Petzl LED headlight users: lithium battery info

Saw this on Paddling.net, but I'll pass it on here. I have no idea if this is generic LED data since obviously other headlamp users use LEDs too these days, but passing it on:

http://en.petzl.com/petzl/LampesNews?News=159

Jay

Good catch, Jay. Both my LED headlamps are on the list -

Jay H said:

Saw this on Paddling.net, but I'll pass it on here. I have no idea if this is generic LED data since obviously other headlamp users use LEDs too these days, but passing it on:

Click to expand...

Thanks for the heads-up.

Under certain conditions, lithium batteries can put out slightly higher voltages than alkaline or NiMH cells. Lithium batteries also put out a higher voltage when new compared to after a bit of use. These can result in the LEDs being run at a higher power level which results in the LED runing hotter. Presumably the higher temp is too much for the LEDs in some of the Petzl headlamps.

The risk is a function of how much margin the manufacturer designed into the system--the chosen power level, how good the heat sink is, etc. The risk will also be less at lower ambient temps (eg winter).

Some of the higher power LED headlamps have temperature sensors (eg Ptec Apex) and will reduce the power level if the LED gets too hot. The regulated LED headlamps (any white LED lamp using less than 3 cells: eg the BD Xenix IQ) should also be immune to this problem because the regulator should provide a constant output over a range of input voltages.

There has been a problem found with some of the recent Garmin GPSes (*x models, using the SiRF III chipset) using new lithium batteries--they detect an overvoltage and shutdown. Garmin's suggested work around is to use the batteries in something else for a bit before putting them in the GPS. (New lithium batteries output a higher voltage when new--it drops to a lower constant level after a bit of use. See http://data.energizer.com/PDFs/l91.pdf.) This would also help to reduce the risk to LED headlamps.

Doug

thanks jay

both of MY headlamps are on the 'no' list.
Ed

Yup..gottem' on the no list too. Thanks.

Now I need to tell the rest of the "crew".