Where to buy 18650 batteries?

I bought 10 in Guangzhou.

Never used them, but :-

Look for 'vape' places, eg:

Theo

Ive used allbatteries.co.uk a few times and been satisfied with them. They vary from 'big brand' to ones I've not heard of but have a look and see what you think.

Google is your friend

Ideally, avoid buying cheaper 18650 cells with a flat end as they don't have protective circuitry against overcharging.

I'm reluctant to buy batteries with "Fire" in their name from eBay/AliExpress/etc

Last year I bought some tagged 18650s from

Thanks, all of you. Some very useful recommendations, there.

Those are 'protected 18650s', and they're typically longer because there's an extra circuit on the end. They often don't fit in 18650 holders and such.

If you're making up a pack, you typically have a separate BMS for protection, as will equipment that expects to take bare 18650s. 18650 chargers will also manage overcharge, so it's only if you are using the cell in an application where you're feeding it from a dumb power supply, or to replace other types of batteries (eg 1x LiFePO4 = 2x AA alkaline)

Theo

You can often spot the fakes or low quality products by looking at the capacity. They will have widely exaggerated claims often 2x the capacity of that from well respected brands.

Says a man with Burns in his name ;-)

Torchy

There are transport regulations for Lithium cells.

This causes all manner of distortions to sales of them.

Panasonic is pretty good about making cells or batteries, but they do not market worldwide.

In China, a company like CATL would make them, but then, the Chinese are focused on Lithium Iron Phosphate, rather than a Cobalt chemistry. Perhaps some smaller company makes Cobalt (NCA) ones there.

As long as you have a handle on the issues, carry on.

There is no electrical difference between the two types, ie the ones with the ‘pips’ are no more protected than the ones without.

If you want to add protection, you can buy small BMS PCBs for modest sums.

I’ve just built a couple of battery packs with charge / discharge protection for some radio equipment.

I am going by what articles like these say ...

The Anatomy of a Protected LiIon Battery

PCB will protect against over discharge, over charge and over current, depending on design the PCB will reset automatic or when placed in a charger.

The next article illustrates a simpler form of protection:

BU-304: Why are Protection Circuits Needed?

"The current interrupt device (CID) is a fuse-type device that cuts off the electrical circuit permanently when triggered by excessive cell pressure, high temperature, or high voltage, depending on design."

The difference is they are specifically made with and labelled as having protection included. Not that they have ‘pips’ / aren’t flat.

Also, in series applications, the protection circuit needs to access the intermediate connection points in the chain and the terminals of the battery ( the two ends of the chain of cells). A battery is two or more cells.

True enough. Although the following page makes a good attempt at categorising the physical differences between 18650s: