You CAN road trip an SE SR

[Rolfe]

Good thinking. (Did you read the bit I added, possibly after you posted reply #118?)

 

[Tig170]

Octopus have said this offer only applies to leccy used for car charging - they even said don't bother scheduling a tumble dryer marathon. I guess they will take the reading from the charger rather than the meter.

... at the end of the day, whether its 7p or 3.5p, for the basic home owner is a saving of less than a pound (and thats only if you take 30kw from the grid)


... yes if there is a million of use then its a £1m to OE, however grid balancing is where the money is??

 

[Rolfe]

Exactly. My car was on 5% when I plugged in, and even so I won't save £2. It's an interesting exercise, but it's not going to matter one way or the other financially.

 

[Rolfe]

The car thinks it's going to be finished by 2.51, which means it should have finished balancing by 3.30 at the latest. It's all good apart from that gap in charging which means it isn't really a properly-completed long charge. I don't know why it does that.

 

[mg4mc]

I think that rather than this, and the previous free hours, being meant to be real benefit to the customers (we know the individual benefit is small); they are experiments by Octopus to see what may be achieved in the future in terms of grid balancing and demand management.

 

[Rolfe]

You're certainly right about that. I wouldn't ignore a free half price charge for the car if the car needed charging anyway, but I think I'll ignore the rest of the shenanigans.

Something else odd happened last night as well as the gap in the charging. I thought that 2:51 was too early for the full charge to be finished, especially in view of the gap, so I kept an eye on it. (Yes this was the middle of the night, why do you ask?)

At around that time (probably about 2:55) the car was showing 100%, but it didn't drop to balancing power. Instead it dropped to 3.3 kW, and kept drawing that for about half an hour, with the finishing time always updating to the current time the way it does when it's balancing. After about half an hour of this (during which time I was thinking, if it's at 100%, where is it putting all this?) it started balancing. Even then though, it had spells of drawing 0.6 and 0.7 kW, which it doesn't often do. That took another half an hour and it finished just before 4 am. The total amount of power supplied by the Zappi was 52.27 kWh. The Octopus app recorded 52.25 kWh. So it surely knows how much discount I'm due.

I have no idea at all what was going on. I've watched the car on public 7 kw chargers and never seen that. Just a slight reduction in power as the advertised finishing time approaches, then on to balancing the same way it does on the granny charger. Weird.

 

[siteguru]

1% of 51 kWh is 0.51 kWh, so when the display showed 100% it may not have quite been 100%, thus there was still a reasonable amount of energy to go into the battery. Also, 0.6 kW for 30 minutes is 0.3 kWh, so whilst the time span may have seemed long the actual amount of energy wasn't as much as it "felt".

Further - this was your "long charge" to (try to) recalibrate the BMS so it probably needed to do more anyway.

In terms of efficiency ... 100 - 5% = 95% x 50.7 kWh = 48.165 kWh into the battery. Thus the charging efficiency was 48.165 / 52.52 = 91.7% ... looks perfectly good.

 

[Rolfe]

It was 3.3 kw for 30 minutes though! Actually, looking at the GivEnergy consumption it wasn't quite that long. The power draw fell off a bit before it reached 100% at 2.55 am. That was actually sooner than I was expecting, given the amount of charge to be added. (And significantly less time than Octopus had allowed for 100% to be added to the battery - it was actually adding 95%.)

Normally I'd have expected the car to start balancing then, but it sat at 3.3 kw until 3.20. That's when I was wondering where it was putting it all. That's over 1 kwh added, which is 2% of the battery capacity! It was only after that that it started to balance normally, although as I said, quite often flipping up to 600 or 700 watts which is unusual for it.

I'm not sure this does count as the long charge though, because it was interrupted for about 15-20 minutes early on. When that happens, how does it know which arm of the hysteresis curve it's supposed to be on?

I don't imagine there's anything wrong, it's just behaviour I haven't seen before.

Thanks for working out the charging efficiency, I hadn't got around to that.

 

[siteguru]

The BMS/battery might report 100% SoC when the battery voltage of a single module reaches the predicted peak voltage, but a lot more power is needed to bring all the modules (and the cells therein) up to the peak voltage.

#speculation

 

[Rolfe]

Maybe. It's odd that it did it though. It was charged to 100% and balanced on a public type 2 charger on Friday evening, and only had a single DC charge of 25% added on Sunday, before this oddity on Monday night. It also seemed to know that it would be at 100% before 3 am, even though as things turned out it took over 1 kwh more after that.

 

[Rolfe]

1% of 51 kWh is 0.51 kWh, so when the display showed 100% it may not have quite been 100%, thus there was still a reasonable amount of power to go into the battery. Also, 0.6 kW for 30 minutes is 0.3 kWh, so whilst the time span may have seemed long the actual amount of power wasn't as much as it "felt".

Further - this was your "long charge" to (try to) recalibrate the BMS so it probably needed to do more anyway.

In terms of efficiency ... 100 - 5% = 95% x 50.7 kWh = 48.165 kWh into the battery. Thus the charging efficiency was 48.165 / 52.52 = 91.7% ... looks perfectly good.

I did a typo. It was 52.25 kwh that was added. 48.165/52.25 = 92.2%. Even better.

