If you're upgrading your motorhome's electrical system, the battery choice is probably the most important decision you'll make. And in 2026, that question almost always comes down to lithium vs AGM.

We fit lithium in everything we install at ASTT. Here's why — and what you should know before making the switch.

Usable capacity: the biggest practical difference

An AGM battery should only be discharged to around 50% of its rated capacity. Discharging deeper shortens its life significantly. So a 100Ah AGM battery gives you roughly 50Ah of usable power.

A lithium LiFePO4 battery can be safely discharged to around 80–90% without damage. A 100Ah lithium battery gives you 80–90Ah of usable power. That means for the same rated capacity, you get nearly double the usable energy from lithium.

In practical terms: one 230Ah lithium battery is roughly equivalent to two large AGM batteries in terms of usable power — but weighs considerably less and takes up less space.

Weight

A typical 100Ah AGM battery weighs around 25–30kg. A comparable lithium battery weighs around 10–13kg. In a motorhome where payload matters, this is significant — especially once you're running 300Ah+ of storage.

Charge speed

Lithium accepts a charge much faster than AGM. It can take high charge rates right up to near-full capacity, whereas AGM slows dramatically in the final 20%. This matters a lot when you're charging from solar or while driving — lithium recovers quickly, AGM can take hours to fully top up.

Lifespan

A quality AGM battery might give you 300–500 full discharge cycles. A quality LiFePO4 lithium battery is typically rated for 2,000–3,000+ cycles. Used daily, a lithium battery should last a decade or more. AGM might need replacing every 2–4 years depending on usage.

The cost question

Lithium costs more upfront — there's no getting around that. But when you factor in longer lifespan, more usable capacity and lower replacement frequency, the long-term cost is often lower than AGM. For serious travellers, the performance difference alone is worth it.

What we fit

At ASTT we use Fogstar Drift Pro and Roamer Smart5 lithium batteries across our package range. Both are proven performers with excellent BMS protection and strong UK support. If you'd like to talk through which battery setup suits your system, get in touch.