RV Battery Calculator
Calculate the battery bank size you need for your RV or camper. Estimate daily consumption and required capacity for your camping trips.
RV Load Profile
Most RVs use 12V. Consider 24V for high-power setups.
Number of days between recharges.
LFP recommended: lightweight and 80% usable DoD.
Sizing Results
System Notes
For 3 days of boondocking with 1,820 Wh daily consumption at 12V LFP, you need a 460 Ah battery bank.
Formulas & Worked Examples
Mathematical Formulas
Daily consumption is the sum of all appliance loads multiplied by their usage hours:
Required capacity accounts for DoD limits and camping duration:
DoD limits: LFP 80%, NMC 80%, Lead-Acid 50%.
Example 1: Weekend Camper — Fridge, Lights, Water Pump
A couple is heading to a state park campground for a weekend trip. They need power for the fridge, LED lights, and a water pump over 2 days without shore power.
Given Values
- Refrigerator: 150W × 8h/day
- LED Lights: 40W × 6h/day
- Water Pump: 60W × 1h/day
- System Voltage: 12V
- Chemistry: LFP (80% DoD)
- Trip Duration: 2 days
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Final Answer
A 12V 350 Ah LFP battery bank (rounded to practical size) provides 4,200 Wh, covering the 3,000 Wh weekend need with a comfortable buffer.
This setup leaves ~30% reserve at the end of day two, accommodating unexpected loads or a late-night fridge cycle. A 350 Ah LFP bank weighs roughly 35 kg—manageable for most truck campers.
Example 2: Full-Time RV Living — Extensive Loads with Solar
A full-time RVer works remotely from a Class C motorhome. The system includes solar charging (400W panel array) that supplements the battery during daylight hours, reducing the required overnight storage.
Given Values
- Refrigerator: 80W × 12h/day (compressor cycles)
- Laptop + Monitors: 200W × 8h/day
- LED Lighting: 60W × 5h/day
- Water Pump: 60W × 1h/day
- Router + Starlink: 75W × 24h/day
- Ventilation Fan: 20W × 10h/day
- Phone/Tablet Charging: 30W × 3h/day
- System Voltage: 12V
- Chemistry: LFP (80% DoD)
- Solar Harvest: ~1,600 Wh/day (400W × 4 peak hours)
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Final Answer
A 12V 750 Ah LFP battery bank provides 9,000 Wh. With 400W of solar replenishing ~1,600 Wh/day, the system achieves near-equilibrium on sunny days.
Full-time living demands a larger bank because remote work makes you power-dependent. The solar array is critical—without it, you'd need 1,100+ Ah. On cloudy days, expect 40–60% solar reduction, so a generator backup is recommended.
Example 3: Boondocking Without Solar — Maximize Autonomy
A boondocker in a truck camper wants 4 days of complete energy independence with no solar, alternator charging, or generator. The goal is to maximize time off-grid before needing to drive to recharge.
Given Values
- 12V Compressor Fridge: 60W × 10h/day (50% duty cycle)
- LED Puck Lights: 20W × 5h/day
- Water Pump: 50W × 0.5h/day
- Device Charging: 40W × 3h/day
- System Voltage: 12V
- Chemistry: LFP (80% DoD)
- Autonomy Target: 4 days
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Final Answer
A 12V 400 Ah LFP battery bank (4,800 Wh) provides 4 full days of power with 1,420 Wh (29.6%) reserve for emergencies.
Without solar or charging, every Wh matters. This setup assumes disciplined usage—no wasteful loads. Consider a small 200W folding solar panel as an emergency backup; even partial sun adds 200–400 Wh/day and extends autonomy to 5–6 days.
