Concerning 18650 cells, at what point do you say "OK, time to retire it"?

I use an age based replacement system, not a symptom or status based system. Works for me. A battery can one day save your life so I like to leave as little as possible to chance.

As i said i would be interested in testing your used batteries to see the 80% drop, even my heaters were at about 50% capacity.

Would a protected cell make any difference?

?!?

I’ve got ancient laptop-pulls (mostly panny-As), from laptops that were used Every Single Day and probably charged accordingly, and while capacity might be down, they still don’t roast when charging, and have at least half their capacity left.

In low-stress lights, they’re perfectly fine.

I’ll usually charge at 1A, and if the cell doesn’t get too warm, it’s fine in my book.

I have had cells (usually those recycled/rewrapped “free” cells from craplights) that did get quite warm, so nope, they’re gone.

Yeah, I’m kind of at a loss as to how a cell might need to be tortured’n’abused to get that worn down.

Too many zeros.

Why would I use a cheap charger? And the whole purpose of having a charger measure IR and charge consequently is for hassle-free operation. Those economical chargers seldom do more than 1 amp which is too low for my cells and my patience. I mean charging 4 x 30Qs or VTC6s individually at 1 amp was taking me some 12 to 24 hours. And the trouble of monitoring and changing the cells. That is the whole purpose of having a 4 bay unit to quickly bring these up.
And as my collection grew, I didn’t want to spend time charging the various cells I used in the day so I got a second charger. Again, for simplicity and speed.

Are you implying a ⅓C charge rate (1 amp w/3000mAh) can heat a worn-out cell? Or the fact the charger changes the rate of charge if the cell heats up. But the latter I didn’t mention. Geez, I’ve been charging at 2 to 3 amps (auto selection) and if I was to see less than 1 amp, I’d check the IR.

I’m not trying to extend battery life. A cell is to be to my expectations and when they show fatigue, they’re replaced.

BTW this is in the context of the 18650s, the 21700s, and the 26650s. My smaller cells auto-charge rate. I expected them to not last as long in cycles being less capacity. But my Sanyos (14500s) are doing fine after 2 years at about 2 recharges per week. In 2 more years will see if capacity is lost.

I get it you may. have the time and inclination to pamper your cells. My working lights have to be dependable and I don’t skim on the batteries. There is an underlying psychology of turning the light on/off from one peak to another, mentally conditioned to extend battery life. The introduction of rechargeable batteries with high capacity and no memory effect should alter this behaviour. I turn the light on and when temporarily not in need, lay or cover the face. I don’t play with the switch. If the light becomes warm, tone down the intensity. I work with gloves and 50ºC is acceptable. If the light gives a low battery signal, I replace it or pull out another light. Always have a backup.

If the protection cuts the cell output before its dangerous then it should be fine.
Though i would toss it on the charger quickly becasue keeping it empty for long periods is not good for it (according to common wisdom).

A 4 or 8 bay charger is not pricey these days.

Oh yeah.

If your cells are not overheating at 2-3 amp then it should not overheat either at 1A.

To each their own.

If you have money to spend then you can push your cells as hard as you wish and replace when the time comes.
Though please recycle your old batteries.

You have to ask yourself what is your goal. Is your goal to keep the $5 battery as long as possible? I have batteries >10 years old. You know what, I would not use these batteries in a light used to light a bathroom
to take a crap.

Is your goal to be able to have the freshest batteries possible, do what I do and replace them often.

If your goal is to learn how to use a DMM, then keep them for 10 years and test them every day and report back the voltage drops on a daily basis.

Personally, life is too precious to be spending time trying to get every penny possible out of a $5 investment.

This is $5 that can save you life one day. Pick another place to save some money. Like a cell phone or cable bill.

I have expressed my goals, your goals may be different and I totally respect that.

I use my almost 10 year old batteries regularly, no problems. In fact my oldest lithium battery is in my newest light.

