The AGM vs lithium battery decision is the most expensive choice you'll make in a campervan build. Lithium (LiFePO4) costs 3-4x more upfront but lasts 4-5x longer. AGM is cheaper now but you'll replace it sooner.
This guide compares real UK prices, total cost of ownership over 10 years, and whether lithium is worth the premium for different use cases.
The Basics
| Feature | AGM (Lead-Acid) | LiFePO4 (Lithium) |
|---|---|---|
| Usable capacity | 50% of rated | 80-100% of rated |
| Cycle life | 300-500 cycles | 2,000-5,000 cycles |
| Weight (100Ah) | 25-30kg | 10-13kg |
| Charge efficiency | 80-85% | 95-99% |
| Self-discharge | 5-10% per month | 1-3% per month |
| Charging voltage | 14.4-14.8V | 14.2-14.6V |
| Discharge voltage | 10.5V cutoff | 10.0V cutoff (BMS) |
| Operating temp | -20°C to 50°C | 0°C to 45°C (charging) |
| BMS required | No | Yes (built-in) |
Real UK Prices (2026)
AGM Batteries
| Capacity | Brand | Typical Price | Actual Usable (50%) | Cost per usable Ah |
|---|---|---|---|---|
| 100Ah | Numax XV31MF | £90-120 | 50Ah | £1.80-2.40/Ah |
| 110Ah | Varta LFD90 | £130-160 | 55Ah | £2.36-2.91/Ah |
| 120Ah | Odyssey PC1200 | £200-250 | 60Ah | £3.33-4.17/Ah |
| 150Ah | Banner Running Bull | £160-200 | 75Ah | £2.13-2.67/Ah |
| 200Ah | Numax DC200 | £180-230 | 100Ah | £1.80-2.30/Ah |
Suppliers: Tayna Batteries (best prices), Halfords (expensive), Euro Car Parts (variable), Amazon UK.
LiFePO4 Batteries
| Capacity | Brand | Typical Price | Actual Usable (100%) | Cost per usable Ah |
|---|---|---|---|---|
| 100Ah | Fogstar Energy (UK) | £300-380 | 100Ah | £3.00-3.80/Ah |
| 105Ah | Renogy (import) | £400-500 | 105Ah | £3.81-4.76/Ah |
| 100Ah | LiTime (Amazon UK) | £280-350 | 100Ah | £2.80-3.50/Ah |
| 200Ah | Fogstar Energy (UK) | £550-650 | 200Ah | £2.75-3.25/Ah |
| 230Ah | Renogy (import) | £800-950 | 230Ah | £3.48-4.13/Ah |
| 300Ah | Fogstar Energy (UK) | £750-900 | 300Ah | £2.50-3.00/Ah |
UK suppliers with stock: Fogstar Energy (Coventry-based, best UK option), Sunstore Solar, Bimble Solar, Amazon UK.
10-Year Cost of Ownership
This is the real comparison. Over 10 years, you'll replace AGM batteries 3-5 times. You'll replace LiFePO4 zero or one time.
Scenario 1: 100Ah System (Weekender, Low Usage)
| Cost | AGM | LiFePO4 |
|---|---|---|
| Initial battery | £110 (Numax 100Ah) | £340 (Fogstar 100Ah) |
| Replacements over 10yr | 3 (year 3, 5, 7) = £330 | 0 |
| Total battery cost | £440 | £340 |
| Additional solar needed | +50W (lower efficiency) | 0 |
| 10-year total | £490 | £340 |
Winner: LiFePO4 by £150 over 10 years.
Scenario 2: 200Ah System (Full-Time, Fridge + Devices)
| Cost | AGM | LiFePO4 |
|---|---|---|
| Initial battery | £410 (2x Numax 200Ah) | £600 (Fogstar 200Ah) |
| Replacements over 10yr | 3 (years 3, 5, 7) = £1,230 | 0 |
| Additional solar needed | +100W (poorer winter charging) | 0 |
| 10-year total | £1,720 | £600 |
Winner: LiFePO4 by £1,120 over 10 years.
