I just received a new Romisen RC C8 flashlight. It works fine with 3AAA batteries. But a 18650 is too long. What am I missing?
Can you measure the length of the battery ?
Protected cells are longer so possibly that’s the problem.
Also, Welcome to BLF. I’m sure we’ll figure it out.
The one I tried to use is 70mm long, including button
Some protected are longer than others. You might just have the longer ones. What is the brand?
Jerry
That’ll be the problem then. 70mm is a protected cell. Some of these single 18650 flashlights are a tight fit even on unprotected cells.
If you have an unprotected 18650 (65mm long) it should fit just fine.
Thanks
The RC C8 is supposed to take the 3 AAA in the holder, a 18650, or 2 CR123A.
Is there a RCR123A that’s short enough, like 32mm?
The RC-C8 doesn't like protected batteries. When I had mine it wouldn't tighten all the way even with my shortest protected 18650.
It still worked though. Does your not work at all?
Hi Joe-
My RC C8 will run fine with 3 AAA’s. The only 18650’s I currently have are 70mm and stick out 18mm before the end cap is screwed on. With the end cap threaded on at any length, it will not light. (I have a 65mm 18650 coming.)
I’m considering a 18500 battery which is ~50mm. I just want to have an alternative when the AAA holder breaks.
Thanks for adding your thoughts, Jon
Ewww… 70mm that is long/max for protected cell for many light.
But 70mm-18mm=52mm I don’t think you find 18650 cell = 650mm good for you?
It looks like you need a 18500 battery.
I drew the same conclusion. However some others in this forum, in reviews and elsewhere have all referred to 18650’s. Only this thread believes 18500 may be the answer.
What’s the chance Romisen changed the RC-C8 light??
Anyway a 18500 has been shipped so I’ll report soon. By the way, my 18650 does work the light if only end cap thread or two is engaged. (Meaning the driver , etc works)
All I was looking for was a light that would accept a wide range of batteries. A widely versatile light was my ideal.
As you say just use a shorter batt with a spacer, I’ve made these out of wood before, just used a nut and bolt through center to get length right.
tabs
The Romisen specs read, “Use a 18650 battery”.
Nope, does not fit/work.— Ordered, received and installed a 18500. Works great in the house, will also check tonite. I wish the specs said to use a 65mm battery.
The postman also brought the 65mm 18650 I ordered. Tada, that also works.
I’ll depend on my i4 Gen2 charger to limit the voltage to 4.2.
Problem solved twice. One smiley for the 18500:) One for a 65mm 18650 
Heads up if your light’s battery is too long.