Tesla Wall Connector (Gen3) randomised delay gotcha

[scdoubleu]

I've been relying on the TWC3's start/end times (recently added for UK customers, to comply with The Electric Vehicles (Smart Charge Points) Regulations 2021, Section 11) to ensure our cars charge only during the off-peak window.

Last night, SWMBO's M3 was at 38% and so in need of a charge. I plugged in with the limit set to 80% in the app, knowing full well the car would not reach that limit within the four hours. So I was relying on the TWC3 to stop the charge at 4.30am. I have the "Randomised delay" option enabled on the TWC3.

Sure enough, car started charging at 0:36am. However, the TWC3 added another randomised delay at the end of the charge session, stopping it at 4:39am. So for nine minutes the car was pulling 3.7 kW from my PW and the same from the grid at peak rate!

Reading the legislation, linked above, I suspect Tesla have taken the definition of "relevant time", section 4(b) to mean that there should be a randomised delay at the end of the session, not just the start. Since you could argue that stopping charging also meets the definition of "decreased [rate of electricity flowing...]".

So just a heads-up to anyone relying on this feature. I've now disabled the randomised delay option in the app.

 

[a1psx]

Can you set the end time to be 4:20 (so 4:20-4:30 with randomization)?

 

[scdoubleu]

Start/end time granularity is, unfortunately, 30 minutes .

 

[Adopado]

So just a heads-up to anyone relying on this feature. I've now disabled the randomised delay option in the app.

You're lucky that the Tesla WC lets you do that ... newer Zappi won't let you permanently disable the randomised delay. You can override manually for a particular charge session but you need to do that in real time at the Zappi or in the Zappi app. (I note that for scheduled charges there is randomised end time too so I suspect it's a requirement of the feature. In practice I don't use a start and end time on the Zappi so though it will randomise the start it doesn't affect the end because it's the car that controls that i.e. it just stops the charge when it reaches my set percentage.)