Charging *between* 80 and 95 percent ... ?

[DB00nowthen]

Hi, my second newbie question

I've spent/invested some time reading through the various discussions about how charging hygiene for the LR models (mine is a new very orange Trophy!). I have solar on the roof and a modestly sized GiveEnergy house battery. Part of the rationale in replacing our non-plug-in Prius with the MG was because we were sending too much surplus generation to the grid for no compensation whatsoever (because British Gas won't fit a Smart Meter until it suits them and it hasn't suited them for over a year - I've signed up for Octopus, but still waiting for a Smart Meter) ... and even if we had a smart meter we'd get next to not much for the export. So having a pure EV, as well as the other benefits, is it's a big battery on wheels that can take the surplus and provide "free" family outings transport for much of the year. Yay!

So it's been sunny and I haven't had a chance to drive the new car much yet as I work from home. So, after the dealer handed it over at 100 percent charge, and we drove it and got it down to 59 percent, the sunshine has brought it back up to the top of the health range at 80. So now we have kilowatts of excess solar going to the grid for no benefit (apart from the consolation that at least someone is using it and that may save a Polar Bear very tiny fraction of a degree of climate change for a tiny fraction of a second ... ) ... and British Gas can have it for free and won't notice or care ...

But I digress.

Do we think that charging to say 90 or 95 percent would be nearly as "healthy" for the battery as the "hard" stop at 80 percent? Then I could store a bit more. If not I just need to deplete the battery more, eg to between 20 and 30 percent before charging.

And I need to charge to 100 percent once a month, to balance/equalise, right? Do I need to do this in one go, so set my Zappi to "fast" (7KW single phase) to get it to 100 percent at a consistent pace, or will variable solar surplus via the Zappi be OK as long as it gets to 100 percent?

And when it is at 100 percent, I need to take it for a drive so it doesn't sit at 100 percent, too, right?

This question was probably too long. And probably to many questions. Sorry.

 

[tsedge]

1. Above 80% the high voltage in the cells will cause some slow deterioration over time, the higher the worse. It is a really small effect though, so irrelevant unless you are keeping the car for years and years. Don't be afraid to go to 100%.

2. Yes you need to charge to 100% at least once a month, recommended for best balancing by MG. Doesn't matter how you get there, just that the car has plenty of time to balance at a low power draw (few tens to few hundreds of watts for an hour should do it). Some say it will balance at other levels (eg 80%), but I prefer to follow MG's guidance.

3. Yes, don't leave it at 100% - it is time spent at high cell voltages (states of charge) that cause the most deterioration. That's more important than how often you hit 100%.

 

[Jomarkh]

You can use the Zappi in eco+ to battery balance.

 

[Themist0]

Feel free to invite us all around so we can top up for free

 

[Annaka]

I bought my Trophy for a very similar reason, feeding grid with no reward !. However I must say I am so happy that I bought the MG4, its hard to put into words how it makes me feel as I drive it around, just found the love for motoring once again. With the added benefit of not paying for fuel all the time, solar at home keeps the car topped up nicely, haven't needed to charge away from home since buying it, therefore in my mind its free motoring...well if you disregard the £10K for solar and batteries, and another £30K for the car !! I try and keep it at 80% but rather than feed the grid I do charge to 100% now and then, good excuse to go for another drive. One happy MG4 owner.

 

[PristDean]

With the British weather being what it is, the sun playing hide & seek with the clouds, I have found a good steady way to slow charge the car using solar, house battery and the 'Granny' charger.
If I leave the house battery at 100% and charge the car via solar, the charge drops in and out as it flits under and over 1.4kwh. Not good
If I attach the 'Granny' charger instead of my Hypervolt, the car will maintain a constant slow charge but draw from the battery to do it. Meanwhile the battery is taking charge from solar at whatever the solar panels can manage with a hide and seek sun.
End result, if you are not in a hurry, steady state of charging for the car from solar with UK sun !

 

[ukslim]

I'd be cautious about the reasoning behind this, the instinct is, as you've said, "I'm throwing away energy from my solar". But does taking it actually achieve anything? Would you benefit from charging to 100%?

If it saves you from public charging on your next journey, then yes, of course. If it saves you from charging from the grid some time soon, then yes. But if you're not driving 250 miles a day, that's not the case.

As long as each day you get enough from solar to replace what you've driven, it doesn't matter if you have excess energy. Better to let the grid have it!

(This ties into my theory that in future, especially people without home chargers, we'll get less anxious about range, and for some lifestyles (town runaround) be more comfortable about the car hovering around 50% some of the time. Plug into a cheap 7kW (or even 3.5kW) public charger wherever you happen to be, regain what you used to drive there, maybe a bit less, maybe a bit more. Sometimes your charge will drift up as a result. Sometimes it might dwindle and you'll need a purposeful boost.

 

[Robf]

Hi, my second newbie question

I've spent/invested some time reading through the various discussions about how charging hygiene for the LR models (mine is a new very orange Trophy!). I have solar on the roof and a modestly sized GiveEnergy house battery. Part of the rationale in replacing our non-plug-in Prius with the MG was because we were sending too much surplus generation to the grid for no compensation whatsoever (because British Gas won't fit a Smart Meter until it suits them and it hasn't suited them for over a year - I've signed up for Octopus, but still waiting for a Smart Meter) ... and even if we had a smart meter we'd get next to not much for the export. So having a pure EV, as well as the other benefits, is it's a big battery on wheels that can take the surplus and provide "free" family outings transport for much of the year. Yay!

