LiFePO4 (lithium iron phosphate) and AGM (absorbed glass mat lead-acid) are the two battery types you'll see most often in 12V camping, vehicle and small solar setups.
Both work. The better choice depends on how you use the battery, how much it's cycled and what charging equipment you have.
1. What "lasts longer" actually means
"Lasts longer" can mean two different things:
- Runtime: how long the battery runs your gear on one charge.
- Service life: how many charge and discharge cycles, or years, before the battery's capacity has dropped too far.
LiFePO4 generally does better on both, but the actual figures depend on the specific battery, how deeply it's discharged, temperature and charging.
2. Usable capacity
Two batteries with the same amp-hour rating don't always give you the same usable energy.
- AGM: manufacturers commonly recommend limiting regular discharge, often to around 50%, to protect service life.
- LiFePO4: manufacturers commonly allow a much larger share of the rated capacity to be used, often 80% or more.
So a 100Ah LiFePO4 battery can often deliver noticeably more usable energy than a 100Ah AGM. Check each manufacturer's recommended depth of discharge.
3. Cycle life
Cycle life is the number of charge and discharge cycles a battery is rated for before its capacity falls to a stated level.
- LiFePO4 batteries are commonly rated for thousands of cycles.
- AGM batteries are commonly rated for hundreds of cycles at deeper discharges, with more cycles at shallower discharges.
Cycle ratings are only comparable when they use the same depth of discharge and end-of-life capacity. Read the datasheet conditions, not just the headline number.
4. Voltage under load
LiFePO4 holds a fairly steady voltage through most of its discharge. AGM voltage falls more steadily as it discharges. Equipment such as fridges with low-voltage cut-outs can therefore behave differently on each type.
5. Weight and size
For similar usable energy, LiFePO4 is usually much lighter than AGM. That matters in caravans, trailers and 4WDs where payload is limited.
6. Charging
- Each chemistry needs a suitable charge profile. Check that your charger, DC-DC charger or solar controller has a setting that matches the battery manufacturer's requirements.
- Many LiFePO4 batteries must not be charged below about 0°C unless they have low-temperature protection or built-in heating. Check the specification.
- AGM batteries are damaged by being left partly discharged for long periods. Keep them topped up.
7. What a BMS does
A LiFePO4 battery normally contains a battery management system (BMS). Depending on its design, it may:
- Disconnect the battery if a cell's voltage goes too high or too low.
- Limit or cut off excessive charge or discharge current.
- Prevent charging when the temperature is outside safe limits.
- Balance the cells so they stay at similar charge levels.
A BMS is a protection layer, not a substitute for correct fusing, cable sizing and charging equipment.
8. Cost
LiFePO4 usually costs more up front. Over its service life, the cost per usable cycle can be lower, depending on how often you cycle the battery and how long it lasts in your conditions. For a battery that's rarely cycled, AGM may still be the sensible choice.
9. Quick comparison
- Usable capacity: LiFePO4 usually higher.
- Cycle life: LiFePO4 usually much higher.
- Weight: LiFePO4 usually much lighter.
- Up-front cost: AGM usually lower.
- Cold charging: AGM is more tolerant. LiFePO4 needs protection or heating below about 0°C.
- Charger compatibility: both need the correct profile.
10. Safety boundaries
Any battery can supply very high fault current. Fuse close to the battery and protect terminals from accidental shorts.
Don't mix battery chemistries in the same bank, and follow the manufacturer's instructions for series or parallel connection.
Lead-acid batteries can release hydrogen gas while charging. Follow the ventilation requirements for the battery and location.
For large battery banks or anything connected to 240V AC or a home solar system, use a qualified installer and, where required, a licensed electrician.
11. The main lesson
LiFePO4 usually lasts longer, weighs less and gives more usable capacity. AGM costs less up front. Match the battery to how you use it, and the charger to the battery.
Continue learning
Revival Academy 101 shares practical tutorials to help you understand electrical systems and make informed decisions.
Explore related Bush & Bench projects:
- BENCH — Cordless Revival: battery repair and workshop equipment.
- BUSH — Wired For The Wild: vehicle, camping and 12V power.
- HOMESTEAD — Home & Workshop Solar: solar, battery storage and off-grid systems.
Disclosure: Some pages may contain affiliate links. Where applicable, purchases through these links may earn us a commission at no additional cost to you.
Technical note: This is general educational information, not a substitute for a design calculation, manufacturer instructions or applicable Australian standards.