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.
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%.
Worked Example
Given: Refrigerator (150W × 8h), Lights (100W × 6h), Devices (60W × 4h), 12V LFP, 3 days
Step 1: Calculate daily consumption:
Step 2: Calculate total energy for trip:
Step 3: Account for DoD and convert to Ah:
Result: A 12V 640 Ah LFP battery bank provides 7,680 Wh, enough for 3 days of boondocking with these loads.
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.
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.
References & Further Reading
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