Thanks Phil for your thoughtful and informative reply (as usual :-) I thought about moving my LiFePO4 ups backup batteries outhouse, but based on the freezing no charge issue, I’ll just leave in the basement.
With regards to Tesla pre conditioning for fast charge - In the summer though (hard to think of with negative temps), but when 90F or so I would think Tesla would cool the battery down to 60ish F since the fast charging process with 100’s of amps naturally heats up the pack. I wonder why my Bolt and other EV manufacturers don’t pre-heat/cool the pack prior to fast charging. Maybe like my Bolt it’s limited to 50KW and takes about an hour whereas my Tesla starts at 200KW and takes about 15min to get to the same 80% point :-) Stay Charged, Mark Sent from my iPhone On Jan 18, 2024, at 11:51 AM, (-Phil-) <p...@ingineerix.com> wrote: Tesla preconditioning is almost always HEATING the battery, and this is a GOOD thing! Apparently what happened in Chicago is there is a large quantity of EV owners that do not have home charging. Supposedly a high proportion are rideshare operators (Lyft/Uber) that lease EVs to use for work. This means they operate 100% on public charging. If you park an EV outside below freezing overnight, the pack will be below freezing in the morning, so if you go to a DCFC station, the car will not be able to charge at all until it first warms the battery over 0C. But it will draw about 3-8kW from the fast charger to heat the battery, but this can take anywhere from 20 minutes to 2 hours depending on how far below 0C the battery is. This means someone could be occupying a stall for an inordinate time waiting for charging to actually start. People who have charging at home do not have these problems, as the pack can warm overnight on grid power without occupying a DCFC stall. Those with garages are in even better situations, as the pack usually doesn't have as much cold soak. You absolutely cannot charge ternary lithium batteries below freezing as it will cause anode plating. This is the same reaction if you attempt to put too much power into a battery than it can take. So the colder a battery is, the less charge amps it can safely absorb, down to freezing where ANY amps is too much. Same thing for high SoC. So if you want to charge a battery fastest, it needs to be hot and discharged. This is why you see tapering as the SoC comes up during DCFC. As a pack gets closer to freezing all charging has to taper, including regen. Below freezing, there can be no regen. The anode plating is not reversible, it causes a permanent loss of capacity. In addition, a cell with a lot of plating damage has a much higher likelihood of separator failure, which can result in thermal runaway and burn your house down! No properly engineered BMS will allow this to happen. For Tesla 3/Y and 2021+ S/X, they use the drive unit and/or heat pump to heat the battery. The drive unit inverter can run in a mode, even stationary, that will generate a lot of waste heat. It makes a recognizable buzzing sound when it's doing this. On Thu, Jan 18, 2024 at 8:28 AM Mark Hanson via EV <ev@lists.evdl.org> wrote: > Hi Phil etc, > When Tesla says pre conditioning the battery prior to a supercharger is it > cooling the battery to say 60F since the charging process heats it up? > > Also why does Tesla (and other EVs like my Leaf and Bolt) disable the regen > below freezing? It draws 100s of amps when driving, you think putting back > the same would be ok for the battery, coming or going shouldn’t matter? > > NBC News last night said Chicago Tesla drivers had to wait at the > Supercharger for an hour or so (wouldn’t allow them to charge till battery > warmed up). I haven’t experienced this at 10F but up there it was 2F. Is > this a real issue or just the news getting it wrong (again). > Best regards > Mark > > Sent from my iPhone > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20240118/96a16404/attachment.htm> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
