Swapping an RV’s lead-acid house batteries for LiFePO4 is one of the most popular upgrades among RV owners, and the batteries themselves are only part of the job: the converter, alternator charging, solar controller and battery monitor all need to match lithium’s charging profile. A typical 12V 100Ah LiFePO4 battery, such as LiTime’s Group 31 model, is rated by its maker for 4,000+ cycles at 100% depth of discharge, compared with a few hundred cycles for typical AGM batteries, according to LiTime’s Amazon listing. This guide lists what a complete RV lithium conversion kit includes, why each part matters, and how to plan the swap.
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I’ve charged and tested LiTime batteries on this site, including in my LiTime 20A lithium charger review. Battery specs below come from the LiTime 12V 100Ah Group 31 LiFePO4 listing; system math is labeled as estimates. Always check your RV’s manuals and use a qualified technician if you’re unsure.
The complete conversion checklist
| Component | Required? | Why |
|---|---|---|
| LiFePO4 batteries with built-in BMS | Yes | The core of the upgrade |
| Lithium-compatible converter/charger | Usually | Older converters may not reach lithium’s 14.2–14.6V charge voltage |
| DC-DC charger for alternator charging | Recommended | Limits current from the alternator and supplies the right voltage |
| Solar charge controller with lithium profile | If you have solar | Correct absorption and float settings |
| Shunt battery monitor | Strongly recommended | Voltage alone can’t show LiFePO4 state of charge accurately |
| Main fuse sized for lithium | Yes | Lithium can deliver very high short-circuit current |
| Cables sized for the inverter load | Check | Bigger loads need heavier cable |
| Battery disconnect | Usually already present | Storage and service |
| Low-temperature protection or heated batteries | Cold climates | LiFePO4 shouldn’t be charged below freezing |
1. Choosing the batteries
Most RV conversions use 12V 100Ah to 300Ah LiFePO4 batteries in parallel. LiTime’s 12V 100Ah Group 31 battery, for example, lists:
- 4,000+ cycles at 100% depth of discharge, and a 10-year design life
- Low-temperature cutoff: stops charging below 32°F and discharging below -4°F
- Expandable up to 4 in series and 4 in parallel (4P4S)
- A 5-year warranty
Sizing worked example (estimate)
Two 100Ah lead-acid batteries give about 100Ah usable if you stop at 50% to protect them. Two 100Ah LiFePO4 batteries give close to 200Ah usable. If your daily use is a 12V fridge (4A average × 24h = 96Ah), lights and water pump (20Ah) and phone and laptop charging (15Ah), that’s about 131Ah a day. A 200Ah lithium bank covers it with margin; a 300Ah bank gives you a second cloudy day.
2. The converter: the part most people forget
Your RV’s converter charges the house battery from shore power or a generator. Many older units charge at lead-acid voltages that are too low to fully charge LiFePO4, and some lack a lithium mode. Options:
- Replace it with a lithium-compatible converter that offers a 14.4–14.6V profile.
- Swap the charging section on converters that accept a lithium drop-in module.
- Upgrade to an inverter/charger if you also want 120V power from the batteries. My guide to replacing an RV converter with Victron walks through that path.
3. Alternator charging
Lithium batteries accept current much faster than lead-acid and can pull more than a stock alternator wants to supply on a long drive. A DC-DC charger sits between the starter battery and house bank, limits current (20–50A is common) and provides a proper lithium charge profile. My Victron Orion XS installation guide shows a typical setup.
4. Solar controller settings
If your RV has solar, set the controller to a lithium or user profile. Typical LiFePO4 values from battery makers like LiTime are an absorption voltage around 14.2–14.6V and a float around 13.5–13.8V, with equalization turned off. Check your battery’s manual for exact numbers.
| Setting | Typical 12V LiFePO4 value | Lead-acid comparison |
|---|---|---|
| Absorption / bulk | 14.2–14.6V | 14.4–14.8V (varies by type) |
| Float | 13.5–13.8V or off | 13.2–13.6V |
| Equalize | Off | Periodic on flooded batteries |
| Temperature compensation | Off | On |
5. Add a battery monitor
LiFePO4 voltage stays nearly flat from about 90% to 20%, so the RV’s built-in voltage-based gauge will be misleading. A shunt monitor counts amps in and out for an accurate percentage. See my Victron SmartShunt review for one popular option.
6. Fusing and cables
Lithium banks can deliver very high short-circuit current, so place a properly rated main fuse close to the battery positive. Many builders use a Class T fuse for larger banks. If you’re adding a large inverter, check that cable gauge matches the current. My guide to what size fuse you need covers the math.
