LiFePO4 vs AGM Leisure Battery: In-Depth Comparison
LiFePO4 vs AGM is the most common battery decision in campervan builds. Both work — but they are different technologies with very different cost profiles over time. Here is the full comparison.
The headline numbers
| Specification | AGM 100Ah | LiFePO4 100Ah |
|---|---|---|
| Usable capacity (safe DoD) | 50Ah (50% DoD) | 90Ah (90% DoD) |
| Cycle life (to 80% capacity) | 400–600 cycles | 3,000–5,000 cycles |
| Weight | 26–30kg | 10–14kg |
| Charge rate | 0.2C (20A for 100Ah) | 0.5–1C (50–100A for 100Ah) |
| Operating temperature (charge) | -20°C to 50°C | 0°C to 45°C (BMS blocks cold charging) |
| Self-discharge | 3–5% per month | 1–2% per month |
| Maintenance | Occasional equalisation | None |
| UK price (100Ah) | £80–160 | £200–500 |
Usable capacity: the most misunderstood comparison
When someone says "100Ah AGM vs 100Ah LiFePO4," the label understates the difference.
An AGM battery should only be discharged to 50% — running it below 50% (below ~12.2V) dramatically reduces its cycle life. So a "100Ah" AGM gives you 50Ah usable.
A LiFePO4 battery can safely discharge to 80–90%. A "100Ah" LiFePO4 gives you 90Ah usable.
To match the usable capacity of one 100Ah LiFePO4, you need two 100Ah AGM batteries. When priced on usable capacity, AGM is often more expensive than it first appears.
Cycle life: the long-term cost difference
This is where LiFePO4 pays for itself.
AGM at 50% DoD: 400–600 cycles before capacity drops to 80%. At 1 cycle per day (typical van life use), this is 1–1.5 years before replacement.
LiFePO4 at 80% DoD: 3,000–5,000 cycles. At 1 cycle per day, this is 8–14 years before replacement.
Real cost over 5 years (100Ah usable):
- AGM: 2× 100Ah =
£300, replaced 3× over 5 years = **£900 total** - LiFePO4: 1× 100Ah = ~£350, not replaced = £350 total
Over 5 years, LiFePO4 is typically cheaper than AGM when replacement costs are included.
Weight: significant for a moving vehicle
A 200Ah AGM bank (two 100Ah batteries) weighs approximately 55–60kg. The equivalent 200Ah LiFePO4 bank weighs 20–25kg. Saving 30–35kg improves payload, fuel economy, and handling — meaningful for a van living vehicle.
Charging speed: faster solar and alternator recovery
LiFePO4 accepts charge at up to 1C (100A for a 100Ah battery). AGM should not be charged above 0.2C (20A for 100Ah) to maximise cycle life.
In practice, this means:
- A 200W solar array can charge a LiFePO4 at its full output
- The same array is wasted on AGM because the battery cannot accept it fast enough
- LiFePO4 can be recovered from empty to full in 1–2 hours with a large charge source; AGM takes 4–8 hours
When AGM makes sense
Low budget, short term: If you are building a van for 6–12 months and want to minimise upfront cost, AGM is the lower-risk investment.
Infrequent use: A van used for occasional weekend trips that sits stored most of the year — AGM on a maintenance charger works fine and the cycle life is less relevant.
Existing system: If you already have a well-functioning AGM setup that is not yet worn out, there is no need to replace it for the sake of it. Run it until it needs replacement, then switch to LiFePO4.
When LiFePO4 is clearly better
- Full-time van life (high cycle count)
- Solar-dependent setup (benefits from fast charge acceptance)
- Inverter use (LiFePO4 handles high discharge current without voltage sag)
- Weight-sensitive builds
- Cold storage situations (LiFePO4 stores better over winter)
FAQ
Can I mix LiFePO4 and AGM in the same bank?
No — different voltage profiles make this damaging to both batteries. Use a single chemistry throughout your leisure battery bank.
Do I need to change my solar charge controller if I switch from AGM to LiFePO4?
You need to reconfigure it, not replace it — most modern MPPT controllers have a LiFePO4 preset. Check your specific model.
Is an AGM battery safe to use with an inverter?
Yes — AGM handles inverter loads fine, but the high current draw of a large inverter (1,000W+) at 12V causes more voltage sag on AGM than LiFePO4. A 100Ah AGM may struggle to sustain a 1,500W inverter load at its peak; LiFePO4 of the same nominal capacity handles it more comfortably.