If multiple 18650s is dangerous is 1 26650 the best choice

ltec · Nov 11, 2017

I have 4 or 5 single 18650 torches but would like a bit more power and better run times. I've read if the batteries are not charged all the same or one a lower voltage it could blow up. If this is correct then is 26650 torches my best choice. Also My charger only charges a single battery so I'd need to upgrade it if you think multiple 18650s is better and not dangerous.
Do you have to check individualy the voltage of each battery every time you charge them if there's more than one.
If this is the case how can you charge batteries together inside a torch.

terjee · Nov 11, 2017

Multiple 18650s can indeed be dangerous, but so can gasoline, and millions of people tank up their cars every day without incident.

It's dangerous in the sense that you need to know what you're doing, respect the dangers, and have quality stuff, but not dangerous in the sense that it randomly blows up even when you get everything right.

If you:
- Buy identical batteries
- Always keep, use and charge them in a fixed set
- Always charge them fully together
- Use protected cells with undervoltage-protection

Then I wouldn't worry way too much.

Good if you try to avoid draining then fully, consider age of the batteries and so on, but the undervoltage protection should have your back for things like overdraining or reversing a cell.

I'm not thrilled about multiple cell lights either, but they can be used fairly safely.

Oh, and the easiest way to check the voltage, is to tell the batteries which voltage they have. ;-) If you charge them fully, and they're the same batch, then they'll pretty much be even. If you've used it more than a trivial amount, you can always charge them back up, for an easy way to sync them.

Using 26650s can be a good option, but they're not always as powerful as some 18650s can be. I'd say it's more about having a longer runtime at a higher load, but it won't necessarily give you more light.

As an example, you can find both 18650 and 26650 lights at around 2000 lumens. I'd expect the 26660 to last longer, but I haven't really seen a major difference in the lumens you'd get from the two classes.

Do you have any target-values you'd like to get, in terms of runtime, lumens or combination of those?

And are you looking for throw or flood?

eh4 · Nov 11, 2017

If you don't mind the soda can layout, you can get a light that runs four 18650 in parallel, which is pretty safe/low maintenance, some of the soda can lights have integrated charging as well.

ven · Nov 11, 2017

As said, multi cell lights are fine with a little understanding(like you will have running single cell lights, dont over charge/discharge etc etc etc). Just make sure you buy the cells together(as a batch) from a reputable seller. A 4 bay charger is definitely the way to go, keeps things so much easier all round. I have many multi cell lights, never had any issues over the years........even with notorious lights with high parasitic drain(TM06).

If you get a charger with a V readout, this makes everything easier as well, saves breaking a multi meter (MM)out all the time. Still anything new, its worth checking the voltages on the cells to compare against a MM. Then you know the voltage you are seeing is within spec . With any new light, i top cells up, use for set time and check the voltage. I do this a few times(every time i place on the charger i always note the V to)to learn the light. This way i dont always need to top off every time(although i do that with some lights so i simply know i am good to go). (example)Your walk maybe 30mins, 250lm you may find adequate , so just need to top the cells off once a week. Then again, you may be a turbo addict, may find you need to top them off every night

My point is if you get an idea of your use and where the voltage is, your very unlikely to be left in the dark. Pretty much most lights have a way to tell you your voltage is getting low, be it dropping out of turbo and not holding higher modes, maybe flashes/blinks or simply shutting off. This is before the manufacturers min spec(2.5/2.7v dependent) and usually around 3v(variable) . At or near this voltage, a light will not hold turbo level........

4 cells in parallel as eh4 mentions, a great light that springs to mind is the noctigon meteor ................

26650 fed lights for me do have a nicer in hand feel being a little more in diameter(just feels better, subjective). They do offer a little advantage over 18650, but nothing major and certainly not comparable to a multi cell 18650 light(typical 4 cell). Certainly a lot more choice in 18650 flavour...............

What is important with a multi cell light(for me anyway)is after use, checking the cell voltage are all very close. I dont want to see 2 cells at 3.8v and 2 cells at 3.2v for example! I want to see them all very close in voltage. So with any new light(could always potentially have a fault/issue as with anything electrical) i always monitor the voltage, know i am putting in(example) 4 cells at 4.2v. When the light is used, i check the cell V usually by placing on a trusted charger and taking note of each voltage. So i may see 3.65/3.64/3.64/3.64 which is cool and i roughly know i have used around 50% of the tank(rough example). These cells would be topped back to 4.2v ready for the next use................being a turbo addict .

