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MG ZS EV Long Range - Rapid Charging Test - 76kW Peak?

Miles Roberts CG

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Last night, myself and Jake @MG ZS EV WEST YORKSHIRE took the Chorley Group Burnley demonstrator on a journey to test the real-world rapid charging capabilities.

I picked up Jake around 7pm from Oakworth, and we headed to the Ionity chargers at Leeds Skelton Lake Services. I used the "Battery Heater" option to ensure that we had warm batteries on arrival. This appears to use around 7kW (20A@360V) at peak, although once the batteries had heated up (after 40 mins), the battery heaters automatically switched off.

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On the way there, the "Low Battery Warning, Please Charge" message came up at 24% (46 miles indicated) remaining.

Unfortunately, when we arrived there just after 8pm, there were 4 cars charging (2 Porsche Taycans, and MG5, and a DPD delivery van, with 2 other DPD drivers queuing to use them. Faced with a potential delay of over an hour (the DPD vans needed 90%+ to be able to do their deliveries the next day), we checked on Zap-Map, and found there were some 100kW+ Instavolt Rapid Chargers in Barnsley, 26 miles away.

We had 15% battery.... and it was mainly motorway, but were showing 30 miles range on the GoM, so figured we might as well go for it.

At 14% (24 miles remaining), another "Low State of Charge, Please Charge" warning came up on the dashboard.

At 7%, the GoM went to "---", and power was restricted - we were on the M1 going up a hill past Woolley Edge services, and our speed (with foot flat to the floor) wouldn't exceed 50mph. We started to get a little bit nervous. We decided to come off the M1 at the next junction, and go on the A/B roads to Barnsley, as we didn't want to be a hazard for anyone.

We finally got to the chargers (next to McDonalds) with 3% battery remaining. Thankfully, the chargers were both available and working (not ICEd).

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We started the charge, and recorded the Amps & Volts from inside the car, to calculate the charging power. The charge was started at 20:56 (nice round number... should have waited a few minutes I guess!).
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Initially, the charge started quite slowly, as the charger and car decided what power was best. At 4%, it was delivering 181A @344V (61kW). By 6%, the current had increased to 200A, where it stayed fairly consistently (did drop to 199A for a bit) until it got to 60% SoC. As the battery voltage rose, so the total kW increased, peaking at 76kW at 59/60% SoC.

From 61-71%, it continued at 179/180A, then from 72% it dropped to 151A, where it remained until 82%. At 83% (21:41 - 45 minutes after we started), it then dropped off quite quickly to 67A, stepping down to 61A by 89%. At 90% it dropped to 52A, and at 91% it was at 40A@403V (16kW). This is where we decided to disconnect the charger (it was 21:56, so exactly one hour from when we started).

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For reference, it got to 22% after 10 minutes, 41% after 20 mins, 58% after 30 mins, and 83% after 45 mins. This compares very favourably to MG's own stated charge times of 42 minutes to 80% when using a 100kW rapid charger.

Graphs showing the Volts/Amps, and then the calculated kW Power are below:

Amps and Volts.png

ZS EV KW Charging.png


In conclusion, the new ZS EV has a great charging curve, where it draws 70kW+ from 7% to 60%, and then maintains 60kW+ up to 80% SoC. The battery heater works well (but bear in mind that the heater will draw up to 7kW, so if you're already low on power, you're going to lose another 20-30 miles of range by using the battery heater). It decimates your efficiency - whilst it was working, I was getting 1.5-2m/kWh rather than 3m/kWh!

The battery heater switches itself off when you turn the car off, so it's not something you can accidentally leave switched on and drain all the battery - you need to actively turn it on for each journey.

I would not recommend running the car down below 10% SoC. The charging speed doesn't benefit, and the reduced power (particularly on a motorway) is not a pleasant experience. It might not be too bad around an urban environment, but hills become an issue when it's limiting you to around 25kW (33bhp!). We struggled up a hill in Barnsley town centre with foot flat to the floor, and scraping to 24mph.

We've got loads of photos etc, but I don't want to make this any more difficult to read than it already is :LOL:

I've added my excel sheet with the values for Volts/Amps that we saw.
 

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  • MG ZS EV Log Range Rapid Charging values.xlsx
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Well, if the battery was cold (let's say below 15C), then it wouldn't achieve a fast charge rate. So if it were a cold day (It was -6C here on Monday morning), and you needed to rapid charge, you could find that you arrived at a charger with 20% battery but it wouldn't charge faster than 30-40kW (doubling your charge time or worse).

So by using the battery heater, you precondition the pack to accept a faster charge rate, and you might need to add an extra 10% charge (costing you ~£2.50 on this charger), but the overall charge time would be 40 minutes instead of 1hr30.
 
