VANPOWERCALC

Size Your Leisure Battery

Easily calculate the required 12V battery capacity (Lithium or AGM) for your camper van conversion based on your power consumption.

List your appliances (Fridge, Heater, Lights...) and find out exactly how much Lithium or Gel battery capacity you need to stay off-grid for 24h or more.
⚡ Expert tip
Size battery for 3 days of average consumption, not 1 day of peak consumption. Van life alternates between coasting days (lower use) and heavy days. 3-day autonomy at average consumption provides the right buffer without massively over-sizing the system.

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Comparison table

ProfileUsage/dayLiFePO4 sizeSolar needed
Weekend light400 Wh100Ah100-150W
Standard vanlife800 Wh200Ah200-300W
Digital nomad1,200 Wh300Ah300-400W
Full-timer comfort1,600 Wh400Ah500-600W

About this tool

Campervan Battery Calculator: Size Your Battery Bank Correctly

Sizing your campervan battery bank is the most important calculation in your electrical build. Get it wrong and you spend two years being anxious about power or freezing in the dark when batteries die unexpectedly. This calculator method gives you accurate results.

The Correct Battery Sizing Formula

Ah = (Daily Wh × Days of autonomy) / (Battery voltage × Usable DoD)

Parameter LiFePO4 AGM Notes
Voltage 12V 12V For single battery systems
Usable DoD 80% (0.8) 50% (0.5) LiFePO4 yields 60% more usable energy
Temperature factor 1.0 (above 10°C) 1.2 (below 0°C) AGM loses 30-40% capacity in cold

Example: 1,000Wh/day × 3 days / (12V × 0.8) = 312Ah LiFePO4 Same example with AGM: 1,000Wh × 3 days / (12V × 0.5) = 500Ah AGM

Consumption Profiles and Recommended Battery Size

Profile Daily Wh 1 Day 2 Days 3 Days
Solo minimalist 400-600Wh 42-62Ah 83-125Ah 125-187Ah
Solo standard 600-900Wh 63-94Ah 125-188Ah 188-281Ah
Couple standard 900-1,400Wh 94-146Ah 188-292Ah 281-437Ah
Couple heavy 1,400-2,000Wh 146-208Ah 292-417Ah 437-625Ah

All figures for LiFePO4 at 12V.

Adding a Safety Margin

Always add 20% to your calculated Ah:

  1. To account for battery aging (capacity reduces 15-25% over lifespan)
  2. To ensure BMS never reaches deep discharge protection cutoff accidentally
  3. To handle higher consumption days (extreme heat = fridge working harder)

Final recommendation: Calculated Ah × 1.2 = battery size to purchase.

Self-Discharge and Storage

LiFePO4 self-discharges at just 2-3% per month — negligible. AGM loses 3-10% per month. If storing your campervan for 3+ months, LiFePO4 is dramatically easier to maintain. Store LiFePO4 at 50% charge in a cool location; it will be fine for 12 months.

Expert tip: For couples on extended trips, size your battery for 3 days of autonomy at your average consumption, not for 1 day of maximum consumption. Camping life involves coasting days (less driving, lower usage) and high-demand days. 3-day autonomy smooths this out naturally.

Temperature coefficient for battery sizing: LiFePO4 batteries deliver slightly less usable capacity in cold weather. At 0°C, expect 90% of rated capacity; at -10°C, approximately 80%. For winter campervan use, add 10-20% to your calculated battery capacity. A system sized for 200Ah summer use should be 220-240Ah for reliable winter performance in northern Europe.

Frequently asked questions

How do I calculate what battery size I need for a campervan?▼
Formula: Ah = (Daily Wh x Days autonomy) / (12V x 0.8 for LiFePO4). Example: 1,000Wh/day x 3 days / (12 x 0.8) = 312Ah. Add 20% safety margin: buy 375Ah (or closest available). For AGM, use 0.5 instead of 0.8.
How many days of autonomy should I plan for?▼
3 days is the standard recommendation for UK and Northern European van life. This covers common grey-weather periods without solar production. In Sun Belt climates (Portugal, Spain, Italy), 2 days often suffices.
What temperature affects battery capacity?▼
LiFePO4 capacity is largely stable above 0°C. Below -10°C, capacity reduces 15-25%. AGM is dramatically worse: at -20°C, AGM delivers only 50-60% of rated capacity. LiFePO4 cannot be charged below 0°C — BMS will prevent it.
How do I know when to replace my campervan battery?▼
Replace when battery holds less than 80% of original capacity at full charge. A 200Ah battery delivering only 150Ah is at end of practical life. LiFePO4 typically maintains >80% capacity for 2,000-3,000 cycles. AGM starts declining noticeably after 300-400 cycles.

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