Rechargeable Battery FAQ

Every week we receive the same question from different customers:
"Why can't I use my "protected" rechargeable batteries on your E Series bodies?"
Therefore, I have decided write an in depth guide about the rechargeable battery.

See the 2 batteries in the photo.
One is a standard AA battery, the other a protected “14500”.

They should be the exact same size and length.
However, they are not.
“14500” means something: 14 being the diameter (14mm), 500 being the length (500mm).
Same with 18650 and other sizes, the numbers meant their diameter and length.

These are standard sizing, but some battery makers have completely disregarded the specs making them much longer, which causes problems on lights designed for standard sized batteries.
When used on Surefire E style flashlight bodies it causes the worst problem because the E bodies have a closed bottom.
Therefore, when used with these “protected” batteries which are significantly longer.
The battery protrudes upwards and will damage the circuit of the lamp/LED assembly or head unit when it is installed.

That is the reason why we advise users not to use "protected" batteries on E Series style flashlight bodies.
Batteries with USB charging port are even worst, they are made EVEN LONGER than normal "Protected' batteries.

What about "protected" batteries or batteries that has a USB charging port that are within spec and are not made longer?
These high quality "protected" batteries and even batteries with a USB charging port made to be within standard sizing specs do actually exist.
But they are quite rare and not easy to find or readily available. (Do NOT ask us where to find/buy them, we do not know.)

The best way to check if your battery is within spec or not is to measure them as strictly as possible.
Follow the standard sizing rule:
First 2 numbers are the diameter in millimeters.
The following 3 numbers are length in millimeters.

For Example:
14500 (14mm in diameter, 500mm in length)
16340 (16mm in diameter, 340mm in length)
16650 (16mm in diameter, 650mm in length)
17500 (17mm in diameter, 500mm in length)
17670 (17mm in diameter, 670mm in length)
18350 (18mm in diameter, 350mm in length)
18500 (18mm in diameter, 500mm in length)
18650 (18mm in diameter, 650mm in length)

Any batteries that are within the spec of the standard sizing is perfectly fine to use them on E Series styled flashlight bodies.
If they are not, then obviously do NOT use them.

If all else fails, use "unprotected" rechargeable batteries for peace of mind.
Make sure the rechargeable batteries are the "button top" type (also known as "nipple") if you intend to use any setups with 2 cells or more as it is needed to make proper contact between cells.

Hope this guide can help you on your flashlight modular lego building journey.

Cheers.