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The Electric Revolution

I decided to take advantage of the free power from Octopus yesterday evening. Plug the car in and set a schedule so they can charge it if they want, and all the power you use above baseline in that hour is free. I exported my home battery during the previous hour so that was charging during the free hour, I set the washing machine to do a load on the short cycle, I used a couple of electric heaters rather than the central heating, and did some cooking I was going to do anyway. But they didn't charge the car. That's their prerogative. Then I set the battery to export again. Well and dandy.

I had been watching the car charging schedule they set and it seemed OK, nothing before 11.30. But then suddenly the car started to charge at 10.30, unexpectedly. It would just have been gobbling up all my export. I wish they wouldn't do that. But they do. So I stopped the charge within a couple of minutes and that was fine.

Then once the cheap period had started at 11.30 I put the washing into the tumble drier so it was dry by morning. All good, what's not to like?

Well, like an idiot I forgot to reset the timings to charge the battery again overnight, so the poor thing was sitting there at a very low charge for hours. Then the house ran on mains power for three hours from 5.30 till 8.30 when the solar took over. And I hadn't turned off the hifi so it wasn't even a true base load. But looking at it, that probably only lost me 20-30p.

Today they have another triple session from 12 noon till 3 pm. I wasn't going to bother, because sun was forecast and if I do that I just lose the export, but now that's the ideal opportunity to charge the battery. Of course it's very sunny, that's why they're doing it, but I let the battery pick up a bit of charge then set it to export all the sunshine till noon. In fact though the battery is picking up a bit more because the generation is over the clipping limit - it has been as high as 6.3 kw.

I'll go put some bedclothes in the washing machine, and in the three hours I can get these both washed and dried. I will lose some solar export, but in fact at this time of year the generation dips after about one o'clock because the sun goes behind a neighbour's house, so not that much. I'm cross with myself for having forgotten to reset the battery to charge overnight, but I'm going to be ahead of the game anyway.

ETA: It's so sunny that the solar is powering everything and I'm not actually getting any free power worth mentioning! This is why I wasn't going to do it in the first place. But there are clouds around and in an hour or so the sun will go behind the house. But if I ever needed a reminder of why not to go for these sunny-day slots, this is it.
 
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I think these guys at Octopus must be psychic, because it's been far far sunnier than I anticipated. I haven't used a single unit of mains power since 8.30 this morning, despite the home battery being on charge and some kitchen appliances running. I saw what was happening pretty quickly and switched things back to their normal configuration, but all I did was run the washing machine on power that I could have exported for 15p. I'd still have been better off running it overnight for 7p as I had intended originally. I've abandoned thoughts of running the tumble dryer. The bedclothes and my dressing gown are on the pulley and I might tumble-dry them after 11.30 pm, I'll see.

In fact it's been so sunny that the home battery might well have picked up enough charge to do me through the evening simply by harvesting the "clipping" without me having to divert anything else to it! It's at 38% at the moment and still getting some solar as the export is still maxed out even at 1.20 - I'm still generating 6.45 kw and the battery is getting about 1 kw over and above the export. I'll let it have some more solar later just to be on the safe side, but so much for the special offer. I won't have taken a single unit during the three hours.

If I ever again show signs of taking up one of these Octopus offers in the daytime, on a day that isn't forecast to be black clouds all day (the offers never appear on such days), just sit on my head until the fit passes.
 
Rolfe said:
I think these guys at Octopus must be psychic, because it's been far far sunnier than I anticipated. I haven't used a single unit of mains power since 8.30 this morning, despite the home battery being on charge and some kitchen appliances running. I saw what was happening pretty quickly and switched things back to their normal configuration, but all I did was run the washing machine on power that I could have exported for 15p. I'd still have been better off running it overnight for 7p as I had intended originally. I've abandoned thoughts of running the tumble dryer. The bedclothes and my dressing gown are on the pulley and I might tumble-dry them after 11.30 pm, I'll see.

In fact it's been so sunny that the home battery might well have picked up enough charge to do me through the evening simply by harvesting the "clipping" without me having to divert anything else to it! It's at 38% at the moment and still getting some solar as the export is still maxed out even at 1.20 - I'm still generating 6.45 kw and the battery is getting about 1 kw over and above the export. I'll let it have some more solar later just to be on the safe side, but so much for the special offer. I won't have taken a single unit during the three hours.

