0V 18650 died stored in headtorch Wizard Pro v3

Noticed my headtorch was unexpectedly dead. Tested the battery to find 0v, "normal" internal resistance~80. During the short time testing the voltage rose to 1.1v and looks like it would keep slowly raising with test probes attached. Confirmed it isn't the tester as alternative 18650 tested normally.
The battery is the armytek 18650 included with the headtorch.
Obviously going to dispose of the battery.
I can see no damage to the battery or the torch. Torch still works with alternative battery.

Torch and battery been used for around 3 years. Seeing most use during winter for running, does get wet from rain occasionally.
Just posting as a heads up and to see if there is anything I should watch for.
The torch has magnetic charging but I use the xstar dragon vp4 to charge and alternate between batteries. I usually store the torch using the magnetic tailcap (to metal) however have never had a problem doing this before.

I assume the battery shorted somehow. Could have been a problem inside the torch or the way I stored it. There is supposed to be a diode preventing the tailcap/charging from discharging this way. Like I say no damage to wrapper etc.

Was this the AT battery? Also, do you lock out the tail during storage?

You really shouldn't have to do a lock-out during storage. It doesn't hurt, of course, but I never do it with any of my lights. They all have very low parasitic drain, so storage for months or even years with a battery installed and ready-to-go isn't an issue.

If his light drained the battery, something else is wrong. It could be the light shorting something out, or perhaps the electronics not properly going into a proper low-drain mode when off. But, my bet is it's the battery. Sometimes, cells can develop internal shorts, and that will slowly drain the battery. Over a few weeks or months, the cell will go completely flat. Since it's a slow self-discharge, the cell can appear normal when you charge it, but monitoring its voltage over several days will show a slow discharge.

My bet is that the light is fine.

Yes it is the original AT battery.
In this case I am not sure if it was locked out. Sometimes I partially twist the tailcap and sometimes forget. I only do it incase I quickly put it in a bag to stop it turning on. Fairly sure it wasn't locked out (tailcap was tight) but not certain.

Hoping it is the battery. I will monitor the battery I have in now to see if the torch is draining it. Would only have been alone for a month at most more likely 2 weeks. I guess it could have been draining it for a while and I put it down to usage as it gets the most use of any light. Will update once I find out which one of my tools to blame for this!

You gave the old battery a bit of a charge. Measure it now and see if it's dropping back towards 0v. If so, you know it was the battery.

Just an update, I have stored a different battery at 4.1v in the torch, it seemed to hold charge with tailcap slightly unscrewed. After tightening tail cap around a week ago it has dropped to 3.56v in storage. Going to re charge and retry.

What do you reckon? Should I not use the torch?

WalkIntoTheLight said:

You gave the old battery a bit of a charge. Measure it now and see if it's dropping back towards 0v. If so, you know it was the battery.

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No I didn't intentionally recharge. The voltage raised from 0V as I was making the voltage measurements. It only raised whilst the probes were in contact, have no idea why. It's voltage now is at 1.7 and I am probably going to dispose it.

Sounds like the light is draining the cell for some reason. Maybe a short or something that is not turning off that drains power.

I would contact the manufacturer and see what they say before using it.

xxo said:

Sounds like the light is draining the cell for some reason. Maybe a short or something that is not turning off that drains power.

I would contact the manufacturer and see what they say before using it.

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Thank you, I will try and contact them.

Lou Minescence said:

Kallyfudge,
I've posted in another thread a similar experience where my Wizard drained its unprotected Armytek battery to zero. I put another battery in and it seemed ok until I noticed the light smoking ! There is some type of short going on in your light. Do not use it.

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Wow! Thank you for that information! I no longer have a headtorch in that case, that is a shame. I wont do any re-testing. Will check out your post now. Thanks again!