Great information thanks. Is there anywhere you can see the battery temperature to see whether the battery heater is needed?
No, but if it's below 20C outside, there will probably be an improvement in charging speed if you use the heater. If it's below 10C, then I'd recommend it. If it's below zero, it's a must.
 
No, but if it's below 20C outside, there will probably be an improvement in charging speed if you use the heater. If it's below 10C, then I'd recommend it. If it's below zero, it's a must.
Yeah that's a reasonable rule of thumb, but would be nice to see a temperature readout for coldgate and rapidgate purposes!:) (and just to get a better idea of how the heater and charging affects battery temperature)
 
Very good writeup Miles, super informative as usual.

That means ev database’s listed 92 kW max charging is complete fiction then? MG ZS EV Long Range
I'd say so. Unless anyone has proof to the contrary. Although the new 51kWh ZS EV could perhaps get that charge rate, if it uses the same pack as the MG5, as the voltage is higher. Will need to test when it arrives next year!
 
Nice, thanks for doing that Miles & Jake, the battery heater sounds like a great upgrade, could have done with that last year when I drove to the west of Ireland in -1 c temps! Ah well will be useful next Christmas!! :) When would be the best time to turn it on (before reaching the charger)?
 
Nice, thanks for doing that Miles & Jake, the battery heater sounds like a great upgrade, could have done with that last year when I drove to the west of Ireland in -1 c temps! Ah well will be useful next Christmas!! :) When would be the best time to turn it on (before reaching the charger)?
You've basically got to make sure that you've got plenty of range to get to the charger, and then turn it on around 30 mins before. It will burn through about 15 miles of range extra in that last 30 mins, so you don't want to be cutting it fine.
 
Thanks Miles & Jake for taking the time to carry out this test !.
I totally see that demonstrating the battery heater was necessary, in attempt to pull the max speed from the rapid unit, but very brave of you given you lowish SOC :eek:.
Forgive me for asking, but I rarely use rapids like the Instavolt units.
But I suspect that these where higher powered units and not your normal run of the mill 50 kw units then ?.
Some of the preheating of the pack was lost, due to having to move to the next charger.
With a warm pack and a very low SOC you would have expected the charge speed to peak a little higher, what do you think ?.
Thanks for putting the video and info together Miles & Jake :giggle: .
 
These were 120kW rated rapid chargers, obviously on a 50kW charger the maximum charge rate would have been 50kW not 76kW.

I don't think the battery would have lost much heat in the interim drive to Barnsley. If it was colder outside, then perhaps it would have done, but it was relatively mild (9°c) out last night.

The peak power is calculated as the current (Amps) multiplied by the Volts. As the battery pack voltage is low when the battery is low on charge, you'd need a higher amperage to give you increased charge rate. These chargers are limited to 200A, so when the battery was empty (330-340V), the maximum charge rate could only be 200x330 = 66000W (66kW).
 
These were 120kW rated rapid chargers, obviously on a 50kW charger the maximum charge rate would have been 50kW not 76kW.

I don't think the battery would have lost much heat in the interim drive to Barnsley. If it was colder outside, then perhaps it would have done, but it was relatively mild (9°c) out last night.

The peak power is calculated as the current (Amps) multiplied by the Volts. As the battery pack voltage is low when the battery is low on charge, you'd need a higher amperage to give you increased charge rate. These chargers are limited to 200A, so when the battery was empty (330-340V), the maximum charge rate could only be 200x330 = 66000W (66kW).
Thanks for explaining that Miles !.
Did you get chance to spot what the pack voltage is showing when fully charged on the face lift ?.
We know the original ZS EV has a voltage on the pack of either 455 - 456 volts on the original BMS.
Or 448 - 450 volts after the latest BMS update on the 15th Jan 2021.
This is after a balance cycle also.
The MG5 appears to be running on a lower pack voltage for some reason ?.
Do you know why this is Miles ???.
Thanks.
 
These were 120kW rated rapid chargers, obviously on a 50kW charger the maximum charge rate would have been 50kW not 76kW.

I don't think the battery would have lost much heat in the interim drive to Barnsley. If it was colder outside, then perhaps it would have done, but it was relatively mild (9°c) out last night.

The peak power is calculated as the current (Amps) multiplied by the Volts. As the battery pack voltage is low when the battery is low on charge, you'd need a higher amperage to give you increased charge rate. These chargers are limited to 200A, so when the battery was empty (330-340V), the maximum charge rate could only be 200x330 = 66000W (66kW).
So do you think there is a chance that a higher rate charger, IE more than 200 amps, might get slightly more?

Not suggesting you should do it ;) , almost running out of charge in Barnsley isn't how anyone should have to spend their evening!!
 
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