AGM vs Lithium Leisure Batteries: Which Is Right for Your Campervan?

The Number Nobody Tells You About AGM

When you buy a 95Ah AGM battery, you're not buying 95Ah of usable capacity.

AGM batteries should only be discharged to 50% of their rated capacity. Discharge them deeper than that regularly, and you shorten their lifespan significantly — sometimes to the point where you're replacing them within a couple of years rather than five.

When you're comparing an AGM to a lithium battery of equivalent usable capacity, you need to double the AGM's rated Ah to get an honest like-for-like. A 100Ah lithium gives you approximately 80–100Ah of usable capacity. A 95Ah AGM gives you 47.5Ah. To match the lithium on usable capacity, you'd need two AGM batteries wired in parallel.

So When Does AGM Make Sense?

Here's the honest answer: if your power requirement is low, AGM is a perfectly sensible choice — and it'll cost you less upfront.

If you only need 30Ah for a weekend trip, a 95Ah AGM battery is cheaper than a 100Ah lithium and gives you everything you need. You have less usable power on paper, but if you don't need more than 50Ah from the battery, the extra capacity is irrelevant.

AGM makes sense when:

• Your daily power demand is low — under 40Ah per day
• You're doing short weekend trips and don't need more than 50Ah from the battery
• You're building a work van where power is occasional, not constant

When Lithium Is the Right Choice

For anything beyond light occasional use, lithium is the better battery. Not because it's premium for the sake of it — because the numbers work out.

• Usable capacity: A 100Ah lithium gives you 80–100Ah to use. A 100Ah AGM gives you 50Ah. For the same usable capacity, you need half the lithium.
• Weight: Lithium is significantly lighter — relevant if you're fitting two batteries in a van you're also living in.
• Charge acceptance: Lithium charges faster and handles partial states of charge better. With AGM, leaving the battery partially charged regularly degrades it.
• Lifespan: A well-maintained AGM lasts around 5 years if not used heavily. Lithium typically lasts 10+ years. Over that period, you're replacing the AGM twice to the lithium's once.

Total cost over 5 years:

• AGM 95Ah: approximately £175. No replacement within 5 years if well maintained.
• Lithium 100Ah: higher upfront cost, but no replacement needed within 5 years — and you've had twice the usable capacity throughout.

For full-time van life, off-grid weekenders who need serious capacity, or anyone pairing with solar, lithium is the straightforward choice.

The Sizing Mistake That Catches Everyone Out

The most common error on a first build: sizing your battery on the rated Ah without accounting for depth of discharge.

Someone reads that their fridge draws 4Ah per hour, runs it for 12 hours, and decides 50Ah is enough. They buy a 95Ah AGM thinking they have headroom. In reality they have 47.5Ah usable — and with the fridge alone they're flat by morning.

Our Campervan Electrics Guide covers battery sizing in full, or use the System Builder to calculate your exact requirement based on your appliances.

What About Lifespan?

A well-maintained AGM battery — charged correctly, not over-discharged, not left flat — will last around five years in a campervan context if it's not used heavily. Treat it badly and you'll see two to three years.

Lithium, under the same conditions, typically lasts ten years or more.

If you're replacing an AGM every five years at £175 a time, over ten years that's £350 and two battery change-outs. The lithium costs more upfront but over the same period often works out comparable — with better performance throughout.

The Honest Summary

Both have a place. The right answer is the one that matches your actual power requirement — not the one that costs less on the product page.

Related: Campervan Electrics Guide  ·  Starter Packs  ·  Pre-Wired Power Boards