After converting trucks to lithium, operators report that the truck display shows the battery as nearly empty, while the pack’s own display shows about 40% state of charge. Some operators park the truck early, and the shift supervisor wants to know which figure is right.
In most cases trust the BMS, because it measures current in and out and knows each cell’s voltage, while many truck gauges estimate charge from voltage using a lead-acid curve. LiFePO4 holds a flat voltage over most of its range, so a voltage-based gauge reads it badly. Fix the cause: integrate the truck display with the BMS (for example over CAN-bus), reprogram the gauge for lithium, or use the pack’s display, then calibrate the BMS with a full charge.
Why they differ
- Truck gauge: often voltage-based and set for lead-acid. Under load, voltage dips, and the gauge reads low.
- BMS: counts charge in and out and uses cell voltages to correct its estimate, usually at full charge.
Check before you trust either
- Compare the BMS SOC with cell voltages at rest. A 40% reading with cells near the lower cut-off would mean the BMS needs calibration.
- Check when the pack last reached full charge. Packs that are only opportunity charged may drift until a full charge resets them.
- Read the truck gauge settings, if accessible, to see whether a lithium setting exists.
Reconcile them
Integration. Redway’s forklift packs list RS485 and CAN-bus, and several models have an on-shell LCD. If the truck accepts SOC over CAN, the display shows the BMS figure. Reprogramming. Some truck makers offer a lithium gauge setting. Process. Until it is fixed, tell operators to use the pack display and set a rule for when to charge.
See our fleet charging checklist, the state of charge guide and Redway’s BMS and telematics page.
Training operators
Show operators both displays on a real truck and explain why they differ. Tell them which one to use and when to charge. A short explanation stops trucks from being parked half full and builds trust in the new packs.
Risk limits
A truck may reduce power or stop based on its own reading, whatever the BMS shows, so test integration before relying on it. Do not change truck or BMS settings without approval from the truck maker and the pack supplier. Redway’s forklift specification tables show 5 years, which is the design life of the pack; the after-sales technical support period is 3 years.
Additional perspectives
Give operators one rule until the displays agree, such as ‘charge when the pack display shows 30%’. Two conflicting gauges and no rule lead to trucks parked half full.
Redway Tech Editorial Team – Shift supervisor perspective
Ask the pack supplier which CAN messages carry SOC and whether they match the truck maker’s protocol. Often only a small mapping change is needed.
Redway Tech Editorial Team – Integration engineer perspective
Include display integration in the conversion quote from the start. It costs less to plan than to fix after operators lose trust in the gauges.
Redway Tech Editorial Team – Fleet manager perspective
Specifications are taken from Redway product pages as of October 2026. Where a figure isn’t published, this article says so. Confirm current specifications for your model with Redway before ordering. This article is general guidance, not a site-specific engineering assessment.
Related products
- 48V 460Ah 450Ah Forklift Lithium Battery
- 48V 300Ah 304Ah Forklift Lithium Battery
- 48V 560Ah 550Ah Forklift Lithium Battery
- 48V 600Ah 630Ah Forklift Lithium Battery
- 24V 280Ah 300Ah Forklift Lithium Battery
Related topics
- How to Understand Forklift Battery State of Charge: A Complete Guide
- Forklift BMS, Fleet Monitoring & Telematics
- Forklift Battery Replacement & Conversion
- Forklift Charging Systems & Troubleshooting
- Forklift Brands, Models & Battery Fitment
- Forklift Battery Maintenance
- Forklift Fast & Opportunity Charging
- Lithium vs Lead-Acid Forklift Batteries
- Forklift Battery Voltage & Capacity
- Forklift Battery Charging
