Changing the batteries in a digital clock often requires the user to reset the time after the batteries are changed. Designers sometimes work around this problem by including a small watch battery to store the time, but these can go dead. Proposed is a clock with two battery compartments, isolated from each other in an obvious manner, together wired in parallel. Normally, one compartment would remain empty. (Let's call that "A".) To change the batteries, insert batteries into B, then remove them from A. In its new working state, compartment B will drive the clock, and compartment A will remain empty until the next change.
-- kevinthenerd, Feb 28 2017

Same with a phone... Double_20Battery_20Cell_20Phone
[bs0u0155, Feb 28 2017]

// a small watch battery to store the time, but these can go dead. //

Multimeters can be purchased for a few dollars, battery testers for even less. Just test the coin cell first ... if dead, replace it before changing the main cells.
-- 8th of 7, Feb 28 2017


"Just test the coin cell first"

Opening the device to expose them is less convenient than replacing the main batteries, and it seems foolish to me to design a system where the backup battery gets out of sync with the main power source.
-- kevinthenerd, Feb 28 2017


It's inevitable.

User A replaces the main batteries whenever they are depleted. Result - the coin cell never gets drained.

User B replaces the main batteries after an interval of 7 days. Result - the coin cell is progressively depleted.

Of course, that assumes that the backup is a primary rather than a secondary cell.

It's very hard to design round the vagaries of user behaviour. It's much more effective to simply cull all occurrences of User B. It's relatively humane, and better and kinder for them.
-- 8th of 7, Feb 28 2017


This is a nice idea, but I think most users would assume you need to put batteries in both compartments, and when it comes to changing them they would pull both out at once.

Also, most clocks only get their batteries changed when the dead batteries are noticeable, i.e. they stop ticking, at which point the game is already over.
-- mitxela, Feb 28 2017


Given the low power requirement of electronic clocks, shirley a capacitor would keep enough charge to keep the clock running while you change the battery? I would guess that it would be simple, even, to add a suitable capacitor to an existing clock, across the terminals in the battery compartment.
-- MaxwellBuchanan, Feb 28 2017



random, halfbakery