Note that an individual tube is called a cell and it is a group of them connected which is called a battery; maybe more appropriately it is a battery of cells.

Recommendations ∞

You desperately want high-quality batteries. Price must not be part of the consideration; high price does not mean high quality.

https://www.illumn.com/
https://liionwholesale.com/
https://www.mtnelectronics.com/
https://convoy.aliexpress.com/store/330416
www.aliexpress.com/store/3391004
https://vapcell.aliexpress.com/store/1084158
https://www.aliexpress.com/store/1382210
- Doesn't have any 21700s
https://www.aliexpress.com/store/1191644
- Doesn't have any 21700s

You can directly search for a very specific phrase, such as buy "LG INR21700M50LT"

Others noted here for reference ∞

LG 21700 M50 INR21700 M50T M50T M50LT M50L 21700 battery cell 5000mah 3.7V battery cell 10A(GRADE A)
- LG INR21700M50LT(life cycle 1000 times)
- LG INR21700M50T(life cycle 500 times)

These seem like clone stores for SEO purposes.

Terms ∞

- (negative) and + (positive)
- When putting a battery in your device, you must match these ends. Some devices simply won't work, and other devices will potentially damage the battery; see below for "protected batteries".
- A button-top will generally be at the + end; see below.
Button top
- The little bump at one of the ends, usually the positive end (the +)
- Many, but not all, protected batteries have a button top; see below.
Protection
- Various measures to deal with common issues and dangers with batteries: Overheating, over-voltage, under-voltage, reversed-polarity, pressure. Protected batteries often have a button top.
Amperage (A)
- A measure of how much power a battery can provide and a device wants to draw. Match them.
- A device that is high amperage will aggressively draw power. If your battery cannot keep up, it will heat up and be damaged. Some heat is normal during use, but if your amperage mismatches you will cause potentially dangerous hazards like fire and chemical smoke.
- Is it okay to use a high amperage battery? (yes)
Voltage (V)
- An absolutely critical number to match with your device. This number has standards across all devices and batteries, but make sure you get it right!
- This is generally not something you need to worry about though. So if your device requires "18650" batteries, just get those (of sufficient quality; see above).
- An https://en.wikipedia.org/wiki/AA battery is 3.7 V
Milliampere hour (mAh)
- Capacity; how much overall energy a battery can store.
  -- This is kind of like the size of a swimming pool holding a certain amount of water.
- This capacity is an estimate, and it is reduced over the lifespan of the battery. Over the lifetime of a battery, some will lose capacity steeply and others gradually.
Charge cycles
- How many times it can be charged then discharged (used) before becoming unusable.
- This number gives you a very rough estimate of how confident a manufacturer is in the battery. It is not a sudden stop, but a gradual decline influenced by how used and well-maintained a battery has been.

Questions ∞

Is it okay to use a high amperage battery? ∞

Universally yes.

Your device has an amperage usage of x
Your battery is of amperage y

y must be equal or greater than x.

Amperage is a measure of how much could be provided, if called for. If your device doesn't ask for additional amperage, that's okay!

Should I get a very high amperage battery? ∞

Some high-drain devices need high amperage.

If none of yours need it, then it does not provide any benefit whatsoever; it is not a measure of quality, uptime, or lifespan.

One advantage is that you have a battery available for other devices which might need the high amperage. The last thing you'd want is to buy some new high-power flashlight and not have batteries which it can use for it's highest setting or at all.

Adapting batteries / extending terminals ∞

I have no experience and cannot recommend this.

I've been told that yes you can adapt smaller batteries so they work in devices that are larger. There are little adapters for this.

All other things considered ^[ 2 ] a smaller battery will probably have a significantly lower capacity.

I've been told to use small magnets to extend the terminals, but I can't find proper information on this. Any conductive metal should work, but again I have no experience.

This seems like a stupid idea to me, but if you're in a desperate situation then it's your risk to take.

Battery codes ∞

Footnotes

was https://web.archive.org/web/20210508005505/https://vapetime.ca/products/samsung-21700-30t-3000mah-battery- [↩]
And consider all other things like Amperage and Voltage! - [↩]

spiralofhope

Batteries