Headlamps and Battery Drain

Why do headlamps drain batteries completely when they are not even being used? I have two lanterns that do not do this - you can leave the batteries in and come back and the lantern will work fine months later. If I leave batteries in my headlamp and come back a month later they are 98% dead.

I've got 3 different brands of Petzl Headlamps and they all do this. Does any brand of headlamps not do this?

I'm guessing there is a software switch - so the light is always checking on lower power for the switch on sequence. This happens with my DiNotte cycling light - so I unplug it from the battery when not in use. My Petzl Tikka doesn't seem to have this problem.

Tim

The only way to save your batteries is to remove them when the light will not be used for an extended period.

Your lantern probably has a hardware switch and many (most? almost all?) modern headlamps have software switches. Any software switch has to consume some amount of power when it is off--good designs draw insignificant amounts of power, poor designs draw enough power to discharge the batteries over time.

FWIW, I have never had this problem with a variety of Princeton Tec and Black Diamond LED headlamps.

Doug

Thanks for the info.

Follow up question - once you start using a battery for the first time, will it lose power even if you take them out of the device? I know batteries lose power over time even if you don't use them, but does this speed up the process, and by how much (roughly)?

roadtripper said:

Follow up question - once you start using a battery for the first time, will it lose power even if you take them out of the device? I know batteries lose power over time even if you don't use them, but does this speed up the process, and by how much (roughly)?

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Loss of power while not in use is called self-discharge (which leads to a finite shelf-life).

I'm not aware of any data indicating that self-discharge is any faster in partially used cells than in unused cells.

I wouldn't worry about it--in either case, your best strategy is to remove the cells when not in use. (If the cells last ~30 days in the device (turned off), you can assume that they lose ~3% of their capacity per day.)


BTW, it may be better to think of devices with a software switch as having a standby state rather than an off state.

Doug

Now you know why the petzl user's manual states to remove the batteries when storing the headlamp.

When the batteries get real low they tend to leak no matter what brand they are.

...and this doesn't just apply to headlamps. Many electronic items and even cars consume a small amount of electricity when they are turned off. I'm surprised DougPaul didn't tell you that. (Hi DougPaul)

DougPaul said:

FWIW, I have never had this problem with a variety of Princeton Tec and Black Diamond LED headlamps.

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I also never had any battery drain problems with my two Princeton Tec LED headlamps.

Marty