What happens when too much current is drawn from a battery? (NCR18650GA)

Maybe that's not phrasing the question correctly but I have an Emisar D4 219C and am using my stock of 18650GA's in it, which are rated for 10A continuous draw.

Apparently this light will try to draw closer to 20A until thermal regulation reduces output to under 10A. This happens pretty quickly in the D4—about 10-15 seconds.

But in general I am wondering what effect that has on a battery.

Any feedback is appreciated!

I would have thought it will simply get as much as the cell can deliver. In this case maybe 10-15a which will tire the cell out quicker than use under the rating. The voltage will also sag under the load, more than a high drain cell. If this cell is what you plan on using, try and use levels bellow the max output. If using max, then there is no real reason to use this cell as it is not ideal for the d4.

Basically(just my thoughts as others will advise better), instead of maybe getting 300 full charge cycles, you may get 200 cycles kind of thing. No actual experience or evidence to this, just a way of saying you will shorten the cell life. So what happens then, well it wont hold as high voltage, wont last as long during use(run time). Simply recycle the cell when you notice performance is tailing off(or even use in a low drain application..............less output flashlight for example.

Personally i would not be too bothered myself, i would limit use high up and keep it to around 1/2 output as a max. Odd burst here and there wont have a huge effect(after all it wont last long anyway with heat!).

Overcurrent can be dangerous

There is a very brief (and simplistic) review here ...

http://www.mpoweruk.com/protection.htm

... including discussion of various protection devices that some cells may or may not contain to help improve safety

Sorry, I had to! I've been slow on my movie references lately.

As far as I'm aware the Emisar uses a FET driver, so current draw will vary based on what the battery can provide. It also steps down very quickly due to thermal regulation so that high current draw won't last for too long. I would not be worried about using GAs in this light.

Thank you for the help. I am no longer as afraid of getting blowed up!