Li-Ion battery pack PROTECTION

[Tidra]

I am building a Li-Ion battery pack with 18650 cells (7.4V/4400 or 6600mAh) and I wonder…

What is better:
- to build a pack with protected cells

or

- to build a pack with protected cells and add protection PCB

or

- to build a pack with unprotected cells and add protection PCB


Is there any advantage or disadvantage in any option?

Cheers,
Iztok

 

[VidPro]

i would give the advantage to the
to build a pack with unprotected cells and add protection PCB

because , that is just how its done
and its less parts and pieces, less to go wrong or diagnose what is wrong.
as long as the protection is proper and taps out all the cells .

next would be, to build a pack with protected cells, but you know protected cells have the band (wire) that runs down the side, and so you have to treat them well, plus the pcb (curcuit) sits on the end, and is more prone to damage.
on the other hand this is great because you can take the cells out and charge them seperate to balance and test.

last would be double protection, while it provides the ultimate protection, your just adding in a mess of stuff that can go wrong, making finding out what did go wrong much harder.

the "Best" still by any term, is to not only have protection, but to have balancing, as over much time or depending on the use , getting out of balance messes things up too. balancing is not normally done by any protection.

ALSO a pack protection can have thermal monitoring, or thermal cutoffs, if the board itself doesnt have it , you can tack in a thermal fuse or thermal breaker.