The dilemma of unexpected necessity and desired battery longevity

I store my batteries at storage voltage. Because it’s said they will last longer. So a dew weeks ago at about 9:30pm we lost power. Pitch black.
I’ve got TONS of great batteries, headlamps, LED lanterns and of course some great flashlights……


All but a couple were at storage voltage. And that’s the dilemma. Keeping them at full charge because you never know when you’ll really need them or keeping them fully charged and risking a reduction in their life expectancy.

I’ve read (here at this forum) that even at storage voltage, most batteries are still able to provide about 75-80% of their rated capacity?
If that’s true, then keeping batteries at storage voltage ALL the time seems like a really good idea?

On the night of the power outage in question….we were without power for about 3 hours. Not long at all. But I was able to use all my battery powered lights for that 3 hours as if they were fully charged. No problem at all. Granted, I didn’t run my lights at full power….when it’s really dark, you don’t have to. A little bit of light goes a LONG way in total darkness.

So what do you think? Why not just keep batteries at storage voltage all the time only topping them up when the fall below that?

(If this has been discussed 100 times before, …discuss it again lol)

The ONLY batteries I have in storage are those that I am not using. I know that sounds like common sense but keep reading and you will understand/see my logic!

Everyone of my torches have their own batteries. Most people will use a set of batteries for several lights which I understand. For some reason I feel the need for each light to have its own batteries!

I have over a dozen torches that are used in a rotation for my trail hikes w/ Capo. Then I have a dozen or so EDC’s laying around, a few key chain lights and about a dozen CR123 for my Nitecore sens that I rarely use. ALL of these batteries are Fully charged.

The power could be out weeks and I would have enough batteries to last me.

I remember another member talking about this same thing and that is why he kept ALL his batteries fully charged.There were people who disagreed w/ him but I certainly see his point. I guess I fall right in the middle because I have about 25 or 30 in storage, mostly older batteries and then about 40 or 50 fully charged and ready to go! :THUMBS-UP:

iirc I remember a thread of yours where you had dozens of batteries[from pulls?] neatly organized in ammunition boxes and other creative containers!

EDIT: I forgot to mention that I have 8 X AAA Enloops that are almost 4 years old and have never been in storage. They did very well in the capacity test on the Opus! Also I have several packs of AA/AAA Alkaline that I use in my DMM, Mini alarm clock and they also can be used in a pinch for my 3 key chain lights! ,2 X Ultratac K18 and 1 X Olight i3S-CU.

I go somwhat the other way around.

All of “daily” lights have full charged “beater laptop pulls” with solder buttons on top. (10 ish)

my “best” new cells I have at a balanced storage voltage. (12 ish)

my better cells I have at a full balanced charge in pairs (I like 2s lights). (10 ish)

my good cells I have at storage volatage in the fridge. (three laptop packs that I can use or break down) (27 cells)
and a few at storage voltage in the freezer. (9 cells)

I think we each have our crazy logic. mine is to use/abuse my lowest quality first (keep-em full who cares) then treat them better as I move up the inventory quality.

Plus solar panels capable of running LiitoKala charger (just need to make it to daylight) then recharge away.

For li ion @ 3.8V is about 30-50% depending on the chemistry.
I keep 3 fully charged as my everyday use batteries (sacrificial batteries if you will) I charge to 100% put in lights and recharge as needed. I would suggest 2-3 li ions at storage equals one fully charged.
Eneloop i keep fully charged at all times since NiMH has no deterioration, emergency light has dedicated Eneloop in it and ready to go (and findable in a dedicated spot in pitch black) and other eneloop i charge use and recharge whenever the spirit reminds me.

I live in the San Francisco bay area and I keep the batteries in my 15 or so flashlights fully charged and ready to go. In addition I keep another 20 fully charged and stored just in case I need them. Given the possibility of an earthquake here the last thing on my mind is worrying about the cost of replacing batteries. If and when I need them I want them all to be charged and ready to go. When they go bad I’ll just replace them and treat them as they are…emergency supplies that need to be periodically replaced.

I agree but full voltage also causes capacity loss, what if your fully charged 1-2 year old battery now has only 1000mAh capacity instead of the [insert here] capacity it had when you bought it even though you used it only a couple times.

I’m the same, most of my lights have their own particular cells.

I keep most lights in storage mode, locked out with cells at 50% but do keep some fully charged, Meteor, Gladiator, DQG Spy, 47 Atom, Nitecore EC 11 18650, Lumintop tool ti, Mi7 ti, OTR M3 and whatever bedside light I have in rotation.

I also keep 6 Sanyo 2600FM and 4 eneloop AA fully charged on standby, the sanyo’s are old but still great cheap batteries and the eneloops are long life too.

You might find this useful Estimating remaing capacity

We very rarely have power failures of more than a few minutes per decade but if there was a chance of them being more frequent or longer duration I would have reserves set up accordingly.

Cycling/ testing your cells every few months is a good idea too.

I also have a couple/three car start units which have capability to charge my flashlights/torches
and my car can provide charge thru the cigarette lighter
butt, I vote to keep those suckas charged and ready when needed

suspenders and belts

Storing batteries at 3.6V / 40% (ish) somewhat defeats the purpose of using flashlights as emergency lighting or other uses where flashlights may be required at short notice.

Personally, I usually recharge if voltage is below 3.9V after use.

I would only store batteries at 40% if they are out of circulation / mothballed. A good example being those who’ve purchased VTC6 or 30Qs ahead of the Q8 being available might want to store them at 40% until the Q8 arrives.

