Can i run this flashlight with two batteries by adding spacer from another ultrafire light? Can i damage the electronic circuit inside?
You will most likely fry the driver (circuit).
Is there any way to confirm this? What is the voltage range for driver(circuit)?
voltage range is up to 4.2V
you could swap the driver for one that is good up to 8.4 and at the same time get rid of the modes you don’t want, but out of the box its 4.2v max
oddly as it sound… but my C8 comes with extension adapter… it doesn’t appear to make it any brighter though… but longer run time… hmm i wonder if i can get another 3 more extensions and so it could double as my walking stick 
Anyone know where I can het an extension tibe for an ultrafire c8?
I really like your light DayLighter!
Two things,
1) Here’s where I got mine from, on ebay:
http://www.ebay.com.au/itm/181016171952?ssPageName=STRK:MEWNX:IT&\_trksid=p3984.m1497.l2648
2) It’s a bad idea, at least with 18650’s it is anyway.
I got 4 c8’s in the mail today, which was awesome, and I went to use the extension tube which arrived about a week earlier. I stuck two 18650’s in, it got quite hot but I didn’t really notice until it had died.
It suddenly turned off. It had also been making a slight high pitched wining sound. Not sure if it was circuit components but I think most likely it was the LED itself.
Anyway turns out the + lead had heated up so much as to break the solder connection and disengage.
So in a way it was lucky because I might have fried the circuit otherwise.
Having said that, I re soldered the lead properly, and even put a little hot glue to hold it there. I’m going to try it again, and see how long it lasts, because I have 4 anyway, so I’ll let you know!
Hi, I can’t stress enough how much of a bad idea this is unless you have driver in that is 3v - 9v input voltage range.
There are drivers capable of doing this, but the chance of one being in a cheap c8 is pretty much zero.
Next, what cells are you using? Because this could lead to further problems.
If you want a c8 with longer run times, get a single 26650 light with a 40mm reflector and use one of the better 26650 cells - king kong, mkne? Etc.
As an example.
As gords said you need a capable driver or you will frie the circuit or damage you led.
And watch out with the cheap chinees 18650’s, if you are planing on using 2 of these in series it can be very dangerous!
You should use 18650’s from a real brand, these are much better quality and much safer.
I really like the looks of the c8 with the expension tube, just a bit longer. Is you hold it at the end, is it top heavy? Or is it easy to hold an switch?