How do you know when it's time to recharge your Li-Ion's? ?

[elwood]

I am awaiting a T100C2 MK II with some EagleTac protected 18650's.

This is my first flashlight using Li-Ions. I have been doing lots of reading as it seems these batteries should not be used by someone that is not informed.

I know you should not discharge them lower than 3.0v (correct me if i'm wrong.)

Now I know not everyone carries around a multimeter when using their flashlight to periodically check the voltage of your cells.

And i know no one routinely or deliberately runs a flashlight till the protection circuit kicks in.

So how do you know when it's time to charge your battery?

 

[yellow]

check the current draw at battery in full power mode,
calculate runtime
calculate how long the light has been used already
when the next use might be considerably longer, charge the cell(s)

every few months, charge all the spares, let them run for 10 mins, change the cell inside the light to another one, store away spares

 

[elwood]

check the current draw at battery in full power mode,
calculate runtime
calculate how long the light has been used already
when the next use might be considerably longer, charge the cell(s)

every few months, charge all the spares, let them run for 10 mins, change the cell inside the light to another one, store away spares

This causes me to have second thoughts of using Li-Ion. This is completely impractical.

I guess there's always a compromise.

 

[csshih]

or.. you can just use the light until the protection circuit kicks in, cutting off the light.

 

[elwood]

or.. you can just use the light until the protection circuit kicks in, cutting off the light.

Correct me if i'm wrong, but from what i read, they are not very reliable?

Another thing i gather is that you're less likely to have problems from overdischarging a battery. The problems arise when you go to charge an overdischarged battery.

So i guess i could take the chance of overdischarging and use the protection circuit to know when to recharge and always check voltage before charging, recycling anything under 3.0v's?

 

[VidPro]

according to this, that particular item will tank in output , when you should stop.
http://www.candlepowerforums.com/vb/showthread.php?t=239366
like many lights do, before the protection kicks in, before the battery gets way to low.

with THAT particular item and 2X li-ion 123s they will NOT tank in output untill fully depleated.
this all has to do with the voltage range of the driver. and voltage range of the battery 2X vrses the one 18650

So when it takes a dive, recharge it, in an emergency, you WILL be able to run it for a "while" even after it takes a dive, then recharge it sooner after that.

Note: i didnt spend a lot of time verifying the info, because it is very common for specific types of lights, but thats pretty much what the graphs show.
lights with different types of drivers will not be the same as the above light, so if you stuff a 18650 in a light that is a boost driver, then it all changes.
this particular item has in it a driver that will handle 2X123 or a 6+volt input fully regulated, that is what makes it common with this type.

 

[elwood]

according to this, that particular item will tank in output , when you should stop.
http://www.candlepowerforums.com/vb/showthread.php?t=239366
like many lights do, before the protection kicks in, before the battery gets way to low.

with THAT particular item and 2X li-ion 123s they will NOT tank in output untill fully depleated.
this all has to do with the voltage range of the driver. 2X vrses the one 18650

So when it takes a dive, recharge it, in an emergency, you will be able to run it for a "while" even after it takes a dive, then recharge it sooner after that.

Note: i didnt spend a lot of time verifying the info, because it is very common for specific types of lights, but thats pretty much what the graphs show.

Aaah! Thanks for bringing this to my attention. I've read that review and charts a hundred times but never realized the lights output would significantly drop when the batteries voltage gets low enough.

I'm assuming that this is due to the circuitry being regulated. I don't think i would ever buy an unregulated flashlight that uses li-ion's.

 

[VidPro]

actually that is a beautifull graph , and what everyone wants in a light , they just dont know it
if you want awesome runtimes and not to be left in the dark, use the 18650, if you want major brightness for short times, use 2x123 primaries.
and that is about how a human uses stuff sorta too. if you have the big fat rechargable in, its because you use it a Lot, and for long times, and over and over again, and are close to a plug.
if you have the 2 expencive throwaways in, then your not close to a plug need light weights, or its sitting on a shelf somewhere waiting patientally for you to use it
best of both worlds, even if you carry 2x123 lightweight primaries as the "spares".

 

[elwood]

actually that is a beautifull graph , and what everyone wants in a light , they just dont know it
if you want awesome runtimes and not to be left in the dark, use the 18650, if you want major brightness for short times, use 2x123 primaries.
and that is about how a human uses stuff sorta too. if you have the big fat rechargable in, its because you use it a Lot, and for long times, and over and over again, and are close to a plug.
if you have the 2 expencive throwaways in, then your not close to a plug need light weights, or its sitting on a shelf somewhere waiting patientally for you to use it
best of both worlds, even if you carry 2x123 lightweight primaries as the "spares".

I'll be using this light quite often and plan to charge the batteries often. I bought two 18650's and two sets of 123 primaries for backups if the power ever goes out and i need it.

You guys ROCK! Thanks for all the help!