Cant do this on battery packs unless open up like the rc40 and x65, but if its an 8.4v(2s3p) pack as an example, you know it should never get bellow 6v(3v+3v). As i always check voltages, my rc40 pack actually terminates a little low(good by me as it can increase the life a little bit over time) . Some packs actually have a gauge, the rc40 for example has 4 lights at the cap, so easy to keep an eye on. I digress.........

ltec · Nov 11, 2017

terjee said:
Multiple 18650s can indeed be dangerous, but so can gasoline, and millions of people tank up their cars every day without incident.

It's dangerous in the sense that you need to know what you're doing, respect the dangers, and have quality stuff, but not dangerous in the sense that it randomly blows up even when you get everything right.

If you:
- Buy identical batteries
- Always keep, use and charge them in a fixed set
- Always charge them fully together
- Use protected cells with undervoltage-protection

Then I wouldn't worry way too much.

Good if you try to avoid draining then fully, consider age of the batteries and so on, but the undervoltage protection should have your back for things like overdraining or reversing a cell.

I'm not thrilled about multiple cell lights either, but they can be used fairly safely.

Oh, and the easiest way to check the voltage, is to tell the batteries which voltage they have. ;-) If you charge them fully, and they're the same batch, then they'll pretty much be even. If you've used it more than a trivial amount, you can always charge them back up, for an easy way to sync them.

Using 26650s can be a good option, but they're not always as powerful as some 18650s can be. I'd say it's more about having a longer runtime at a higher load, but it won't necessarily give you more light.

As an example, you can find both 18650 and 26650 lights at around 2000 lumens. I'd expect the 26660 to last longer, but I haven't really seen a major difference in the lumens you'd get from the two classes.

Do you have any target-values you'd like to get, in terms of runtime, lumens or combination of those?

And are you looking for throw or flood?

I think a mixture of flood/throw. My 18650 are all around 1000 lumens max but I never use it that high as battery time is no good at that. I was thinking something like a pd40r. It would be nice to have 500 or 600 lumens with long running time, maybe 2000 top end for occasional searching, looking for lost calves etc.

ltec · Nov 11, 2017

I like the torch simple to use like my pd35. Sometimes the olight I have is a bit confusing. Also bought a convoy for long distance but too complicated. It needs to be simple so my father can use it too

ltec · Nov 11, 2017

ven said:
As said, multi cell lights are fine with a little understanding(like you will have running single cell lights, dont over charge/discharge etc etc etc). Just make sure you buy the cells together(as a batch) from a reputable seller. A 4 bay charger is definitely the way to go, keeps things so much easier all round. I have many multi cell lights, never had any issues over the years........even with notorious lights with high parasitic drain(TM06).

If you get a charger with a V readout, this makes everything easier as well, saves breaking a multi meter (MM)out all the time. Still anything new, its worth checking the voltages on the cells to compare against a MM. Then you know the voltage you are seeing is within spec . With any new light, i top cells up, use for set time and check the voltage. I do this a few times(every time i place on the charger i always note the V to)to learn the light. This way i dont always need to top off every time(although i do that with some lights so i simply know i am good to go). (example)Your walk maybe 30mins, 250lm you may find adequate , so just need to top the cells off once a week. Then again, you may be a turbo addict, may find you need to top them off every night My point is if you get an idea of your use and where the voltage is, your very unlikely to be left in the dark. Pretty much most lights have a way to tell you your voltage is getting low, be it dropping out of turbo and not holding higher modes, maybe flashes/blinks or simply shutting off. This is before the manufacturers min spec(2.5/2.7v dependent) and usually around 3v(variable) . At or near this voltage, a light will not hold turbo level........

4 cells in parallel as eh4 mentions, a great light that springs to mind is the noctigon meteor ................

26650 fed lights for me do have a nicer in hand feel being a little more in diameter(just feels better, subjective). They do offer a little advantage over 18650, but nothing major and certainly not comparable to a multi cell 18650 light(typical 4 cell). Certainly a lot more choice in 18650 flavour...............

