Originally Posted by
gheezbiker
Well... respectfully... I don't think I'm wrong
. I said there's no such thing as a 4 or 5 AH 18650, and that's true - there isn't! Just because you can combine many of them in series or parallel doesn't make that untrue. When speaking of 18650's (or AA batteries, or whatever), it's customary to talk about the capacity for just one. You don't say "An AA battery can be 28 AH!" just because I can combine 10 AA's in parallel each with 2.8 AH. The false claims of those knockoff vendors are also talking about one 18650. They claim some fairly absurd capacities, like 4 or even 5 AH
per individual 18650, which is a good sign to stay away from that brand! The best 18650's I'm aware of at the moment are 3400 mAH, and those are new and fairly expensive.
It is not customary to talk about the capacity of an individual
cell when talking about the capacity of a battery
pack. It would really be absurd to do so. If you combined two individual cells to series to make a 7.4 V battery
pack, you wouldn't say that the pack was 3.7 V because the cells are 3.7 volts. If you took two 3.7V 2.8 Ah 18650 cells to make the pack, the pack's charge capacity would be 2.8 Ah. If you put take 4 batteries (the most common configuration for bicycle battery packs) and put two in series and then put the two halves of the pack in parallel, you now have a 5.8 Ah
pack made of 4 individual
cells of 2.8 Ah charge capacity each.
I haven't seen any individual cells that are advertised as being 4 Ah each but there are lots and lots of packs with that kind of charge rating.
Originally Posted by
gheezbiker
True, but you might be surprised how bogus some of the claims are! Lights that run on high for 2 hours on a good, name brand 3.1AH 18650 have been tested to get 20 or 30 minutes of runtime on some of the knockoff batteries, which is in line with 10% of their "rated" (i.e, totally bogus) capacity. Obviously some do better than 10% of course, but you never know what you're going to get. Some of the less scrupulous vendors sell take-offs from other products with a new label stuck on. Li-ion batteries lose overall capacity with time (as a function of temperature and state of charge), so if the cell is already a few years old and has been stored in a high state of charge in warm temperatures, it can easily be in pretty bad shape. A few years of shelf life under those conditions can put it at 50% of its original capacity, which may have been 2.1AH, so it may be effectively a 1 AH battery being sold as a 5 AH battery. The worst cases seen are indeed in the 10% range.
I have 8 battery packs at home from various manufacturers and various ages. I've had as many as 10. Some came with lights and some were purchased from other vendors. Even the ones that came with the lights came from a variety of vendors Generally speaking, they have all had consistent run times. I even number them and cycle through them to keep from having any jus sitting around. I have yet to run across a battery pack that give only 20 to 30 minutes of charge time unless I did some thing wrong and didn't charge the battery. I'd expect, if the problem were wide spread, that I would have run across a stinker by now.