18650 - Are protected batteries ALWAYS better?

[Gauss163]

Fires/explosions are super rare in relation to the millions and millions of sold battery cells. And even less common on proper brand cells.

Only because 99.9% of Li-ion cells aren't sold directly to consumers. Rather, they are encapsulated in professionally designed systems with adequate safety features (e.g. laptop and power tool packs). Only recently has consumer use of loose cells greatly increased (mainly due to vaping), and evidence of just how unsafe this can be can be seen by perusing the smoke and fire... subforum.

Of course battery packs and charging systems can also be unsafe if incompetently designed, e.g. the recent "hoverboard" incidents.

 

[Connor]

Only because 99.9% of Li-ion cells aren't sold directly to consumers. Rather, they are encapsulated in professionally designed systems with adequate safety features (e.g. laptop and power tool packs). Only recently has consumer use of loose cells greatly increased (mainly due to vaping), and evidence of just how unsafe this can be can be seen by perusing the smoke and fire... subforum.

Of course battery packs and charging systems can also be unsafe if incompetently designed, e.g. the recent "hoverboard" incidents.

True, but I'm only talking for myself as a knowledgeable and careful user. As such I don't benefit much/at all from protected cells (in conjunction with a good charger/flashlight and proper handling).

If you don't know better and put a 35A unprotected cell in your pocket with your keys your burning pants will be your teacher. ;-)

 

[Gauss163]

True, but I'm only talking for myself as a knowledgeable and careful user. As such I don't benefit much/at all from protected cells (in conjunction with a good charger/flashlight and proper handling)...

That's a different claim than your prior statistics based claim. Yes, of course, knowledge of safety guidelines can help one to be safer, but only if combined with the discipline to rigorously follow those guidelines without ever slipping up. Even experts may lack such discipline, e.g. the case of a hobby shop owner with decades of experience whose shop burned down when he left for 10 minutes while charging.

 

[markr6]

You can get killed walking your dog.

I park a 21 gallon gas tank in my home every night within feet from a 50ah battery and cabinet full of explosive tanks, chemicals and flammable items. I live dangerously.

 

[Connor]

That's a different claim than your prior statistics based claim.

No, it's still the same "claim". If you are responsible for the fire by mishandling the cells in some way earlier, you are responsible for mishandling the cells (IMHO).

I was talking about cells that explode/catch fire because of a manufacturing defect of some kind. Those failures are extremely rare and a protection circuit likely won't help at all if the cell fails internally (e.g. shorts internally while charging).

That doesn't mean I would recommend unprotected cells for everyone. The thread title is "18650 - Are protected batteries ALWAYS better?", though. IMHO they are not.

 

[msim]

You can get killed walking your dog.

Very true! A crazy person threw a glass bottle at my dog and I one night while on a walk (it completely missed).

 

[Gauss163]

No, it's still the same "claim". If you are responsible for the fire by mishandling the cells in some way earlier, you are responsible for mishandling the cells (IMHO).

I was talking about cells that explode/catch fire because of a manufacturing defect of some kind. Those failures are extremely rare and a protection circuit likely won't help at all if the cell fails internally (e.g. shorts internally while charging)...

Your original claim made no mention of manufacturer defects. But fyi internal shorts were reported to be the major causes of failures in laptop batteries a decade ago (before improvements were made to help manage internal shorts, e.g. ceramic separators).

 

[Connor]

Fires/explosions still are a very rare occurrence even if you count in user error. Which I don't, because IMHO it's your own fault if you handle potentially dangerous technology without educating yourself properly.
Regarding vapers: every good shop I've seen has strongly worded handling security information placed prominently on their website.

 

[Gauss163]

Fires/explosions still are very rare occurrence even if you count in user error. Which I don't, because IMHO it's your own fault if you handle potentially dangerous technology without educating yourself properly.
Regarding vapers: every good shop I've seen has strongly worded handling security information placed prominently on their website.

Depends on your definition of "rare". Most likely the frequency of incidents are at least an order of magnitude greater for consumer use of loose cells vs. cells used in competently professionally designed systems.

 

[KeepingItLight]

Fires/explosions still are a very rare occurrence even if you count in user error. Which I don't, because IMHO it's your own fault if you handle potentially dangerous technology without educating yourself properly.

I understand the point you are making, but I do not agree. We know, for instance, that many airplane crashes are caused by pilot error. That does not mean we should not design pilot-proof systems.

Cell phones, tablets, laptop computers, and power tools all have built-in circuits to manage battery care. Unfortunately, flashlights do not. That is why I think there is a place for protected batteries in the flashlight world.

In my opinion, flashlights need to have the same battery-protection circuits as the other products mentioned above. Period.

