I had strongly considered the LiPo type secondary-cell power packaging option and rejected it.
Energy density in that chemistry/package is amazing of course. But that equation is also true of a bomb. I have no problem with the LiPo in my iPad, Galaxy S5 phone, and laptop, so, it's not a blind bias. It doesn't take too much YouTube searching to find dramatic examples of LiPo powered RC vehicles and the like bursting into flames. There's a good reason that *all* these lithium cells are considered hazmat now, not just the lithium thionyl chloride ones ... on failure, those burn and emit nerve gas; they are Class 9 hazmat! They are also not rechargeable anyway. Because this particular power pack would be fully enclosed in the metal-cased K2, and would be in the 9 ampere-hour range in this desired form factor ... if such a LiPo pack decided to self-immolate, the rig would not only be destroyed but I'd have a real secondary incendiary hazard on my hands. The charging, power regulation and protective circuitry, etc., needed to use the LiPo chemistry/packaging inside a K2 took that consideration off the table for me. YMMV. The 'safe-failure-mode' secondary-cell chemistries I considered were NiMH and LiFePO4. The NiMH almost won. By the way, I have the special spot-welder device and strap/bracket supplies needed to fabricate my own packs. Extensive experimenting with NiMH cells really had me convinced to go that way for some time. Then, I got some newer LiFePO4 cells and also some new LiCoO2 cells, and started the "2015 edition" revisiting of the selection analysis. I had last looked at the issue in 2010. It didn't take long before my own clumsiness lit one of the 18650-size LiCoO2 cells up. I caught the mistake just as it was about to get really serious. Lesson learned. Now I know why the manufacturers of those include the built-in-per-cell safety circuit option! The cells I tried were the 'raw' and unprotected type, selected purposefully so as to not have the size, cost, and loss of the protective circuitry. For these and other reasons, this chemistry/packaging option was rejected for the particular use-case. I could not achieve a better-than-the-SLA result with NiMH. Hope my describing a portion of the ferreting process in a bit more depth is of use to others. The K2 is a remarkably competent field radio. Being able to actually use it in the field, conveniently, makes my now-teenage rig all the more valuable to me. Having a modern internal power source will just be icing on an already tasty cake. 73 Steve KZ1X ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