Scenario 3: 300Ah System (Heavy Use, Electric Cooking)
| Cost | AGM | LiFePO4 |
|---|---|---|
| Initial battery | £600 (3x Numax 200Ah) | £820 (Fogstar 300Ah) |
| Replacements over 10yr | 3 = £1,800 | 0 (may need replacement at year 8-10) |
| Additional weight | 75kg | 30kg |
| 10-year total | £2,400 | £820 |
Winner: LiFePO4 by £1,580 over 10 years.
Verdict: Over 10 years, LiFePO4 is cheaper in every scenario. The upfront premium is repaid within 3-5 years even for light users.
When to Choose AGM
Despite the maths, AGM still makes sense in specific situations:
-
Budget constraint — if you can't afford £300+ for a single battery and need power now, a £110 AGM gets you running today. Upgrade to lithium next year.
-
Winter storage — if your van sits unused for 3-4 months over winter (no solar, no maintenance charging), AGM handles storage better. LiFePO4 needs to be stored at 50% charge and above 0°C.
-
Extreme cold — if you regularly van life in sub-zero conditions (Scottish Highlands, Norwegian winters), AGM is more forgiving. LiFePO4 cannot be charged below 0°C without a heated BMS (£50-100 extra).
-
Engine starting — AGM is better for starter batteries. LiFePO4's high instantaneous current can trip its BMS during engine cranking. Use AGM for your starter, LiFePO4 for your leisure.
When to Choose LiFePO4
-
Full-time van life — the maths is overwhelming. Lithium saves you money within 3 years.
-
Limited roof space for solar — lithium's higher charge efficiency (95% vs 80%) means you get 15-20% more power into the battery from the same solar panel.
-
Weight matters — 30kg vs 90kg for a 300Ah system. That's a lot of payload saved.
-
You use solar — the faster charging acceptance of LiFePO4 captures more solar energy in the limited daylight hours (especially in UK winter).
-
Fogstar has a sale — Fogstar Energy's prices have been dropping. A 100Ah Fogstar at £299 is the best value in UK campervan batteries right now.
Installation Differences
AGM
- Simple: positive to positive, negative to negative
- Can use a basic PWM solar controller (though MPPT is better)
- No BMS — charge directly from alternator, solar, or mains
- Heavier cabling recommended (lower voltage under load means higher current)
- Must not be discharged below 50% — you need a battery monitor (Victron BMV-712, £120)
LiFePO4
- Same wiring as AGM (both 12V nominal)
- MUST use an MPPT solar controller with a lithium profile
- Most LiFePO4 batteries have a built-in BMS that handles low-voltage cutout
- Some alternators need a DC-DC charger (£80-150) because the BMS can confuse a standard alternator regulator
- The BMS may disconnect if charging at freezing temperatures — check the spec before buying
UK Supplier Recommendations
| Battery | Price | Best For | Supplier |
|---|---|---|---|
| Fogstar Energy 100Ah | £299-380 | Best value LiFePO4 | Fogstar Energy (UK stock) |
| Fogstar Energy 200Ah | £550-650 | Full-time van life | Fogstar Energy (UK stock) |
| LiTime 100Ah | £280-350 | Budget LiFePO4 | Amazon UK |
| Numax XV31MF 100Ah | £95-120 | Budget AGM | Tayna Batteries |
| Varta LFD90 110Ah | £130-160 | Reliable AGM | Tayna Batteries |
| Odyssey PC1200 120Ah | £200-250 | Premium AGM | Tayna Batteries |
Fogstar Energy offers a 5-year warranty on their LiFePO4 batteries and has UK-based customer service (Coventry). Their pricing undercuts imported brands. If you're buying lithium for a UK van, start with Fogstar.
