Typical leisure batteries for caravans sit between 100Ah and 200Ah. For small-to-moderate use, a 100–120Ah lead-acid (or AGM) battery is common; for larger rigs or lithium systems, 150–200Ah (or more) is typical.
To pick the right size, estimate energy use, decide on battery chemistry, and account for charging options such as solar, vehicle alternator, and mains hookup. This article explains how to size a caravan battery accurately, with practical guidelines and examples.
Key concepts in caravan battery sizing
Battery capacity is measured in amp-hours (Ah). Usable capacity depends on the chemistry and how deeply you discharge. In caravans, the leisure battery powers 12V appliances when you’re not plugged in, so choosing the right size requires considering your power draw, how often you recharge, and the climate.
Battery types and usable capacity
Lead-acid types (flooded, AGM, GEL) are robust and affordable but typically limit depth of discharge (DoD) to about 50% to prolong life. Lithium (LiFePO4) offers higher usable capacity (often 80–90%) and longer cycle life but at a higher upfront cost. This difference drives how much capacity you effectively get from a given battery bank.
How to calculate the right size
Estimate your daily 12V energy use and plan the number of days between charges. Then pick a battery with enough usable capacity and add a buffer for inefficiencies and aging.
Gather your typical daily device usage to inform the numbers before listing the calculation steps.
- Step 1: List every 12V device you expect to run, note its current draw (amps) and how many hours per day it runs.
- Step 2: For each device, multiply current (A) by hours per day to get Ah, then sum to obtain total daily Ah.
- Step 3: Choose the depth of discharge you’ll use for your battery chemistry (about 50% for lead-acid/AGM, about 80–90% for LiFePO4).
- Step 4: Compute required total battery capacity: daily Ah ÷ usable fraction. Add a 20–50% margin to account for inefficiencies, aging, and higher loads.
Concluding: This method yields a target total Ah for your battery bank. In practice, choose the next standard size up to give you headroom in real-life conditions.
Practical sizing by usage level
Light use with solar assist
For minimal daily needs (LED lighting, phone charging, and occasional 12V fridge use), a 100–120Ah lead-acid (or AGM) bank with a modest solar setup (about 100W) is common. This balances cost with the ability to recharge during a sunny day.
Moderate off-grid living
If you regularly stay off mains and use a more demanding fridge or freezer, consider 150–200Ah. A LiFePO4 bank of 100–200Ah is popular for its high usable capacity and longer life. Pair with 150–300W of solar to maintain daily recharge.
High-demand or full-time off-grid
For heavy power use or extended off-grid living, a 200–400Ah LiFePO4 bank is common, often with 300–600W of solar and an efficient inverter. Note that the upfront cost is higher, but the depth of discharge and long cycle life can justify it for frequent travelers.
Charging options and tips
Charging sources and strategies determine how quickly you can replenish battery capacity between uses. Use a combination of solar, tow vehicle alternator, and mains when available.
- Solar: Install a solar panel array and a modern MPPT charger. Size solar to cover your daily demand and climate; even with lithium, more sun means less downtime.
- Tow vehicle: A battery-to-battery charger or smart split-charge system can replenish some energy while you drive.
- Mains hookup: When connected, use a charger compatible with your battery chemistry to optimize charging rate and battery health.
Concluding: A well-balanced charging setup reduces the likelihood of deep discharges and extends battery life.
Summary
In practice, the right caravan battery size ranges from about 100Ah to 200Ah for typical setups, with larger or lithium-based banks pushing to 200–400Ah for heavy off-grid use. Size is driven by daily energy consumption, desired autonomy, charging capabilities, and budget. Start with a conservative 100–120Ah lead-acid or 100Ah LiFePO4, then adjust as you measure real-world usage and charging performance.