Sorry if this message is not in the flow - I am a digest-only subscriber. I have been helping John through this via direct email for maybe a couple of weeks, and it was Willie who said it most accurately.
John's pack has probably never been properly balanced and an fire early on due to improper mounting of the cells didn't help. Instead of the usual thick plastic case on these prismatic LFP cells there was (by this particular manufacturer) a relatively thin transparent plastic film around the metal case (apparently an electrode) of the cells according to his description. The cells must have been mounted in a sheet metal battery box. Very likely the replacements for the burnt cells were not matched in voltage when installed. And I think the BMS was only configured via CAN to the charger to prevent overcharging. As far as I know the BMS was *not* configured to shut down the motor inverter either via CAN or using the (active low) Discharge Enable line on the Orion BMS. It seemed logical to suggest a one-time bottom balance as this mix of old, new and perhaps damaged cells might never top balance within a reasonable timeframe and I didn't want to hear of the car being test-driven with an unbalanced pack. I suggested 2.8v as a reasonably safe bottom but the manufacturer spec sheet apparently stated 2.5v. My idea was to expedite the balancing process by starting at a low SOC and let the BMS stop the charge when the lower capacity cells came up to 3.6 something or whatever the BMS was set to. Then short drives would rout out rather quickly any cells that were still significantly lower in capacity. And I emphasized before going much further to enable that very important *other* function of the BMS, the one which should at least alert the driver if not outright stop the motor inverter. I believe that this oversight reverse-charged some of the cells. For individual cell charging I suggested a commonly available bench power supply and John did take delivery of a (5A or 10A?) unit but apparently it failed before very long. - Gordon Wong PS John is a member of the Vancouver EV Association as am I. He is some 80 miles to the east. I haven't seen Roger Stockton for a couple of years. He's running a Leaf now and I think he is still part of Delta-Q. All are welcome to come visit VEVA via Zoom (Tuesdays 7-9 Pacific and Saturdays 10-12) - register at veva.ca. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20210313/3879f974/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