 

[Rolfe]

Charged again last night. Needed 70% added after a long trip yesterday afternoon and evening. Octopus said 11.30 till midnight, then midnight till 5.30. Damn car charged without a hitch or a hesitation right through, finished at 100% with little reduction in power, and went straight into a normal balance charge. As well as I could tell from the MyEnergi app this morning.

Why couldn't it have done that on Monday night, when I was trying to do the long charge, dammit.

 

[Tig170]

Charged again last night. Needed 70% added after a long trip yesterday afternoon and evening. Octopus said 11.30 till midnight, then midnight till 5.30. Damn car charged without a hitch or a hesitation right through, finished at 100% with little reduction in power, and went straight into a normal balance charge. As well as I could tell from the MyEnergi app this morning.

Why couldn't it have done that on Monday night, when I was trying to do the long charge, dammit.

Its free again on IOG 1-2pm tomorrow - not that i need it ?

 

[Tight Git]

Its free again on IOG 1-2pm tomorrow - not that i need it ?

Not had my notification yet - guess I will have to unplug it later this evening to get the free hour!

 

[Rolfe]

I'm not even sure it will be worth my while plugging the car in. We have wall to wall sunshine forecast all day and I would lose all the solar from that hour (maybe close on 5 kwh), losing 15p a unit, when I could just charge the car as usual at 7p.

I haven't actually done the sums but I suspect I'd come out at a loss.

 

[Rolfe]

Thinking about this as I pushed a trolley round Sainsbury's.

Maximum solar export in an hour at noon is 4.8 kwh I think. That's 72p in export payment.

Maximum the car is likely to draw in an hour is 7.2 kwh, if I'm really on the ball. At off-peak prices that would cost 50.4p.

So I lose 72p to gain 50.4p. Not going to happen.

Yes there are other things I could do, maybe heat some water, maybe put off tonight's dishwasher run till tomorrow, but I'd be going some to offset that lost 72p. It begins to feel like the Red Queen in Alice in Wonderland. Running as hard as you can to stay in the same place.

I think it's no coincidence that these "free" hours are happening on very sunny days. They know they'll have more solar than they know what to do with. Might be worth it for people with no solar (or maybe on a FIT l) but I'm not playing.

 

[siteguru]

Max. your (and my) car will draw is 6.6 kW ... although I've seen 7.3 kW in my Wallbox app. So your sums are right, but not quite for the reason you think.

#pedant

 

[Rolfe]

I actually edited that, because the electricity that I'll be charged for is what the system supplies, not what the car gets. I originally typed 6.5 kwh, but changed it. So I didn't completely edit the wording. So sue me.

 

[Rolfe]

I'm off to Sussex again.

After the three days in Lochaber and Ardnamurchan, sleeping in the car, then the week up the north west Highlands to Durness, ditto, then the day trip to Lancashire to test drive the e-bike, I'm going back to Glyndebourne sooner than I imagined.

I picked up an email earlier in the week from Glyndebourne offering me a code to book for an Open Day event in late November which is part of their programme for people who are paid-up Friends. I suspect they didn't get enough take-up so extended the offer to hangers-on. It's just a couple of days after my birthday so I decided to treat myself. I've booked a hotel in Lewes because I feel I've imposed enough on my Portslade friends for this year.

It will be interesting to see how the drive goes in what will almost be winter by then. That's twice I've only made it to Tebay on the way south, last week I got there on just 7%. I think there were strong head winds crossing the Beattock Summit but it's only about 110 miles. And there was a diversion that slowed my speed a bit. Head winds are common going over the Southern Uplands and it's bound to be colder. Tebay is a great place to stop though, and if I get that far it still leaves the possibility open to do the whole thing in only three charges, so maybe I need to moderate my speed a bit.

ABRP is trying to send me to Trentham Gardens for my second charge and that would be great if I could make it, but these Tesla chargers are the old type and so may be closed to non-Teslas by then. Boo. I may need to make other arrangements.

 

[QLeo]

I'm off to Sussex again.

After the three days in Lochaber and Ardnamurchan, sleeping in the car, then the week up the north west Highlands to Durness, ditto, then the day trip to Lancashire to test drive the e-bike, I'm going back to Glyndebourne sooner than I imagined.

I picked up an email earlier in the week from Glyndebourne offering me a code to book for an Open Day event in late November which is part of their programme for people who are paid-up Friends. I suspect they didn't get enough take-up so extended the offer to hangers-on. It's just a couple of days after my birthday so I decided to treat myself. I've booked a hotel in Lewes because I feel I've imposed enough on my Portslade friends for this year.

It will be interesting to see how the drive goes in what will almost be winter by then. That's twice I've only made it to Tebay on the way south, last week I got there on just 7%. I think there were strong head winds crossing the Beattock Summit but it's only about 110 miles. And there was a diversion that slowed my speed a bit. Head winds are common going over the Southern Uplands and it's bound to be colder. Tebay is a great place to stop though, and if I get that far it still leaves the possibility open to do the whole thing in only three charges, so maybe I need to moderate my speed a bit.

ABRP is trying to send me to Trentham Gardens for my second charge and that would be great if I could make it, but these Tesla chargers are the old type and so may be closed to non-Teslas by then. Boo. I may need to make other arrangements.

Looking forward to your report on this trip. We're due to drive from here at the Centre of the (known) Universe in the north west Highlands to the south of England, London via Hampshire, in February, and we've only been as far south as Kirkby Lonsdale so far.