There is a protected Li-Ion pack for the K2 available. With Lio-Ion, proper battery management is essential.
https://www.batteryspace.com/custom-lifepo4-18650-battery-12-8v-4500-mah-57-6wh-7a-rate-w-pcb-and-connector.aspx I briefly looked at putting together a LiFePO4 pack for the K2, but haven't yet done anything with that idea. LiFePO4 is more forgiving and more lead-acid-like in its care a feeding. Lower energy density than Li-Ion, but still much better than lead-acid. Lou W7HV On Tuesday, July 20, 2021, 7:52:06 PM MDT, jerry <je...@tr2.com> wrote: On 2021-07-18 19:50, Douglas Hagerman via Elecraft wrote: > Next step, adding the the immensely heavy internal lead-acid battery. *** I wonder how hard it would be to add instead a much lighter lithium-ion battery pack? Individual 18650 cells are now routine at 2.5A-H, and available up to 3.5A-H. The technology has gotten standardized, and you can buy a BMS ( Battery Management System ) card off the shelf. The only hard thing is spot welding the tabs. A 3S1P ( three cells in series, 1 in parallel ) pack would probably do fine. I just got back from the garage where I repaired such a pack. It was out of an 85W cordless vacuum cleaner. Just four cells. Like any battery, the voltage varies with charge. These cells are about 4.2V fully charged, and 3.4 when dead. For three cells, that would be 12.8V fully charged, and 10.2 when it's time to recharge. I got all set up to weld the cell tabs for an ebike project. The ratio of energy storage to battery weight is much better than lead-acid. - Jerry KF6VB ______________________________________________________________ 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 louand...@yahoo.com ______________________________________________________________ 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