What are the advantages of protected vs unprotected cells?

What type of batteries do I get for the following flashlights? Total newbie here. I have some Samsung 30Q.

Astrolux S42
BLF Q8
Zanflare F1

Thanks.

Protected
Pros:

- short circuits does no damage

- no dramatically overcharge or -discharge
Cons:

- depending on the MOSFETs used the internal resistance is higher, so in DD lights less output

  • in high current flashlights protection board trips, rendering turbo mode useless

Unprotected
Pros:

- in DD lights more output

- no problems with tripped PCB

- less internal losses lead to higher runtime in boost or buck drivers
Cons:

- short circuit will damage the light like molten springs
and the internal electro-mechanical protection might render the cell dead

- can be overdischarged from drivers without LVP

  • can be overcharged in bad chargers

What he said…

I used to tout protected cells from a “what can it hurt?” perspective, but as long as the lights/drivers have LVP, protection isn’t needed, and can get in the way.

My biggest problem is that protected cells have parasitic drain, and will sloooowly drain your cells just sitting around doing nothing. Never had an unprotected cell go garbage, but have had protected cells get bricked and refuse to charge.

Yes, the parasitic drain from protection will brick a full 18650 cell in about 50 years

Thanks everyone. Can you comment on which type of cells I should use for my 3 flashlights? Thanks.

When you forget about a half-spent 18350 for a few years, it happens.

Tried the usual tricks to “jump-start” it, but no joy.

Still got a 26650 that’s bricked, too.

30Qs are fine. I have mainly panny-Bs and 30Qs.

I suppose I can say that more cells in series means more potential safety problems (due to uneven wearing of the cells), so in 3-4S light I’d advise using protected. Unless, of course, someone check the volatges and capacity regularly and knows what he is doing :).

Out of curiosity - is the battery discharged to deathly 0V? Or just the IC problem?

BTW Unprotected is cheaper and smaller in size so more likely to fit.

When the protection IC kicks in it just cuts off power delivery.
The cell itself isn’t discharged. The heat from a potential discharge would blow it up :slight_smile:

I know. However, since we were talking about parasite drain of the ICs , there were two possibilities:

  1. IC slowly discharged the cell to low voltage. (possibly there was some drain even after cutoff). With, say, 1mA draw or lower the heat would be safely dissipated (even hard to notice).
  2. IC got damaged and ‘stuck’ while the cell still had some charge.

An 1mA parasitic drain would be quite big.
If a cell shows 0V then most probably the protection has stuck open the circuit.
Just zap the cell with 5-8V and if doesn’t work just rip the protection apart.

I agree… I had plenty of issues with protected cells but most are reviewed after pcb removal and I rarely have an issue with uprotected ones. Even when my charger got broken and charged sanyo battery till 5,5 A or so… I still use it after that :slight_smile:

I really don’t know how this things are produced but it has to be calibrated and tested to withstand much higher overcharge current in order to market release it.

For some unregulated configurations(turn it on and use till protection kicks) protected ones could be more desirable but they will probably fail sooner or later… Depends how often PCB kicks. And that small pcb electronics does not look reliable in long terms use to me. I would probably regain the trust if in the future PCB’s will be made rock solid and shock proofed, pressure proofed + calibrated on much more “kicks” before they die (lets say 1000 as standard).

So in this present days I would not rely on pcb to much and so far my vote goes to unprotected ones.

The current could be like 10uA or even 1 uA - but evenwith 1 mA the heat would not ‘blow it up’.

~1: Thats why I asked for the cell voltage, without IC; that means IC circumvented and checking the cell directly.
~2: Zapping the cell? Well, imagine the scenario where IC got damaged and during charging suddenly causes a short between positive and negative pole of a fully charged battery…

Both. Unwrapped them and pulled off the boards, nekkid cells measure near-0.

Oh yeh, tried putting the now-unprotected cell in a dumb charger, showed “charging” (red light) overnight, yet nothing held.

I can’t get my 30Q to work in the F1. The light will power on momentarily when I plug it into the charger and appears to be charging but it won’t turn on after 5 hours of charging. I noticed there is a clear wrapper over the pink wrapper. Do I need to cut the clear wrapper off before it’ll work?

if it covers the contacts, yes.
Mine arrived with clear plastic wrapper over both positive and negative contacts - had to remove it :slight_smile:

Do you have a voltmeter to check the battery? But yes, make sure that the clear wrapper isn’t covering the contacts obviously.

It’s just a clear plastic wrapper but doesn’t cover the contacts. It’ll flash once when I plug it in but won’t charge or turn on afterwards. Maybe I’m just stupid but using a light shouldn’t be this complicated!

Maybe post a photo…