MikeHig,
I'm sure you're right about EV owners keeping a close eye on range and, really, that matters far more than voltage readings (or whatever) in a data log. That's why I found tomo's suggestion that Tesla might be working a separate set of figures a bit improbable. It *might* come down to a legal wrangle on the wording of Tesla's warranty, but consumer law (in Australia at least) doesn't look kindly on such word games.

I was wondering what sort of figures would be logged. My understanding is that cell voltages tell you *very* little with at least some of the Lithium cell chemistries — that 20% to 80% capacity only makes 0.1V difference or so — so it's very hard to tell from that simple measure. Googling turned up this forum topic which does seem to be logging some useful measurements, though a too short-term to make interesting graphs.

tomo,
Yes: When I said avoid blackouts at all costs, I didn't mean ...

Been listening to more John Anderson podcasts. Enjoyed his chats with Peter Hitchens, Bettina Arndt and Lord Sumption. Sumption completes a square for me. Lots of people believe both climate and COVID alarm, and lots, like me, believe neither. TinyCO2 and Jo Nova were amongst a fair number who accepted alarm over COVID but not climate. Sumption is the first I'm aware of who rejected COVID but accepts climate alarm. Anderson gave him some push-back on climate, but Sumption shrugged it off easily enough. Smart guy, but a bit of a cold fish.

Robert; from what I have read, most EV owners keep a very close eye on their cars' range. There are many comments on the forums to the effect of "mine is only showing xx miles in cold weather: what's others' experience?".
The more techie ones buy themselves a dongle which lets them plug a PC into the car's service port. They can then look at the state of the cells, charging history, spare capacity, etc. to their heart's content.

tomo

I guess a couple of electric fires and a kettle might show up switched in sync. An electric shower would help too.

You are correct that grid frequency is allowed to wander, but that there is a general requirement to keep it to a long term average of 50 or 60Hz. Grid codes specify the limits,which include the levels at which automated disconnection is supposed to cut in, and the maximum normally permitted limit for larger deviations. In GB they are supposed not to let frequency drop below 49.5Hz for more than a minute, and the first shedding frequency is 48.8Hz. Normal permitted operation is +/-0.2Hz around 50Hz. I'd have to look up the cumulative clock error that requires correction.

Here's a print from Ercot at the key moment of the Texas blackouts 8n Feb 21

https://web.archive.org/web/20210215075245/http://www.ercot.com/content/cdr/html/real_time_system_conditions.html

The print recorded at 59.334Hz is a hair's breadth above the 59.3Hz LFDD level, and you can be sure there were places on the network that thought they saw 59.3Hz and disconnected demand circuits, maybe a second later given the speed of fall of the frequency, although the official report tries to deny that happened and pretends that the control room selected cuts. The cumulative clock error is over 25 seconds slow with 8 successive minutes of increase. There was a cascading trip of generators in progress, likely triggered by the rate of change of frequency as there was no reserve left to arrest the fall, each trip making it worse.

There are attempts to set looser standards for frequency to try to make the grid more robust to the sort of frequency excursions that become a regular feature with increased renewables penetration and dependence on interconnectors that can suddenly trip out, sending frequency suddenly wildly higher or lower. At the same time, grid reinforcement with batteries that are supposed to leap into action and statcoms and synchronous condensers have become de rigeur. Lowered grid inertia speeds the rate at which events get out of control. It's an accident waiting to happen.

GB got close to some blackouts on 22nd December last year. Initially 1GW of IFA interconnector I port tripped our, allegedly followed by a small CCGT generator. However, the frequency fell to 49.275 Hz, which implied a much bigger loss of generation that has not been officially admitted, although some grid traders reckoned it included a bunch of wind in Scotland. It seems that the Grid batteries failed to stomp on the original trip for reasons that are unclear: there are plenty of previous examples where they coped well with even 1.4 GW loss on NSL. Officially it took 59 seconds to restore frequency above 49.5Hz, thus avoiding a rather more in depth official investigation. I do wonder if a print was "corrected". The main correction came from pumped storage about 12 seconds after the initial trip. If that had been 4 seconds later there would have been blackouts.