RV Power System Architecture
Alternator charging, solar input, and battery storage powering RV loads
RV Battery Chemistry Comparison
| Feature | LiFePO4 | AGM Lead-Acid | Gel Cell |
|---|---|---|---|
| Weight (100Ah) | 12 kg | 30 kg | 28 kg |
| Usable Capacity | 80–90 Ah | 50 Ah | 50 Ah |
| Cycle Life | 5,000+ | 500–1,000 | 1,000 |
| Charge Rate | 0.5–1C | 0.1C | 0.1C |
| Price (100Ah 12V) | $800–1,200 | $200–300 | $250–350 |
| Self-Discharge | 1–3%/month | 3–5%/month | 2–4%/month |
| Maintenance | None | Water check | None |
LFP has higher upfront cost but superior lifecycle economics for RV use
Frequently Asked Questions
How do I calculate my RV appliance loads?
Check the wattage rating on each appliance or multiply amps × volts. Common RV loads: LED lights (10W each), refrigerator (150W when running), laptop (60W), phone charger (10W), water pump (60W), ventilation fan (20W). Multiply each by daily hours of use.
What battery chemistry is best for RV use?
LFP (LiFePO4) is the best choice for RV applications: lightweight, 80% usable DoD, 5,000+ cycle life, and safe for enclosed spaces. AGM lead-acid is a budget option but limited to 50% DoD and heavier. NMC lithium is lighter but more expensive than LFP.
How many camping days should I plan for?
For weekend trips (2–3 days), a moderate battery bank is sufficient. For extended boondocking (5–7 days), you need significantly more capacity or a way to recharge (solar, generator, shore power). Most RVers plan for 2–4 days with recharging capability.
Should I size for 12V or 24V?
Most RVs use 12V systems. If you have high power demands (air conditioning, induction cooking), consider a 24V system with an inverter. 24V systems use thinner wire and have lower current losses for the same power.
How do I account for my RV refrigerator's power consumption?
A propane/electric fridge uses minimal battery power (2–5W for the control board). A 12V compressor fridge (Dometic, Isotherm) draws 40–80W when the compressor runs, cycling 30–50% of the time—so average draw is 20–40W. A residential-style fridge with an inverter draws 100–150W but requires a larger battery bank.
What parasitic draws should I account for?
Even with everything turned off, RVs have phantom loads: CO/smoke detectors (1–2W each), fridge control board (2–5W), water heater pilot (3–5W), stereo memory (1W), and solar charge controller standby (0.5W). These add up to 15–40W continuously—draining 360–960Wh per day even when the RV is parked.
Can I charge my RV battery while driving?
Yes—your vehicle alternator charges the house battery through the RV's charging system or a DC-DC charger. A standard 50A alternator provides ~50Ah per hour of driving. A dedicated DC-DC charger (e.g., Victron Orion) can provide 20–60A of controlled charging, protecting both starter and house batteries.
How does cold weather affect RV batteries?
LFP batteries lose 10–15% capacity below 0°C and should not be charged below -10°C without a battery heater. Lead-acid loses 20–30% capacity at -10°C. For winter camping, insulate your battery compartment and consider a low-temperature charging cutoff. AGM batteries handle cold better than flooded lead-acid.
What is the difference between Class A, B, and C RV battery needs?
Class B vans have limited space (200–400Ah LFP typical). Class C motorhomes support larger banks (400–800Ah). Class A coaches can accommodate 800–1200Ah+ with multiple battery banks. Size matches available storage space and the typical power demands of each RV class.
Do I need a battery monitor for my RV?
Yes—highly recommended. A battery monitor with a shunt (Victron BMV-712, Renogy 500A) provides accurate state-of-charge reading, remaining runtime estimates, and historical usage data. Voltage-based SOC reading is unreliable for lithium batteries due to their flat discharge curve.
How do I reduce my RV power consumption?
Switch to LED lighting throughout (saves 80% vs incandescent). Use a 12V compressor fridge instead of propane/electric. Charge devices from 12V DC directly instead of through an inverter (avoids 10–15% conversion loss). Turn off phantom loads when parked. Use a timer for ventilation fans.
Can I run an air conditioner from RV batteries?
