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Petzl Myo XP disaster: a word to the wise
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Brian James
(bjamesd) - F

Locale: South Coast of BC
Petzl Myo XP disaster: a word to the wise on 03/29/2008 13:27:20 MDT Print View

So I installed one battery in my headlamp backwards to prevent it from accidentally coming on and discharging.

I left it that way for days.

Today I picket it up by the battery pack to move it, and noticed that it was hot. I opened it up and the middle (backwards) battery had swollen up. All three batteries were warm/hot to the touch.

So a word to the wise: These batteries will cook themselves for some reason if you flip one around.



Christopher Holden
(back2basics) - F - MLife

Locale: Southeast USA
Hindsight is 20/20 on 03/29/2008 13:39:03 MDT Print View

A better move would have been to remove one or all. By flipping one, you upset the evil electrons that will impose their wrath upon the batteries, and quite possibly the circuit of the device too. Of all lessons to be learned, this one is pretty inexpensive. Consider it a bonus that you learned it at home instead of out in the backcountry.
Pour a drink and enjoy the rest of your weekend!

Dave .
(Ramapo) - F
Another thing on 03/29/2008 14:11:16 MDT Print View

Along similar lines, another thing you should never do is absent mindedly put a battery in your pockets with loose change or other bits of meatal as that's a recipe for conductivity city and acid in your crotch...which is to be avoided to be sure.

I thoughtlessly put a pair of AAs in my pocket once, then, later that night, took my pants off at night and tossed them on the floor... The next morning one of the AAs had burst and there was a giant hole in the pants and even some burns on the carpet where they'd been tossed.

Not smart.

Daniel Strange
(strangdj) - F
worthwhile caution on 03/29/2008 15:42:54 MDT Print View

The backwards battery trick only works if you have an even number of batteries, and they are all at equal state of charge. Otherwise you are running current through the odd battery backwards, hence cooking it. Should not have happened if the headlamp was off, but then again the whole point was to protect against accidentally turning it on. Defeats the purpose if accidentally turning it on cooks the batteries anyway.

Brian James
(bjamesd) - F

Locale: South Coast of BC
Re: worthwhile caution on 03/29/2008 17:25:19 MDT Print View

So I take it that I turned it on by accident, and that's what completed the circuit?

Can I trust the headlamp anymore??

Rick Dreher
(halfturbo) - MLife

Locale: Northernish California
Re: worthwhile caution on 03/29/2008 23:14:55 MDT Print View

Yikes, I guess you must have switched it on accidently, but being familiar with the XP's switchgear it's hard to guess how. I suppose closing the circuit created a Battery War, with the two cells facing off against one, with the results you experienced. (This is a very scientific speculation hat I'm wearing here.)

Either the headlamp works or it doesn't--there's no middle ground. Reversing polarity on an LED will kill it pronto. Luckily, the battery box is far away from the electronics so they didn't share in the heat event.

For anybody wanting a failsafe battery disconnect while keeping them in place in the flashlight, slip a little piece of cardboard or plastic between one of the batteries and a terminal--guaranteed dead circuit. Store it in the battery container between uses.

Edited by halfturbo on 03/29/2008 23:15:22 MDT.

Greg Vaillancourt
(GSV45) - F

Locale: Utah
FYI - Petzl does not recommend Lithium batteries on 03/30/2008 15:58:24 MDT Print View

They have issued overheating warnings for them even when installed in proper order.

This is a quote from the REI site.
"Petzl warns against the use of lithium batteries with this headlamp as doing so might cause the lamp to overheat and damage the LED bulbs."

You may choose to use them but I don't know if Petzl's stance is widely known.

darren stephens
(darren5576) - F

Locale: Down Under
lithium batteries on 03/30/2008 16:14:46 MDT Print View

Just a note on the XP with lithium batteries. I have one of these and use it nearly every day at home around my farm as well as hiking. I thought id try a set of expensive lithium batteries but i found they only lasted about half the life of normal HD batteries. I found no other problems though.

Edited by darren5576 on 03/30/2008 16:15:31 MDT.

Brian James
(bjamesd) - F

Locale: South Coast of BC
Re: FYI - Petzl does not recommend Lithium batteries on 03/30/2008 16:45:25 MDT Print View

Yes I was aware of Petzl's stand on Lithiums. The problem is that modern Lithium batteries produce more current that the theoretical maximum spec for AA's. Since the Petzl circuitry is unregulated, this overcurrent situation can cook your LED. Petzl says it's not their fault, since it's technically a non-standard battery causing the problem.

