Upgrading to a Leisure Battery Bank: AGM, Gel & Lithium Explained

What This Is

A battery bank upgrade is one of the most impactful improvements you can make to a motorhome for off-grid camping. This guide explains the options and the correct installation procedure.

Tools & Parts Required

Step-by-Step Instructions

1. 1

   AGM: maintenance-free, 50% usable capacity, good for most use. Gel: similar to AGM, slightly more tolerant of deep discharge. Lithium (LiFePO4): 80–100% usable capacity, 3–5x the cycle life of AGM, much lighter, but requires a lithium-compatible charger and split charge relay. Cost is 3–4x AGM but total lifetime cost is often lower.

2. 2

   List all 12V loads and their current draw. Multiply current (amps) by hours of use to get amp-hours (Ah). Add 20% safety margin. For AGM, double the calculated Ah (50% usable capacity). A typical motorhome uses 40–60Ah per day — a 200Ah AGM bank provides 2 days of use.

3. 3

   For a 12V bank, connect batteries in parallel (positive to positive, negative to negative). Use identical batteries of the same age and capacity. Use equal-length cables between batteries. Minimum cable size: 25mm² for up to 200Ah, 50mm² for larger banks.

4. 4

   Fit a 100A ANL fuse within 300mm of the battery positive terminal on the main supply cable. This is a critical safety device that prevents cable fires in the event of a short circuit. Never omit this fuse.

5. 5

   Install a battery monitor (Victron BMV-712 is the industry standard) with the shunt in the negative cable between the battery and the vehicle's negative distribution point. Configure with your battery bank capacity.

6. 6

   Set your mains charger, solar controller, and split charge relay to the correct voltage profile. AGM: absorption 14.4V, float 13.6V. Gel: absorption 14.1V, float 13.8V. Lithium: absorption 14.6V, float 13.6V. Incorrect charging voltages significantly reduce battery life.

Common Mistakes to Avoid

Safety Warnings

When to Call a Professional