Touchless trash can batteries and power

Sensor cans run on large alkaline cells — C or D, not AA — because the lid motor draws a real current for a moment and small cells sag under it.

Two honest observations from that table. Ninestars' 10,000-cycle figure is the only comparable number any brand in this category publishes, which is why it carries weight in our touchless roundup out of proportion to its price. And iTouchless is the only brand here that publishes an AC option, which is a more useful feature than it sounds — see below.

Work it out rather than guessing, because the answer varies by a factor of three depending on where the can sits.

1. Count your opens per day. Two people is roughly fifteen to twenty; a family of four is nearer thirty.
2. Divide the cycle figure. Ten thousand cycles at twenty a day is about 500 days — over a year.
3. Subtract for false triggers. A can in a walkway can easily add a third again. This is the single biggest variable and it is free to fix.
4. Subtract for cold. Alkaline cells lose capacity below about 10 degrees Celsius, so a can in an unheated garage or utility room will do noticeably worse.
5. Subtract for the motor working harder. An overfilled can, or a bag jammed under the lid, makes the motor strain on every cycle.

The realistic range for a well-placed household can is nine months to eighteen. If you are replacing cells every couple of months, the can is almost certainly false-triggering — move it out of the traffic path and clean the sensor window before you blame the can. Why it false-triggers.

The NiMH caveat is the one worth testing before you commit to a set. If the can becomes noticeably less sensitive on rechargeables, that is the voltage difference and not a fault — go back to alkaline. And do not mix old and new cells, or brands: the weakest cell sets the behavior of the whole pack.

If there is an outlet within reach of where the can lives, mains power is the upgrade nobody talks about.

It is not mainly about the cost of batteries. It is that a mains can never enters the erratic phase. With a battery can, the last stretch of every battery cycle is a period of weakened emission where the can misses opens and triggers at nothing — and that is the experience people remember and complain about. On mains, the emitter runs at full voltage forever and the can behaves identically on day one and day one thousand.

Two caveats. A trailing cable across a kitchen floor is a genuine hazard and a mopping nuisance, so this only makes sense where the outlet is close and the run can be tucked behind the can. And check whether the can still opens by hand on mains — in a power cut a can with no manual override becomes a sealed box.