Energizer Lithium Batteries in an LED Lenser P7

[Zatoichi]

In my opinion, if the manufacturer strongly advises against certain types of cells, that is evidence they may cause problems. Not proof, but evidence. Limiting the types of batteries you can use is hardly a selling point, so I'd assume there's something in it.

Having said that, I'd be inclined to risk using NiMH's in them if other people weren't noticing any problems. I wouldn't care too much about damaging a Lenser though. :devil:

 

[Marduke]

So Marduke, do you have you any evidence that NiMH batteries damage Lensers or is it your assumption that there will be problems?

None of it is unclear thanks.

What part of this is unclear:

I know that Lenser precludes their use and thanks to you I now understand why but I still want to know if there is any evidence of NiMH causing problems.

Thanks

It is a very common experience to burn out direct drive lights on NiMH that were designed for alkalines. The required resistor values simply do not match up for both chemistries. Little time with the search engine gives you a couple dozen complaints of 3xAAA direct drive overheating, and LED's burning out.

And here is the "heatsink" of the P7

A tiny little pencile thin stand of aluminum, and even then the main "heatsink" is sitting isolated inside the heat with an air gap to the outside. There is no path to the exterior until you get all the way down to the threads. That is a LONG way for heat to travel. And it looks suspiciously that there might be a plastic insulator stuck in there also!!!

And we already know from multiple people that the P7 "doesn't get hot", which when driven at the levels it is, is a very BAD thing.

From here.

 

[wingnutLP]

I do agree that the heaatsink looks crap but you still aren't answering my question.

If there is then I will sell the light if there isn't then I will keep using it and be a guinea pig.

 

[Marduke]

I do agree that the heaatsink looks crap but you still aren't answering my question.

If there is then I will sell the light if there isn't then I will keep using it and be a guinea pig.

Well, the P7 has not been out terribly long, and is not terribly popular among CPF for the reasons stated above. However, there is plenty of incidents of similar lights overheating when running on NiMH vs Alks.

Until someone wants to sacrifice their light for testing, only time will tell just how pronounced the problem is.

 

[wingnutLP]

only time will tell just how pronounced the problem is.

Or if there is a problem at all

 

[wingnutLP]

PS if I had seen the insides I probably wouldn't have bought it.

Now I have it I will run it on NiMH because I sure as hell will not be buying packs of alkalines!

I will let everone know how I get on.

Alex

 

[jupello]

A tiny little pencile thin stand of aluminum, and even then the main "heatsink" is sitting isolated inside the heat with an air gap to the outside. There is no path to the exterior until you get all the way down to the threads. That is a LONG way for heat to travel. And it looks suspiciously that there might be a plastic insulator stuck in there also!!!

And we already know from multiple people that the P7 "doesn't get hot", which when driven at the levels it is, is a very BAD thing.

From here.

I'd say that the main reason P7 does not get terribly hot in use is that the head is not airtight unlike in many other lights, so the hot air actually has a way out from there.

You cant judge light's heatsinking just by the temperature of the body after prolonged use. The heat HAS TO go somewhere somehow, so even IF the heatsink would suck, the light would still get hot after a while when the hot air inside has warmed up the aluminium body.. unless the heat has some other way out from the light.

And maybe you mean the O-ring by that suspicious "plastic insulator" there

 

[Marduke]

I'd say that the main reason P7 does not get terribly hot in use is that the head is not airtight unlike in many other lights, so the hot air actually has a way out from there.

So, a "waterproof" light has airflow INSIDE the head??

You cant judge light's heatsinking just by the temperature of the body after prolonged use. The heat HAS TO go somewhere somehow, so even IF the heatsink would suck, the light would still get hot after a while when the hot air inside has warmed up the aluminium body.. unless the heat has some other way out from the light.

You don't have any thermodynamics background, do you?? :shakehead

 

[jupello]

So, a "waterproof" light has airflow INSIDE the head??

You don't have any thermodynamics background, do you?? :shakehead

It is not waterproof. Maybe more like splash proof or something, but the head of the light is definitely not airtight. The free air movement is needed for the smooth movement of the slide focus too if you think about it.
Btw. I'm pretty sure it would survive all those submerging & freezing tests that has been seen here just fine.. there would just be some water in the head, that could distort the beam a bit..

And no, I don't have much thermodynamics background, please enlighten where I went wrong?
You say that aluminum light with bad heatsink (and airtight head) would not get hot after long use?

 

[Marduke]

And no, I don't have much thermodynamics background, please enlighten where I went wrong?
You say that aluminum light with bad heatsink (and airtight head) would not get hot after long use?

LED's get hot, and NEED to get rid of that heat. If the outside body of the light is not hot, that means the heat is not able to reach the exterior (the only place to dissipate it), and is instead built up somewhere else inside the light. That means it's cooking the LED.

