Robert L Cochran <[EMAIL PROTECTED]> wrote: > ... -- if it is safe to solder those wires, I mean...the heat from a > soldering operation on the battery wires won't explode the battery, > will it?
Of course, you can solder them unless you're soldering it with a hydrogen torch. ;-) I don't really understand why the danger of LiIon and LiPo cells is often exaggerated. Yes, they can burn when being handled improperly. But about any kind of battery with enough stored energy in it is dangerous, in one way or another. Your 44 Ah car battery is probably much more dangerous than an 800 mA LiIon cell. It contains lead acid, and its stored energy can easily arrange for an explosion if you shortcut the battery e.g. by dropping a tool onto it that doesn't evaporize within a few hundred milliseconds. Yet, nobody talks about banning lead acid batteries... Li coin cells have been around for much longer than LiIon cells, and they are *way* more dangerous. Nobody really made much fuzz about them during the 20+ years they are in use. First, they contain metallic Li (unlike LiIon cells) which is much more reactive -- after all, that's the entire point of the LiIon rechargables to not contain metallic Li anymore. (There have been metallic Li rechargables for a short term, but they were really, really dangerous.) Second, they are sealed to stand the high pressure which can happen at the upper end of the usable temperature range (plus a safety margin), so *if* you manage to increase the pressure high enough to explode them, already the mechanical forces set free by that are already quite high. Of course, Li coin cells are normally not charged, and discharging them doesn't yield a very strong current, so in normal operation, nothing happens. However, a standard circuit for using them as backup batteries contains of two diodes with a common cathode, and one anode connected to the main power supply, the other one to the coin cell. Now imagine what happens if the diode in front of the coin cell breaks... the cell gets charged from the main supply. And it will really explode by that. There are photos of damaged computer mainboards caused by such an explosion, and they really don't look like you want to have that. ;-) Back to the LiIons, when properly handled, their mass application in cell phones, cameras etc. shows that they are pretty safe. The RC model people run them at the edge of their parameters, both when discharging as well as charging -- because RC models always take the last out of the batteries. So well, these folks might have been a bit surprised that while you can run a NiMH or Pb cell quite a bit beyond its parameters, and it will not spit into your face, you'd better avoid that with a LiIon cell. One note of caution: usually, these battery packs are required to have a secondary protection circuit inside the battery when the pack can be removed from the device. You can find that kind of devices e.g. when you look into the product catalog of Texas Instruments (who acquired Benchmarq which used to be a leading manufacturer of that kind of devices). The purpose of that circuit is to avoid just the severe effects mentioned when you remove the battery pack from the device, and accidentally shortcut the connector pads outside the device, and and also from too high charging current. When you change the connector, just keep that protection circuit within the pack. > I can set it up for not more than 800 mAh and 1C charging. Do that, but monitor the actual capacity, e.g. by discharging it once afterwards. That way, you can adjust the parameters subsequently. > I can put everything in a 9 mm ammunition container I happen to have. Non-US citizens don't have that kind of devices around, and we're still alive anyway. ;-) -- cheers, J"org .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/ NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-) _______________________________________________ AVR-chat mailing list AVR-chat@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-chat
