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

Lithium battery size

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

Lithium battery size

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.

Lithium battery size

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.


11 thoughts on “18650 Lithium Rechargeable Battery Lengths

  1. Pete, Please re-assure me that you were not putting a short circuit on those batteries just as you closed the calipers to make the measurement…

    1. NigelTwo, that was the first thing which went into my head when I saw that but I also own both metal and composite calipers and notice the color indicated composite. Otherwise, the comments Peter posted would have included some interesting language, photos and probably would have been more about battery safety.

      I also wondered how many might see that and not know you don’t use metal calipers to measure battery length only to later learn for themself the hard way.

  2. I have loads of reclaimed 18650 cells from discarded laptop batteries most work OK but I bought an XTAR VC4S 4 bay charger that charges and grades the battery to give a true capacity of the cell, it works great and I can sort the good batteries from the not so good and not waste my time with those that have little or no real capacity.

  3. Dear Peter,

    Thanks for your overview, just one note – your measurements are incorrect – (please check where 0 mark is on the sliding part of your calliper). From the photos it looks like that pink Samsung is exactly 65mm, brown/white – 67mm, but green one – 68.7mm 😉 (check how to use the bottom scale of the calliper)

    1. You are of course correct Aidas – and you caught me just before giving up for the night – I’ve replaced the photos and updated the measurements. See above and thanks. The calipers are brand new, just purchased yesterday – (obviously) not something I use a lot of.

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