How do I know when to recharge?

I have my first 18650 light.

MH20vn

I bought 2 qty INR Samsung 3000mAh from Vinh
I'm pretty sure they're unprotected.

So this light has built-in recharger. How do I know when to recharge the cells?

I'm guessing the light flashes when cell is getting low.
Though that might be real low.

One hint would be when you can't select full power output, like no access to high mode.
That's why I'm using protected, I enjoy runtime ignorance on my behalf. That's just me though.

I wondered if people carry some type of meter around. Lol. Maybe they do?

My guess is they guesstimate.
Keeping a running track record and watching for clues like no high mode.
Also probably pack a extra cell, where I pack an extra light and run it till I'm satisfied and if it fails, the second finishes the job at hand.
Though, that is also a safety, lately I pack three lights, no loose cells.

Also,

You can:

Slap the batteries in a charger that accurately and precisely shows amps, volts.

Use an electric meter.

Rely on whatever indication the flashlight can supply for you.

Charge often, to keep the batteries/flashlight in top performance condition. But, this may not be very nice for battery lifespan.

Charge less often, and charge when light output is noticeably diminished.

I charge often, because I am currently using unprotected IMR in an extreme drain light.

I either carry a second set of fresh batteries with me and swap when needed or if I'm beginning to sweat, I know it's time to throw the batteries on the charger.

WarRaven said:

One hint would be when you can't select full power output, like no access to high mode.
That's why I'm using protected, I enjoy runtime ignorance on my behalf. That's just me though.

Click to expand...

A word from the wise to anyone who is unsure of what they're doing yet is to re-read that sentence if.

Undesired operation characteristics are undesirable. Begin troubleshooting.

EDIT: No offense was intended, the "newbies" in this case refer to lurkers and folks who are uncertain. Guess it was enough to get me reported. WarRaven really knows what he is doing. I wasn't referring to him as a newbie. Post updated for clarity.

Was trying to be helpful.

That's why I'm using protected, I enjoy runtime ignorance on my behalf. That's just me though

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I feel the same way, that is a great sentence. I try to do the same thing! I don't want my slip-up to overdischarge a cell.

Hmm i have the Mh20 and dont even know if it has low voltage cut off. If someone knows if it does please inform us. This could be of help to the OP as well.

I currently cant find anything on this issue, my google kung-fu has fail me

Rider57 said:

Hmm i have the Mh20 and dont even know if it has low voltage cut off. If someone knows if it does please inform us. This could be of help to the OP as well.

I currently cant find anything on this issue, my google kung-fu has fail me

Click to expand...

Get a multimeter and check the cells every couple of minutes with the light running on high while you're not in the middle of checking. Start with a not-so-full cell.

Look for warnings, blinks upon power on, or anything out of the ordinary once the cell shows 2.9v. Something should happen around 2.7v. PULL THE PLUG at 2.6v, experiment is over. Go no lower than this, it isn't worth it. Might not do this with a cell that you like. I have a fairly recent Nitecore that blinks blue under the switch boot at 2.9v, undocumented feature. I found out with a runtime test. It cutoff at 2.7, but that's no guarantee that the one in your hand will cut off!

The greatest risk of lions is during charging, assuming matched sets are matched or otherwise using a single battery light.

Note that a protected cell can cut off by itself, an unprotected cell relies upon the light to avoid problems.

When the cell's resting voltage is 3.6v, it is time to recharge it.

Look for reduced output, or a step down immediately after turn on.
Swap your unprotected cells for protected ones, if Vinh's light allows it.

Just keep in mind that step-down isn't always accurate. Make sure your threads/connection points are clean otherwise that can cause false readings on a full cell to the driver causing it to think it needs to drop power.

Capolini caused a missed step-down with snow one evening. Think the light had a thermal chip in it and the extra cooling made it decide not to step down.

Lotsa variables...

more_vampires said:

Capolini caused a missed step-down with snow one time.....

Lotsa variables...

Click to expand...

Exactly, lots. Often to many to account for. Hence why a decent dmm is a must imho when it comes to lithium batts.... Espc in a multi-series cell setups. I keep a mental runtime clock in my head and that is okish but I still pull cells and meter them to be safe.
I've seen/read too many mishaps occurring from unchecked, undercharged cells to risk myself, family/friends and property.