Anyway, I find that having fully charged lights seems to prevent blackouts. Haven’t had one for years!

I would assume a discharge rotation that allows for routine periodic capacity checks. It would be part of the cost/benefit analysis to decide at what capacity it’s time to replace them.

Fair enough I don’t have enough batteries to have considered that before!
I have 5 18650s for rotation so 3 always in use, two in cold storage, pulled out and used if i need them, plus 4 26650s, none in current use since my 26650 light is put away and barely used. I’ve considered a lumintop 26650 light that may see more use for my 26650 batteries.
I love my capacity resting charger, my laptop pulls had dropped to 1100ish mAh which is about half they had started with, ended up tossing them all since they started heating up badly while charging

I live in California as well but the far more likely need is winter storms which are predictable far enough in advance to charge up some more cells. Don’t need that many as I have a few kerosene lamps and a gas stove and propane bbq for cooking if need be. Mostly I keep a few of each size in active use for mod testing or general edc use that get charged as needed. The one thing I don’t do is run a cell down and leave it there. Power pack pulls are the ones most likely to be stored long term at or near full charge.

I’m kinda the same way, only I don’t keep many cells in storage. By the time I’d burn through any of these in my lights to need a new one, any unused ones would probably be nigh unusable from just sheer disuse.

Most of mine take 18650s, so if I’d need a charged cell in a pinch to replace a spent one, I’d just pull it from another less-used light. Eg, for 26650s, if I needed one for an F13 or DV-S9, I’d pull one from my L2, which I hardly ever use except when I’d need an überthrower. I’d probably end up pulling one from a “specialty” C8 to go into my headlight or EDCed ’502.

I never saw the appeal of keeping so many spare cells “in storage”, because as I mentioned, I’d not have to burn through a cell in even my most-used lights for years. I’d love to get in on that GB for 30Qs, but even now I for 3 out of a 4-pack that I’m not using and are just sitting on the bench Just In Case.

In case of the Zombie Apocalypse, I’d find some way of recharging the cells I got (even plugging it into a car) than just burning through “stored” cells.

And worst case, really scraping the bottom of the barrel, I got enough alkaleaks to feed my Jet Is, WK50s, BLF348s, and little bobofett, for a looooooooong time. Bobofett will finish off the “spent” AAs from other lights, even if only in “moonlight” mode (it’s a good 30lm+ or so on a fresh AA).

I only have a few NEW cells, four waiting at storage voltage for the Q8, and a couple others which are in rotation in lights. The rest of them are laptop pulls which I have run through my Li-500 and saved those with 2000 mah or more, these were left at full charge after the ‘normal’ test.

My Li-500 runs on 12VDC and came with an automotive power adapter, so I can charge batteries from any 12 volt source. I have a 1500 VA battery backed UPS running the computers and router, and a spare smaller one that I salvaged (it needed two new batteries) and keep plugged in out in my shop. If power goes out, I have enough stored capacity to top off all my cells, giving me time to analyze the situation and decide where to go from there.

I used to have a 10k generator, (may it rest in peace) but I still keep four 6 gallon jerry cans of fuel that I rotate fresh non-ethanol gasoline into, one can per month. My neighbor has a small Yamaha generator, but virtually no stored fuel, so we work together. I should probably find an alternator and an old lawn mower that I can make a small charger with, but I keep hoping the money fairy will stop by and allow me to pick up a small Honda or Yamaha inverter style genny.

For emergency lights, buy lights that take AA cells, and keep Eneloops fully charged in storage. Alternatively, you can keep some lithium primaries (Energizer Lithium) for a bit more capacity, but regular Eneloops will do fine.

If most of your lights use lithium-ion cells, then just keep them fully charged and use them. Or, store your cells 50% depleted and don’t use them. If you really need lithium-ion for emergency use, then you probably have some kind of solar system to recharge them anyway. Otherwise, stick with AA for your emergency batteries.

Yes that’s correct. Part of having an emergency supply is periodic review and replacement of things that need that. I also have a Goal Zero solar charger that I’ve tested and confirmed will charge batteries using either a Miller ML-102 directly plugged into it or connected after the 4 cell NiMh charger that comes with it (better the second way to get a more stable output).

Also emergency supplies don’t get used in the normal course of life. Otherwise they wouldn’t really be emergency supplies :slight_smile:

Why not store them at 3,8V
On a lower mode gives one light.

For lithium batteries that I use “somewhat frequently”, I try to keep them around 4.0V. The reason why is that in my research, I read that battery deterioration starts to become noticeable above 4.1V. At 4.0V, according to HKJ an NCR18650B will be at roughly 80%+ capacity. So, I consider 4.0V a nice middle-ground between managing battery life and ensuring that I have a cell ready to go if I needed it without notice. I really wouldn’t have any hesitation about storing cells at this voltage, personally. If I’m planning on using a light, I’ll charge them up to 4.2V that day.


I don’t disagree with that, but that gives up most of the benefit of lithium-ions. You may as well use (fully charged) Eneloops, which will store 10+ years. (Though, I’d charge up the Eneloops every couple of years just to be sure.) Or, even use alkaleaks, if you’re only going to use low modes.

I agree but the reduced lifetime and capacity loss stored at high voltage while waiting for an emergency means li ion is just not the best emergency power source
Hence my emergency batteries are Eneloops that are stored fully charged in strategic locations