Flashlight with built in protection for use with unprotected recycled 18650 batteries

condor22

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Feb 1, 2014
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Recommend to me flashlights that have protection for unprotected recycled 18650 batteries. I have amassed a small collection of used unprotected 18650 batteries and would like use 'em and give my nephew a light that won't over discharge unprotected 18650 batteries. Most likely I'll be recharging for both of us, or I'll point him to the CPF's battery safety threads.

This light seems to be what I'm looking for, if it's not please explain and recommend flashlights that can safely use unprotected 18650 batteries.:thanks:

www . illumn . com Convoy M2 XM-L2 T6 Neutral White 18650 with "Low voltage protection at 2.8V"
 
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THE_dAY

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Nov 28, 2003
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sfv, california
From reading around I see that even lights with 'low voltage protection' have the ability to drain cells.
The protection kicks in and light goes to a low level but if left unattended can still drain a cell empty.

I have a few lights that use pretty much the same AMC7135 linear driver as in the Convoys (with voltage protection) and would not feel safe having someone who has little or no knowledge of li-ions use it for long period of time.
I've had a cell go below the 2.8V cutoff but luckily I caught it before it got to an unsafe level.

There's probably other lights that have a real cut off at 2.8V and I'm hoping someone else can chime in with examples.
 

hiuintahs

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What I have found is that when the voltage drops below 3v and before it gets to 2.5v, the light starts to get dimmer than normal. Use that as a hint that its time to recharge the battery.

Let me make some assumptions:

I know a couple of Fenix lights like this and I'd think many are this way simply because the forward voltage drop of an XP-G2 or XM-L2 is in the 2.8 to 3.0v range and that would necessitate that the circuit switch from buck to boost mode. And knowing that is a more complicated driver scheme, my bets are that most lights that utilize a 18650 do not have buck-boost circuits. then for the most part it can be counted on that when the battery voltage drops to the Vf of the LED which is higher than 2.5v..........you can count on the light dimming. And that dimming is your notice that its time to recharge the battery.

Granted this isn't a fail safe method. But for users with knowledge of lithium ion and have volt meters and can track their batteries..........running non-protected batteries has never been a problem for me.

Battery voltage levels that affect dimness on the Fenix PD32:
http://www.candlepowerforums.com/vb...ower-cutoff)&p=4478509&highlight=#post4478509
 
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reppans

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Mar 25, 2007
Messages
4,873
What I have found is that when the voltage drops below 3v and before it gets to 2.5v, the light starts to get dimmer than normal. Use that as a hint that its time to recharge the battery.

Let me make some assumptions:

I know a couple of Fenix lights like this and I'd think many are this way simply because the forward voltage drop of an XP-G2 or XM-L2 is in the 2.8 to 3.0v range and that would necessitate that the circuit switch from buck to boost mode. And knowing that is a more complicated driver scheme, my bets are that most lights that utilize a 18650 do not have buck-boost circuits. then for the most part it can be counted on that when the battery voltage drops to the Vf of the LED which is higher than 2.5v..........you can count on the light dimming. And that dimming is your notice that its time to recharge the battery.

Granted this isn't a fail safe method. But for users with knowledge of lithium ion and have volt meters and can track their batteries..........running non-protected batteries has never been a problem for me.

Battery voltage levels that affect dimness on the Fenix PD32:
http://www.candlepowerforums.com/vb...ower-cutoff)&p=4478509&highlight=#post4478509

+1 to everything he said.

I test my high voltage Quarks (3-9v) on 2xAA tubes to see how it would perform if I needed to scrounge AA/AAAs in an emergency. It gradually steps down through the modes depending on voltage and will even limp along on moonlight and low on near dead Eneloops (<2.5V). At ~3V resting (2xAlks, 1xCR123 or CRAA) it'll run high well enough, but not max.

So I just use my usually AA/Eneloop "light meter" test - when I think I might be running low, I'll just compare the outputs between Max and High - when I can't see any difference, I know the cell is nearing the end.

One other really nice thing about Li-ions is that their discharge curves are very even/linear and voltage is an accurate indicator of remaining capacity. If you measure your voltage frequently for 5-10 battery cycles, you get a very good feel of how much juice you're using. It's similar to if your car's fuel gauge where to fail - you'd have a good sense of where you were and perhaps just need to fill-up a bit more often to be safe. Not a bad practice for flashlights anyways. :)
 

P_A_S_1

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NYC
HDS lights do but they currently don't have 18650 battery tubes. On the HDS thread this occasionally comes up and those close to the company state they're 'in the works', however HDS is notorious for long delays and items that just never seem to make it to production. They have made them in the past, you can check the market place, but they won't be compatible with the new generations of HDS lights and from what I understand they're kind of rare.
 

StorminMatt

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Joined
Oct 30, 2012
Messages
2,263
Location
Norcal
From reading around I see that even lights with 'low voltage protection' have the ability to drain cells.
The protection kicks in and light goes to a low level but if left unattended can still drain a cell empty.

I have a few lights that use pretty much the same AMC7135 linear driver as in the Convoys (with voltage protection) and would not feel safe having someone who has little or no knowledge of li-ions use it for long period of time.
I've had a cell go below the 2.8V cutoff but luckily I caught it before it got to an unsafe level.

There's probably other lights that have a real cut off at 2.8V and I'm hoping someone else can chime in with examples.

I have a couple of Foursevens Maelstroms (MMU-X and MMU-X3). And they both switch off when battery voltage gets too low. Of course, these are 26650 lights. I'm not sure how their 18650 lights handle low voltage. But I would imagine it's much the same.
 

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