So it's been sunny and I haven't had a chance to drive the new car much yet as I work from home. So, after the dealer handed it over at 100 percent charge, and we drove it and got it down to 59 percent, the sunshine has brought it back up to the top of the health range at 80. So now we have kilowatts of excess solar going to the grid for no benefit (apart from the consolation that at least someone is using it and that may save a Polar Bear very tiny fraction of a degree of climate change for a tiny fraction of a second ... ) ... and British Gas can have it for free and won't notice or care ...

But I digress.

Do we think that charging to say 90 or 95 percent would be nearly as "healthy" for the battery as the "hard" stop at 80 percent? Then I could store a bit more. If not I just need to deplete the battery more, eg to between 20 and 30 percent before charging.

And I need to charge to 100 percent once a month, to balance/equalise, right? Do I need to do this in one go, so set my Zappi to "fast" (7KW single phase) to get it to 100 percent at a consistent pace, or will variable solar surplus via the Zappi be OK as long as it gets to 100 percent?

And when it is at 100 percent, I need to take it for a drive so it doesn't sit at 100 percent, too, right?

This question was probably too long. And probably to many questions. Sorry.

Assuming you have a power diverter to use immersion for water heating?

 

[DB00nowthen]

Assuming you have a power diverter to use immersion for water heating?

Yes, since sometime in April we have effectively used no grid gas or electric. Only paying for utility’s standing charges, which Martin Lewis is right about being a disincentive for saving energy or investing in renewables. Before the Trophy arrived, I exported 1025 kWh to the grid for free, having heated all the water we can store and washed all the cushion covers etc whether they needed it or not! Today I have a fully heated hot water tank 80% soc in the car, full house battery and am batch cooking/roasting to use the surplus and it isn’t midday yet. I’ll have to give in and let the rest of todays surplus go to the grid. Will be different in nov to end of march though. Make hay while the sun shines…

But I am planning a drive accross the country line to Cornwall tomorrow PM, so I am tempted to let the car change to 95 percent today. Not 100 because I think I’ve picked up one should not leave it sitting with 100 percent. Or do we think that leaving it like that overnight or for a day is ok?

 

[tsedge]

Yes, since sometime in April we have effectively used no grid gas or electric. Only paying for utility’s standing charges, which Martin Lewis is right about being a disincentive for saving energy or investing in renewables. Before the Trophy arrived, I exported 1025 kWh to the grid for free, having heated all the water we can store and washed all the cushion covers etc whether they needed it or not! Today I have a fully heated hot water tank 80% soc in the car, full house battery and am batch cooking/roasting to use the surplus and it isn’t midday yet. I’ll have to give in and let the rest of todays surplus go to the grid. Will be different in nov to end of march though. Make hay while the sun shines…

But I am planning a drive accross the country line to Cornwall tomorrow PM, so I am tempted to let the car change to 95 percent today. Not 100 because I think I’ve picked up one should not leave it sitting with 100 percent. Or do we think that leaving it like that overnight or for a day is ok?

100% overnight is fine, it is extended periods that cause the problem. Shorter is better but a few hours won't hurt.

 

[ukslim]

But I am planning a drive accross the country line to Cornwall tomorrow PM, so I am tempted to let the car change to 95 percent today. Not 100 because I think I’ve picked up one should not leave it sitting with 100 percent. Or do we think that leaving it like that overnight or for a day is ok?

Good lord, if you plan to require a charge tomorrow, then absolutely take it to 100% today. That's what 100% is for.

 

[DB00nowthen]

Assuming you have a power diverter to use immersion for water heating?

Yes, since sometime in April we have effectively used no grid gas or electric. Only paying for utility’s standing charges, which Martin Lewis is right about being a disincentive for saving energy or investing in renewables. Before the Trophy arrived, I exported 1025 kWh to the grid for free, having heated all the water we can store and washed all the cushion covers etc whether they needed it or not! Today I have a fully heated hot water tank 80% soc in the car, full house battery and am batch cooking/roasting to use the surplus and it isn’t midday yet. I’ll have to give in and let the rest of todays surplus go to the grid. Will be different in nov to end of march though. Make hay while the sun shines…

But I am planning a drive accross the country line to Cornwall tomorrow PM, so I am tempted to let the car change to 95 percent today. Not 100 because I think I’ve picked up one should not leave it sitting with 100 percent. Or do we think that leaving it like that overnight or for a day is ok?

Good lord, if you plan to require a charge tomorrow, then absolutely take it to 100% today. That's what 100% is for.

that’s kinda what I was thinking, just looking for some validation

 

[JimD]

Even though I get paid by Octopus for export (15p/kwh) at this time of year I begrudge it when during the winter I have to pay 32p to get it back, so I also sometimes let it charge to over 90% from the solar if there's surplus. Isn't there supposed to be a battery buffer so 100% isn't really 100% anyway?

It never gets wasted if it goes in the car, and who knows what the weather will do tomorrow.

 

[DB00nowthen]

Even though I get paid by Octopus for export (15p/kwh) at this time of year I begrudge it when during the winter I have to pay 32p to get it back, so I also sometimes let it charge to over 90% from the solar if there's surplus. Isn't there supposed to be a battery buffer so 100% isn't really 100% anyway?

It never gets wasted if it goes in the car, and who knows what the weather will do tomorrow.

I've switched to Octopus having been fobbed off for nearly two years by British Gas saying I am on a waiting list for a smart meter. Octopus can't tell me when they can fit a smart meter until I've been with them a month, so that's in my diary. I'd not mind getting paid at least something for the KWHs I can't use or store, and I can't try any of the interesting Octopus tariffs until I get a mart meter.