Life is too precious to take care of batteries? Its knowledge and habit since long ago. And like many BLFers i have more than one battery. Lets say one has two dozen batteries. And replaces them at $7 a pop every 3 years. In 9 years that is $672 (initial, 3 year, 6 year, 9 year). And tax depending on where purchased. I spend more than $5 each, most are $7-10 each.
Some BLFers have dozens or hundreds of batteries, replacing them every 3 years is several thousand dollars in 9 years. Thats ridiculous.

And my cell phones last much longer than 3 years as well, my last phone is over 3 years old and has 96% battery life.

I want to know how you eat 80% of your batteries lives in 3 years, what are you doing to them?

Agreed!

I typically go for the highest capacity because i like runtime so i typically buy higher priced batteries. Some 21700s i am looking at are about $13 each plus shipping. Also being Canadian the exchange rate is about 1.25CAD per USD.
But lets go with this battery and stick to USD, if you buy 12 batteries plus shipping it will be about $7 each. So $84.5/dozen. As i mentioned earlier imagine one has a modest two dozen batteries in their collection. And replaces them every 3 years. $169 times 4 changes is $676 USD. Or $845 CAD :confounded:
This is more than my whole flashlight collection cost me.

I would prefer to keep my money by adopting some simple battery practices so i’m not throwing away lots of cash.

From reading on another thread — people are having more trouble with newer cells —— I have plenty of cells that are over 5yrs old — most of the Good Name Brands (Panasonic- Sony Samsung ) are as new — But like the OP stated it’s what you’re into ( I test my cells Capacity /4 wire resistance ) — even with so called good cells and lights, It’s always best to have a Backup

Well, heat kills so I’d guess that some user’s batteries last longer depending on how they are used and what kind of lights they get used in. Put an 18650 in a D4V2 and use Turbo every chance you get and I bet it dies sooner than if you put it in something more conservative and use medium modes except when necessary. Plus, if you are a busy or absent-minded person you might not charge the batteries exactly when you should every time. You might miss a low-battery indicator or forget to check the voltage and then the flashlight sits for a week at about 3 volts with parasitic drain on top of it.

If he does this with all his batteries without fail all the time i would be impressed.

I can intentionally kill batteries if want to, i have many tricks up my sleeve that have not even been brought up in this thread. But i have no reason to throw away money.

Replacing your batteries every three years is not going to protect you from the possibility of having one explode and burn down your house. At any point within these three years an unmonitored cell could drop below safe levels and be recharged, exposing the risk of failure. Additionally for every cell you’re throwing away that is known to have a history of NOT exploding you’re replacing it with a new cell that DOES NOT and may have manufacturing defects that may cause it to explode unexpectedly and burn your house down.

This doesn’t go for just flashlight batteries but anything with lithium ion batteries which are in pretty much everything these days.

I semi-annually check every device that has lithium ion batteries in it and top it off when needed in the event a device has been discharging it, and periodically capacity test each cell and factor in age, use (i.e. vaping batteries), etc. and discard any cells or devices which fail acceptable parameters.

Yes, it is a chore. I am upwards of ~300 lights and dozens of other devices.

Haven’t had one fail yet but not willing to push the envelope unknowingly.

Approximately 300 lights? WOW! :sunglasses:

That’s a tough one to figure out. I have a set of Orbtronics that are going on 7 years old that are still holding strong. I own well over a hundred cells and I charge them full every 3 to 4 months and have not had one die on me yet. I know you are not supposed to keep them fully charged when stored but its been working for me for years and years now. I have an Eagle Eye 35W HID flashlight with the original 13.2V tubular cell that is over 12 years old that still powers the flashlight. I must be doing something right.

For me good sign is voltage equal to 0V or less.
Most of my 18650s older than 3 year. Some of them even 10 years old. But all of them have >80% of initial capacity.
The internal resistance of course is hi, but I am not fan of FET toys)