Displayed current when charging MG ZS Exclusive on 7Kw charger

[techjunkie]

Displayed current when charging MG ZS Exclusive on 7Kw charger.

I have rocked up at the local Tesco Podpoint chargepoint with about 63 miles left on the GOM a few times. The displayed current in ready mode is never more than minus 15A when I am expecting around minus 30 (nominal 32). I have bought and resold a couple of leads rated at 32A (no complaints). My latest one has the correct resistors at both ends for the 32A 3mm cables within between PP & earth. (I did not check the others)
So yesterday I hooked up to my tethered 32A wall charger at home and again the car claimed only minus 15A. The smart meter showed 7 Kw so the car was getting around 30A - just wish I had tried this test before.
My question is: Is my car unique or do they all show minus 15A or so amps when "fast" charging rather than the expected 30ish amps?

Apologies if this in the manual, which I have read, or been posted before.

 

[Deleted member 2439]

It’s easy!

The current being displayed is the DC current into the battery. C15 amps x c400 volts = 6000 watts. The balance is the lost power in the efficiency of the charger.

The AC current will be higher, 7000/240 = c30 amps.

Sorted ?

The c means nominally.

Cheers - Rob

 

[techjunkie]

It’s easy!

The current being displayed is the DC current into the battery. C15 amps x c400 volts = 6000 watts. The balance is the lost power in the efficiency of the charger.

The AC current will be higher, 7000/240 = c30 amps.

Sorted ?

The c means nominally.

Cheers - Rob

Thank you so much for your explanation. Wish I had known this before. Is this explained anywhere in the manual and I missed it?. Unfortunately I have yet to successfully rapid charge - perhaps I would have twigged it then. I get it now.

 

[JodyS21]

I believe you need to use whatever the current battery DC voltage is in your calculation i.e. it's not always 400 or 450v etc.
In your example photo it's showing 398v @ -15Amps = 5,970Wh.
So....when you're nearing full charge you should see the Amps reduce to -14.

 

[Coulomb]

The balance is the lost power in the efficiency of the charger.

That's part of the balance. There is also the DC-DC converter and its inefficiency, powering the various 12V loads. Most of the computers will be on, that's 60W or so. Then all the various pumps, relays, etc. There may be some lights on when you're in the car looking at the battery voltage and current, etc. The current is also displayed only in whole amps, so it could be nearly 15.5, or nearly 16.0 A, depending on how they round the measured value, and of course there could be a small inaccuracy in the measurement.

 

[Deleted member 823]

Oh this is way too technical for me! ?

 

[bloggsy]

Oh this is way too technical for me! ?

Yeah, my head hurts now!!

Cheers

Bloggsy

 

[rbpasapera]

FYI

W = power

Wh, kWh = energy

 

[Deleted member 823]

That takes me right back to school!

 

[Deleted member 2439]

Thanks for that. I was beginning to feel like a lost voice in the wilderness regarding the incorrect use of kW & kWh on this site. Hopefully it will gradually start to sink in as it’s quite an important distinction!

 

[notdodgy]

FYI

W = power

Wh, kWh = energy

View attachment 3538

At least we haven't resorted to plumbing analogies...