Lithium iron phosphate (LiFePO4) batteries changed full-time RV living. Where AGM batteries required you to stop discharging at 50% and took 8+ hours to recharge, LiFePO4 lets you use 80–90% of capacity and accepts charge at 3–5x the rate. For off-grid full-timers, the upgrade pays for itself within two years in avoided campground fees and generator fuel.
Why LiFePO4 Over AGM
The practical advantages for full-timers:
- Usable capacity: 80–90% vs. 50% for AGM. A 200Ah lithium bank gives you effectively the same usable power as a 300–400Ah AGM bank.
- Charge acceptance: LiFePO4 accepts 0.5–1C charge rates (100A into a 100Ah battery). AGM maxes out at 0.2C safely. This means lithium charges fully in 2–3 hours of good solar vs. 6–8 hours for AGM.
- Cycle life: 2,000–4,000+ cycles vs. 400–600 for AGM. A LiFePO4 battery used daily will last 5–10 years. AGM lasts 1–3 years in full-time service.
- Weight: LiFePO4 is roughly half the weight of equivalent AGM capacity.
How to Size Your Battery Bank
The formula: calculate your daily power consumption in watt-hours (Wh), then size the bank to hold 2 days of consumption at 80% depth of discharge.
Step 1: Calculate daily load. List every 12V and AC appliance you run. Multiply watts × hours of daily use. Sum everything.
Common daily loads for a working full-timer: residential fridge (150 Wh) + laptop (120 Wh) + external monitor (80 Wh) + lighting (30 Wh) + phone/tablet charging (20 Wh) + router/modem (30 Wh) = ~430 Wh/day baseline. Add CPAP (50 Wh), fans (40 Wh) = ~520 Wh/day typical.
Step 2: Size for 2 days reserve. 520 Wh × 2 days = 1,040 Wh needed. At 80% usable: 1,040 ÷ 0.8 = 1,300 Wh total capacity. At 12V, that's ~108 Ah. Round up to 200Ah for headroom. Two 100Ah batteries wired in parallel = 200Ah at 12V.
Battle Born vs. SOK vs. Renogy — 100Ah Comparison
| Feature | Battle Born 100Ah | SOK 100Ah | Renogy Smart 100Ah |
|---|---|---|---|
| Price | ~$950 | ~$499 | ~$650 |
| Cycle life (rated) | 3,000+ | 4,000+ | 2,000+ |
| Warranty | 10 years | 5 years | 5 years |
| Bluetooth BMS app | — | ✓ | ✓ |
| Built-in heat pad (cold weather) | Some models | — | Some models |
| Made in USA | ✓ (Reno, NV) | — | — |
| Max charge current | 50A | 100A | 50A |
| Max discharge current | 100A continuous | 100A continuous | 100A continuous |
| Weight | 31 lbs | 26 lbs | 26 lbs |
| Best for | Premium, long-term reliability | Budget-conscious builds | App monitoring priority |
BMS Explained
Every LiFePO4 battery has a Battery Management System (BMS) — a circuit board that monitors cell voltage, temperature, and current, and disconnects the battery if any parameter goes out of safe range. A good BMS prevents overcharge, over-discharge, and thermal events.
What to check: the BMS's rated continuous discharge current should meet your maximum expected load. If you're running a 2,000W inverter from a 12V system, you need 167A continuous (2,000W ÷ 12V). Most 100Ah batteries handle 100A continuous — two in parallel handles 200A.
Wiring Basics: Series vs. Parallel
Parallel (same voltage, more capacity): Two 12V 100Ah batteries wired positive-to-positive and negative-to-negative = 12V 200Ah. This is the standard configuration for most RV builds.
Series (higher voltage, same capacity): Two 12V 100Ah batteries wired positive-to-negative = 24V 100Ah. Used in larger systems where 24V reduces wire gauge requirements. Requires a 24V-compatible inverter and charge controller.
Wire sizing rule: Always use the correct gauge for your maximum current. For 100A loads at 12V, use 2 AWG minimum. For 200A, use 4/0 AWG or copper busbars. Undersized wire is a fire risk.
Bottom Line
SOK is the value winner — $499 for 100Ah with 4,000-cycle rated life, Bluetooth BMS app, and a 5-year warranty. At half the price of Battle Born with similar real-world performance, the savings buy a second battery. Choose Battle Born if you want US manufacturing and a 10-year warranty. Choose Renogy Smart if you want deep app integration with a Renogy solar system.