12 volt lithium iron phosphate battery
Quick answer: A 12V LiFePO4 battery is 12.8V nominal — four 3.2V cells in series — and it drops into the applications that a 12V lead-acid battery serves, at roughly 40% of the weight and with two to five times the cycle life. It suits RV, marine, solar street lighting, CCTV, small off-grid storage and any lead-acid replacement. The one requirement is a charger with a LiFePO4 profile.
Why 12V LiFePO4 replaced so much lead-acid
LiFePO4 sat on the shelf for years as an expensive novelty until the electric-vehicle industry industrialised it. Once LFP cells were made in volume for buses, storage and entry-level EVs, the cost fell to the point where a 12.8V LiFePO4 pack can be priced close to an equivalent AGM or lead-acid battery — while offering a fraction of the weight and many times the cycle life. That cost crossing is the whole reason the 12V lead-acid replacement market moved.
The technical case was always there. A lead-acid battery tolerates only about 50% depth of discharge before its cycle life collapses, weighs several times as much for the same usable energy, and vents hydrogen during charging. LiFePO4 uses far more of its nominal capacity, needs no ventilation, and is the most thermally stable of the mainstream lithium chemistries.
Applications
| Application | Why 12.8V LiFePO4 suits it | Typical capacity |
|---|---|---|
| RV and campervans | Deep discharge tolerance for overnight house loads, no fumes in the living space | 50–200Ah |
| Marine | Weight saving aft, no acid spill risk, long storage life | 50–200Ah |
| Solar street lighting | High-temperature performance, thousands of cycles on daily discharge | 12–50Ah |
| CCTV and security | Long float life and reliable operation over wide temperature range | 7–20Ah |
| Off-grid small loads | Lighting, fans, pumps and instruments at low system voltage | 20–100Ah |
| Lead-acid replacement | Drop-in voltage equivalence with a LiFePO4 charge profile | 7–100Ah |
| UPS and backup | Instant high-current discharge with no maintenance | 7–50Ah |
| Portable power and instruments | Weight and energy density matter for hand-carried equipment | 7–30Ah |
The advantages, in engineering terms
| Property | 12V LiFePO4 | 12V lead-acid |
|---|---|---|
| Nominal voltage | 12.8V | 12V |
| Usable depth of discharge | 80–95% | About 50% |
| Cycle life | 2,000–5,000 | 300–500 |
| Weight for the same usable energy | About 40% | Baseline |
| Maintenance | None | Water topping, terminal care |
| Ventilation | Not required | Required — hydrogen during charge |
| Self-discharge | Very low | Higher |
| Low-temperature charging | Needs cut-off or heating | Tolerated |
Cycle life deserves a note on its own. A LiFePO4 cell retains around 80% of its rated capacity after thousands of full cycles, and its self-discharge rate is among the lowest of any rechargeable chemistry — which is why these packs survive long idle periods. It is also the chemistry’s weakness that matters least in practice: its lower energy density relative to NMC is irrelevant in a stationary or vehicle-mounted installation where volume is not the binding constraint.
Cell formats we build with
| Cell type | Format | Used for | Note |
|---|---|---|---|
| 18650 | Cylindrical | Compact packs, 7–40Ah | Widely available; flexible pack geometry |
| 26650 | Cylindrical | Mid-capacity packs | Higher capacity per cell than 18650 |
| 32650 | Cylindrical | Larger cylindrical builds | Fewer cells and interconnections |
| Prismatic | Rectangular | 50–100Ah and above | Best energy density per volume |
Cell choice follows the shape the application allows. Cylindrical cells give the most freedom in pack geometry and are the natural choice for the smaller standard sizes; prismatic cells pack more energy into a defined volume and cut the number of connections, which is why the larger capacities are built from them.
BMS and the 4S configuration
A 12.8V pack is four cells in series. Series strings are where lithium packs fail, because the cells drift apart in voltage as they age and the charger only sees the total. Left uncorrected, the weakest cell is driven above its limit on charge and below it on discharge, and it degrades faster than its neighbours — a failure that accelerates.
The BMS exists to prevent that. At minimum it balances the cells and protects against over-charge, over-discharge, over-current, short circuit and over-temperature. Where the application demands it, we add communication, low-temperature charge cut-off, or a fuel gauge with state-of-charge reporting.
Off-the-shelf capacities
Standard 12.8V packs run from about 7Ah to 100Ah, covering the common RV, marine, CCTV and lighting sizes, with any intermediate capacity available as a custom build. See the LiFePO4 battery range for the current list, or our solar storage pages for the larger 48V systems.
12V LiFePO4 FAQ
What is the actual voltage of a 12V LiFePO4 battery?
12.8V nominal. A LiFePO4 cell is 3.2V nominal, and four in series give 12.8V. The pack is called “twelve volt” because it drops into the same applications as a 12V lead-acid battery, but the working voltage is higher — which is why a LiFePO4 pack usually yields more usable energy than a lead-acid battery of the same nominal rating.
Can I use a 12.8V LiFePO4 battery to replace a lead-acid battery?
In most cases yes, and the usual requirement is that the charger or charge controller has a LiFePO4 profile. The charge voltage differs from lead-acid, so a fixed lead-acid charger will under-charge the pack. Do not mix the two chemistries on one bus.
How many cycles does a 12V LiFePO4 battery last?
Typically 2,000 to 5,000 cycles to 80% of original capacity depending on depth of discharge, temperature and charge rate. That compares with roughly 300 to 500 cycles for a lead-acid battery at a much shallower discharge.
Is a 12V LiFePO4 battery safe?
LiFePO4 is the most thermally stable mainstream lithium chemistry. The phosphate cathode is far less prone to thermal runaway than the oxide chemistries, and a pack with a properly specified BMS will not catch fire or explode under normal charge and discharge, including fast charge.
Do I need a BMS in a 12V LiFePO4 pack?
Yes. Four cells in series drift apart in voltage over time, and series cells can be driven outside their limits by a charger that only sees pack voltage. The BMS balances the cells and protects against over-charge, over-discharge, over-current, short circuit and over-temperature.
What is the difference between cylindrical and prismatic cells?
Cylindrical cells (18650, 26650, 32650) are flexible in pack shape and widely available. Prismatic cells pack more energy into a given volume and use fewer interconnections. We use both, choosing according to the shape the application requires and the capacity target.
Can a 12V LiFePO4 pack be charged below freezing?
Charging below 0C damages the cells, so outdoor or cold-store applications should specify a BMS with low-temperature charge cut-off, or a pack with a heating element. Discharge at low temperature is less harmful but reduces available capacity.
What capacities are available?
Standard off-the-shelf packs run from about 7Ah to 100Ah and beyond, and any intermediate capacity is available as a custom build. The common mainstream sizes are 7Ah, 12Ah, 20Ah, 50Ah and 100Ah.
Explore related pages
- LiFePO4 battery range
- Residential lithium battery storage 5kWh / 10kWh
- Rechargeable LiFePO4 for solar storage
- 14.4V and 14.8V 4S lithium-ion packs
- Custom battery pack design
- Certifications and compliance
Request a 12V LiFePO4 quote
Send the capacity, the dimensions you have to work within, the connector or terminal arrangement, the charge source and the target certification — we return a specification and a quotation.