Since about 6 months I have been testing the self-discharge of a bunch of blue CALB LiFePO4 cells. The good news is that after half a year of sitting, their average voltage has changed from the (parallel) charge voltage of 3.00V (meaning that they were charged to approx 10% SoC to allow me to see how quickly they would fall off again, as the voltage changes are larger to wards the extreme ends of the charging curve) (after which I disconnected them to measure the individual self-discharge of just each cells by themselves by occasionally connecting a DVM to check and record voltage by hand) to a self-discharged voltage of between 2.78 and 2.86V. The current highest cell has the lowest self-discharge, losing only about 80mV in that half year, while the fastest self-discharging cell has lost almost double that voltage - 140mV Note that this is not from the original 3.00V but from their state a few weeks after I disconnected them, when I started recording voltages. So, while the sitting of a cell over a half year (in winter) apparently removes less than 10% of the charge, there definitely is a marked difference in self-discharge between cells of almost 100% higher discharge for the worst cell than the best cell in this sample set of 16 cells.
I thought this might be of interest to some here. Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.com Skype: cor_van_de_water XoIP: +31877841130 Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
