Robert, I personally think the hype about Li-ion batteries is a little overdone. I haven't evaluated one of your high voltage mods, as I don't personally think high voltage is the right way for most people to vape. I think your design is satisfactory with respect to venting, voltage protection, for the experienced vaper.
There are people out there that have no business with anything that could be considered dangerous in any way. Notice: if you are stupid, do not use high voltage MODS. Thus the common reference to the little desiccant bag packaged with almost any electronic device as "THE DO NOT EAT". I'm referring to people that have no business having cars, guns, or sex organs. And you want to give them Li-ion batteries? Maybe an IQ test before you sell one of your MODS
Li-ion batteries can vent and spew fire and brimstone and melt your laptop, cellphone, camera into a blob of plastic. A metal cased, un-vented device could explode, blammmm. Vent it and you only have to worry about the fire part.
The CR2/CR123, rechargeable/non-rechargeable, 3.0/3.6 volt battery creates a lot of confusion and the opportunity for those people to create a potentially dangerous situation.
There are 3.0 volt 3.6 volt and 3.6 charge/3.0 discharge models of this battery size. Now a Ni-Chrome wire heater (atty) with a regulator is pretty insensitive to wrong battery voltage (where a cell phone or camera might not be) the batteries themselves may allow an unsafe condition if the user does not know what they are doing.
Two good batteries, in a good state of charge, and the protections and construction methods you use should produce a (relatively) safe 2 cell MOD. I say should, because you must also include user IQ in the safety equation
Do you notice a trend in my comments?
OK the Bad:
Two cells connected in series can cause two types of problems, primarily due to the charge condition of the individual cells.
Referring to the attached sketch, the diagram "2 cell mod, equal charge" shows 2 series connected cells and a "load resistance". No regulator, protection circuit, or switches shown, just the series current path with both batteries in a charged condition. The diagram "charger" is what happens when you charge one battery from another voltage source, like a PCC, battery charger, OR if you stick two batteries in series and put one in BackFlippinAshWords. If both have the same level of charge not much happens. Except a return asking for their money back :this thing don't vape".
(I wonder why).
Now the problem with multi cell Li-ion devices: One weak or discharged cell in series with a fully charged cell. Now who would try that? After a little current flows in this circuit, the charged cell discharges the weak cell and actually will try and reverse charge the weak one. Not Good. A Kirchoff's voltage loop analysis needs to be performed using maximum battery cell voltage range (including unexpected conditions), the load range/voltage drops possible with low to high resistance attys, and the operating parameters of your regulator circuit. If any of the loop sums allow current to flow when weak cell voltage drops below 2.5 volts (I think 2.5 for a 3.6 Li-ion is correct) then Lithium metal plating and thermal runaway is possible. One potential scenario would be a fully charged 3.6 volt Li-ion battery comes off the charger at 4.2 volts. 4.2 volts from one good cell and 2.5 from a crappy cell is 6.7 volts, enough to start operating, both cells at 2.5 volts and the mod stop operating. But what if one is high and one is low?
Even the 3.0 volt type is 3.6 volts off the charger, 3.6 plus 2.0 is 5.6 so it would start operating with one of the cells low.
Using a weak, low voltage cell with another good cell is sort of like sticking a one battery in backwards. You wouldn't expect good results. Mismatched cells, either mah capacity, or state of charge is not a good thing to try.
I think user error, cell or charger failure could create an unsafe condition with any multicell application without active cell balancing circuitry (like laptop batteries). Even protection circuitry can fail, so I guess nothing is safe, right?
Not recommended for anyone but I have a handfull of UNPROTECTED 18650 cells removed from laptop supplies. NO PROTECTION CIRCUIT AT ALL. Oh No ! ! !,
But I stop vaping when my one cell MOD stops vaping, duh, and it stops vaping long before 2.5 volts.
The preceding safety comments are from a modder that uses unprotected Li-ion cells, go figure, huh?
The Rocket
(and still have not found the maximum character count for a single post)
02-05-2010, 01:13 AM
