A battery powered time clock exists for one reason: there is no socket where people clock in. That constraint makes runtime, charge visibility and the failure routine more important than anything on the feature list.
Runtime claims are laboratory numbers
Quoted battery life assumes a mild room, a modest number of punches and a screen that is mostly asleep. A unit in an unheated store in January, woken forty times in ten minutes at shift change, will do considerably less. Ask for the test conditions, then plan around roughly half the quoted figure until your own site has proved otherwise over a month.
Make the state of charge visible to the person who can act
A charge level shown only in a web dashboard is useless to the supervisor standing next to the device. What you want is an indicator readable across the room and an escalation that reaches a named person before the battery dies, not after. This is a process question the vendor cannot answer for you, and it is the difference between a swap and a lost morning.
Decide the routine for a dead clock in advance
Somebody will find a blank screen at six in the morning. The good version is a written fallback: a paper sheet with names pre-printed, a named person who keys it in the same day, and an agreed marker in the system so the entries are visibly manual. The bad version is invented on the spot and reconstructed from memory a week later.
Charging discipline beats battery capacity
Most flat-battery incidents are scheduling failures rather than hardware failures. A docking point where the unit lives overnight, or a rota entry for charging, removes almost all of them. If the site cannot support that, a mains unit with a small backup supply is usually the better purchase than a larger battery.
Questions people ask about battery powered time clock
Are replaceable batteries better than a built-in pack?
For remote sites, usually yes, because a spare pack turns a failure into a swap. Built-in packs are tidier and better suited to a fixed indoor location.
Does cold really matter?
Enough to plan for. Battery capacity falls in low temperatures, and outdoor or unheated locations should be specified with that in mind.
What if punches are missed while the clock is dead?
They are added manually and flagged as manual. Keeping them identifiable is what protects the record later.