Lumen difference using 3 or 4 SF123's VS using 2 Li-ion Olight 3600 mAh 18650's

CREEXHP70LED · Jul 24, 2018

I know I will get more runtime using two 18650's in my Olight Javelot M3XS-UT, However I don't know about the brightness. I hear lights are brighter on Li-ions, but it looks brighter with the primaries. Can someone chime in? Thanks.

Random Dan · Jul 24, 2018

I don't have any specific experience with that light in particular. Generally lights that have a wide voltage range will either regulate a steady output by adjusting the current draw, or they will draw roughly the same current which means more power from higher voltage. Two li-ions is 8.4v while primaries are 3v a piece, which means either 3 or 4 primary configuration is higher voltage than two li-ion.

The lights that are brighter with li-ion is generally comparing single-cell setups, where a 4.2v li-ion outshines a 3v primary.

etc · Aug 6, 2018

Interesting question.

With 2x18650, protected, you will get regulated runtime. With 4x123, you will be brighter initially by a hair but quickly decline from there.

fivemega · Aug 8, 2018

Pair of 18650 definitely will be brighter than 3 primaries 123A
4 primaries 123A might start slightly brighter for short time but 2x18650 will be winner.
If you use 2x18650 for some times, then you will never go back to primaries.

etc · Aug 8, 2018

2x18650 is the winner runtime wise, you generally get flat, regulated runtime then it suddenly cuts off.

With primaries you will get more or less slow, immediate decline and they never 'suddenly' cut off on you.

The only advantage of primaries is that they are cheap and convenient in cases where you cannot deal with 18650s. Such as travel.

Primaries are also much lighter. So Li-ion are generally better but primaries have a reason to exist as well.

fivemega · Aug 8, 2018

2x18650 in series are 7.4 Volt at 3500mAh or 25900mW/h
4x123A primaries are 10 volt at 1500mAh or 15000mW/h
As you see, there are huge difference of energy.

---------------------------

etc said:
2x18650 is the winner runtime wise, you generally get flat, regulated runtime then it suddenly cuts off.

Suddenly cut off is when you use protected cells.

etc said:
With primaries you will get more or less slow, immediate decline and they never 'suddenly' cut off on you.

If you are using primaries for an hour and now your batteries are almost dead and need to replace, 2x18650 are still going and have probably another 40 minutes to go.

etc said:
The only advantage of primaries is that they are cheap and convenient in cases where you cannot deal with 18650s. Such as travel.
Primaries are also much lighter. So Li-ion are generally better but primaries have a reason to exist as well.

Primaries are excellent for emergency use. They have long shelf life and can be used several years after purchase or use flashlight few minutes per month.

etc said:
I got authentic Panasonic 18650, the protected 3400 mAh version for 7 bucks each - shipped.

Cost for pair of 18650 probably is about $25 and can be recharged 500 times or more. Each charge gets about 100 minutes run time
Cost for 4 primary 123 probably is about $10 and can be used once only. Each set gets about 60 minutes run time.
Using 2x18650 for 100 times of recharge will get about 100x100=10000 minutes. (cost of one set 18650 about $25 include shipping.)
Using 668 pieces (167 sets) of CR123A for 167 times will get about 167x60=10020 minutes. (cost of 668 pieces primary 123A is about $1336 at $2 per piece. No shipping.)
Above calculation is based of 100 recharge life for 18650 cells. Most 18650 cells can be recharged way more than 100 times.

etc · Aug 8, 2018

Olight the latest greatest 3600mAh which was asked about in the OP is $20 - each. I cannot wait for the price to come down, which it must, eventually.

etc · Aug 8, 2018

I still keep the Li-ions I got 10 years ago, the AW brand. And they still work.

hardly anybody uses 123 anymore, except dot gov that gets it for free.

often, recharging is not a possibility. e.g. hiking, camping, must keep the weight to a min, etc. travel.. are you going to take a dozen 18650 with you and then carry them around when depleted? 123 do offer a degree of user friendliness. That's why they will never die. Although I do wonder if they ever offered a 18mm version of 123s primary. wouldn't that be interested. Probably cost-prohibitive. IOW, not gonna happen.

CREEXHP70LED · Aug 16, 2018

etc said:
I still keep the Li-ions I got 10 years ago, the AW brand. And they still work.

hardly anybody uses 123 anymore, except dot gov that gets it for free.

often, recharging is not a possibility. e.g. hiking, camping, must keep the weight to a min, etc. travel.. are you going to take a dozen 18650 with you and then carry them around when depleted? 123 do offer a degree of user friendliness. That's why they will never die. Although I do wonder if they ever offered a 18mm version of 123s primary. wouldn't that be interested. Probably cost-prohibitive. IOW, not gonna happen.

Yes, I do use the primaries when I am away from a power source. I have at least 80-90 new SF123A's ATM. A dozen of them to me weigh next to nothing.

Lumen difference using 3 or 4 SF123's VS using 2 Li-ion Olight 3600 mAh 18650's

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