AC Fast Charging

[rickwookie]

Saw that three new 7kW double fast chargers had gone in near me, and are currently on free vend. Rude not to try them out, right?

Anyway, I’ve only ever used an a.c. fast charger once or twice before, but never one like this that had a power output display. I was surprised therefore to see that plugging in the car, which only had 56% SOC, only 4.7 kW or the maximum claimed 7.2 kW was being delivered. I wondered if the charge points themselves were being limited, so I turned on the heating in the car, and sure enough the display shot up to 7.2 kW (although went down after about half a minute to 6.9 kW)

Have just spent a small fortune getting cables ducted to my drive for a new 7 kW home charge point, is this how it is with the e, that the onboard charger can only stuff just under 5kW into a half empty battery pack?!

I assumed that if the car can regularly pull 30 kW+ from a rapid d.c. charger, it would always be able to draw that full 6.9 kW (as I think it’s supposed to be rated at) from a 7.2 kW a.c. fast charger.

I’m about to move onto a new electricity tariff trail (since I had my smart meters fitted) that will offer a rate of just 5p (inc. VAT) per kWh, but only for five hours (22:00-03:00) per day. I had assumed I’d always be able to grab a full charge during that window, even if I’d emptied it first. Now it looks like I will only get a 2/3rds charge in five hours.

Can anyone of you that has their own 7.2 kW home charger confirm how much power the car can take (for charging only, not charging AND heating)?

[bogga]

When I plug mine in, it uses around 7kw, with the heating off... but I guess the charge rate is determined by a number of things, SOC, temperature of the battery.

[londiniumperson]

Have a look a read of this thread:
Type 2 vs CCS charging speeds
viewtopic.php?f=8&t=669
in particular my posts on 7kWh charging & you should find this helpful.
I'd recommend regularly checking the 'Unread Posts' under the quick link menu to up to date on everything being discussed on this forum

[rickwookie]

Interesting, particularly Mr_Helge's data: http://hellgreen.se/honda/Honda_e_7%2C4kW.pdf

That, along with londi's graph now his Ohme isn't being hyper switchy due to the Agile tariff, reassures that the car SHOULD be able to pull 7 kW+ for most of the charge cycle.

I wonder why then it was so abysmal today? I stopped charging just shy of an hour (58 mins I think) and the car display showed I was then on 68% (from 56%). At that poor rate, it would take over 8 hours to grab a full charge. The charge point display showed the equivalent of 5.5 kW average power over the session, but I'd had the heating on the whole time (well it was -2 °C as well as a nasty wind-chill today!).

However, by the time I'd exited the car park, that reading was already down to 56%, and as I pulled onto the drive at home (a 2.5 mile journey), it hit 62%. So 6% to drive just 2.5 miles averaging probably around 26 MPH?!

This car never ceases to disappoint me with it's naff battery capacity AND naff charging ability.

[keithr]

However, by the time I'd exited the car park, that reading was already down to 56%, and as I pulled onto the drive at home (a 2.5 mile journey), it hit 62%. So 6% to drive just 2.5 miles averaging probably around 26 MPH?!

This car never ceases to disappoint me with it's naff battery capacity AND naff charging ability.

I presume that 56% was a typing error - perhaps should have been 67%?

Yes, cold weather makes charging slower. It might even have been the charger that was not giving its full power. In one of Bjorn's videos he tried a rapid charger at very cold temperatures (less than -10°C, although I can't remember exactly what it was) and it would only supply a fraction of what it should have done (the car's battery was warm enough to accept higher power). He tried another charger right beside it and that did charge at a faster rate, so it seemed that it was the temperature sensor in the charger that was faulty or incorrectly calibrated. At warmer ambient tempertaure there would probably not have been a problem.

On another occasion, he demonstrated using a rapid charger at less than -20°C ambient temperature and with a cold battery pack, and although the car can normally take about 125kW (it was a Tesla Model 3 I think, or perhaps a Polestar) at that temperature it was barely charging at all - less than 1kW! It was not until the battery had heated up (it had a battery heater - not all electric cars do) that it started to increase the charge rate, but it took ages to charge the car. He then repeated the test after having warmed the battery up to demonstrate how important it is to get the battery warm if you want to get the higher charge rates.

I've not been aware of cars having to reduce the charge rate on AC charging before, so I would suspect the charge point. I suspect if you try the same charge point again when the weather warms up then you'll get the full 6.6kW.

[ChesterUK]

Can anyone of you that has their own 7.2 kW home charger confirm how much power the car can take (for charging only, not charging AND heating)?

I regularly see a 'flat-top' when we're charging overnight using a Zappi 2 of over 7kW. It tapers off at about 97-98% and trickles in the last bit. I can't comment too much on sub-zero charging, because I think we've only done this once overnight, definitely during the day but that's on solar surplus which doesn't really count.

[rickwookie]

However, by the time I'd exited the car park, that reading was already down to 56%, and as I pulled onto the drive at home (a 2.5 mile journey), it hit 62%. So 6% to drive just 2.5 miles averaging probably around 26 MPH?!

This car never ceases to disappoint me with it's naff battery capacity AND naff charging ability.

I presume that 56% was a typing error - perhaps should have been 67%?

*66%

I've not been aware of cars having to reduce the charge rate on AC charging before, so I would suspect the charge point. I suspect if you try the same charge point again when the weather warms up then you'll get the full 6.6kW.

Yes, but when I turned on the car's heating, I was able to get the charge point to deliver 7.2 kW, so that strongly suggests the limiting factor was the car.

[rickwookie]

Can anyone of you that has their own 7.2 kW home charger confirm how much power the car can take (for charging only, not charging AND heating)?

I regularly see a 'flat-top' when we're charging overnight using a Zappi 2 of over 7kW. It tapers off at about 97-98% and trickles in the last bit. I can't comment too much on sub-zero charging, because I think we've only done this once overnight, definitely during the day but that's on solar surplus which doesn't really count.

That's useful, and seems to confirm what others have found. So I WILL get a 32 Amp home charger, and if I find that I continue to get such poor a.c. charging rates, I'll contact Honda about it.

[londiniumperson]

Here's a chart using my home charger from 8pm on 10 Feb until 1am on 11 Feb 2021 (x-axis) with sub zero external temperatures, showing Watts on the left y axis & °C on the right y-axis, starting at 34% charge & finishing at 100%:

[advance2020]

Hi Rick,

I think others have answered yours about Home Charging. As I am still using Granny with limited info I can't compete with Londinium's graph and others.

However I regularly charge at free 7kW or 7.2kW Fast chargers - Tesco/Pod Point and BP Polar posts. I consistently get 6.2 to 6.5kW/h from Pod Point and more from Polar around 7.1kW/h not sure why they differ, but this is based on several different locations. So I don't think my car limits rate, in the range of 40 - 85% it is function of the Charge points.

I have noticed charging rate drop down, when I have tried tried to top up to 100%, which is understandable. Battery protection.

These figures are based on what % battery increase I actually get free, in the time logged by the Apps, not the Energy used as claimed by the Apps, which is typically about 5-10% greater.

I would be interested to hear from others using free public Fast Chargers