If I ever again show signs of taking up one of these Octopus offers in the daytime, on a day that isn't forecast to be black clouds all day (the offers never appear on such days), just sit on my head until the fit passes.
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The house always wins.
 
In fact the evening session was quite good. They did it because excess wind was forecast, and since I don't have a wind turbine messing up the calculations, it was worth it. My first mistake was not unplugging the car once the hour was past, but that wasn't a big deal. My second mistake was forgetting to put the home battery on charge overnight. That maybe cost 20-30p. My third mistake, which was the biggie, was thinking that the empty home battery meant I should try to take advantage of the free period the following day (today). No I should not have done that. Will I never learn? If the sun is shining, don't touch it!

I'm ahead of the game, but I wasted time doing things I didn't need to do when it would have been absolutely fine if I'd just left the system alone to do its usual thing.
 
Rolfe said:
In fact the evening session was quite good. They did it because excess wind was forecast, and since I don't have a wind turbine messing up the calculations, it was worth it. My first mistake was not unplugging the car once the hour was past, but that wasn't a big deal. My second mistake was forgetting to put the home battery on charge overnight. That maybe cost 20-30p. My third mistake, which was the biggie, was thinking that the empty home battery meant I should try to take advantage of the free period the following day (today). No I should not have done that. Will I never learn? If the sun is shining, don't touch it!

I'm ahead of the game, but I wasted time doing things I didn't need to do when it would have been absolutely fine if I'd just left the system alone to do its usual thing.
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It's so weird managing, even micromanaging something most of us always essentially took for granted and paid little to no attention. Being off grid I pay little attention to my electricity until this time of the year when it's almost an obsession.
 
When my installer brought a prospective customer round to look at my system I was at pains to explain to her that it's entirely possible to set it up so you never look at it again, and you'll be absolutely fine. The obsession comes when you realise that by fiddling here and there you can panhandle small amounts of cash that add up to a moderate amount of cash over the month and the year. And Octopus are absolutely egging people on to do that.

I said, I know people who maintain spreadsheets and can tell you exactly how much they're spending and saving, and how long before the system is paid off, but at least I haven't gone down that rabbit-hole! I can hardly turn to Duward here and say, it's not working out, please remove the system and refund my capital, can I? She then said, "I'm an accountant. I can see my future right there."
 
Rolfe said:
When my installer brought a prospective customer round to look at my system I was at pains to explain to her that it's entirely possible to set it up so you never look at it again, and you'll be absolutely fine. The obsession comes when you realise that by fiddling here and there you can panhandle small amounts of cash that add up to a moderate amount of cash over the month and the year. And Octopus are absolutely egging people on to do that.

I said, I know people who maintain spreadsheets and can tell you exactly how much they're spending and saving, and how long before the system is paid off, but at least I haven't gone down that rabbit-hole! I can hardly turn to Duward here and say, it's not working out, please remove the system and refund my capital, can I? She then said, "I'm an accountant. I can see my future right there."
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I probably would be that guy if I was on the grid with time of day incentives. I would love to get through a winter without the generator. This is the time of the year when buying an EV doesn't make sense. It might make great sense if there was a fast charger close and then I could use it as a home battery in the winter. But driving 40 minutes each way charging for an hour and then driving 40 minutes home doesn't work for me.
 
I don't see that it would work for anyone. That's a ridiculous distance from a charger. My friend who is doing that is only seven miles from the charger. Also, he travels quite a lot so he charges on the road.
 
Thinking about what people have been saying, I think the original criticism of my harvesting of the over-export-limit solar was entirely baseless. There is absolutely nothing there to be concerned about, and it's not doing anything the battery doesn't like.

I do wonder though about the points people are making about the export-recharge cycles I'm doing of the battery. It may be that I should be setting a higher lower limit of discharge on the battery. When I got the system it was set to 4% and I never varied that because I thought that was set for a reason. I could set it higher, say to 10%, what do people think? (It does stop discharging at a higher % when the weather is cold, which suggested to me that it was looking after itself.)