Running a 13,500 BTU RV AC requires ~1,500W continuous (~3,500W startup). A 48V 400Ah LFP bank (19.2 kWh) can run it for 6–8 hours. This requires a high-capacity inverter and significant battery investment. Portable evaporative coolers (200–400W) are a more practical alternative for most RVers.
What Is RV Battery?
Why This Calculation Matters
→ Undersized RV battery banks leave you without refrigeration or lighting by midnight—ending your camping trip early or forcing an emergency generator purchase.
→ Oversized banks consume precious cargo weight and storage space; on a Class B van, every 100Ah of LFP capacity takes up about 30cm × 20cm × 20cm of cabinet space.
→ Ignoring alternator charging limits means driving all day doesn't fully replenish your bank—a 50A alternator needs 4+ hours to recharge 200Ah from 50% DoD.
→ Using lead-acid batteries at 80% DoD repeatedly can reduce cycle life from 500 cycles to under 100—costing more in replacements than an upfront LFP upgrade.
→ Not accounting for parasitic draws (CO detectors, fridge control boards, phantom loads) can drain 20–40Ah overnight even with all appliances turned off.
Practical Applications
Weekend Camping Trips
Size a moderate 200–400Ah LFP bank for 2–3 days of off-grid camping with fridge, lights, and device charging without shore power.
Full-Time Boondocking
Calculate the 600–1000Ah+ bank needed for full-time RV living with high-draw appliances like induction cooking, microwave, and coffee maker.
Solar-Augmented RV Systems
Plan battery capacity to store solar energy harvested during the day for overnight use, reducing reliance on alternator or generator charging.
Van Conversion & Camper Builds
Design compact, weight-efficient battery systems for Class B vans where every kilogram and cubic centimeter matters for payload and handling.
Common Mistakes to Avoid
✗ Ignoring alternator charging limits — a 50A alternator needs 4+ hours to recharge 200Ah from 50% DoD, not the 1 hour many RVers assume.
✗ Sizing for continuous load only and forgetting parasitic draws — CO detectors, fridge control boards, and phantom loads drain 20–40Ah overnight.
✗ Using lead-acid batteries at 80% DoD — this halves cycle life from 500 to under 100 cycles; stay within 50% DoD for lead-acid.
✗ Oversizing the battery bank without checking cargo weight limits — every 100Ah of LFP adds ~12 kg, which matters on Class B vans.
✗ Ignoring temperature derating — LFP loses 10–15% capacity below 0°C and should not be charged below -10°C without a heater.
✗ Undersizing the inverter for high-draw appliances — a microwave or induction cooktop needs 2,000W+ continuous, not just the battery capacity.
✗ Mixing battery chemistries in parallel — lead-acid and lithium have different charge curves and create safety risks when combined.
✗ Not accounting for voltage drop on long wire runs — a 3-meter 12V cable run at 100A can lose 0.5V, reducing effective capacity.
✗ Assuming solar panels fully recharge the bank daily — a 200W panel in 4 peak sun hours produces only 800Wh, not enough for a 2,000Wh daily load.
✗ Forgetting to budget for inverter standby draw — many inverters consume 5–15W continuously, adding 120–360Wh per day.
Why Trust These Calculations?
This calculator applies standard RV electrical design methodology used by Airstream, Winnebago, and custom van builders. Load profiles are based on manufacturer wattage ratings and typical usage patterns from RV industry surveys. All formulas are transparent and independently verifiable.
View our methodology and formula derivations →Runtime Calculator
Verify how long your battery bank will last.
Energy Conversion
Convert between Ah and Wh for your system voltage.
Battery Sizing Calculator
Full battery bank sizing with temperature derating.
Inverter Battery Calculator
Size inverter capacity for AC RV appliances.
Parallel String Calculator
Design custom battery pack configurations.
Voltage Drop Calculator
Ensure cable runs meet RV voltage drop specs.
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