Just want to make a general talk on battery choose, so that I can make a flashlight design.
As we know, beyond 18650 batteries, no there are some new size batteries which are same in rate with 18650’s. The same voltage,can be charged with almost same chargers, and all are cylinder shape. The difference is 20700 and 21700 has a bigger volume than 18650,and then the capacity is larger. For example, the Sanyo 20700 has a 4250mAH capacity. We found there are few models of those 2 kind of batteries:
Sanyo 20700,
Samsung 21700，
and it is said that Panasonic will produce 21700 for electricity car company TESLA. But I cant find any onsale Panasonic 21700 battery in market.
A 20700 and 21700 battery is 70mm long, which is just double of 2pcs CR123A. So I decide to make a flashlight that can fit 1pcs 2X700 and 2pcs CR123A. But to choose 20700 or 21700, I am puzelled. 20700 is thiner so that we can make the light smaller, and now Sanyo 20700 is available everywhere. If there is only 2 kinds of battery, Sanyo and Samsung, I am surely to choose Sanyo. According to my experience in past years, Sanyo is much better than Samsung,or LG.
I’ve dropped an 18650 cell into a 26650 light without even a sleeve without incident. It might shift position if dropped or slapped hard enough, but that’s it. The springs hold the cell firmly enough.
Make the tube big enough to accommodate a double-wrapped (ie, protected) 21mm cell and be done with it. There’s zero reason to shave 1mm off the diameter and limit yourself.
You know, I understand about different cells and there’s so many new ones coming out almost every other day but this stuff is getting crazy!
Seriously folks, some of these new cells have slightly larger capacities and everything else but who the heck wants to buy new cells that promise a slight increase in capacity that might not fit in a lot of our lights? We already have more different lights that take different cells and I wonder if that’s enough already?
We don’t live in caves anymore and might rely on a light that will give us 24 to 48 hours, (or more), of light in an emergency.
Why do some of you want more cells that increases our already overstocked amount of different cells? Just asking.
20700 was meant to be the next standard driven by Tesla, but Tesla changed their minds and added another 1 mm to the diameter.
A number of 20700 batteries showed up with the old sizing, of which Sanyo ones were good.
Then 21700 started appearing on the market….I thought all major manufacturers will cease to develop 20700 and switch to 21700 but was wrong. Sanyo released 20700C well after others came up with their 21700.
When it comes to 21700, Samsung is not alone - there are LG 21700 on the market as well. Sony is backing the 21700 standard as well, though their cells are not available yet.
Panasonic says they’ll do 21700 for Tesla only, for others they offer 20700 (the same as Sanyo).
So yeah, we’ve got quite some mess on the market.
I would go for 21700. Because of:
21700 is closer to the middle between 18650 and 26650
Sony makes better cells than Sanyo
The best high-discharge cell on the market is Samsung 21700-30T - and is unlikely to be beaten by 20700 in the predictable future
when it comes to flashlights, 21700 seems to be winning. Though my view to the market is not wide enough to say this with certainty. Anyway, it’s good if we have 1 standard…
21700, the smaller cell will fit, maybe add a single wrap of insulation tape to stop any rattle but no way to use the bigger cell with the smaller tube.
Yeah, with flashlights, 20700 is going to be obsolete well before 21700 will. IMO, it’s already obsolete.
My progression in cell size is AAA, AA/14500, 18650, 21700, 26650. Yeah, there’s sizes in-between, but with the exception of CR123 you’re looking at fringe sales that might disappear at any time.
My order of obsolescence is
26650 (it’s really only supported by custom manufacturers)
14500 (same)
21700 (this is a guess, but if Tesla goes bankrupt, the demand for this might plummet)
18650 (large base for this, but it’s not a consumer cell so it will probably go away at some point. It’s better for heat dissipation than 21700 though.)
AA/AAA (These will be around long after humanity has wiped ourselves out. The robot civilization will still use these.)
That’s encouraging. At least in the War With The Machines, the robots’ll go extinct ’cause those hateful little alkaleaks will ruin everything they’re put into.
I’m wishing out loud for some competent programmer to write a shopping application that takes the reviews that HKJ has done, searches the Web for price and shipping information, and adds that to HKJ’s table of battery information. Oh, and yeah, figures out who manufactures each of the cells. The vape shops seem to sell a whole lot of rewrapped cells.