Ohme pro + charge percent confusion

[ryamoo]

I have a ZS EV Trophy, bought in November, so 2022/2023 model, standard range.
I know that the Ohme won't "know" my car's battery percent because of the API thing, so I have to set it to the % I want to add. My post isn't about that, I do set it to the % I want to add based on what the car is telling me the current % is and what I want it to get to.
I've just had the Ohme Pro charger fitted last week, have used it to do a bigger charge in the first day or so but didn't note any added % or kWh, and used it a little to keep the battery topped up since then.
Sorry in advance for the long post/info dump.

Tuesday evening, the car was at 71 or 72%, so I set the schedule to add 30% by 9am, plugging in at about 9pm.
It scheduled some charge at 11pm-midnight, then more throughout the night.
I checked just after midnight, and the car was at 100% and I'm confused about how.

The Ohme app showed that it had added 17 of 60 miles (the MG app shown more than 17 miles added, was 50-60 miles higher than when I plugged it in). 17 of 60 miles is 28% of the charge it thought it needed to add, and 28% of the 30% I wanted it to add would be 8.5% of the total battery capacity (50kWh), so 8.5% added should be 4.25kWh.
Looking at my usage on Octopus, that checks out. ~4.9kWh of electricity was used between 11pm and midnight. House usage was probably about 0.4 of that, so charger used about 4.5kWh.

30% of the 50kWh capacity is 15kWh, so I'm so confused about how it managed to get from ~72% to 100% in that 1 hour.
Is this a cold weather thing? Is the car reporting a % based on the range or something? I can't quite wrap my head around that. Is it possible the car was just reporting the wrong %?

The car's been used again this morning, and I'll probably be using it again this evening. Tempted to schedule a charge now so I can monitor what it does (currently showing 79% battery, 93 miles range).

 

[drmcw]

If you have a SR then you want to charge to 100% each time really so I'd just set the Ohme to 100% and let the car decide when it's full.

 

[mg4mc]

If you have a SR then you want to charge to 100% each time really so I'd just set the Ohme to 100% and let the car decide when it's full.

Not very friendly or how IOG is supposed to work though is it.

Octopus provide the great 7.5p rate on the basis that you give them sensible estimates on what power you need so they can schedule everyone's charges to make best use of the available surplus (if any).

 

[drmcw]

If you have a cheap rate during the night then can't you just schedule the charge for that time period? I don't have Ohme but am on Octopus and just set my charger to be on for the cheap rate time period.
I'm not on IOG and without the feedback from the car then it's not going to work properly but Id just do what you're doing and maybe experiment and add 5% or 10% to ensure it gets to 100%?
The LFP battery is notorious for giving bad state of charge readings because the voltage curve is so flat hence the additional % to be safe..

 

[mg4mc]

If you have a cheap rate during the night then can't you just schedule the charge for that time period?

Because it's against the T&Cs of IOG, if you want to do that then you should be on the Go tariff.

 

[drmcw]

Probably worth a read of this thread

 

[linkandnavi]

I have a ZS EV Trophy, bought in November, so 2022/2023 model, standard range.
I know that the Ohme won't "know" my car's battery percent because of the API thing, so I have to set it to the % I want to add. My post isn't about that, I do set it to the % I want to add based on what the car is telling me the current % is and what I want it to get to.
I've just had the Ohme Pro charger fitted last week, have used it to do a bigger charge in the first day or so but didn't note any added % or kWh, and used it a little to keep the battery topped up since then.
Sorry in advance for the long post/info dump.

Tuesday evening, the car was at 71 or 72%, so I set the schedule to add 30% by 9am, plugging in at about 9pm.
It scheduled some charge at 11pm-midnight, then more throughout the night.
I checked just after midnight, and the car was at 100% and I'm confused about how.

The Ohme app showed that it had added 17 of 60 miles (the MG app shown more than 17 miles added, was 50-60 miles higher than when I plugged it in). 17 of 60 miles is 28% of the charge it thought it needed to add, and 28% of the 30% I wanted it to add would be 8.5% of the total battery capacity (50kWh), so 8.5% added should be 4.25kWh.
Looking at my usage on Octopus, that checks out. ~4.9kWh of electricity was used between 11pm and midnight. House usage was probably about 0.4 of that, so charger used about 4.5kWh.

30% of the 50kWh capacity is 15kWh, so I'm so confused about how it managed to get from ~72% to 100% in that 1 hour.
Is this a cold weather thing? Is the car reporting a % based on the range or something? I can't quite wrap my head around that. Is it possible the car was just reporting the wrong %?

The car's been used again this morning, and I'll probably be using it again this evening. Tempted to schedule a charge now so I can monitor what it does (currently showing 79% battery, 93 miles range).

So I'd probably I'd probably not talk about "miles added" in this kind of context, because it's a completely meaningless metric. The only thing added during a charging session is kWh. The car will estimate the range it will get from the percentage of its charge combined with the weather and previous driving patterns etc. The charger will have absolutely no way of knowing (given the lack of API integration) what the car is estimating, so there's always going to be a significant difference between the chargers "mile" estimate and the car's.

What's needed for your issue is kWh added and battery percentages. I assume you're confident that the car was actually at 71-72% when it started charging? Did you check that via the in-car screen or via the app? If via the app then it's notoriously unreliable and if it can't wake the car to check it's current battery percentage then the app will often show the percentage as whatever it was the last time it successfully connected to the car which could have been days ago.

