why unprotected cells?

thermal guy

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OK after being on cpf for a while now it seems clear to me that protected cells are defiantly the way to go why than do company's still sell unprotected cells? that being said i have been forced to buy unprotected cell but that was for my hds tube and no protected cells would fit but i think that is a rare application.Are there any benefits to using unprotected cells?
 

MatajumotorS

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Notebooks uses unprotected cells, but there are special charging-protection-monitoring circuit for them all 3, 4, 6, 8, 9 cells.

1. maby it is price
2. maby it is custom protection needs

P.S. AW could know the answer.
 

Yenster

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There's protection, and there's more protection. The protection may be for over-charge and under-charge. The more protection may additionally detect short-circuit.

I think the over-charge and under-charge protection is always a good idea. And they have slightly more capacity and are not too much larger in size.

The additional short-circuit protection is good as a safety measure too (one time I melted the spring in a tailcap right after a mod, since I wasn't using a short-circuit protected 18650). But that short-circuit PCB can sometimes cut the power (open) when used in some non-led flashlights. Also, it can abruptly cut-off the light when used with some boost drivers, which can be annoying.

So for me, I will select different levels of protection for different flashlights.
 
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thermal guy

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OK i Will buy that if protected cells are not made for a particular size that would make sense
 

SilverFox

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Hello Thermal guy,

Keep in mind that unprotected cells are more reliable than protected cells.

Tom
 

Cuso

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Hello Thermal guy,

Keep in mind that unprotected cells are more reliable than protected cells.

Tom
How is this? I thought protected cell offered more protection to the user , thus making them more reliable than unprotected ones...:thinking:
 

thermal guy

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by reliable do you mean more dependable? also as long as were on that topic can i rely on my 18650 in my hds tube when the temp gets down to 0c?
 

mdocod

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because (responding to reliability question) when you add more components to a system, you increase the number of potential failure points. If the PCB in a protected cell fails in some way, then a potentially good cell may no longer work as a result of this failure. So for pack builders who are going to incorporate their own form of cell monitoring, there is no need to have additional failure points on the cell itself, "externally" serviceable components make more since for many applications. (by externally I mean not as part of the cell itself).

There are a few flashlights out there that provide low-volt cutoff to prevent over-discharge on an unprotected cell, so combined with a quality charger, a higher capacity unprotected cell (like for example a 2600mAH 18650) could be used pretty safely.

There are also specialized circumstances where hobbyists desire to push the limits of the cell, and the PCB will not allow the current drain required by the user, in this case an advanced user who is careful and knows what they are doing can benefit from the use of unprotected cells.
 

SilverFox

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Hello Cuso,

I will basically echo what Mdocod said... and expand by mentioning that I have had several protection circuits on cells go bad. If you are playing around with your light, this is no big deal, however if you need your light to work, it is a big deal.

Tom
 

Curious_character

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I've also had a couple of failures of cell protection boards.

I'll add to the list a couple of other reasons I sometimes use unprotected cells:

1. I salvage cells from defunct laptop supplies.
2. I have a couple of lights that only unprotected cells will fit into.

c_c
 

DM51

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It is not difficult to damage a protection circuit, by dropping the cell or by applying excessive spring pressure (>15 lbs). The circuit sits on the end of the cell, and being a small printed circuit board, it is actually quite fragile.

As long as it is treated carefully, it will be fine. Problems can arise when people rely on the protection circuit too much, and think it will always protect against every adverse eventuality. Damage to a protection circuit is not always obvious or visible.

10mm diameter cells (10440s, 10280s, 10180s etc) do not have protection circuits, as there is no circuit currently made that is small enough to fit them. Users of these cells have to understand the risks.

It can be more dangerous to discharge unprotected cells slowly, as the dimming of the light as the cell empties may be gradual, and not so quick and noticeable as it would be at a high discharge rate. Also, with a slow discharge rate, the voltage sag will have been less, so the cell will not always recover adequately.

It is worth repeating here that Li-Ion cells are fully-charged at 4.2V, and effectively empty at 3.5V (resting voltages). It is better to recharge a Li-Ion cell before it drops to 3.5V resting.

Maximum life for a Li-Ion cell will be achieved if it is operated between 3.6V – 4.1V.

Users should always keep careful track of run-time and remain aware of the state of charge of their cells.

Damage will have occurred to a Li-Ion cell if its resting voltage is below 3.0V, especially if it is left at that voltage for an extended time. Recovering an over-discharged cell is possible, but the correct procedure for doing this is not without risk, and not always successful. The incorrect procedure (putting an over-discharged cell on a charger for a normal ~0.5C charge) is very risky, and this is when most over-heating and venting incidents can occur.
 

BVH

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A year or so back, there were some mods like the Minimag, Litho123 1499 Hot Wire that would not operate unless using the unprotected cells. The protected cells would not provide the current flow without their circuit tripping off. The new protected have a higher flow threshold before tripping.
 

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