Mountain Bike Reviews Forum banner

18650 education needed

1412 Views 3 Replies 4 Participants Last post by  goyo46
A little OT but I recently bought a Fenix HM65R-T. Absolutely killer headlamp, blows away my Zebralight Mk's in functionality.

Anyway, the Fenix came with its own branded 3400 mAh battery. The thing is, it's noticeably bigger than my other 18650 batteries. It is both bigger in circumference and longer as seen here.

Unfortunately my existing 18650 cells will not work in the Fenix. While it's a tight fit in my Zebrlight, the Fenix 18650 does work in that headlamp. This is a bit annoying as I in part stuck with the 18650 platform for universeality.

Is this simply just a matter of being a button top 18650?

Can I buy some type of copper disc etc, to make my existing cells work in the Fenix?

What are the best button top 18650 cells going and where would you recommend getting them?

Also, any recommendation for a good charger? I'm still using an ancient Nightcore

Sent from my Pixel 4a (5G) using Tapatalk
See less See more
1 - 4 of 4 Posts
Unfortunately not all buttons tops are the same length as Fenix’s proprietary battery lengths.

Some 18650’s are let’s say 18.1mm x 65.2

Then their button might only be 4mm, whereas another might be 5mm and the cell is 18.1 x 65.1 which overall is the same length.

I’d measure the battery in question and email a few companies like LiionWholesale, IMR batteries etc if they could give you the actual length since all batteries have an acceptable variance.

Example: Samsung 30Q data sheet

Can be acceptable between 64.7 - 65mm then button top can vary

Any charger that can accept it is fine… even nitecore, just better chargers can charge at a higher rate, which honestly isn’t always better. NC just drops to like .350mA when all bays are in use if the typical older .75a dual bay or 1.5a 4 bay

The only upside to a protected circuit is the crush factor for them, if you drop a light and it crushes the circuit it won’t hard short and possibly cause thermal runaway..

The positive of a cell is obvious, but the whole can is the negative and why cells are wrapped and have an insulator under the wrap on the positive side for some added protection against a hard short when the rolled edge wears.

TL;DR not all protected cells are of proper length to be utilized in flashlights, measure call and buy at least a 10a cell for a single cell light

Sent from my iPhone using Tapatalk
See less See more
  • Like
Reactions: 1
That is a protected 18650. It has an electronic circuit breaker on top of the cell.

I wouldn't have a clue who makes good, protected cells, as I only use unprotected 18650's and 21700's.

Get another nitecore charger. I bought a new one a couple of years ago, with more bells and whistles. My old one still works perfectly, and is ready as backup, but the need hasn't arisen.
  • Like
Reactions: 1
Yes, a protected cell. Technically, you don't need one for a single cell unit, the protection circuit is a failsafe for multicell units; if the charge differs significantly between cells they can overheat and burn. Also for charging, if you don't have protection built into the charger. Double protection circuits are overkill and may prevent charging to max capacity. Any conductor can be used to fill the length gap. I have a collection of the panasonic green cells that work pretty well and they're cheap, and I hear the pink cells are also pretty good. That 18650 size is common for vaping, laptops, and Teslas. Hit up Budget Light Forum for all your questions.
  • Like
Reactions: 1
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.