NiMH Battery Safety Issue

[brooklynboro]

Hi I'm new to the forum and am very glad to be here. I recently decided to quit smoking, and decided to purchase a device called a portable vaporizer. For those of you who are unfamiliar with a vaporizer, it is essentially a device that heats smokable material to its point of vaporization without burning the material thereby minimizing the actual smoke, tar and other byproducts. Vaporizers are used for various smokables including marijuana although I do not condone nor endorse drug use.

A little background:
The exact unit I purchased is called a Magic Flight Launch Box.(http://www.magic-flight.com) It's design is simple and nifty. It runs on a single NiMH battery. Its comprised of 2 separate chambers, one for the tobacco and the other for the battery. A copper wire(positive) runs from the inner end of the battery chamber, through a drill hole in a separation wall, through and around the vaporization chamber, and finally back into the battery chamber through another drill hole in the wall(negative). Once inserted into it's chamber, the battery makes contact with the copper thereby heating a steel screen which holds the tobacco. On a final note, the copper wire fills the majority of the drill holes, yet still allows a miniscule amount of air to pass from one chamber to the next.

The issue:
I am addressing the safety of the unit. I recently discovered that NiMH batteries utilize a venting system. I am familiar with charge and discharge chemistry and read that batteries usually vent while overcharging as a result of hydrogen and oxygen gas pressure build up.

The questions that I am proposing:
Can someone confirm that the pressure is indeed what mechanically triggers the battery to vent?
Is there any remote scientific possibility whatsoever that the battery will vent in a discharging/in-use situation?
Is there a possibility that the spring gasket will defectively remain in an opened position following the venting process?
I read that a potassium carbonate film may develop over time and settle at the top of the battery, is this a hazard?
The manufacturer claims that the unit is safe, and that the batteries will not vent during use. They also claim that in a worst-case-scenario the gas cannot pass through the small crevices in the drill holes. I am still skeptical and would appreciate any assistance on the topic. Again, I'm happy to be here.

 

[TimBishop]

Magic-Flight has addressed these concerns on other forums.
Here is their reply, copied from another thread:

Hi,

There was one poster a while back that asked a lot of questions about this. This reply is a summary.

- 1) To be clear, we must distinguish between the events of charging the
battery and discharging the battery. With improper charging (ie, a
cheap or malfunctioning battery charger) the battery can be made to
vent (its not common, but it is possible). However, venting does not
happen during discharging. The box only uses the battery in discharge
mode. Therefore, there is no risk.

- 2) The previous poster did not understand the function of the back
construction hole and battery compartment and incorrectly claimed that
it was coupled to the vapor chamber -- it is not. Therefore, even if
the battery did vent (see 1 above) it would not be available for
inhalation. Again, no risk.

- 3) Assuming that somehow the battery did vent, in considering risk
it is also worthwhile to consider what kind of gasses are involved and
how much might be generated. From the chemistry the gas would only be
H2 (hydrogen) and quantity is tiny (a few cm at most). Both the kind
and the amount are biologically harmless. Again, no risk.

In sum, the chances of this being any sort of issue while *using* the box is of no interest -- for those who like to worry, there are better candidates. For people who work with batteries in general, the above is considered to be common knowledge.

However, in the interests of safety, I must also report that some chargers do not do as good a job detecting when a battery is already charged. If people put an already mostly charged battery into a fast charger, and that fast charger is not smart enough to detect this condition, it could potentially overcharge the battery causing it to get hot, and in particularly bad cases, to leak (not the end of the world). For some chargers, it can also be rather bad to put the battery in backwards (don't try it!). High quality chargers generally handle both of these conditions gracefully.

We are currently working with our vendors to see if a custom charger without any of these flaws can be made. This will take time. Until then, I would recommend using the battery as fully as possible before recharging. I am aware that I have previously suggested that people could put the batteries back into the charger regardless, and that was known/verified to be true at the time. However, there are a lot of different kinds of chargers out there. For simplicity sake, and also to get the best value and life from the batteries I now recommend using them out before recharging.

-- Magic-Flight