Three inputs decide the days figure
Runtime is arithmetic wearing a marketing hat. The cell stores a fixed amount of energy - quoted in milliamp-hours at its nominal voltage. The motor and board spend it, and the spend rate depends on the strokes band, the mode the user lives in and the electronics that stay awake between sessions. The assumption closes the loop: a days figure only means something against a stated usage pattern, and the category has settled on two two-minute sessions per day as the reference. Change any input and the figure moves. A handle quoted at thirty days can honestly deliver eighteen for a user who runs three sessions in top mode, and the same handle can stretch past its figure for a once-a-day traveller. When the desk reviews quotations, the days number is read together with the cell figure and the assumption line, never alone.
The typical ranges by line
| Line | Cell | Typical runtime | Reference assumption |
|---|---|---|---|
| Sonic, rechargeable | 800-1,400 mAh at 3.7 V | 14-30 days | Two two-minute sessions per day |
| Travel, rechargeable | 500-1,000 mAh | 20-60 days | Low frequency of use on the road |
| Battery (AAA or AA) | 2 x AAA or 1 x AA | Roughly 90 days per set of cells | Twice-daily use; category rule of thumb |
| Kids, rechargeable | Small lithium pack | Within the sonic band | Shorter sessions, gentler modes |
| U-shaped | Small lithium pack | Short sessions of 45-60 s stretch days far | One or two automatic sessions daily |
The table explains a pattern buyers notice: travel models quote more days from smaller cells. The usage assumption does the work - a brush used twice a week on the road does not need a big pack to look generous. Comparing day counts across lines without the assumption column is the classic listing error.
Why the same cell delivers different days
Two handles with identical 800-1,400 mAh packs can diverge by a week. The mode profile is the first lever: a user who lives in top intensity drains the pack faster than one who stays in soft mode. The drive type is the second - linear voice-coil drives and eccentric motors convert energy at different rates, and a board that scales motor duty to the mode spends accordingly. Electronics idle draw is the third: LED rings, Bluetooth radios and pressure sensing all sip power between sessions, and a smart handle that sleeps deeply will outlast one that keeps its radio chatty. Cell quality closes the gap over time: packs age, and a runtime figure measured on a fresh cell will sag across the ownership period. All of which is why the runtime line in a datasheet carries test conditions, and why the desk asks what conditions were behind the number - the cell options sit on the battery guide and the cell chemistries in the cells note.
How the handle communicates its state belongs to the same discussion. The category convention is a multi-segment LED or a ring that fills during charge and depletes across days, with a low-battery warning before the motor fades; better boards show a distinct charging-complete state instead of leaving the light on. Two behaviours matter to reviewers and returns teams alike. The first is the low-battery performance curve: a well-managed board warns early and fades gently, while a crude one jumps from full speed to nothing, which users read as a fault rather than an empty pack. The second is display honesty on smart models - a percentage readout is a firmware estimate, and an estimate that drops in chunks invites support tickets. Specifying the indicator behaviour alongside the runtime figure costs nothing at briefing time and saves explanation later, a detail the not-charging note circles back to from the repair side.
Charging path and the full cycle
Runtime pairs with refill speed in any honest spec. A USB or Type-C cable recharges a typical handle in about 4 to 6 hours; a wireless dock takes longer, commonly 12 to 16 hours, because power crosses a plastic gap at lower transfer rates. Neither figure includes the charger's own behaviour - output rating and cable quality move the clock - so the datasheet states the charger assumed. For range planning the trade mirrors sealing: cabled charging refills fast and keeps the bill lean but adds a port to waterproof, while wireless docks seal elegantly and refill slowly, which suits a nightly-dock habit. Users with the dock habit care less about days-per-charge; travellers care intensely, which is why travel lines push the days figure hardest. The charging hardware options are laid out in the charging types note.
The paperwork a lithium program carries
A rechargeable handle is a lithium-battery product the moment it leaves the plant, and two document sets attach. Transport: UN 38.3, the test series a lithium cell and pack must pass to move by air or sea, with the packaging and labelling rules that go with it under air transport rules. Safety: IEC 62133-2, the lithium-cell safety standard markets expect for the cell and pack, polymer cells included. Add the appliance-level certificates - IEC/EN 60335-2-52 for most markets, UL 859 via UL or ETL for North America - and the file is complete for customs and retail. The routes and timeframes are summarised in the battery standards note and the wider picture under compliance and certifications; AAA models skip the lithium file entirely, one of their quiet commercial advantages.
Aging and service close the life-cycle view. A lithium pack's capacity fades across charge cycles, so a handle honest on day one drifts downward over years of use, and listings that promise a years-wide runtime window invite disappointment. Range planning answers this two ways: programs built for long ownership spec a larger cell than the days figure strictly needs, leaving fade headroom, and programs built around replacement cycles match the cell to the expected service life instead. The parts view runs in parallel - the battery pack line exists because importers and service centres do occasionally need cells as spares, and any spare-cell program inherits the same UN 38.3 and IEC 62133-2 paperwork as the finished handle. A brief that states expected service life alongside the days figure lets the plant propose the cell size that fits both, rather than the largest that fits the shell.
Specifying runtime in a brief
A runtime line worth signing names four things: cell capacity and chemistry, the session assumption, the measured days against it, and the documents that travel with the pack. With those, the figure becomes an inspection item - sample units drained against the stated pattern - rather than a debate. Bring the target to the quote form and keep the program frame on MOQ and lead time; both files, confirmed in writing per program, are what let a days figure survive contact with a reviewer, a customs officer and a customer.