NEED HELP WITH BATTERIES

[scottshad]

Being in law enforcement my lights get a lot of use. I recently changed from primary batteries to rechargable.
When I was using primaries (CR123A) the light would slowly lose it brightness when using it for a extended period. Which was GREAT, because it still gave you light and it notified you that would have to replace the batteries shortly.
BUT, I switched RCR123A because I have been using a lot batteries and was thinking about being more "GREEN"
HERE is the problem---when using the RCR123A, instead of the battery losing its power slowly, the light just shut down. No warning, just shuts off.
I was told I might be using the wrong charger, and so I bought a recommeded charger and new batteries and it the same thing. When used for extended amount time the light just shuts off.
I am using Olight M20, M21, and M30.
Is this normal for rechargeable batteries? Do they just shut off when the power gets to a certain level?
Thank you

 

[hcb]

As I understand it, rechargeable Li cells often have built-in protective circuitry to prevent the cells from being over-discharged which is why your light just drops dead. Primaries like the CR123a lose voltage (more) slowly when they are discharged and you get the gradual dimming you experienced.

Someone with more knowledge will undoubtedly be here shortly to correct any mistakes from my side

 

[Roger999]

Protected LiCo cells like AW RCR123 have a circuit that cuts the power when it is close to being out of power because full discharges will lead to less cycles out of your battery.

LiMn batteries (AW IMR 16340) could be an option because will dim with use because they do not have a protection circuit, but if you are repeatedly draining the batteries 100% then they might not last more than a couple dozen cycles, since many LEDs are semi-regulated the light might not dim until the light is almost fully discharged(which is good for the light but bad for the batteries).

 

[joe1512]

Note that some lights themselves have undervoltage protection and THEY shut off after the battery goes below 2.8 volts.
So depending on the light it is not necessarily the battery.

Some lights also shut down a bit more gracefully too, by giving a low-battery warning LED.

You can either,
a) Read and see if its the flashlight. If not, try the IMR route.
b) Get a flashlight that has a low battery warning.
c) Charge them more frequently. As long as they are topped off reasonably often, this won't be an issue. The catch is finding an 18650/RCR123 charger that will work in your car!
d) Buy a few extra sets of batteries. After a good X minutes of use, swap the batteries. Then each night, charge em all back up.

 

[Mjolnir]

I would suggest using a single lithium ion cell in those lights, such as an 18650 or 17670 (depending on what fits, I know that the M20 takes 18650s).

Depending on the Vf of the LED, a single 18650 will run the light at full brightness for a certain period of time, until the battery voltage drops below the Vf of the LED. After this it will drop out of regulation, and the light will dim until the protection circuit is tripped. This is because most lights that can run off of 2 CR123's and 1 18650 are not regulated for both and only have circuitry that lowers the voltage (buck), not the boost circuitry required to raise the voltage of a single cell when it drops below the Vf of the LED.

Note that some CR123/18650 lights don't dim when using 18650s, because the Vf of the LED is very low.
You can see the 18650 regulation if you scroll down to the first graph here on Light-Reviews:
http://www.light-reviews.com/olight_m20/

 

[scottshad]

WOW, now that is what I call service. I thank you all very, very much for the insight and for the options that you have given me!
People, I don't come here as much as I would like to (between work, my granddaughter, and keeping my home up) but I know if come to ask for answers I will surely get them!
Again, I thank you and I thank the staff members who keep this site running professionally!
Take care all.................
scott