Charging 18650s, Again

[Jammer Six]

I realize this subject has been beaten to death, but I did quite a bit of searching here and I still don't have an answer to my question.

I'm storing TK 75s in each of our vehicles and TK 35s in the house, all for emergencies. None of them see much use, one of the vehicle lights has never been used. They just sit, ready in case an emergency dictates that I need a flashlight.

I store a full set of charged 18650s in each light, and an extra full set in a pouch in the vehicles. The batteries are all Fenix brand 2900 18650s, and I have a Fenix ARE-C2 charger.

How often should I recharge them?

Please answer in TIME. Not amps or volts. I've always been an idiot where electricity is concerned. I'm a stomp-down expert where wood or concrete is concerned, but not electricity. After six decades, that isn't going to change this week. I'm not going to test any of the batteries, and the discussions about charging rates and levels just confused me. What I will do is set reminders on my calendars, jerk all the batteries out of everywhere, regardless of what level of charge they have, charge them up to 100%, and shove them back into their storage.

What I want to know is how often I should do this, how often I should pull all the batteries out and recharge them when they've just been sitting in the cars or on the shelf, without being used.

Every month? Every 60 days? Every other day? `

What is the consensus of the assembled wisdom?

 

[archimedes]

With lithium ion chemistry, the problem with battery storage is not so much self-discharge as permanent capacity loss over time.

Storing 18650 at maximum state-of-charge is pretty much nearly the worst condition for them long-term.

But conversely, having stored them at ~ 40% SoC is not so great, if and when you suddenly and unexpectedly need them for an "emergency"

So, these priorities are in conflict, and you will need to decide which is more relevant and important for your particular situation.

Also, for a variety of reasons (this and others) 18650 are not my battery of choice for emergency purposes.

 

[LRJ88]

I realize this subject has been beaten to death, but I did quite a bit of searching here and I still don't have an answer to my question.

I'm storing TK 75s in each of our vehicles and TK 35s in the house, all for emergencies. None of them see much use, one of the vehicle lights has never been used. They just sit, ready in case an emergency dictates that I need a flashlight.

I store a full set of charged 18650s in each light, and an extra full set in a pouch in the vehicles. The batteries are all Fenix brand 2900 18650s, and I have a Fenix ARE-C2 charger.

How often should I recharge them?

Please answer in TIME. Not amps or volts. I've always been an idiot where electricity is concerned. I'm a stomp-down expert where wood or concrete is concerned, but not electricity. After six decades, that isn't going to change this week. I'm not going to test any of the batteries, and the discussions about charging rates and levels just confused me. What I will do is set reminders on my calendars, jerk all the batteries out of everywhere, regardless of what level of charge they have, charge them up to 100%, and shove them back into their storage.

What I want to know is how often I should do this, how often I should pull all the batteries out and recharge them when they've just been sitting in the cars or on the shelf, without being used.

Every month? Every 60 days? Every other day? `

What is the consensus of the assembled wisdom?

It's hard to give you an answer on that, it's kinda the same as asking "How often should i refuel my car", the batteries will have a certain self-discharge rate that's pretty damn slow, there might be parasitic drain in the TK75 which'll shorten that period but we're still talking years until it drains 4 full batteries, your question is really hard to tell without getting the voltage involved at all.

What you could do is let them stay where they are and see how long it takes for the batteries to go down to 4.0V, then set that as your interval. The batteries will still age but with that it should give you a rough estimate and that could vary drastically based on the environment and application, the batteries will also age but in your case it seems more unlikely that that'll become an issue.

 

[Jammer Six]

So, these priorities are in conflict, and you will need to decide which is more relevant and important for your particular situation.

That's easy.

It's far more important to have fully charged batteries (or, at least, as fully charged as possible) available if I need them.

I'll buy new batteries if I need to. But empty batteries right when I need them would be bad.

 

[dcraig]

Since you do not want to overthink this, recharge them once a year.

If you can, loosen the tailcap to prevent accidental activation or parasitic drain. But you also have an extra set.

For your application, consider switching to flashlights that take AA lithium primary batteries ("Energizer Ultimate Lithium"), and replace them every 5 years to be safe.

 

[Mr. LED]

Personally I'd never store lithium ion batteries inside lights for emergencies, especially inside a car where temperature goes up in the summer. Ideal battery chemistry for this is primary non rechargeable lithium batteries, like CR123 and L91 (AA). They last at least 10 years and don't leak, also withstanding low and high temperatures.

 

[LED Monkey]

Li-ion cells self discharge very slowly I've checked voltages months later with almost no loss or at least very little, but as stated the cells will age quicker leaving them stored for long periods time at 100% state of charge. With lights I'm not going to use for some time but I still want usable if I need them, is I store them with the battery at about 3.9v to maybe 4.0v I think this will ease the damage to the batteries by a good deal. The Fenix TK75 takes 4 cells so even at 3.9v x 4 you'll still have a good deal of run time and 3 steps down from "turbo" you will still have 1000lm to work with. The other thing is the extreme temperatures the batteries see in a car from summer heat to extreme cold in the winter. And it's not good to recharge ice cold li-ion batteries too.

