Swapping a lead-acid forklift battery for a lithium one looks like a like-for-like change: same voltage class, same compartment, same connector. In practice, a lithium forklift battery changes four things the truck was designed around: its weight, its voltage curve, its charging and the way it reports trouble. Get those right and the conversion is straightforward. Miss one and you get a truck that tips more easily, shuts down mid-shift or never fully charges.
This guide walks through what to check, in the order we check it when an OEM or fleet program asks us for a LiFePO4 (LFP) forklift pack.
1. Why fleets convert
Lead-acid forklift batteries need watering, equalizing charges, cool-down time after charging and, in multi-shift operations, battery swaps and a battery room. LiFePO4 packs need no watering, can be opportunity-charged during breaks and hold a steady voltage through the shift, so the truck doesn't get sluggish as the battery drains.
The trade-offs are a higher upfront cost and the integration work in the rest of this article. For a broader side-by-side, see LiFePO4 vs lead-acid for industrial equipment.
2. Match the voltage class, then the voltage window
Electric forklifts commonly run in the 24V, 36V, 48V or 80V class. A lead-acid battery reaches those numbers with 2V cells; a LiFePO4 pack uses 3.2V cells, so the series count is different:
| Truck voltage class | Lead-acid cells (2.0V) | LiFePO4 cells in series (3.2V) | LiFePO4 nominal |
|---|---|---|---|
| 24V | 12 | 8S | 25.6V |
| 36V | 18 | 12S | 38.4V |
| 48V | 24 | 16S | 51.2V |
| 80V | 40 | 25S | 80.0V |
The nominal numbers line up closely. The full-charge and empty voltages don't. A 16S LiFePO4 pack charges to about 57.6–58.4V and spends most of its discharge between about 52V and 50V, then falls quickly near empty. A lead-acid battery sags steadily through the shift. That's why the next step matters.
See lithium battery pack voltage explained for the cell-level numbers.
3. Reset the controller's low-voltage cut-off
Most truck controllers have a battery discharge indicator and a low-voltage cut-off set for lead-acid. On a lithium pack those settings can be wrong in both directions:
- Too high: the truck reads a healthy lithium pack as discharged and limits lift early.
- Too low: the truck keeps drawing current after the pack is nearly empty, and the BMS has to disconnect the pack under load. That's the worst moment for a shutdown.
The fix is to set the truck's discharge indicator and cut-off to the lithium pack's real window, and to let the BMS report state of charge directly where the truck can read it (section 6). The BMS stays the last line of protection, not the first.
4. Meet the minimum battery weight with ballast
This is the step that's easiest to miss and the one that matters most for safety. Many counterbalanced forklifts use the battery as part of the counterweight. The truck's data plate states a minimum battery weight, and the truck's stability depends on it.
A LiFePO4 pack of the same energy is much lighter than the lead-acid battery it replaces. So a conversion pack is designed with a steel tray and ballast that bring the installed weight up to at least the data-plate minimum, with the ballast fixed so it can't shift.
Things to confirm before the design is frozen:
- the data-plate minimum (and maximum, if stated) battery weight;
- compartment dimensions, including the space the ballast can occupy;
- the position of the centre of gravity, if the truck maker specifies it;
- lifting points and how the pack is removed for service.
Pallet trucks, stackers and other trucks that don't use the battery as counterweight have more freedom here, but the compartment and retention still need checking.
5. Replace or reprogram the charger
Lead-acid chargers with equalization or float stages aren't suitable for LiFePO4. A lithium pack needs a charger whose voltage and current profile match the pack's series count and the BMS limits: for example, a 16S LiFePO4 pack is normally charged to about 58.4V.
Plan these together:
- Charger output matched to the pack's chemistry and series count. Our lithium battery charger catalog is organized by chemistry, series count and output voltage.
- Charge current within the BMS and cell limits. Fast and opportunity charging only work if charger power, the charging schedule and the BMS current limits line up.
- Charger communication, where the charger can take its current limit from the BMS.
- Connector and cabling rated for the charge current.
Opportunity charging changes the shift plan. Instead of one long charge and a swap, the truck tops up at breaks. LFP tolerates partial state-of-charge cycling well, but the BMS needs regular full charges to recalibrate its state-of-charge estimate, so plan at least a periodic full charge.
6. Connect the BMS to the truck
A lead-acid battery can't tell the truck anything. A lithium pack's BMS can report state of charge, current limits, temperatures and faults over CAN or another protocol. When the truck uses that information, it can reduce speed or lift before the pack reaches a limit, instead of losing power suddenly.
During the design review we confirm:
- which protocol and messages the truck controller and display accept;
- what the truck should do at each warning level;
- the regenerative current the truck pushes back into the pack during braking or lowering, especially when the pack is nearly full;
- the peak current during a full-load lift or a ramp start, so cells, busbars, fusing, contactors and the BMS are sized for it.
See battery management systems for custom packs.
7. Plan for cold storage
LiFePO4 must not be charged below freezing without heating or reduced charge current. Trucks that work in freezers or on cold docks need heating, insulation and BMS charge limits designed together, and a charging location and schedule that suit them.
8. Validate on a pilot truck
Before converting a fleet, run a pilot: one truck or a small lot, on a real shift pattern. Check:
- installed battery weight against the data plate;
- fit, retention and connector;
- discharge indicator and cut-off behaviour across a full shift;
- charging time and temperature at the charger you'll actually use;
- BMS messages on the truck display;
- behaviour at the end of the shift and after an opportunity charge.
Once the pilot passes, the design is frozen under change control and released for volume. Lead times run from weeks to months depending on cells, design scope and validation, and your quote confirms them. See OEM battery pilot production.
Conversion checklist
- Truck make and model (or your own truck design) and voltage class
- Battery compartment dimensions
- Minimum battery weight from the data plate
- Battery connector
- Shifts per day and charging windows
- Existing charger, or a new one needed
- Operating temperature, including cold storage
- Truck communications (CAN or other)
- First-order quantity and annual volume
Where to start
Our lithium forklift battery packs page lists current reference designs, including a 51.2V 200Ah LiFePO4 pack for 48V-class trucks and a 25.6V 40Ah pack for 24V-class pallet trucks and light equipment. If your truck isn't covered, we design to its voltage class and compartment. Lithium Battery Company has designed and built lithium battery packs since 2014, with hundreds of thousands produced for OEM programs. Catalog packs start at 10 units and custom designs at 25.
Request a forklift battery quote · Lead-acid to lithium replacement · Industrial lithium battery packs
FAQ
Can I put a lithium battery in a lead-acid forklift?
Usually, yes, if the lithium pack matches the truck's voltage class and compartment, meets the minimum battery weight on the data plate, and is paired with a LiFePO4 charger and the right controller settings.
Why does a lithium forklift battery need ballast?
Many counterbalanced forklifts use the battery as part of the counterweight. A lithium pack is lighter than lead-acid, so the tray and ballast are designed to bring it up to the minimum battery weight on the truck's data plate.
Can I use my existing lead-acid forklift charger?
Usually not. Lead-acid chargers with equalization or float stages aren't suitable for LiFePO4. The charger has to match the pack's chemistry, series count and BMS limits.
How many LiFePO4 cells are in a 48V forklift battery?
Usually 16 in series, for 51.2V nominal and about 58.4V at full charge.