I'll go further: Multi-battery flashlights should have full-on battery management systems, just like the rest of these devices. Each battery in a multi-battery device should have its voltage level independently monitored. Frankly, I think that the absence of such circuitry is a sign that the Li-ion flashlight industry is still in its infancy.

When all flashlights have low-voltage cutoff circuits, then we can talk about eliminating protected batteries.

Can you really say that your flashlight will never be accidentally activated (and over-discharged)? Can you say that you will never put a flashlight down, and forget that it is on?

I cannot.

I got surprised recently by one of the Nitecore flashlights I own. Like many recent Nitecore releases, my Nitecore P36 has a significant standby drain. It uses the batteries even when the flashlight is off. I usually unscrew the tail cap to lock mine out, but this time, I forgot to do that. When I came back a couple of months later, I found that one of its batteries had been drained to 3.6 volts.

I learned something about my flashlight in this episode. For some reason the second battery in this 2x18650 model had not been depleted as much.

The KeepPower 3400mAh batteries I use are a matched pair. They were purchased together, and they have always been used together. They are always charged together. Evidently, however, the standby drain does not discharge them at the same rate. Since these batteries only have a few cycles on them, I was surprised. Anyway, now I know about this, and I am keeping my eye on them.

And I am happy to report that these batteries are protected!

 

[recDNA]

Very true! A crazy person threw a glass bottle at my dog and I one night while on a walk (it completely missed).

I was throwing the bottle at YOU! J/K

AW told me his IMR 800 mAh contains an internal heat resistant layer (HRL). I believe this is found in many Panasonic batteries. If there is a short outside the battery in the flashlight itself does HRL prevent thermal runaway?

 

[recDNA]

That's a different claim than your prior statistics based claim. Yes, of course, knowledge of safety guidelines can help one to be safer, but only if combined with the discipline to rigorously follow those guidelines without ever slipping up. Even experts may lack such discipline, e.g. the case of a hobby shop owner with decades of experience whose shop burned down when he left for 10 minutes while charging.

Don't tell me stories like that. I'll be back in a gargage staring at my charger for 6 hours.

 

[Gauss163]

I was throwing the bottle at YOU! J/K

AW told me his IMR 800 mAh contains an internal heat resistant layer (HRL). I believe this is found in many Panasonic batteries. If there is a short outside the battery in the flashlight itself does HRL prevent thermal runaway?

Yes, ceramic separators help prevent thermal runaway, e.g. see The Role of Separators in Lithium-Ion Cell Safety by CJ Orendorff, Electrochemical Society Interface 21(2):61 · May 2012.

 

[Dr. Mario]

Oooh, Ceramic separator. Panasonic, correct? I may be shopping for better IMR / INR cells soon.

 

[recDNA]

Yes, ceramic separators help prevent thermal runaway, e.g. see The Role of Separators in Lithium-Ion Cell Safety by CJ Orendorff, Electrochemical Society Interface 21(2):61 · May 2012.

I had no idea they were ceramic. It was my impression it was just a thin membrane. Is there more than 1 type of HRL?

 

[Gauss163]

I had no idea they were ceramic. It was my impression it was just a thin membrane. Is there more than 1 type of HRL?

There are many, many different types of separators in use. Some have a multilayer structure that acts as a thermal fuse to inhibit thermal runaway, e.g. PE-PP bilayer, or PP-PE-PP trilayer membranes. Here the PE layer melts first, filling the pores in the other layers, which greatly inhibits ion flow. This increases internal resistance so much that current flow is reduced to near zero, so inhibiting thermal runaway. But the other layer(s) have higher melting points so they retain their mechanical strength, so they still keep the electrodes insulated. Also multilayer separators often have higher resistance to punctures.

 

[Gauss163]

Oooh, Ceramic separator. Panasonic, correct? I may be shopping for better IMR / INR cells soon.

HRL (heat resistant layer) is Panasonic's name for their ceramic separators. Almost surely all of the top-tier manufacturers have made analogous safety improvements to their separators, but it is all proprietary so not easy to find public details. Also it is difficult to determine when these improvements first appeared, i.e. which older cells are less safe.

 

[recDNA]

Do these separators react fast enough to stop thermal runaway in external short? I read it can take milliseconds.

 

[magellan]

Yes, ceramic separators help prevent thermal runaway, e.g. see The Role of Separators in Lithium-Ion Cell Safety by CJ Orendorff, Electrochemical Society Interface 21(2):61 · May 2012.

Good article, thanks.

 

[Gauss163]

Do these separators react fast enough to stop thermal runaway in external short? I read it can take milliseconds.

Separators with shutdown capability are designed so that the separator fuses at temperatures much lower than the thermal runaway temperature. Thermal runaway typically takes minutes, not msecs (but the actual time depends on many parameters).