Thread: Helmet Light
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Old 09-27-10, 12:19 PM
  #13  
mwatkins
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Originally Posted by (Y(L|S+
Yes, there is a chance that your LiIon cell can explode. There is also a chance you'll get hit by a car on your ride. The latter is probably more likely to happen.
I don't agree with the analogy as presented.

Riding a bike without due care and attention to cars and traffic is inherently dangerous and in the same vein so is using li-ion cells in typical "consumer" fashion. You and another here claim to behave differently - that's terrific. Clearly in your research you've discovered that li-ion cells need to be thought of differently than standard primary cells or NiMH rechargeable cells. Commendable.

Perhaps I'm a stickler for safe use of these cells because I'm a technology geek by profession or maybe it's because I've been a systems integrator and understand risk and who owns it. Or maybe I'm just a safety geek.

If the discussions being held were more balanced then one could be sure the safety message is getting through clearly enough. As of this writing that doesn't seem to be the case. Li-ion cells are virtually by definition not suitable for the average consumer, yet the preponderance of discussion around li-ion cells and flashlights is decidedly consumer oriented in the nature of "I know what you need - just buy this and that off of ^insert internet site(s) here^".

There is a reason why you don't see li-ion rechargeable cells with Duracell or Energizer or Sanyo labels on the shelves of your local grocery store today and it has nothing at all to do with market share and everything to do with safety. They are not, I repeat, suited for consumers primarily because they are inherently more dangerous. On their own they are not an "end user" product. They are truly meant to be used by systems integrators such as laptop vendors who build entire solutions (packs, chargers, charging and monitoring software in firmware) to make them "safe enough" for consumers. These vendors either own or control the entire power ecosystem in their product, and are responsible for it. Such is not the case with pot-pourri light and power technology mix and match done by lay people like you and me.

One could argue that some flash light manufacturers are taking on at least part of the systems integrator role, and indeed if the light is designed from the ground up to use cobalt based li-ion technology and will absolutely shut off the light before the li-ion cell reaches a dangerous level of discharge, then that is a light to consider. If you don't know that for a fact, the light isn't worth buying at any price. Over-discharge is one of the worst things you can do to a common LiCo-ion rechargable cell - it is here where you've potentially created a time bomb.

But even having identified a good reliable light that will only safely discharge a li-ion cell you've still only considered one aspect of the product ecosphere -- discharging. You still have the cell and charging components to take into account.

By selecting cell A, charger Y, flashlight N you -- the end user -- have taken on the role of systems integrator. By taking on that role you take on all the risk. The experience is not at all like walking into a hardware store and buying a flashlight, charger and some cells, even though it feels like the same experience. It simply isn't.

The consumer goes to a hardware or drug store, sees a plethora of mostly multi-cell flashlights, and makes a purchase decision. There are no warning signs on the displays because generally speaking what they buy isn't ever likely to explode in their face. They'll often run down their lights until there is barely any output and then swap the cell(s). Even if they are slightly courageous and venture into rechargable NiCd or now NiMH cells for their lights, the worst situation they'll likely run into is diminished cell cycle life, no matter how wanton their treatment of the cells in and out of the light and charger is.

That's "consumer" use of cells and lights.

Despite the world wide availability of li-ion cells (largely via the internet) li-ion cells are not consumer grade products. If used in the same manner many abuse alkaline and NiMH cells, li-ion cells are inherently dangerous. Your car analogy is truly apt in this case.

Last edited by mwatkins; 09-27-10 at 12:25 PM.
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