RV Battery Calculator
How many amp-hours does your RV battery bank need? Enter your usage and autonomy — get exact Ah with AGM and lithium configurations.
| Battery size | Qty needed | Total Ah |
|---|---|---|
| 100 Ah | 10 | 1000 Ah |
| 200 Ah | 5 | 1000 Ah |
| 230 Ah | 5 | 1150 Ah |
| 280 Ah | 4 | 1120 Ah |
| 300 Ah | 4 | 1200 Ah |
How to Use This Calculator
Enter your daily energy usage
The daily energy usage in watt-hours is the total power your RV or van consumes per day. If you don't know this number, use the RV Solar Calculator or the Electricity Usage Calculator to add up your appliances. A typical minimalist RV uses 500-1,000 Wh/day. A full-timer with AC might use 3,000-5,000 Wh/day.
Set days of autonomy
Days of autonomy is the number of days you need to run solely on battery power, with no solar input. This directly multiplies your battery bank size. For weekend van life, 2 days is typical. Full-timers in cloudy climates often plan for 3-4 days. More autonomy means a heavier, more expensive battery bank — balance it with your travel style.
Choose system voltage and battery type
12V is the default for RVs and vans — it works with the vehicle's existing 12V loads. 24V reduces wire sizing for the same power and suits larger systems. Choose your battery chemistry carefully: LiFePO4 (lithium) allows 80-90% depth of discharge; AGM and flooded lead-acid should be limited to 50% to preserve cycle life and avoid sulfation.
Depth of discharge (DoD)
The DoD is the single biggest factor in how large your battery bank needs to be. At 50% DoD, you need twice the Ah you'd need at 100%. Keeping AGM batteries above 50% state of charge dramatically extends their service life from 300 cycles to 500+. LiFePO4 at 80% DoD is the industry standard — you get nearly twice the usable capacity from the same rated Ah compared to AGM.
The Formula
The C/5 charge rate (20% of capacity per hour) is the standard recommended charge rate for most batteries. Charging at C/5 means a 200Ah bank takes about 5 hours from empty at 40A. LiFePO4 batteries accept faster charging (up to C/2 or C/1 with a proper BMS) but C/5 is a safe default for all chemistries.
Example
Taylor — Full-time RV traveler comparing AGM vs Lithium
Taylor uses 2,000 Wh/day and wants 3 days of autonomy at 12V. They're comparing AGM (50% DoD) vs lithium (80% DoD).
AGM (50% DoD)
Lithium LiFePO4 (80% DoD)
The lithium bank weighs less than a third of the AGM bank and takes up much less space — critical in an RV. Over a 10-year lifetime, the lithium bank will outlast multiple AGM replacements, making the total cost of ownership lower despite higher upfront cost.