the batteries can accept it. LiTime and Redodo list 20A as the recommended everyday charge current for each 100Ah battery, with a higher maximum. Here’s how the two chargers compare against common bank sizes:
| Bank | Recommended total (20A per 100Ah) | Victron 120A | Xantrex 150A |
|---|---|---|---|
| 200Ah (2 × 100Ah) | 40A | Set the limit near 40A for everyday use | Set the limit near 40A |
| 300Ah (3 × 100Ah) | 60A | Set near 60A; higher only within battery max | Set near 60A |
| 600Ah (6 × 100Ah) | 120A | Full output fits | Set near 120A |
Recharge time from shore power (estimate)
For a 300Ah bank from 20% to full (240Ah): hours ≈ Ah needed ÷ charge amps, plus a short finishing stage.
- At the recommended 60A: about 4 hours.
- At 120A (only if the battery maker allows it): about 2 hours.
- At 150A: about 1.6 hours.
Step 4: check your shore power and generator
The charger draws from the same pedestal or generator as the rest of the RV. A 120A charger at 14.4V delivers about 1,730W DC, roughly 1,900W from the AC side at about 90% efficiency, or about 16A at 120V. On a 30A pedestal, that leaves around 14A for everything else.
| Source | Available (approx.) | Charger at 120A (about 16A) | Tip |
|---|---|---|---|
| 30A pedestal | 30A at 120V | Leaves about 14A | Set the input current limit to protect the breaker |
| 50A pedestal | 50A per leg | Plenty of headroom | Charge at full rate within battery limits |
| 2,200W inverter generator | About 15A continuous | Would overload it | Lower the input limit or charge current |
Victron’s PowerAssist adds battery power on the L1 input when a weak pedestal or small generator can’t keep up. Combined with an input current limit, that lets a small generator handle peaks.
Step 5: program the lithium profile
- Get the battery maker’s numbers: absorption voltage, float (if any), maximum and recommended charge current, and low-temperature charge limits. LiTime, for example, specifies 14.4V ± 0.2V for its 12V 100Ah.
- Set absorption to that voltage and keep absorption time short.
- Set float low, around 13.5V, or the lowest your unit allows.
- Disable equalization and temperature compensation.
- Set the charge current limit to the battery’s recommended total.
- Set the input current limit to match your usual pedestal or generator.
- Verify with a meter or shunt during the first charge: check the voltage at the battery and current into the bank.
Victron units are programmed through VictronConnect or VEConfigure. My MultiPlus-II programming guide covers the steps.
Don’t forget the rest of the system
- Fuse and cable: follow the manual. Victron lists a 400A fuse with 2 × 1/0 AWG under 5 m; Xantrex lists 350A max with 4/0 AWG under 5 ft.
- Old converter: an inverter charger usually replaces the converter’s charging role. Make sure the old converter isn’t also charging the lithium bank with a lead-acid profile.
- Alternator charging: a DC-DC charger protects the alternator from lithium’s high charge acceptance.
- Neutral-ground bonding and GFCI: inverters switch neutral bonding in inverter mode. My RV GFCI and bonding guide explains why that matters.
FAQ
Do I need a new inverter charger when switching to lithium?
Not always. If your current unit lets you set absorption voltage, set float low and disable equalization and temperature compensation, it may work. Fixed lead-acid profiles are the main reason owners upgrade.
What size inverter charger do I need for my RV?
Add up the loads you’ll run at once and include about 25% headroom. A microwave, fridge and TV together land around 2,200W, which suits a 2,400W–3,000W unit.
Can a 120A charger hurt a 200Ah lithium bank?
It can exceed the batteries’ recommended rate. Set the charge current limit to the battery maker’s recommendation, about 40A for two typical 100Ah batteries.
Will the inverter run my 240V appliances?
Not the Victron 2x120V on battery. In inverter mode its output is 120V on both legs, and 240V loads only run on split-phase shore or generator power.
How many batteries does a 3,000W inverter need?
About 278A at 12V at full output, so three 100Ah batteries with 100A BMS limits in parallel. More capacity adds runtime and headroom.
Will the charger trip my 30A pedestal?
It can, combined with other loads. Use the input current limit setting, and on Victron units PowerAssist, to stay under the breaker.
What about charging below freezing?
Standard LiFePO4 batteries shouldn’t be charged below about 32°F. Use batteries with low-temperature protection or self-heating, or keep the bank inside the heated space.
Bottom line
A lithium-friendly RV inverter charger lets you set the charge voltage and current, disable lead-acid features, and fit your shore power. Size the inverter from your loads, the battery bank from the DC current, and the charger from the batteries’ recommended rate. The Victron MultiPlus-II 2x120V and the Xantrex Freedom XC PRO 3000 are two well-documented examples that cover most coaches.