Why Use Unprotected While Protected Works Fine?

[vicv]

Ok. Spring loaded pins in the tube? That would be very difficult to manufacture inside the tube of the light. And I'm not talking about lights with battery carriers. I'm just talking a simple tube with a switch at the tail and a head at the other end. I think you're over worried about cell balance though. I use almost exclusively Incan lights. Some draw a lot of power. Never a problem of cell balance. A tenth of a volt or so doesn't matter. And I don't even have low voltage protection. With incans it's easier because I can see when the batts are dead. If an led light takes 2x18650 and lvp of 6v. If one cell is 2.9V and the other is 3.1V it's still not a problem

 

[StorminMatt]

If an led light takes 2x18650 and lvp of 6v. If one cell is 2.9V and the other is 3.1V it's still not a problem

And THIS is why I don't worry about running unprotected cells in series. If you take a worst case scenario where you run one cell down to 2.5V, the other would have to be at 3.5V when a 6V low voltage protection or warning kicks in. Unless you do something grossly negligent like not fully charging your batteries before use, use batteries of different capacity, or run a new cell with one that is a few years old, this is simply NOT going to happen. Even if the cells are not perfectly matched in terms of age and cycles, getting a voltage diference of more than .2-.3V is pretty unlikely so long as you stick with quality cells and age/cycles are not GROSSLY different. And even if there is no low voltage protection and/or warning of any kind, it is really just a matter of knowing your runtime and giving yourself some wiggle room. For instance, if you have a two cell light that can run two hours on two 18650s, you really have NOTHING to worry about so long as you run your light for, say, an hour and a half and always fully charge both batteries before use. You just might wnat to periodically do a runtime test to make sure that you adjust your runtime expectations (or relegate the cells to single cell use) as the cells age.

 

[vadimax]

Tough men use unprotected only! Hardcore rocks But not stupidity. DMM is a must.

Yesterday have checked more than a year old Thrunite TN32. All three unprotected 18650 cells happened to be exactly the same voltage with mV precision.

 

[dc38]

Tough men use unprotected only! Hardcore rocks But not stupidity. DMM is a must.

Yesterday have checked more than a year old Thrunite TN32. All three unprotected 18650 cells happened to be exactly the same voltage with mV precision.

Impressive, as I was sure the tn32 runs in series. Was that resting voltage?

 

[vadimax]

Impressive, as I was sure the tn32 runs in series. Was that resting voltage?

That was a bit depleted voltage. Were charged, got some use, then I did a check -- all three were at 4.07V. The case showed 12.21V accordingly.

 

[stephenk]

There are a few things that can catch people out in series lights. Parasitic drain running cells below 2.5V, and mixing up full and empty cells causing reverse charging (there is a thread in this forum of a serious li-ion explosion caused by this). As far as I'm aware, a good protection circuit should prevent both. Sadly, humans are humans, and even the best of us can make mistakes. I've started using unprotected cells in single cell lights with LVP, but still prefer to use protected in series lights (even though I've never done anything that would require the protection circuit to kick in).

 

[vadimax]

A protected cell is like a gun you are unable to shoot your own foot , but cannot kill a dog that already has clung into your leg. I prefer responsibility because it leaves me an option to deplete batteries dry in SNAFU situation and not to find myself in position of unexpected darkness (protection kicked in) and forced battery change.

 

[Gauss163]

Keep in mind that protected cells protect against not only user error, but also against faulty devices, e.g. a defective charger that charges to too high voltage or at too high current. Even if you are very knowledgeable about safety and also highly-disciplined enough to rigidly follow safety rules (a rare combination), you have little if any control over device faults. That's one reason why it's worthwhile having multiple levels of fault protection.

 

[vadimax]

Well, may be. But the only experience I had with protected cells so far -- is kicking in current protection of Olight 16340 cell inside Olight S1 Ti

 

[StorminMatt]

There are a few things that can catch people out in series lights. Parasitic drain running cells below 2.5V, and mixing up full and empty cells causing reverse charging (there is a thread in this forum of a serious li-ion explosion caused by this).

That's why you (1) don't store your cells in your light (unless the light does NOT use an electronic switch OR you can lock out the light), and (2) ALWAYS fully charge your cells before using the light.

 

[stephenk]

That's why you (1) don't store your cells in your light (unless the light does NOT use an electronic switch OR you can lock out the light), and (2) ALWAYS fully charge your cells before using the light.

That is true, but sadly not everyone has that common sense.

 

[TinderBox (UK)]

I have a habit of holding a small flashlight in my mouth leaving my hands free to work, I use an protected cell in that case or an nihm flashlight.

John.

 

[stephenk]

I have a habit of holding a small flashlight in my mouth leaving my hands free to work, I use an protected cell in that case or an nihm flashlight.

John.

Maybe you need a headlamp?