I could also set it to charge and discharge more slowly. There might not be any issue setting it to charge more slowly, so would that be advisable? However I wouldn't want to limit its discharge speed because that's the limiting factor on avoiding using mains power when there's a heavy load on the battery, particularly when I'm cooking. As it is I have to rotate my appliance usage when I'm cooking to avoid exceeding the battery's discharge capacity and so pulling mains power, so I'm not going to limit that.

I'm certainly open to advice, and the advice about the discharge limit seems to be coming from a number of people and to be rationally based, so fire away.
 
Rolfe said:
I don't see that it would work for anyone. That's a ridiculous distance from a charger. My friend who is doing that is only seven miles from the charger. Also, he travels quite a lot so he charges on the road.
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That's probably an exaggeration. More like 20 to 25 minutes each way. But there is a 2 car charging station in the small town 3 miles away. I just don't think it's a fast charger. The good news about it is I rarely see cars charging there this time of the year.
 
America seems to be pretty slow with charger installation. Unless you're really keen, it might be better to hold off. But you could investigate the practicalities in more detail. If there is an AC charger three miles away, what power can it deliver? If it's more than 7 kw and you went for a car that could AC charge at more than 7 kw, it might be practical. Well, if you have business in the town anyway. But if it's a long wait in a place where you have nothing to do, it's not worth it.
 
Rolfe said:
Thinking about what people have been saying, I think the original criticism of my harvesting of the over-export-limit solar was entirely baseless. There is absolutely nothing there to be concerned about, and it's not doing anything the battery doesn't like.

I do wonder though about the points people are making about the export-recharge cycles I'm doing of the battery. It may be that I should be setting a higher lower limit of discharge on the battery. When I got the system it was set to 4% and I never varied that because I thought that was set for a reason. I could set it higher, say to 10%, what do people think? (It does stop discharging at a higher % when the weather is cold, which suggested to me that it was looking after itself.)

I could also set it to charge and discharge more slowly. There might not be any issue setting it to charge more slowly, so would that be advisable? However I wouldn't want to limit its discharge speed because that's the limiting factor on avoiding using mains power when there's a heavy load on the battery, particularly when I'm cooking. As it is I have to rotate my appliance usage when I'm cooking to avoid exceeding the battery's discharge capacity and so pulling mains power, so I'm not going to limit that.

I'm certainly open to advice, and the advice about the discharge limit seems to be coming from a number of people and to be rationally based, so fire away.
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When I started delving into the solar and battery world, the big thing I was warned about was draining the batteries below 50%. But that was they were deep cycle lead acid batteries. Totally draining a battery supposedly hurt them by 20 percent or more.

And that was one of the beautiful aspects of lithium batteries. You could drain a lithium battery and not suffer a longevity hit. Or at not least a major hit.

But I still do my damndest not to drain my batteries below 50%. Paranoia I think.

I have friend that owns I think a 2018 Tesla Model S. And IIRC, the computer shows a range that is half of what it was when he bought it. That tells me that while lithium batteries last a lot longer than lead acid batteries, they do have a cycle life.

I baby my batteries since they were very expensive when I bought them. They are so much cheaper today. I also believe they will be half the price in a year. But I could be wrong. Still, I'm not in the habit of throwing money away.

I love the idea of being to charge up an EV and use it to supplement my off grid home in the winter. But I question the wisdom of using an EV as part of a home battery bank. As inexpensive as home batteries have become, replacing EV batteries is a big expense in labor and for a unique manufacturer 's proprietary battery bank.

My concern is that you might be accelerating the wear and tear on the batteries. Is it worth it? . How much money do you gain vs the expense of replacing your batteries sooner? But I would never presume to question your application. Only you can look at all the factors and assess your risk reward.
 
Rolfe said:
America seems to be pretty slow with charger installation. Unless you're really keen, it might be better to hold off. But you could investigate the practicalities in more detail. If there is an AC charger three miles away, what power can it deliver? If it's more than 7 kw and you went for a car that could AC charge at more than 7 kw, it might be practical. Well, if you have business in the town anyway. But if it's a long wait in a place where you have nothing to do, it's not worth it.
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OK, here's the question I'm asking. Please forgive my newbie EV ignorance.

