Fogstar Battery Sizing Guide: What Ah Size Do You Need? 🔋
From 105Ah to 628Ah, here's how to work out which Fogstar battery capacity actually fits your camper van, self-build or motorhome.
Step 1: List what you're powering
Start with every 12V and inverter-fed appliance you'll run: lighting, fridge, water pump, USB/laptop charging, and anything bigger like a coffee machine or induction hob if you're running those through an inverter. For each one, note its wattage and roughly how many hours a day you'll use it.
Step 2: Work out your daily Wh usage
Multiply each appliance's wattage by its hours of daily use to get watt-hours (Wh), then add them all together. For example, a 40W fridge running 24 hours a day uses roughly 960Wh, while 20W of LED lighting for 4 hours adds another 80Wh. Add up every appliance on your list this way to get your total daily Wh usage.
Step 3: Convert to Ah and size your battery
Divide your total daily Wh by your system voltage (12V for most camper and motorhome setups) to get your daily Ah usage. Because LiFePO4 batteries like Fogstar's Drift range can typically be discharged to around 80 to 100% of their rated capacity, you generally don't need to double your battery size for safety margin the way you would with AGM or lead-acid.
It's still sensible to size up slightly beyond your calculated daily usage, both to allow for a cloudy day or two without charging, and to avoid discharging the battery to its absolute limit on a daily basis, which helps preserve long-term cycle life.
Rough capacity guide by use case
- Occasional weekend trips, light usage (lighting, USB, small fridge) — smaller capacity batteries in the 105Ah to 150Ah range are often enough
- Regular camper van or self-build use, fridge plus general electrics — mid-range capacities around 230Ah to 280Ah tend to suit most builds
- Extended off-grid living, heavier inverter use, multiple appliances — larger capacities from 300Ah upward, or multiple batteries wired in parallel, are worth considering
- Large-scale or commercial off-grid setups — Fogstar's biggest Drift models go up to 628Ah for builds that need serious capacity from a single battery
This is a starting point, not a substitute for doing your own Wh calculation, since every build's power needs are different.
Shop the Fogstar range by size
We've broken our Fogstar range down into Eco Range, Gen1, Gen2 and Pro, plus Accessories, so you can find the right capacity and spec for your build more easily.
Shop the Fogstar range here:
https://sonniesadventures.com/collections/fogstar
New customer? Use code FOGSTAR10 at checkout to save 10% on any Fogstar battery, valid throughout July and August 2026, with free delivery and full authorised dealer warranty included. Once you've picked your capacity, check our current Sonnie's Adventures Fogstar battery offer. Sonnie's Adventures promotion, valid only at sonniesadventures.com — not redeemable at fogstar.co.uk.