 

[Dr. Mario]

As for the chargers, I usually check the chargers, loaded or unloaded, with the DMM before I can truly trust them. Built-in protection is good to have, but as everyone knows, it's both a blessing and a curse.

I usually follow very strict rules of Lithium-ion battery handling (ie. doing homework before buying the particular batteries for whatever they will be used in - in term of peak short-circuit amperage rating which is occasionally important in pocket rockets, and capacity, down to charging them with proper chargers, all from cradle to grave).

If you can properly follow the safety rules, there's little need for the built-in circuit breaker for overall usage. Still, good point on LED driver failure mode, which I would think it is a good idea to have the built-in circuit breaker board inside the protected battery - up to a point there's a big difference between the nuisance trip or legit short-circuit trip in term of end LED current consumption (some LEDs like Nichia 219 / 319 LEDs can easily survive 6 Amps current no problem) and the LED driver current consumption as well as circuitry topology (switchmode or linear regulation).

 

[Gauss163]

[..] If you can properly follow the safety rules, there's little need for the built-in circuit breaker for overall usage [..] .

As I emphasized above, even if you could unerringly, robotically follow safety rules, that doesn't eliminate the need for protection circuitry, because it protects not only against user errors but also against device failures, such as chargers that have gone awry, or were improperly designed etc.

As for following safety rules, even experts make mistakes, e.g. the hobby shop owner who's shop burnt down when he stepped out for 10 minutes while leaving some packs charging. The problem here is that it's easy to get too comfortable, thinking, ah, I've charged hundreds of Li-ion batteries and never had a problem, so it should be ok to step far away from the charger for 15 minutes to do xyz. But if you want to be safe, you should never do that, even if 99% of the time you can get away with it.

 

[Dr. Mario]

Still, you have to always allow redundancy - if you don't think to follow strict rules, expect trouble. It's not your father's Nickel Cadmium battery, that thing pack a punch so you have to always be sure, even though some Lithium-ion battery types allow rooms for some mistake, you certainly won't with classic Lithium Cobalt Oxide cells (which is why I don't handle Li : CoO2 cells anymore, they easily overheat as much as you sneeze at them).

Robotically? Not so, as there are so much warning points in the datasheets especially for the Sony 18650 cells that you have to take that very seriously.

 

[Dr. Mario]

Also, most newer 18650 cells are now of Lithium Polymer types, so extra cares have to be heeded - personally I prefer that over handling the pouch cells as it's easy to blow one of them up even from slightly bending it due to the pouch cell being so soft. Metal cans mitigate the risks somewhat, so you're left to deal with electrical details like LVP (low voltage protection) and charging process.

 

[Gauss163]

Still, you have to always allow redundancy - if you don't think to follow strict rules, expect trouble [...e]

Yes, that's exactly the point I was making above. Maybe your earlier statement ("if you can properly follow the safety rules, there's little need for the built-in circuit breaker for overall usage") meant something different that what I thought. I interpreted it as implying that there was no need for protection circuitry (e.g.protected cells) if one can follow safety rules.

 

[Dr. Mario]

I suppose. There's some redundancy in the LED drivers nowadays and you can ask to have desired voltage cutout put in for extra fees anyways. We're now seeing less and less of the "dumb" LED drivers (not defined by firmware as such) though, as microcontrollers now only cost a couple of changes.

I would still use protected Lithium-ion batteries in multi-celled setup as we would never know, in term of voltage balance of entire cells under load. I never find protected Lithium-ion cell necessary in the single-celled flashlight anyhow, and it's up to the others to interprete. (One exception, however, is that I would use protected Lithium-ion battery at first in new, stock flashlight like Olight or four-sevens for example, so I can be sure the software-defined LVP is working as intended, without tripping the circuit breaker inside the protected Lithium-ion battery before I decide to chuck unprotected Lithium-ion battery in it the next time - and all my DIY flashlights I assembled trip out at 3.0 Volts.)

For those new to Lithium-ion batteries, I technically recommend the protected Lithium-ion batteries until they gain enough experience and knowledge to use the unprotected Lithium-ion batteries in their flashlights safely. It's like the gun, which you have to have knowledge to use it safely; it can either be your friend or your enemy.

 

[Tachead]

On both occasions the thin flat wire shorted to the metal case. Once, on the edge near the positive end and the other near the neg end when the cell was dropped.

When this happens you need to watch out as the flat wire heats up quickly and will melt the wrapper.
Both of the cells were fine after I removed the PCB and rewrapped. In fact, I'm still using them regularly.

These were genuine cells purchased directly from Andrew's old thread on CPFMP.

Many new high quality protected cells no longer use the thin metal strip down the side and have riveted steel enclosures to protect the PCB. Some can also handle 10 amps continuous draw now and have a full 1 year warranty as well. Protected cells have advanced along with cells in general. It's still hard to beat the price of unprotected though.