How long would it take a 7kw charger to charge an empty 70kwh EV to full? Because that sounds like 10 hours.
 
acbytesla said:
OK, here's the question I'm asking. Please forgive my newbie EV ignorance.

How long would it take a 7kw charger to charge an empty 70kwh EV to full? Because that sounds like 10 hours.
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Yes, it does. That sort of charging is intended for overnight use. But there are 22 kw chargers and cars that can use that, so I was wondering about that possibility. Also, you don't go to empty, remember the conversation we were having?

I've just been watching a MacMaster video where he's struggling to pretend that he's struggling with his new EV. The number of ultra-fast chargers around is ridiculous. And the better cars' range gets, the less they'll be used, so the less likely you are to find them full with a queue. I was also just checking charger availability for a 450 mile drive I have to do on Wednesday. Spoiled for choice, frankly.
 
Rolfe said:
Yes, it does. That sort of charging is intended for overnight use. But there are 22 kw chargers and cars that can use that, so I was wondering about that possibility. Also, you don't go to empty, remember the conversation we were having?

I've just been watching a MacMaster video where he's struggling to pretend that he's struggling with his new EV. The number of ultra-fast chargers around is ridiculous. And the better cars' range gets, the less they'll be used, so the less likely you are to find them full with a queue. I was also just checking charger availability for a 450 mile drive I have to do on Wednesday. Spoiled for choice, frankly.
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Thank you. I have more information about the charger now. I went on Google maps. It shows the charger with about 10 reviews. Most are not that good though. Stil, it's better than 7kw. There are complaints about the terminal not working by some. But a couple were semi-positive.

"This charger charged my Solterra from 20% to 80% in an hour!! (I looked up the Solterra, it has a 72kwh pack..... That would be 43.2 kw in an hour)
"Works as of 25FEB. Pulled 38kwh."

So I can see the benefit
 
acbytesla said:
When I started delving into the solar and battery world, the big thing I was warned about was draining the batteries below 50%. But that was they were deep cycle lead acid batteries. Totally draining a battery supposedly hurt them by 20 percent or more.

And that was one of the beautiful aspects of lithium batteries. You could drain a lithium battery and not suffer a longevity hit. Or at not least a major hit.

But I still do my damndest not to drain my batteries below 50%. Paranoia I think.

I have friend that owns I think a 2018 Tesla Model S. And IIRC, the computer shows a range that is half of what it was when he bought it. That tells me that while lithium batteries last a lot longer than lead acid batteries, they do have a cycle life.

I baby my batteries since they were very expensive when I bought them. They are so much cheaper today. I also believe they will be half the price in a year. But I could be wrong. Still, I'm not in the habit of throwing money away.

I love the idea of being to charge up an EV and use it to supplement my off grid home in the winter. But I question the wisdom of using an EV as part of a home battery bank. As inexpensive as home batteries have become, replacing EV batteries is a big expense in labor and for a unique manufacturer 's proprietary battery bank.

My concern is that you might be accelerating the wear and tear on the batteries. Is it worth it? . How much money do you gain vs the expense of replacing your batteries sooner? But I would never presume to question your application. Only you can look at all the factors and assess your risk reward.
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I think it's a reasonable point. I haven't seen anything about not draining the battery regularly, but then I haven't read every word of the bumph that came with it. There's no doubt that LFP batteries are pretty robust, and it's also true that there are built-in protections, but maybe it is wise to be a little more cautious.

Nobody is going to be charging their EV up when it gets to 50%, that's for sure. It's bonkers. Especially as it is recommended not to charge NMC batteries above 80% routinely, and everybody is advised to unplug at 80-85% on a DC charger and get going because the top of the charging curve is so slow. What would your range be? 50 miles? People who know their cars and can calculate their range regularly drive below 10%. They seldom leave the cars there for any length of time though, because obviously you want to get on, or at least you want the car ready for next day or even an unexpected trip. So I'm not sure why I should treat my home battery any different.

Your story about the Tesla driver only having 50% SOH in a 2018 car is not credible unless there was something very wrong with that battery. These cars have a battery warranty of eight years, that triggers if the SOH falls below 80%. YouTube is crawling with people looking at old cars and being amazed by how well the batteries have stood up. Even old Leafs, which are notorious for degradation as they didn't have thermal management. I have never heard of an EV with a battery SOH as low as 50%.