Assuming you are on single phase electricity, then it is impossible to add 15kWh in a single hour. The maximum on a 32A charger will be a 7.2 kW rate of charge and for an MG that tends to work out at closer to 6.8 kW. So either the car was at a higher state of charge than you thought when it began charging (hence my question above) or it wasn't actually at 100% when you checked at midnight and the app was displaying the wrong information.

This is an assumption on my part but given you were checking it at just after midnight I'd guess you did so via the app? In which case, I suspect the app was reporting the wrong data. You said you checked the Octopus app and it showed 4.9kWh of usage (and it'll be kWh, not kW. kWh is the total energy used, kW is the rate of energy usage) between 11pm and midnight. Now that its morning and there will have been time for the Smart Meter to have updated, does the Octopus app show energy usage later in the night? If so, I'd guess that it carried out the first scheduled bit of charge between 11-12pm as it said it would, when you checked the app at midnight the 100% figure was incorrect, and then it carried on charging for the other scheduled periods throughout the night.
[ Edit moderator: corrected numerous unit errors in the above. ]

If you have a SR then you want to charge to 100% each time really so I'd just set the Ohme to 100% and let the car decide when it's full.

Not very friendly or how IOG is supposed to work though is it.

Octopus provide the great 7.5p rate on the basis that you give them sensible estimates on what power you need so they can schedule everyone's charges to make best use of the available surplus (if any).

There's absolutely nothing wrong with this and it isn't contrary to the purpose of IOG. He's talking about charging the car to 100%, not overriding the smart charging schedule provided by IOG. It's entirely open to him and within IOG's terms to charge the car to whatever percentage he wants, which with a standard range MG and its sodium battery, is likely to be 100%.

If you have a cheap rate during the night then can't you just schedule the charge for that time period? I don't have Ohme but am on Octopus and just set my charger to be on for the cheap rate time period.
I'm not on IOG and without the feedback from the car then it's not going to work properly but Id just do what you're doing and maybe experiment and add 5% or 10% to ensure it gets to 100%?
The LFP battery is notorious for giving bad state of charge readings because the voltage curve is so flat hence the additional % to be safe..

Because it's against the T&Cs of IOG, if you want to do that then you should be on the Go tariff.

This bit however would be against the IOG terms and conditions as you say, because this is about preventing IOG from managing the charging schedule for when it the grid has surplus energy and one of the terms and conditions is to permit Octopus to control the charging schedule. If you were going to "dumb" charge the car this way, then I agree that it should be done via the Go tariff and not IOG.

 

[UncleBob]

Could I be a -bit- of a pedant and point out that kW is power, therefore the rate at which energy is put into the battery, essentially joules per second. kWh is the total amount of energy you've put in, essentially Joules. So if you have a 5kW charger charging for an hour you've put in 5kWh.
I have a second gen ZS, the app sometimes reports legacy percentage if it can't communicate. The car dash readout is usually correct. The range on a cold day is -hopelessly- optimistic. Still a great car though

 

[Coulomb]

with a standard range MG and its sodium battery

Err, sodium battery? I don't think MG are working with sodium batteries just yet. Maybe in a few years.

Could I be a -bit- of a pedant and point out that kW is power,

Could I be a bit of a pedant and point out that kW is spelled with a lower case k (k for kilo); K is reserved for the kelvin, the unit of absolute temperature. And yes, when the kelvin spelled out in full, it takes a lower case k. Similar with V and volt, A and amp/ampere, etc.

Similarly of course kWh for energy; h is for hour, and H is for Henries (the unit of inductance).

I've edited the OP's post for unit correctness. I've been correcting many posts in the hope that people will get used to the correct spelling and units and use them.

 

[linkandnavi]

Err, sodium battery? I don't think MG are working with sodium batteries just yet. Maybe in a few years.

Sorry, yes. I meant lithium phosphate. I blame the 5am toddler wakeup...

 

[ryamoo]

I assume you're confident that the car was actually at 71-72% when it started charging? Did you check that via the in-car screen or via the app?

Yes - I'd driven to a store, bear with my memory here, but it was at 75-76% when I got there, and I knew I'd lost 4% to get there, so knew I'd lost about the same coming back.
When I got back, I'd checked on the in-car screen, then set the ohme app to add the 30% based on the car being 71-72% (I say 71-72 because I don't remember exactly, but do know it was 71 or 72, most likely 72%).

This is an assumption on my part but given you were checking it at just after midnight I'd guess you did so via the app?

I checked on the MG app after midnight once I noticed on my IHD that the current usage had stopped, so was interested on seeing how much charge it had put into the car. The app said 100% battery, so I actually decided to go out - the curiosity was too strong.
Charger confirmed 8% added so far. I unplugged the car. App still shown 100%, I didn't check the in-car display at this point but the next morning it was at 100%.

This was Tuesday night (11pm-midnight), then unplugged at ~00:35 Wednesday.
I'd waited until Thursday so I could see Wednesday's electricity usage on Octopus, to see if there was any after midnight, and it was 0.13 kWh, which is typical usage for that time.

Which is all why I posted, after the confusion. I can only assume the car's % isn't right for some reason, and I'm not sure how I deal with that. Maybe it is just the cold weather.

Bonus find, me unplugging the car at that time I've drawn on it too because the image is rubbish