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Discussion Starter · #1 ·
Hi all, medium time lurker, first time poster etc etc. Admins please move this post if it's in the wrong place, but I did do a forum search and don't think it's a duplicate.

My parents plugged their new Audi E-Tron into one of their local council's lamppost Ubitricity chargers for the first time today (they don't have off street parking) at about 9am, and for about 7 hours the car charged happily, reporting a charging speed of 5.2Kw (it reports 6.5Kw on a 7.6Kw wall-box unit so the on board charger is obviously only about 85% efficient).

However, at about 4pm today, just as the car hit 70% charged, the speed has absolutely plummeted down to 2.5Kw. I'm guessing that 2.5Kw is a 12amp charge after efficiency losses, or exactly half the 24amp they can deliver at max power. However, it was also just as the car had taken on the equivalent of 40Kwh of charge.

So I'm wondering if anyone knows if the following are true:
  1. Ubitricity rate limits a charge once the vehicle reaches 70% (and if so why)
  2. Ubitricity rate limits a charge once a vehicle has taken on 40Kwh
  3. Ubitricity rate limits between 4&7pm (I know these are the grid's peak hours, so it 'makes sense' to me if they do)
  4. Something else (the car has happily charged at 6.5Kw all the way up to 100% on AC before, so I doubt it's on the car here)
They were due to make a 160 mile round-trip tomorrow so wanted to charge to 100%, but the ETA from that has now slipped from 11pm to 6am tomorrow, not the end of the world, but they'd like to know if this rate limit behaviour is 'normal'.
 

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Discussion Starter · #2 ·
Just an update: slap bang on 7pm the power returned to the full 5.2Kw.

I'm guessing it's a rate limit for the national grid peak hours.
 

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There is no mention in their Q&A's about that. Just a few mini calculations for the time taken to fully charge a car at the standard 5 kWh rate. And those examples include a continuous charge of a Tesla plugged in for 19 hours with the same rate of transfer used throughout. So that specifically rules out any reduced periods caused by peak demands. They do, however, have a caveat over the speed of charge based on other factors such as the car's battery. I can't imagine an e-Tron plugged in at 5 kWh having any issues such as overheating etc so that probably isn't the problem either. Perhaps an email to Ubitricity would solve this.
 

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Type 2 AC using the regular protocols has no way of telling how full the car battery is.
It's almost certainly to help the grid, or even the load on the local street lighting circuit.
They are almost all run off street lighting circuits using spare capacity when the lights were upgraded to LED with lower power draw, which is why they're much lower output than most public AC charging, or indeed, most home charging. A clever idea and a better-than-nothing solution.
If they had multiple chargepoints fitted on the same street lighting circuit, I'd expect the charge rate to drop as a second vehicle was connected.
Ubitricity chargers aren't even aimed at being destination chargers where you're likely to get a useful charge in a few hours. They're designed to help residents without off-street charging to charge their vehicles overnight.
 

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New ID4 plugged in to ubitricity lamppost on my street last night. 33% to 74% (34kWh) has taken 16 hours so far, still going...so 2kW delivery on average. It has swung higher and lower over that time. Gahhhh, thats rubbish...I didn't count on this!!!
 

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Discussion Starter · #6 ·
New ID4 plugged in to ubitricity lamppost on my street last night. 33% to 74% (34kWh) has taken 16 hours so far, still going...so 2kW delivery on average. It has swung higher and lower over that time. Gahhhh, thats rubbish...I didn't count on this!!!
34kwh in 16 hrs is an average of 2kw, which is under half of what these chargers SHOULD deliver - so it sounds like that one is rate limiting.

It's pants, I agree, basically the same speed as a 13amp granny charged (albeit safer in its delivery in terms of fire risk and trailing extenion leads across pavements).

I did actually reach out to their support about rate limiting and they denied they have a rate-limiting or demand management policy, partly blaming the car. They obviously do manage demand if power delivery fluctuates during the charge, and it would be nice if they were more transparent about that.

As an aside, Ubtricity support sucks, with very condescending replies both by email and a totally disinterested L1 tech I reached by their support number (for a different issue - a charger where the car claimed there was no detectable mains voltage).
 
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