People are already using their EVs to run their houses. Leafs are particularly favoured for this. VtG is going to see cars partially charged and discharged a lot as their batteries are used to buffer the grid. There is honestly nothing to worry about. The issue about old EVs (Leafs, Zoes and the like) is that they were built with small batteries and people want more than that now that it is available. Not that these batteries are spectacularly less capable than they were when they were new. Yes there is some degradation, and yes this is more of a worry when you only had 90 miles of range to start with, but imagine a car with 300 miles of range. Its battery is technically "end of life" when it reaches 80% SOH. But it still has 240 miles of range? Would you think that car was useless? But the fact is that even today's batteries aren't getting down to 80% SOH in their first ten years, and this is only going to get better.

But now, update on my home battery. I set it to export with an export limit of 10%. And it went right on exporting until it hit 5%, which is as low as it wants to go under normal circumstances. I have no idea why this was. It usually does what it's told, but not this time. I think second-guessing the future when technology is advancing so rapidly is probably a mug's game. My home battery currently has far more capacity than ai actually need, and if it loses 20% of its capacity it would still be fine for my purposes. But on the other hand in ten years there might be something much more capable available for a few hundred pounds, and an upgrade to the whole system might make sense. Nobody has a crystal ball.
 
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acbytesla said:
Thank you. I have more information about the charger now. I went on Google maps. It shows the charger with about 10 reviews. Most are not that good though. Stil, it's better than 7kw. There are complaints about the terminal not working by some. But a couple were semi-positive.

"This charger charged my Solterra from 20% to 80% in an hour!! (I looked up the Solterra, it has a 72kwh pack..... That would be 43.2 kw in an hour)
"Works as of 25FEB. Pulled 38kwh."

So I can see the benefit
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That is obviously a DC charger, and possibly not just a basic 50 kw one either. If you were prepared to tell me where it is I could check it out on ZapMap for you. If you don't want to say in a public post, DM me the location.
 
acbytesla said:
When I started delving into the solar and battery world, the big thing I was warned about was draining the batteries below 50%. But that was they were deep cycle lead acid batteries. Totally draining a battery supposedly hurt them by 20 percent or more.

And that was one of the beautiful aspects of lithium batteries. You could drain a lithium battery and not suffer a longevity hit. Or at not least a major hit.

But I still do my damndest not to drain my batteries below 50%. Paranoia I think.

I have friend that owns I think a 2018 Tesla Model S. And IIRC, the computer shows a range that is half of what it was when he bought it. That tells me that while lithium batteries last a lot longer than lead acid batteries, they do have a cycle life.

I baby my batteries since they were very expensive when I bought them. They are so much cheaper today. I also believe they will be half the price in a year. But I could be wrong. Still, I'm not in the habit of throwing money away.

I love the idea of being to charge up an EV and use it to supplement my off grid home in the winter. But I question the wisdom of using an EV as part of a home battery bank. As inexpensive as home batteries have become, replacing EV batteries is a big expense in labor and for a unique manufacturer 's proprietary battery bank.

My concern is that you might be accelerating the wear and tear on the batteries. Is it worth it? . How much money do you gain vs the expense of replacing your batteries sooner? But I would never presume to question your application. Only you can look at all the factors and assess your risk reward.
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Like I said before- the deeper the discharge, the shorter the service life (this applies to ALL battery types btw)

50% DOD (depth of discharge) is considered the MAXIMUM discharge level a L/A can handle safely- you can take them deeper, but the service life drops VERY rapidly once you go past 50%...
(a L/A battery (that covers flooded, AGM (some AGM's have a SMALL increase in charge cycles in comparison to others), SLA, tubular etc) will get about 300-500 charge cycles at 50% DOD, you are looking at 1200-1500 charge cycles at a more gentle 25% DOD, you can get 2500-3000 charge cycles at 10% DOD but you are literally using only 10% of its rated storage capacity!!!! Once you go past that 50% DOD level though, the cycle count drops dramatically- at 80% DOD its down to less than a hundred charge cycles, and down to 100% DOD- it is literally a single handful!!!!)

