LiFePO4 vs AGM Batteries
LiFePO4: 2,000+ cycles, 100% DoD, £120-500. AGM: 500-1,000 cycles, 50% DoD, £100-200.
LiFePO4 costs 2× upfront but lasts 4× longer and delivers 2× usable power.
Weight Comparison
LiFePO4 100Ah: ~10-12kg AGM 100Ah: ~25-30kg
LiFePO4 is nearly half the weight — critical for van conversion where every kilogram matters.
Cycle Life
LiFePO4: 3000-5000 cycles (80% DoD) AGM: 500-1000 cycles (50% DoD)
LiFePO4 lasts 5-10x longer. Over a 10-year van life period, you only need 1-2 LiFePO4 batteries vs 5-10 AGM replacements.
Depth of Discharge
LiFePO4: 80-100% usable capacity AGM: 50% usable capacity
A 100Ah LiFePO4 gives you 80-100Ah usable. A 100Ah AGM gives you only 50Ah usable. Real-world advantage is 2x.
Price Over Time
LiFePO4 100Ah: £300-500 AGM 100Ah: £100-200 LiFePO4 costs 2-3x more upfront but lasts 5-10x longer = better long-term value.
LiFePO4 (Lithium Iron Phosphate)
LiFePO4 batteries have become the gold standard for UK van lifers willing to invest upfront. A typical 100Ah LiFePO4 battery costs £300-500 on Amazon UK.
Key advantages:
- 2,500-5,000 charge cycles at 80% depth of discharge — far exceeding AGM
- True 100% usable capacity — you can safely drain 90-100% (vs 50% for AGM)
- Lightweight — 100Ah LiFePO4 weighs ~11kg vs ~30kg for AGM equivalent
- Fast charging — accepts up to 0.5C charge rate (50A for a 100Ah battery)
- Built-in BMS — protection against overcharge, over-discharge, short circuit
- Consistent voltage — maintains ~12.8V through most of the discharge cycle
Cons:
- Higher upfront cost — 2-3x more than AGM per unit
- Cold weather performance — charging below 0°C requires a BMS with heating element
- Inverter compatibility — some older inverters don't like the flatter discharge curve
AGM (Absorbed Glass Mat)
AGM batteries remain popular for budget builds. A 100Ah AGM costs £120-200 in the UK.
Key advantages:
- Cheap upfront — less than half the price of LiFePO4
- Proven technology — AGM has been used in cars and vans for decades
- No BMS needed — simple plug-and-install
- Cold weather — performs well in UK winters down to -20°C
- Wide availability — Halfords, Amazon, all car parts shops
Cons:
- Only 50% usable capacity — a 100Ah AGM gives you effectively 50Ah
- 500-1,000 cycles — 5-10x fewer cycles than LiFePO4
- Heavy — 30kg for 100Ah means you need a good floor structure
- Slower charging — limited to 0.2C (20A for 100Ah)
Head-to-Head: 100Ah Comparison
| Metric | LiFePO4 100Ah | AGM 100Ah |
|---|---|---|
| Price (UK) | £300-500 | £120-200 |
| Usable Capacity | 90-100Ah | 50Ah |
| Cycles (to 80%) | 2,500-5,000 | 500-1,000 |
| Weight | ~11kg | ~30kg |
| Max Discharge | 90-100% | 50% |
| Charging Speed | 50A (fast) | 20A (moderate) |
| Lifespan | 7-10 years | 3-5 years |
| Cost per Ah (lifetime) | £3-5 | £4-8 |
The Cost Per Ah Reality Check
Most people pick AGM because it's cheaper upfront. But let's do the math for UK van life:
A LiFePO4 battery at £400 gives you 90 usable Ah for 3,000 cycles = £0.015 per Ah per cycle
An AGM battery at £150 gives you 50 usable Ah for 800 cycles = £0.023 per Ah per cycle
Over the lifespan of one LiFePO4 (3,000 cycles), you'd need ~3x AGM batteries = £450 for AGM vs £400 for LiFePO4, with half the usable capacity the whole time.
LiFePO4 is actually cheaper over the long run — and lighter too.
Best For UK Van Life
Get LiFePO4 if: You're full-time or do more than 2 weeks per trip. The double usable capacity and longer lifespan make it the clear winner for anyone who isn't living on a tight budget.
Get AGM if: You're on a strict budget, doing short trips (under 1 week), or need maximum cold-weather performance without a heated BMS.
FAQ
Can I mix LiFePO4 and AGM in the same bank? No — different discharge curves will cause issues. Stick with one chemistry.
Do LiFePO4 batteries work in UK winters? Most modern BMS units include auto-heating that kicks in below 0°C. For UK winters, a LiFePO4 with heating is the sweet spot.
AGM (Absorbed Glass Mat)
AGM batteries remain popular for budget builds. A 100Ah AGM costs £120-200 in the UK.
The Cost Per Ah Reality Check
Most people pick AGM because it's cheaper upfront. But let's do the math for UK van life:
A LiFePO4 battery at £400 gives you 90 usable Ah for 3,000 cycles = £0.015 per Ah per cycle
An AGM battery at £150 gives you 50 usable Ah for 800 cycles = £0.023 per Ah per cycle
LiFePO4 is actually cheaper over the long run — and lighter too.
