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jackadam

Back to back AAA cell whim, bad idea?

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I have a laser spirit level which takes two AAA cells. they slide lengthways into the side of the level, one positive end first, one negative end first. the battery compartment cover has a sheet of copper which connects the two exposed cell ends together, so that the cells end up in series once installed. 

more: xe dongben

It occurred to me that with a 7 year old lad wandering round, I might be sensible to avoid leaving a laser device around that could be easily turned on and stared into.

so, I took out one cell and turned it round so that both cells had the same polarity end facing the cover. I can't recall if I had the + or - ends both sticking out.

figured, it might prevent an inadvertent retinal burn whilst still leaving the level ready for use at the drop of a hat, with the only inconvenience being, having to reconfigure the cells before use.

at this stage I thought, hell, what you doing messing around, just stick the darn thing in the shed & lock the door, problem solved, no need to worry 

It did start me thinking though.. what actually would happen if one did that and then left the device lying around for say 6 months, with the device's 'on' switch in either position?

simple thinking, two back to back fresh cells of the same type would cancel out, no voltage across the resulting battery, no current flow, the cells would just sit there and do nothing, as if they were entirely disconnected. they'd maybe discharge slowly at the normal self-discharge rate but otherwise would remain as ready for action as if they had been left in the unopened packet.

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but i bet it's not as simple as that.. I mean if one cell were slightly more highly charged than the other then you'd have some small voltage being applied to the device, not enough to turn it fully on maybe, but perhaps enough to allow a nonsignificant flow of current.

is that likely to be a situation that would be self extinguishing as the more highly charged 'winning' cell discharged more rapidly than the other? or would it go the other way with one cell doing some kind of runaway self-flattening?

Could you end up damaging the device doing this, I guess the worst you could end up with would potentially be 1.5V the wrong way round across a circuit expecting 3V in the other direction (maybe for an extended time)

Is it a recipe for a leak in the battery compartment?

Thoughts?

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