Quick answer
LiFePO4 (lithium iron phosphate) costs more up front but lasts several times longer, lets you use almost all of its capacity, weighs about a third as much, and needs no maintenance. Lead-acid is cheaper to buy and fine for occasional backup, but it wears out quickly when used every day. For solar and daily cycling, LiFePO4 is usually cheaper over its lifetime.
Side-by-side comparison
| LiFePO4 | Lead-acid | |
|---|---|---|
| Cycle life | About 3,000–6,000+ cycles | About 300–1,000 cycles |
| Usable capacity | 80–100% | ~50% (deeper discharge shortens its life) |
| Efficiency | ~95% | ~80–85% |
| Weight | Light (about 1/3 of lead-acid) | Heavy |
| Maintenance | None | Flooded types need water top-ups |
| Heat tolerance | Good | Life drops fast in hot rooms |
| Charging speed | Fast | Slow, especially the last 20% |
| Upfront price | Higher | Lower |
| Lifetime cost | Lower for daily use | Higher for daily use |
What is LiFePO4?
LiFePO4 is a type of lithium battery that uses iron phosphate. It’s the chemistry most solar and home backup batteries use today because it is stable and far less prone to overheating than the lithium batteries in phones and laptops. Every pack has a BMS (battery management system) that protects the cells from overcharging, over-discharging, and short circuits.
What is lead-acid?
The older, familiar technology found in cars, older UPS units, and many inverter setups. Three common types:
- Flooded (wet): cheapest; needs distilled water top-ups and ventilation because it releases gas while charging.
- AGM: sealed and maintenance-free; common in UPS units.
- Gel: sealed; handles deep discharges a bit better than AGM, but charges slowly.
Why usable capacity matters
Battery capacity on the label isn’t what you actually get. A 100Ah lead-acid battery should only be drained to about half to keep it healthy, so you really get about 50Ah. A 100Ah LiFePO4 gives you 80–100Ah. In practice, you need about twice the lead-acid capacity to match one LiFePO4.
The real cost: price per cycle
Compare what you pay for each full use of the battery, not the sticker price. A rough example:
- Lead-acid: half the price, but ~500 useful cycles at half capacity.
- LiFePO4: double the price, but ~4,000 cycles at nearly full capacity.
Even at twice the price, LiFePO4 delivers many times more energy over its life. If you cycle a battery every day (solar, frequent brownouts), lead-acid may need replacing every 1–2 years while LiFePO4 can last 10 years or more.
Which should you choose?
Choose LiFePO4 if you…
- Have solar and cycle the battery every day.
- Get frequent or long brownouts.
- Want to run heavy loads like an aircon (see how long a 1HP aircon runs on LiFePO4).
- Have limited space, or the battery is in a hot room.
Lead-acid is still fine if you…
- Only need short backup a few times a year, like a small UPS for a PC.
- Have a tight budget right now.
- Are replacing a battery in equipment that only supports lead-acid.
Can you switch from lead-acid to LiFePO4?
Often yes, but check your charger or inverter first. LiFePO4 needs different charge voltages. Many modern hybrid inverters have a lithium setting; older chargers and some UPS units don’t, and forcing it can damage the battery or trigger faults. Never mix the two types in one bank.