Exoskeleton Lift Endurance Calculator
How this exoskeleton endurance calculator works
This tool estimates how long a powered exoskeleton can keep lifting before the battery is depleted. It focuses on repetitive vertical lifts and uses basic physics to connect load mass, lift height, repetition rate, actuator efficiency, and battery capacity to operating time and total number of lifts.
Typical users include robotics and controls engineers, industrial safety teams, exoskeleton manufacturers, and advanced hobbyists who want a transparent, first-pass estimate of powered exoskeleton battery life under steady lifting.
Core physics: energy needed for each lift
Each time the exoskeleton raises a load against gravity, it increases the load’s gravitational potential energy. The mechanical work per lift is:
Where:
- m = load mass in kilograms (kg)
- g = gravitational acceleration, about 9.81 m/s2 near Earth’s surface
- h = lift height per repetition in meters (m)
This gives E in joules (J), the ideal mechanical energy to lift the load once.
From lifts per minute to power draw
If the exoskeleton performs R repetitions per minute, the average mechanical power output is:
P_m = (m × g × h × R) / 60 (in watts)
Actuators are not perfectly efficient. If the actuator efficiency is η (expressed as a fraction, e.g. 0.7 for 70%), the electrical power drawn from the battery is higher than the mechanical power delivered:
P_e = P_m / η
The higher the repetition rate or the heavier / higher the lift, the more power is required, and the more quickly the battery is drained.
From battery capacity to operating time
Battery capacity is typically specified in watt-hours (Wh). To connect it to the power equations above, we convert watt-hours to joules:
E_b = B × 3600
Where:
- B = battery capacity in watt-hours (Wh)
- E_b = total stored energy in joules (J)
Combining the relations, the number of possible lifts N is, in idealized form:
N = (E_b × η) / E_l, where E_l = m × g × h
Operating time in minutes T is then:
T = N / R
The calculator applies these equations directly using your inputs for mass, height, repetition rate, efficiency, and battery capacity.
Worked example: industrial lifting exoskeleton
Suppose an industrial powered exoskeleton is assisting a warehouse worker with repetitive box lifting. Assume:
- Load mass m = 20 kg
- Lift height per rep h = 0.5 m
- Lift rate R = 10 reps/min
- Actuator efficiency η = 70% (0.70)
- Battery capacity B = 500 Wh
Energy per lift:
E_l = m × g × h = 20 × 9.81 × 0.5 ≈ 98.1 J
Battery energy:
E_b = 500 × 3600 = 1{,}800{,}000 J
Number of lifts (idealized):
N = (E_b × η) / E_l ≈ (1{,}800{,}000 × 0.70) / 98.1 ≈ 12{,}850 lifts
Operating time:
T = N / R ≈ 12{,}850 / 10 ≈ 1{,}285 minutes, or about 21.4 hours of continuous, perfectly repetitive lifting under these optimistic assumptions.
Real-world endurance will be lower due to control electronics, idle power, motion other than vertical lifting, and variations in efficiency. Use the result as an upper bound or best-case estimate.
Interpreting the results
When you run the calculator, you can think about the outputs in three main ways:
- Total lifting time: How long the powered exoskeleton can sustain the specified pattern of lifts before a battery swap or recharge is needed.
- Total number of repetitions: The cumulative number of lifts possible at the given load and height.
- Relative changes: How endurance increases or decreases when you adjust one input (for example, testing a higher-efficiency actuator or a larger battery pack).
For design work, treat the calculator as a way to compare scenarios: different batteries, different payloads, or different operating modes. It is more reliable for relative decisions (A vs. B) than for predicting the exact minute when a battery will cut off.
Key drivers of exoskeleton battery life
| Parameter | Effect on endurance | Practical design insight |
|---|---|---|
| Load mass (kg) | Higher mass increases energy per lift and reduces endurance roughly in proportion. | Reducing payload, sharing load with the human user, or restricting peak loads can extend battery life. |
| Lift height (m) | Taller lifts require more energy per rep and shorten operating time. | Optimizing workstation layout to minimize vertical travel can significantly reduce energy demand. |
| Lift rate (reps/min) | More reps per minute increase average power draw and drain the battery faster. | Choosing realistic duty cycles and allowing rest periods can improve practical endurance. |
| Actuator efficiency (%) | Higher efficiency reduces wasted energy and extends operating time. | Upgrading motors, transmissions, or hydraulics can deliver more lifts from the same battery. |
| Battery capacity (Wh) | Larger capacity increases total available energy and extends endurance approximately linearly. | Heavier batteries may impact ergonomics; use this calculator to weigh battery size vs. run time. |
Using the calculator for real-world planning
You can use the endurance estimates in several ways:
- Battery sizing: Start from a target shift length and duty cycle, then adjust battery capacity until the calculated time comfortably exceeds your requirement with margin.
- Technology comparison: Compare different actuator types or drive trains by changing efficiency while holding other parameters constant.
- Operational policies: Explore how reducing lift rate or limiting maximum load can extend powered exoskeleton operating time between swaps.
- What-if studies: Estimate the impact of battery aging by testing smaller effective capacities (for example, 70% or 80% of nominal Wh).
Assumptions and limitations
This calculator is intentionally simple and is meant for preliminary estimation, not for safety-critical or mission-critical guarantees. It relies on several idealizations:
- Constant gravity: Assumes operation near Earth’s surface with g = 9.81 m/s2.
- Vertical lifting only: Only the vertical component of motion is modeled. Walking, horizontal transport, and arm motions are not explicitly included.
- Steady, repetitive operation: Assumes a constant repetition rate and load, with no pauses, accelerations, or variable duty cycles.
- Single efficiency value: Uses one actuator efficiency percentage that does not vary with speed, torque, or temperature.
- Battery behavior: Ignores voltage sag, temperature effects, aging, and current limits; it treats the full labelled watt-hours as usable.
- Other power consumers: Control electronics, sensors, communication links, and onboard computing are not explicitly modeled.
Because of these simplifications, the calculated endurance should be viewed as an approximate, best-case value. Real systems will typically achieve less. Always validate results against hardware testing and follow relevant safety standards when deploying powered exoskeletons in industrial, medical, or defense environments.