Inverter current example (estimate)
A 2,000W inverter at full load on a 12V bank draws about 2,000W ÷ 12V ÷ 0.9 efficiency ≈ 185A. That calls for heavy cable (often 2/0 AWG or larger over short runs) and a fuse sized accordingly.
7. Cold weather
LiFePO4 must not be charged below freezing. Batteries with low-temperature charge cutoff, like LiTime’s, protect themselves automatically, but they won’t charge until warmed. If you camp in winter, mount batteries inside the heated space or choose self-heating models.
Step-by-step swap plan
- Turn off shore power, solar and the inverter; open the battery disconnect.
- Photograph and label existing wiring.
- Remove the lead-acid batteries.
- Fully charge each lithium battery individually before paralleling them.
- Install and secure the new batteries; connect in parallel with equal-length cables.
- Install the main fuse, shunt and any new charging gear.
- Program the converter, DC-DC charger and solar controller for lithium.
- Reconnect, test each charging source and sync the monitor to 100%.
Shopping list by RV style
| RV style | Lithium bank | Charging upgrades | Extras |
|---|---|---|---|
| Weekend campground use, mostly on shore power | 100–200Ah | Lithium-ready converter | Shunt monitor |
| Occasional boondocking, no big AC loads | 200–300Ah | Converter, 20–30A DC-DC charger, solar controller set to lithium | Shunt monitor, main fuse |
| Full-time or long boondocking with an inverter | 300–400Ah+ | Inverter/charger, 30–50A DC-DC charger, 400W+ of solar | Class T fuse, heavy cables, monitor |
How long will each source take to recharge? (estimate)
Lithium’s big everyday advantage is that it accepts high current almost all the way to full, so charging time is mostly charging current ÷ amp-hours needed. For a 200Ah bank at 50% (100Ah to refill):
| Charging source | Typical current | Time to refill 100Ah (est.) |
|---|---|---|
| 20A DC-DC charger while driving | 20A | ~5 hr of driving |
| 30A DC-DC charger | 30A | ~3.3 hr |
| Lithium-ready converter, 55–60A | ~55A | ~1.8 hr on shore power or generator |
| 400W solar (~25A peak, less in morning and evening) | Varies | About a full sunny day |
Combining sources adds them together. A short drive with a DC-DC charger plus a sunny afternoon on solar usually refills a weekend’s use.
Tips for wiring batteries in parallel
- Charge every battery to full on its own first so they start at the same voltage.
- Use equal-length cables between batteries so each one shares the load evenly.
- Take the main positive and negative from opposite ends of the bank (diagonal connection), or use bus bars, to balance current.
- Use matching batteries of the same brand, model, capacity and age.
FAQ
Can I just drop in lithium batteries and keep everything else?
Many RVers start that way, but the converter and solar controller may undercharge them, and alternator charging can be hard on the alternator. Plan on at least adjusting settings and adding a monitor.
How many lithium batteries do I need for my RV?
Add up daily amp-hours. Most weekend RVers do well with 200Ah; boondockers running inverters often go to 300–400Ah.
Do I need a new converter for lithium?
If yours can’t reach about 14.2–14.6V or lacks a lithium mode, yes.
Are lithium batteries lighter?
Typically about half the weight of equivalent lead-acid, which helps with cargo capacity.
Can I mix lithium and lead-acid batteries?
No. Their charging voltages and behavior differ; replace the whole bank.
Can I charge lithium batteries from my generator?
Yes. The generator powers the RV’s converter, so once the converter has a lithium profile, generator charging works the same as shore power.
Do I need to change my RV’s battery gauge?
The built-in gauge usually reads voltage, which barely changes on LiFePO4 until it’s nearly empty. Leave it in place if you like, but rely on a shunt monitor for the real state of charge.
How long do RV lithium batteries last?
LiTime rates its Group 31 battery for 4,000+ cycles at 100% depth of discharge. A weekend camper who uses about 50 full cycles a year would take decades to reach that, so age and storage usually matter more than cycle count.
Where should the batteries go?
Many owners use the original battery compartment. Lithium batteries don’t vent gas like flooded batteries, so mounting them inside the heated space, where allowed by the battery maker, also helps with winter charging.
Bottom line
A full RV lithium conversion kit is more than batteries: a lithium-ready converter, a DC-DC charger for the alternator, correct solar settings, a shunt monitor and proper fusing. Plan each piece, charge the batteries before paralleling them, and you’ll get the long life, light weight and usable capacity that make lithium worth it.