Think of it like blowing up a balloon. The air is heat, and the rubber is the exterior of the light. You can blow more air (heat) into the balloon, but it cannot exit without breaking the surface (skin) in some fashion. It can't magically just disappear inside and everything "just be okay".

 

[Marduke]

It is not waterproof. Maybe more like splash proof or something, but the head of the light is definitely not airtight. The free air movement is needed for the smooth movement of the slide focus too if you think about it.
Btw. I'm pretty sure it would survive all those submerging & freezing tests that has been seen here just fine.. there would just be some water in the head, that could distort the beam a bit..

Just checked their website, they are marketed as "water resistant", so....

 

[jupello]

LED's get hot, and NEED to get rid of that heat. If the outside body of the light is not hot, that means the heat is not able to reach the exterior (the only place to dissipate it), and is instead built up somewhere else inside the light. That means it's cooking the LED.

Think of it like blowing up a balloon. The air is heat, and the rubber is the exterior of the light. You can blow more air (heat) into the balloon, but it cannot exit without breaking the surface (skin) in some fashion. It can't magically just disappear inside and everything "just be okay".

And if the heat is not able to reach the exterior, it means that there would have to be some insulation between the heat source and the exterior preventing that. I don't see such thing in this case. As far as I know, aluminum conducts heat pretty well, and IF the air inside the head would be hot, the aluminum in contact with that air should become hot too.

Just checked their website, they are marketed as "water resistant", so....

Yeh, not airtight.. I have tested it :huh:

 

[Hitthespot]

 

[Marduke]

And if the heat is not able to reach the exterior, it means that there would have to be some insulation between the heat source and the exterior preventing that. I don't see such thing in this case. As far as I know, aluminum conducts heat pretty well, and IF the air inside the head would be hot, the aluminum in contact with that air should become hot too.

It doesn't necessarily mean there is an insulator, but just that there is a poor thermal path. In this case, it's a matter of being on a tiny little pencil thin pedestal.

Although you speak of the air gap with even if not sealed is an excellent insulator. Air is a horrible heat conductor by itself.

 

[Patriot]

Air is a horrible heat conductor by itself.

Exactly! I don't think some folks are understanding that part. The fact that the light isn't getting hot is a good indication that the thermal path, in this case is the air, isn't being conducted. This is why suggesting that the LED would superheat a pocket of air which would then warm up to the same temperature and transfer to the body is flawed. The air itself IS the insulator. With a good conductor such as copper or aluminum the transfer is very rapid.

I think anyone at this point wanting to still run L91's or rechargeables in the P7 Lenser should just go for it. Much of this CPF is about pushing equipment to it's failure point and Marduke knows that better than most. Just put a sticker on your light that says "experimental" so that if it does fail you're not shocked by the result. Treat it like a toy and don't pack it inside of your hurricane, earthquake, or bug out kit. In the mean time, catalog your hours of use and then report back here about how well your experimental light is holding up.

Hopefully this solution to the dilemma satisfies both the "I warned you" and "hot rodder" crowds.

 

[Egsise]

Amen to that.

With the 100% or 130% setting there should be no problem if you use it only short bursts, or make sure that it is very well cooled.
_Should_
But if you blow your led, could you post here what kind of conditions it happened.

 

[jupello]

Yes, air is bad conductor, so the led+heatsink would need to have enough surface area to transfer the heat into the air to make it hot(I didn't come to think about that earlier).. it would be interesting to test if the light heats up more when the airholes are shut..if that does not have any effect, it might indeed have too little heatsinking.

But I've been thinking about it way too long now anyways, time to sleep now :tired:

 

[deusexaethera]

It is a very common experience to burn out direct drive lights on NiMH that were designed for alkalines. The required resistor values simply do not match up for both chemistries. Little time with the search engine gives you a couple dozen complaints of 3xAAA direct drive overheating, and LED's burning out.

And here is the "heatsink" of the P7

A tiny little pencile thin stand of aluminum, and even then the main "heatsink" is sitting isolated inside the heat with an air gap to the outside. There is no path to the exterior until you get all the way down to the threads. That is a LONG way for heat to travel. And it looks suspiciously that there might be a plastic insulator stuck in there also!!!

And we already know from multiple people that the P7 "doesn't get hot", which when driven at the levels it is, is a very BAD thing.

From here.

That's when you buy the extra-large tube of Arctic Silver 5 and soft-pot that SOB.

 

[Helstar]

I have a P3 and I emailed Coast about energizer lithiums and they told me that they worked fine with them. But, they also said that they built the LED lenser so that you would not have to use Liths. I have not tried it yet. But they said that it was fine in my P3

 

[Patriot]

I have a P3 and I emailed Coast about energizer lithiums and they told me that they worked fine with them. But, they also said that they built the LED lenser so that you would not have to use Liths. I have not tried it yet. But they said that it was fine in my P3

That's not surprising since there is a big difference in the heat these two LED's are capable of generating. The P3 will never push the thermal envelope like the P7 will if allowed enough power.