Very Confused Please Help

carl8190 · Sep 14, 2010

I have got some 18650 torches. I use ultrafire 18650's. They say on them that they cut off at 4.25v and 2.75v. Now i know im meant to get 3 hours on full out of my jeatbeam rrt2 on full but after 1 hour my 18650 is at 3.7v and I read and have been told not to let them below this or its dangerous to try recharge them. So why am i not getting the runtime and why do they cut out at 2.75v when you shouldnt let them past 3.7v?
I look forward to your experience answer.

pwatcher · Sep 14, 2010

you'll get more experienced answers than mine, but if you have a protected ultrafire cell that is designed to prevent overcharging or undercharging, I would consider those limits as "worst case" that should not be approached if you can help it.

a good charger (like Pila IBC) will cut off at 4.19 or so, for example, which is much better for a rechargeable's life expectancy than anything over 4.2 would be.

as to when a protected cell should be recharged, I suppose it depends a little on the battery or the chemistry involved, but 3.7 would be a good target I think. with experimentation, you'll get an idea how long you can run your lights before depleting the charge to that level. most accidents seem to occur when charging an over-depleted cell, so to be on the safe side, I'd never let a cell get down to your Ultrafire's lower limit.

btw, the reason you may not be getting as long runtime from you Ultrafires as expected could be the cell's capacity? there's a difference - my AW's are 2600mAh, I think. yours may be 2200?

PerttiK · Sep 14, 2010

https://www.candlepowerforums.com/threads/237586

According to that thread, rrt-2 only got 2 hours with 18650.

What's the voltage in your cell 1 hour after charging, and better yet, one day after charging?

If you drain the cell all the way, and the protection kicks in, the voltage bounces soon back up to more than 3 volts.

^Gurthang · Sep 14, 2010

Standard Li-Ion [LiCo] batteries should NOT be discharged below 3.7V.

Run time is dependent on: the driver discharge current, the charge state of the battery, the mAh rating of the battery, and the battery "age".

If the battery has a protection circuit run time will also depend on how the circuit reacts as the battery discharges.

pae77 · Sep 14, 2010

It's also worth noting that the stated capacity, particularly on ****fire cells, is often (with very few exceptions) very optimistic, if not downright inflated. The real capacity is often lower than the stated capacity.

One exception to the above seems to be the Trustfire red/black "true" 2400 mah protected 18650's. At least the ones I have seem to be pretty close to their stated capacity and to perform pretty well so far.

Very Confused Please Help

carl8190

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pwatcher

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PerttiK

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^Gurthang

Flashlight Enthusiast

pae77

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