18650 Lithium Rechargeable Battery Lengths

I won’t bore you with the usual warning about Lithium battery safety and as for capacity – that’s a whole other issue – we all know that some suppliers make ridiculous claims for 18650 capacity (if you see a capacity rating of over 3500maH, there’s a good chance you’ve been conned – “Ultrafire” branded batteries are routinely sold with claimed capacity twice the above) – but just for information, some time ago, Banggood sent me some Lithium batteries – “Meco” branded 18650. In my ignorance I put them to one side as they seemed to be too tall – I figured just bad tolerance. I’ve only just twigged to the simple fact that not all 18650 batteries are the same size – so if you are unaware of this – read on…

At first I blamed the batteries – then I realised that it might be simple short-sightedness on behalf of some charger manufacturers – specifically two inexpensive charger models I own. And sure enough, it looks that way.

Lithium batteries come in various sizes, even with the same type number like 18650. There are the flat-top ones you find soldered together in laptops (I have loads), normal button-top types and largest of the lot – “protected” button-top types. See the photos below:

Notice the length of my MECO “protected” batteries: 69mm

And now a pretty standard unbranded 18650 battery (from my very standard torch): 67mm

And it doesn’t end there. The ex-laptop 18650 flat-topped batteries) – example shown below: 65mm – so from the shortest to tallest of the batteries I own – there is a 4mm height difference. The reason I wanted the new Meco batteries was two-fold – the flat-tops don’t fit some devices and the steadily diminishing capacity of my ex-laptop batteries.

The good news is: I’ve ordered from Banggood a (spotted on their website) which has very flexible length settings – more on that in a short while. If this was all new to you, I hope you find this info useful. Given the scare stories we see from time to time about Lithium batteries, it is probably worth giving the taller, “protected” batteries a second look.

I’ll follow this up but for now, I’m cheating – I’m charging the protected batteries (don’t do this at home) on my variable power supply set to 4.2v max and a current limit of 1A, using single 18650 battery holders I had lying about – note these holders DO handle all three size variations. Up to now, my office is still intact.

I’m sure I’ll get feedback on this – take it easy….

And sure enough, as Barbudor has correctly pointed out in the comments, the length of the 18650 batteries can be increased by the overcharge/discharge circuitry built into some – and of course by whether or not the battery has a “button” at the top. All in all, knowledge worth having.