Liions for "high tech" single cell flashlights - to protect or not to protect

Liions for "high tech" single cell flashlights - to protect or not to protect

Some years ago Liion powerd LED flashlights had very simple buck converters, and of course we equipped them with protected Liions. Protection from overdischarging, protection from overcharging in terribly regulated chargers (my first wolf-eye charger had 4.5 V standby voltage), protection from short circuit. Avoiding a thermal runaway with exploding flashlights, fire and toxic gases.

Nowadays we have perfectly fine regulated single cell flashlights with voltage cutoff at 2.5 - 2.9 V, reverse polarity protection and thermal regulation. Look at Zebralight, for example. And we have chargers that limit the charging voltage at 4.2 V. So can't we say it is "safe" to use unregulated Liions there?

(Please remember: I'm ONLY talking about lights equipped with one single cell, of course. Using unprotected cells (no matter of primary / rechargeable) in series is a risk and should be avoided in any case!)

At the moment I'm using both, surely only high quality brands. Protected AW3400 and unprotected Panasonic 18650B. Same cells, the unprotected are cheaper and are providing a little bit more capacity.

Of course I'm taking care that they never will catch heat, frost, water or damage. I'm storing them one by one in tough plastic containers, so they are safe from short circuit. And I'm exchanging them after 2 or 3 years.

In theory, when you look at a light like the SC600 L2, the only failure where a protected Liion gives us additional protection is an internal short circuit inside of the flashlight. Caused by an electronic failure, by some kind of misassembly in the factoring process, caused by... whatever.

What do you think?

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

It would be nice if flashlights had a one-way safety pressure vent.

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

For a regularly used cell and light like the admirable ZL600MkII, for the observant cautious user I can't see anything wrong with using an unprotected cell. The newer high capacity (3200mAh IMR in particular) cells seem made for this purpose.

But not everyone is fastidiously checking their cell voltages out of the light, and off the charger.

Beyond a modern light like the ZL600MkII (have one too), where protected cells may also help protect you from mishap is in the charger, or in the drawer when you've not used them, quite by accident, for years.

For modern lights with modest current draw an unprotected cell doesn't buy you much - maybe slightly better voltage during the runtime (which might not matter depending on the circuit)... and a few bucks off per cell. If it's all about cost, is it really worth it? Or is the protection layer worth the extra few dollars?

For many the answer to the latter will be yes.

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

I think it's quite acceptable and safe to operate even unprotected LiCo's in single cell flashlights that have a reliable overdischarge protection and are otherwise reliable. This would also apply to multi-cell serial designs if they were designed accordingly - that's how laptop battery packs are constructed, and I think they are very safe.

However, that's not my preference and not how I roll. For general flashlight use, I mostly rely on the protective pcb on the battery (plus a manual voltage check before recharging). If the light itself offers low voltage cut-off or low voltage warning, that's also nice to have, but not strictly necessary. I never use a conventional li-ion battery without at least one form of aggressive and automatic overdischarge protection.

I have used unprotected IMR's in some unprotected devices, but there is always this uncomfortable feeling of uncertainty, sometimes borderline paranoid.

In some applications it's arguably better to not have a cutoff mechanism, so that in an emergency operation can be continued to the point of knowingly sacrificing the battery, which might be the least of concerns. If I was into diving or cave exploring, this would be my number one safety guideline. This would also be acceptable for me in a backup light source such as a keychain light, if there is a 100% foolproof switch that never accidentally acticates. Of course this necessitates a voltage check before every recharging event, but that's what I do anyway.

I currently only use protected "conventional" li-ions and unprotected manganese type for flashlights and comparable purposes, and I'm keeping it that way for now. Sure, my laptop packs, power tool packs and a little cellphone power bank have unprotected cells - but these have what I think is equivalent protection by other means.

I do try to keep track of my batteries' performance even that I don't have a capacity-measuring charger unit, would recycle without hesitation in case of serious overdischarge(waiting to happen), have always recycled immediately in case of physical damage or DOA. However, I don't define any maximum age for batteries. They are good to go if otherwise up to standard, no matter how old.

tandem said:

for the observant cautious user

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Words of truth. Most of the time, the human element is the most important - I guess you could say defining - factor of safety. If we assume the user as observant and cautious (which is admittedly rare in the general population) and the light's circuit is otherwise safely designed, an on-battery protection pcb is not very important anymore.

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

I am still learning. I actually am getting into the flashlight hobby because of ecigs. So i use my unprotected cells from my vaporizer in these. Sony vtc series, samsung 25r, and aw are the only cells i use.

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

tandem said:

... The newer high capacity (3200mAh IMR in particular) cells ...

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That would be an idea, especially for flashlights that draw high currents.
Do you know a certain cell model? A search returned some hits that finally pointed to Panasonic NCR18650BD and NCR18650BE. Couldn't find reliable specs for the cells. Some shops sell both as Hybrid IMR, some people are saying that the one is IMR and the other "regular" chemistry. Does someone know it for sure?

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

I have no problems with using naked ICRs in my lights, as I'm careful about checking them. If not naked ICRs, I use some hybrids like the Samsung 25Rs.

Chris

Re: Liions for "high tech" single cell flashlights - to protect or not to protect

oeL said:

Nowadays we have perfectly fine regulated single cell flashlights with voltage cutoff at 2.5 - 2.9 V, reverse polarity protection and thermal regulation. Look at Zebralight, for example. And we have chargers that limit the charging voltage at 4.2 V. So can't we say it is "safe" to use unregulated Liions there?

(Please remember: I'm ONLY talking about lights equipped with one single cell, of course. Using unprotected cells (no matter of primary / rechargeable) in series is a risk and should be avoided in any case!)

Click to expand...

http://batteryuniversity.com/learn/article/safety_circuits_for_modern_batteries

Each cell in a string needs independent voltage monitoring. The higher the cell count, the more complex the protection circuit becomes.

Click to expand...

Some say that when you start stacking more and more lions in series that the on-cell protection may become confused. In that case, protection would be at the pack level and not inside an individual cell.
Example item 18650x4 in series with protection at pack level: http://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-4S1P-With-2.6-long-20AWG.aspx

Single cell lights, I'd suggest to use protected no matter what (unless it is a super-high-drain light.)

oeL said:

In theory, when you look at a light like the SC600 L2, the only failure where a protected Liion gives us additional protection is an internal short circuit inside of the flashlight. Caused by an electronic failure, by some kind of misassembly in the factoring process, caused by... whatever.

Click to expand...

Most good lights will shut down if the battery is being overdischarged. Can we trust that circuit 100%? This is why protected cells in a single cell light would be good. If some resistor in the light changes value (it can happen,) then it's another safety net to stop overdischarge, overcurrent, that sort of thing.

In my opinion, single cell lion lights are safer than multicell lion lights across the board. With the outputs we're getting these days off of a single cell lion, I find myself wondering if multicell should be limited to the "big lights only." Even a NiMH AAx1 light can do some really great things these days.

Super on topic: What Tandem said, post #23 http://www.candlepowerforums.com/vb...ies-with-primary-batteries-in-the-same-device