Core Definitions and the Simple Formula
- Kilowatt (kW) = power. It describes how hard the machine can work at any moment (digging force, travel speed under load, simultaneous hydraulic functions).
- Kilowatt-hour (kWh) = energy. It describes how long the machine can sustain that work.
The fundamental relationship is:
Energy (kWh) = Power (kW) × Time (hours)
A machine drawing an average of 80 kW for 6 hours consumes 480 kWh. If the usable battery capacity is only 400 kWh, the shift ends early unless opportunity charging or a battery swap is available. Peak power demands are higher still—excavator swing and boom functions or a loaded mining truck climbing a grade can briefly pull 1.5–2× the continuous rating. The battery and its BMS must support those peaks without voltage collapse or thermal shutdown.
Why kW vs kWh Matters on the Jobsite
Heavy equipment duty cycles are highly variable. A mid-size electric excavator may idle at low power for long periods, then surge to near peak power during trench digging or truck loading. A large haul truck may run at high continuous power for extended periods while climbing, then recover energy on the downhill. In both cases the battery must deliver the required kW when demanded and still have enough kWh remaining to finish the planned work window.
Key practical implications:
- Peak kW capability determines whether the machine can match diesel performance on tough material or steep grades.
- Usable kWh determines shift length and the frequency of charging stops.
- C-rate (the ratio of power in kW to capacity in kWh) indicates how aggressively the pack is being discharged or charged. High C-rates accelerate aging if not properly managed by the BMS and cooling system.
- Opportunity charging of 15–40 % capacity during breaks is only useful if the charger and battery can accept the corresponding kW power level.
LiFePO₄ (LFP) chemistry remains the dominant choice for most 2026 heavy-equipment applications because of its thermal stability, cycle life of ≥3,500–5,000 cycles at 80 % depth of discharge, and ability to support moderate-to-high C-rates when properly engineered.
Real-World OEM Examples
The following table illustrates how leading manufacturers balance motor power (kW) and battery energy (kWh) on current production or late-stage trial machines.
| Machine | Peak / Continuous Motor Power | Capacidad de la batería | Typical Runtime | Notas |
|---|---|---|---|---|
| Volvo EC230 Electric (high-capacity) | 160 kW peak / ~110 kW continuous | 450 kWh | 7–8 hours | 600–650 V system; 250 kW DC fast charge to 80 % in ~1–1.5 h |
| Caterpillar 320 Electric | — | 387 kWh | Application-dependent | 750 V architecture |
| Caterpillar 793 XE Early Learner | 480 kW | 564 kWh LFP | Regenerative recovery enables extended operation | Formal validation at BHP Jimblebar (2025–2026) with Rio Tinto collaboration |
| Caterpillar R1700 XE LHD | High continuous + peak | 213 kWh | Ultra-fast onboard charge <20 min with dual MEC500 | 715 V system; up to 840 kW charge rate |
| Typical 3–3.5 t electric forklift | 10–25 kW class | 20–40 kWh | Full single shift | Lower absolute numbers but same sizing logic |
These figures demonstrate that simply matching the diesel engine’s rated kW is insufficient. The battery must also supply enough kWh for the expected duty cycle after accounting for auxiliary loads, temperature derating, and a recommended minimum state of charge of 20–30 %.
Sizing Guidance for Fleet Managers
- Measure or estimate average power draw (kW) across a representative shift, including idle and high-load periods.
- Multiply by planned operating hours to obtain daily energy requirement (kWh).
- Apply a 1.1–1.2× factor for reserves, temperature effects, and aging.
- Verify that the pack’s continuous and peak power ratings (kW) meet or exceed the machine’s motor and hydraulic demands.
- Confirm charger power (kW) is sufficient for the desired opportunity-charge window (typically 15–40 % of capacity).
- Prefer packs certified to UL 2580 or IEC 62619 with integrated BMS that reports accurate SOC and SOH.
For multi-shift operations the combination of adequate kWh capacity plus high-power opportunity charging frequently yields better uptime and lower capital cost than an oversized single pack.
Selection Criteria for Electric Heavy Equipment Batteries
Prioritize in this order:
- Usable energy (kWh) matched to the longest continuous work block plus reserves.
- Continuous and peak power (kW) sufficient for the most demanding tasks without thermal limiting.
- Chemistry and cycle life — LFP preferred for ≥3,500 cycles at 80 % DoD in industrial environments.
- Charging acceptance — ability to absorb 15–40 % capacity in short windows at the available charger power.
- Safety and certification — UL 2580, IEC 62619, and robust thermal management.
- Telematics / BMS transparency — real-time SOC, SOH, cell temperatures, and fault logging.
- Total cost of ownership — energy cost, maintenance reduction, and residual value over 5–10 years.
