Noob question about rechargeables

[sdl]

I found a review here about a First Light Tomahawk flashlight that I had just bought and was looking into info about rechargeable 123's. I bought a charger and protected RCR123 batteries from AW and plan to recharge the batteries from my car.

Being a noob, is there any serious issues I need to know about recharging in a car? Are there temperature extremes I need to avoid when charging? Anything else that comes to mind would be to great. Thanks.

 

[mdocod]

Hi sdl,

Welcome to CPF!

I just spent some time on tomahalk's website and can't find anything on their that indicates compatibility with 3.7V cells.

This is not to say that they are not compatible, but I think it would be important to know for sure before using those cells and finding out the hard way.

Anyone know more about this? It would be good information to have on tap for future reference.

-----------------

As for temperature extremes, it's not great for li-ion cells to charge them when they are really cold, and it's not good to store them really hot. But taking a moment to consider how many millions of li-ion powered GPS units there are in cars, stuck to windshields, year round from arizona to north dakota, I don't see it as a major problem, but any pro-active steps you could take to keep the cells out of those temperature extremes whenever possible will certainly help extend their useful life and reduce the risk of fire/explosion.

Eric

 

[SilverFox]

Hello Sdl,

I will welcome you to CPF too.

The Tomahawk lights will run on a single 17670 cell, but you loose the brightest white LED setting. Two R-CR123 cells will result in too high a voltage and you will damage the light.

It will also run on one R-CR123 + a spacer or dummy cell. Once again you will only have medium and low on the white LED. The colored LED's will function properly with all three levels.

Tom

 

[sdl]

Thanks for the info. The forum member who reviewed the flashlight was using RCR123's. I wonder if his light burned out yet?

Silverfox, where did you get your information? Thanks for the heads up!

 

[SilverFox]

Hello Sdl,

I had a chat with the manufacturer.

Tom

 

[sdl]

That is strange. I just got off the phone with the manufacturer a few hours ago and they told me the RCR123's would work fine. In fact I was told that they use the "little blue rechargeables" in their Tomahawk's all the time at the factory. I guess I'll have to do a little more digging and speak directly to an engineer (he went home early today). Thanks for the info.

 

[mdocod]

That's interesting...

Most lights that have 5mm LEDs in them, don't use a true regulator for those 5mm LEDs, but instead, a carefully chosen resistor to mate with the intended power source. So often, the "main" beam will work fine with the higher input voltage as it will have a real regulator on it, but the 5mm LEDs will fail prematurely.

Some examples of lights that I am thinking of: The inova X5, the SureFire A2, and just about every LED cluster light ever sold.

This doesn't mean that tomahawk hasn't done something different, it sure would be nice if they had a true regulator on those 5mm LEDs that could handle the higher input voltage from RCR123s.

 

[SilverFox]

Hello Sdl,

I should have also mentioned that the Tomahawk is in a state of evolution. I have had mine for several months now, and the current lights may be a little different.

One of the issues they were trying to resolve is the parasitic drain when the light is turned off. If they revised the circuit to eliminate this, they may also have adjust things to allow for using 2 R-CR123 cells.

Tom

 

[sdl]

Not a problem Tom. I'll talk to an engineer before I put any RCR123's in it. Thanks again for the heads up!

 

[sdl]

Silverfox,

Now that you have had the light awhile, is your positive opinion of it still hold true? My LE model will arrive Tuesday.

 

[SilverFox]

Hello Sdl,

Yes.

The only issue I have is that the batteries will gradually discharge over time with the light turned off. For storage, remember to remove the batteries and you should be good to go.

Tom