 

[LED Monkey]

Primary lithium AA batteries have approximately 3000mah per cell and have a good temperature working range from hot to cold and long storage ability. Maybe a 4xAA light would be a good vehicle emergency light like a Nitecore or Thrunite or something along the line.

 

[Jammer Six]

I warned you.

The only part of any of that I understood was "once a year".

I was thirty years a general contractor.

Every time, EVERY TIME the current (ha! ha!) project electrician heard that The Man doesn't understand electricity, they'd convince themselves that after all this time, he would be the one who could explain it to me so it would make sense, the light would come on, (ho! ho!) and they'd be my electrical sub for life.

And they'd all come up with the same tired story-- something about a hose, and the diameter of the hose and the size of the reservoir and the water pressure and the volume and ohms and volts and water being stuffed through the hose by the ohms. Or something. And there was a circle. And the water had to spill onto the ground. (Wouldn't that make mud?)

These are guys who think there's nine cubic feet of concrete in a cubic yard, but never mind that. They were all bright guys, they were just a little self-centered, and none of them could understand how or why I don't understand and that I don't care.

If I had trouble with electricity, I'd just fire the electrical sub. Simple. I hired him so I wouldn't have to understand any of it.

So he'd pigeon hole me and start talking about his damn hose and his damn water. If I got lucky, the plumber would happen to hear, and he'd always interrupt and say that that's not how water in a reservoir and a hose works, and then I'd get bored and waddle off to my next task, and leave them arguing about some theory that had nothing to do with the current project.

I'll start with once every six months. And thanks, guys, I appreciate the answers, including the ones I don't understand. :thanks:

 

[WalkIntoTheLight]

Yeah, every 6 months is certainly enough. Check the run-time on your lights every couple of years, to make sure the battery capacity is still acceptable. If not, replace the cells.

 

[LED Monkey]

Well as WalkintoTheLight has stated,yeah 6 months should be an ez interval of time to check them out. That would at least let you know if you had a bad cell in your light or something. The capacity will probably not have dropped much from 4.2v (full charge) and charging it back up from 4.1v to 4.2v will not really do much good for run time, but it could increase resistance and shorten the light to run on high, the opposite of what you're looking for. There is a reason Tesla has active heating and cooling for their batteries on their cars.

 

[LED Monkey]

Fwiw. Batteries can explode! And not just for "the other guy". How do I know? Because it happened to me. I had batteries in series and did not use proper battery precautions and a battery blew up in a light that was in my hand at the time. Luckily it was in a very durable light and it bent the spring in the head and blew out the tail cap. The fumes were terrible and my hand was not over the tail cap.

 

[archimedes]

Fwiw. Batteries can explode! .... I had batteries in series and did not use proper battery precautions and a battery blew up in a light that was in my hand at the time....

Yes, I am not familiar with the particular models listed in OP, but this is one reason that I strongly prefer single-cell emergency torches.

Not only do individual cells risk becoming mismatched during the aging process, but most multi-cell devices will stop functioning with the failure of only a single cell.

More batteries = more potential points of failure.

 

[LED Monkey]

Totally agree! I lucked out being outside at the time and my hand or face was not over the tail cap. My point was it does happen. Btw the light still works after cleaning it up (PITA) and a new tail cap you would never know what happened. .
Free tail cap provided by Elzetta, Thankyou.

Totally my fault for what happened too.

 

[Jammer Six]

Okay, after 6 months in the two vehicles, the batteries that came out of the lights all read 4.02 to 4.16.

(I figured out that the number on the recharger was what you guys were talking about.)

So since one or two of the batteries was (were) down to almost 4, I figure that six months is about right for recharging everything.

 

[WalkIntoTheLight]

Yes, 6 months should be fine. You really should measure the voltage with a DMM, not a charger. Chargers are usually horribly inaccurate with resting voltage levels.

While resting voltage isn't the best way to determine capacity or charge level, it's usually good enough.

I'm a little concerned about the range of voltages you cite. That might mean the batteries aren't well matched. Or, it could just be the charger giving a wide range of inaccurate readings. Again, use a DMM next time.

 

[Jammer Six]

They were all Fenix brand name 18650s, but some were 2500, some 3500.

 

[Jammer Six]

No idea what a DMM is. Perhaps you haven't read the thread.

 

[WalkIntoTheLight]

No idea what a DMM is. Perhaps you haven't read the thread.

Digital multi-meter. If you're charging lithium-ion cells, it's almost a required tool to check safety. Sorry for not expanding that abbreviation, but I thought anyone on this forum for more than a few weeks (days?) would know what it means. A simple Google search on this site alone turns up 6700 results.

 

[Sanford02]

No idea what a DMM is. Perhaps you haven't read the thread.

Speaking of not reading threads.... my thought is that perhaps lithium-ion rechargeables are not for you, considering your apparent unwillingness/inability to learn a few simple parameters for safely charging, using, and storing the cells. If I hired a general contractor who didn't know enough or care enough about his sub's work to have at least some confidence in the quality of the work, I'd just fire the general contractor. Simple. I hired him so I wouldn't have to understand any of it.