Lithiums can accept a deeper DOD and still have more cycles than even a babied L/A but they still have the same drop in cycle life the deeper the DOD goes...

LFP can go to 90% (100% is VERY risky and NO manufacturer does it- as it may fail in a single charge cycle- some play a numbers game and 'say' 100%- but meaning 100% of its USABLE capacity- not its rated capacity...two different things) at 90% DOD, you can expect much less than a thousand charge cycles, while dropping it to 80% will see you an increase to 2500-3000 charge cycles, and dropping it to 70% DOD increases it again to 3500-5000 charge cycles... (temps over 40C can cause a serious reduction in charge cycles/service life again- remember thats CELL temps- not air temps...)
LYP on the other hand can handle higher temps (and lower temps) than LFP or L/A- and has an increased service life again... at 80%DOD they get 5000 charge cycles plus, and at 70% that increases again to 7000 charge cycles

NCM batteries have the shortest service life (about half LFP if treated gently) which is one reason (that and their tendency to go into thermal runaway far more easily than the other lithium types)

Remember that most people are cycling once a day- so 'roughly' its charge cycle a day- how many days in a year????
 
acbytesla said:
When I started delving into the solar and battery world, the big thing I was warned about was draining the batteries below 50%. But that was they were deep cycle lead acid batteries. Totally draining a battery supposedly hurt them by 20 percent or more.

And that was one of the beautiful aspects of lithium batteries. You could drain a lithium battery and not suffer a longevity hit. Or at not least a major hit.

But I still do my damndest not to drain my batteries below 50%. Paranoia I think.

I have friend that owns I think a 2018 Tesla Model S. And IIRC, the computer shows a range that is half of what it was when he bought it. That tells me that while lithium batteries last a lot longer than lead acid batteries, they do have a cycle life.

I baby my batteries since they were very expensive when I bought them. They are so much cheaper today. I also believe they will be half the price in a year. But I could be wrong. Still, I'm not in the habit of throwing money away.

I love the idea of being to charge up an EV and use it to supplement my off grid home in the winter. But I question the wisdom of using an EV as part of a home battery bank. As inexpensive as home batteries have become, replacing EV batteries is a big expense in labor and for a unique manufacturer 's proprietary battery bank.

My concern is that you might be accelerating the wear and tear on the batteries. Is it worth it? . How much money do you gain vs the expense of replacing your batteries sooner? But I would never presume to question your application. Only you can look at all the factors and assess your risk reward.
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Someone just posted this video on the EV forum where I'm a moderator. I think you might find it interesting. It's about replacing the battery of an elderly Leaf to give it twice the range it had before.


I wouldn't be at all surprised if this is something that becomes common in the future, at least for popular cars. If you offered me a battery upgrade for my MG4, five years from now, that would give me twice the range and at least double the DC charging speed, for £5,000, I might be inclined to treat myself. And if these things are £5,000 now, what will they be in five years? (And the point is, this isn't a necessary repair that I'd have to get done or lose the use of the car, it would be an optional enhancement. A birthday present to myself.)
 
acbytesla said:
OK, here's the question I'm asking. Please forgive my newbie EV ignorance.

How long would it take a 7kw charger to charge an empty 70kwh EV to full? Because that sounds like 10 hours.
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Near enough (there's a slight increase because 'nothings 100% efficient' but LFP is actually pretty good, close to 90% efficiency while charging)
The thing is that very few people with a home charger will be coming home with an 'empty' battery pack every single night with a 70kWh car...

The BYD Dolphin for example uses 11.5kWh per 100km in city cycle, and 14-17kWh per 100km on country cycle (highway) with a 62kWh battery pack- you would have to be driving two hours to work- each way- at freeway speeds every day!!!! and ignoring every other charger inbetween (in Australia you would be going past dozens in the country, hundreds in the cities lol)- and doing that every single working day.... every single day.... UGGHHHH!!!!!
The standard Seal can charge at up to 110kW on DC fast chargers (most of the public ones here are 100kW or more) and can recharge from 10% to 80% in under 35 minutes.... giving over 300km extra range... (BYD are all about '100km every ten minutes of charge' on their max charge rate)

If thats your situation- I'd be looking for another job closer to home....
:jaw-dropp
 
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