Running on Li-on's - How to determine?

I've got the bug to run my lights on Li-on cells where possible. I learned about running my U2 on 18650's and my HDS (2x123 tube) on 17670's from reading posts here.

But, what about other lights? How do you determine a light is a good candidate to try a Li-on in? For example, I have a Nuwai TM-301X-3 (2x123) that I would like to run on a 17670. If the cell physically fits, do I just try it? There must be other electrical considerations to making the switch.

I'll sit tight and not risk any light damage until I hear from anyone with experience on this.

Thanks for any information,
Bill

if your worried about RISK , you dont TRY anything just do what the manufacture suggests.

the things your mentioning represent little risk.
if you were using a SERIES set of 2x3V batteries, then there is an asumption that the device can handle the 6V. if it can handle the 6V then it most likely could handle the 4.25V of a li-ion.

If on the other hand it was running off of 1X3v battery before, then there is a very good chance that a 4.25V battery will at least run it hotter, and might damage something. it might just make it last less time, even if it works.

same thing with 2X1.5V batteries, if it INTENDS to have alkilines, or even primary lithiums in it, that would be a max of 3.4V.
A 4.25V battery or worse 2 of them, could be to high. from what i have seen MOST devices that want your usual AA or AAA battery will be ruined with Li-Ion batteries put into it.
because it wants about 1.5V and your slamming it with 4V. 3 TIMES as much.

A simple cheap DMM, could be used to measure what the battery(s) your using now are in voltage, then measure what you are about to stick into it the same way. if the voltage is higher, then your taking a risk.

also you need to be carefull that the battery contact point wont cause a short. a big fat tab on the li-ion, could make different contacts, than the normal battery.
look up where the top connection is going to go, is there adequite seperation to insure that the battery will not short something?

if your not using a "protected" cell, will the curcuit of the device try and drain the battery to low, damaging it.

if you ARE using a protected cell, will jamming it into the case, get it stuck, or cause the insulation of the battery and that wire(band) running down the battery to short.
never jam a cell into anything, because of insulation, and protection stuff.

in most instances, a 2x3v (end to end / series) will not be damaged by the 4.25V of the li-ion rechargable battery, as long as you check all that other stuff.

that discludes modifying it to work with the higher voltage.

for example, the 3xAAA series wired lights have a 4.5 type of voltage.
if you put a SINGLE Li-Ion at its 4V, then that works out pretty good.
so some stuff can be changed from series, where you stacking up the voltage to reach higher voltages, to Parellel or single.

it also discludes that some stuff the battery is very weak, and puts out little current. like a stack of tiny hearing aid batteries, might have the voltage, but they dont put out the current a good rechargable could.
for example: a Photon uses 2x3v tiny coin batteries, and if you replaced that with a omnipotent 4V battery, it would still be more powefull than the little tuny battery that was in there.

VidPro, thanks so much for your detailed and well thought out answer! You mentioned many variables I didn't even consider. Could have cost me.

I should have mentioned, I'm mainly concerned about alternative single cell power for my 2x123 torches. I like the "free lumens" and am concerned about the reports of venting / exploding multiple 123's.

Plus, I just removed the sleeve in my U2 so I can use 18650's. I guess that was officially my first mod. No big deal really, but it felt kind of exciting to change my light for the better.

I have printed your post and am placing it on my workbench to act as a checklist to go over before getting too creative with my experimentation.

Thanks again for taking the time with this.:goodjob:

Bill