Protected vs Unprotected cells

[barbs00]

Hi All,
Going to build my first battery soon 14S4P

About to pull the trigger and buy some 18650s but am wondering if I need to get protected cells or not?

I am planning on using a BMS so don't know if I should worry about the second level of protection.

Thanks

 

[redilast]

Protected cells are cells that have their own protection circuit to prevent overcharging, overdischarging, short circuits, overcurrent etc. These batteries are primarily designed for use in flashlights.

You do not want protected cells for an e-Bike as you will be using a BMS to protect the whole pack.

 

[barbs00]

Thanks - that is what I thought

 

[DVDRW]

Most common protected cells use 6A 20V 8205 FETs. So if your pack is over 20V then magic smoke escapes.
Some cells like Panasonics have internal pressure valve (CID). Even if you apply directly 12V to cell with unlimited amps then no fire.

 

[barbs00]

Cheers

 

[spinningmagnets]

Here's an example (the "protection" circuit board also makes the cell a hair taller). That protection is useful for vapes and flashlights that have a low-Ohm circuit with no controller, just an on/off switch...

 

[barbs00]

Nice pic - thanks!