Since I live in freakin' Canada, though, the headlamp is not worth bringing if it's going to dim out every time it gets cold out. My solution was to never run it on high power when the Lithiums were fresh, thereby theoretically preventing an overcurrent situation in the LED.

It was either that or throw it out, since I don't need all that light in the summertime!

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Re: FYI - Petzl does not recommend Lithium batteries on 03/30/2008 17:19:39 MDT Print View

Why not use a light designed to handle lithium batteries? There are a number of them out there.

Brian James
(bjamesd) - F

Locale: South Coast of BC
Re: FYI - Petzl does not recommend Lithium batteries on 03/30/2008 20:07:47 MDT Print View

I bought it before they issued the warning about Lithium batteries.

I traded emails with them about how my $70 winter headlamp was now useless in the winter, but they just insisted that it's the fault of the battery makers and they take no responsibility. I understand both sides of the issue.

I was kind of secretly hoping that I'd cooked mine through my little misadventure, but alas it still works.

Monty Montana
(TarasBulba) - MLife

Locale: Rocky Mountains
Re: FYI - Petzl does not recommend Lithium batteries on 03/31/2008 00:06:23 MDT Print View

The Complete Walker also disavows the use of lithium batteries with LED flashlights, saying they're not compatible. In cold weather I keep my batteries in a pocket (sans coins and keys) so they'll be warm, preventing the power from falling off so rapidly.

Jason Brinkman
(jbrinkmanboi) - MLife

Locale: Idaho
Re: Lithium batteries on 03/31/2008 08:51:11 MDT Print View

I have used lithium batteries in my Princeton Tec headlamps for a couple of years now without issue. However, I have never tried lining up all the batteries in the same direction! My current headlamp - the Princeton Tec Quad is voltage regulated, which would presumably solve the Petzl concerns.

Rick Dreher
(halfturbo) - MLife

Locale: Northernish California
Re: FYI - Petzl does not recommend Lithium batteries on 03/31/2008 11:00:02 MDT Print View

NiMH cells perform well in the cold, and while their output is lower than fresh Li or alkaline cells, they should still perform adequately in the Myo. They're also vastly less expensive to run.

Fresh Li cells can put out 1.6V or so, and that's the risk they pose to an unregulated light (such as the Petzls). They're quite safe in the regulated PT lights, and are almost freakishly good in the Eos.

Of course, LED overheating wasn't the problem in the OP here. It was a case of battery self-destruction.

Greg Vaillancourt
(GSV45) - F

Locale: Utah
wombats on 04/05/2008 17:35:49 MDT Print View

"I have used lithium batteries in my Princeton Tec headlamps for a couple of years now without issue."

Yep me too.

Ditto on Rick's observations re: the EOS.

greg degler
(gregdegler) - F

Locale: West
Petzl MYO XP update on 07/18/2009 14:10:22 MDT Print View

Greetings BPL friends,

I've used the MYO XP for 3 years with Alkalines, Rechargeables and Lithiums. I LOVE this light, and have had no negative issues with it (NONE!). That is until it just plain stopped working about a year ago. I called Petzl, customer service said "send it up" and within the week a brand spankin' new one arrived via mail. Turns out there was/is a recall of some sort. I mention this to reflect a MOST EXCELLENT PETZL Customer Service experience!
However, while on one of the other outdoor gear websites discovered a new model, an update of the MYO XP. The MYO RXP. Was surprised and saddened to find that it does not come up at all on the BPL "search". If you like this headlamp, look into the updated version. I find the improvements highly desireable.
I am getting one !


Walter Carrington
(Snowleopard) - M

Locale: Mass.
Lithiums in Myo XP on 07/18/2009 14:23:17 MDT Print View

My understanding from correspondence with Petzl is that the problem with lithium AA batteries in the Myo XP is that these batteries can put out much higher currents than alkaline batteries. So, if the wires get worn and short out, quite a lot of energy is put out instantly. This can cause a fire or even an explosion. My solution is to inspect the wires and connections as the headlamp gets older and to replace or repair anything that could cause a short circuit. The same is true of the Tikka XP.

I don't think that the higher voltage of new lithiums will damage the circuitry but I could be wrong. I'll find out next winter.

I like both the Tikka XP and the Myo XP quite a bit.