Sustained use of haptic motors measurably drains the battery

What it is

Vibration motors are significant power consumers. Their peak draw is modest next to a display, but a motor must run or repeatedly start and stop, and the accumulated energy becomes noticeable over long use—especially where high-frequency feedback such as keypress haptics fires densely.

Why it happens

Energy depends on two things: the energy of one vibration and the rate of vibration. Single-vibration energy follows motor type, amplitude, and duration; an ERM draws a large inrush to overcome inertia, so "short and many" costs more than "long and few." Rate then determines the accumulated total: triggering once per second, even briefly, drains continuously. Haptics are also commonly triggered by sensors and the processor, so the real cost includes computation and sensing, not just the motor.

Studying it

Device-level power measurement yields the marginal cost of haptics: under controlled conditions, compare whole-device current with haptics off and on, attributing the difference to a single vibration. Variables include motor type, pattern duration and amplitude, trigger rate, and whether sensing is involved. Outcomes include per-vibration energy and additional watt-hours per hour, the latter being more useful for design decisions.

Where it stops holding

On external power or with ample battery, haptic power is not a constraint and experience can lead. If haptics serve safety alerts, energy is not grounds for trimming. On wearables the battery is far smaller than a phone's, making the same pattern relatively much more expensive, so conclusions must be re-derived per device class.

Applying it

• Measure per-vibration energy and typical additional hourly draw on the target device as design input.
• In high-frequency contexts, cap trigger rate or shift to cheaper patterns (shorter, fewer start-stop cycles).
• Under low battery, keep critical haptics and trim high-frequency low-value ones.
• Verification: compare power curves with haptics on and off and confirm the added draw in critical scenarios stays acceptable.

Related

• Within the group: D3.15.2 High-rate haptic feedback needs restraint when battery is low · D3.15.4 Some devices automatically reduce or disable haptics at low battery
• Adjacent: D3.08.3 The haptic budget should follow event importance · K3.04 Battery and performance tradeoffs on mobile devices
• Search terms: haptic power · battery drain · energy cost