What is important with a multi cell light(for me anyway)is after use, checking the cell voltage are all very close. I dont want to see 2 cells at 3.8v and 2 cells at 3.2v for example! I want to see them all very close in voltage. So with any new light(could always potentially have a fault/issue as with anything electrical) i always monitor the voltage, know i am putting in(example) 4 cells at 4.2v. When the light is used, i check the cell V usually by placing on a trusted charger and taking note of each voltage. So i may see 3.65/3.64/3.64/3.64 which is cool and i roughly know i have used around 50% of the tank(rough example). These cells would be topped back to 4.2v ready for the next use................being a turbo addict .

Cant do this on battery packs unless open up like the rc40 and x65, but if its an 8.4v(2s3p) pack as an example, you know it should never get bellow 6v(3v+3v). As i always check voltages, my rc40 pack actually terminates a little low(good by me as it can increase the life a little bit over time) . Some packs actually have a gauge, the rc40 for example has 4 lights at the cap, so easy to keep an eye on. I digress.........

If the batteries are different voltage are all 4 then scrap.

terjee · Nov 11, 2017

ltec said:
If the batteries are different voltage are all 4 then scrap.

No, not at all. Worst case you'd split the back, but you can try to bring them into sync first. Just be a bit more careful and pay attention to if they stay in sync, or drift apart. If they do drift fairly rapidly (on each time you use them), split the pack and you have 4 individual cells for use in single-18650 lights.

Vapers do this all the time btw. I have mods taking multiple batteries, and after a while I'll split the pack, and use the cells individually.

richbuff · Nov 11, 2017

Quote: "If multiple 18650s is dangerous is 1 26650 the best choice"

It depends on your individual danger tolerance.

For me, if 8 x 18650 is dangerous, gimme 8 x 26650.

For Granma, if one 18650 is dangerous, give her AA alkaline.

It is not the equipment, it is the individual person and his training and his risk tolerance and his individual needs and his individual comfort level.

ven · Nov 11, 2017

As said not scrap if voltages are different. Could be an issue with a specific cell or the light(even both). Cells are scrap when the voltage gets too low and left. For example, I drain a cell(highly unlikely I may add) down to 2v, I can still try and recover the cell if it's not left over discharged for any length of time. Monitoring the process goes without saying, but not enough to recycle a cell. Then if a cell won't hold voltage and drops significantly over a short period of time, or the internal resistance becomes too high.......many factors. I have many cells in use of various ages, some must be over 7yrs old easy(had 18650 cells well before joining here). I am yet to experience cells that drop significantly or won't charge up.

The cells that get the hardest work out are my vape cells. These do get changed every 12-18m for new, simply for safety reasons and then get used in flashlights(providing they hold charge....which they do).

If a multi cell light, I do some research and find as much as I can about it. Can it be locked out, any parasitic drain after the usual wants and needs for the choice. All lights that allow get locked out, usually by undoing the tail cap when not used. This works well for preventing acidental activation and any potential drain.....just a habit I have got into.

novice · Nov 12, 2017

I am not as knowledgeable as some of the previous posters, but I would say that you should buy the best quality rechargeable cells that you can find (I prefer AW brand; 2nd choice Panasonic), and the best quality charger you can find. I don't know what the best is anymore, but I currently use a Nitecore VC4 because it is supposed to be good, and it will charge both NiMH and Li-Ion cells, and it will charge any size from AAA to D-cells or 26650 cells. My Pila IBS is backup now, mainly because it doesn't have the versatility of the VC4, but it's good quality, and wasn't cheap. Economize on lights if you must, but try not to save too much money on cells and chargers. I have a cheap $5 DMM from harbor freight, and use that to check voltages of cells coming off of the charger. Reading some of the previous posts, I should probably be more diligent in checking cells before I put them in the charger.

[Edit] Geez. I meant XTAR VC4, not Nitecore.

ven · Nov 12, 2017

My charger has a V readout, so saves breaking the MM out all the time. But anything new(introduced to my flashlight world) gets checked prior and after the first charge or so . This will show me the charger is within spec and not over charging, or any of my cell/s V is too low after use in a light. Once i have confidence in the equipment(light/cell/charger) then i do not check every time. Charger wise, all my main use chargers have the V readout, so it does make my life a lot easier. I can build a picture of how much juice i am using over time with specific lights. More so for multi cell lights or battery packs to make sure things are under control. I am pretty good at guessing the voltage on most lights before even going on the charger, certainly work lights that get similar use day in day out. If the charger has a % readout, you can still get an idea to build a picture, you know how much you have used but % rather than V. I just prefer the V as i am use to this over the years.

If multiple 18650s is dangerous is 1 26650 the best choice

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ven

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