Octopus Intelligent Go

[frb123]

I'm finding Octopus Intelligent Go great, particularly whilst my solar is out of action. A couple of observations:

It seems you can (entirely legitimately) go beyond the generally recognised 6 hour window, if you need more juice. Eg. By "requesting" 100% charge at 7.30pm, the schedule generated will (in my case) be pretty much all night, way beyond the 2330-0530 perameters. I have checked this with Octopus and they said it's fine, basically whatever is scheduled is 7.5p end of story. So it's quite open to "abuse" if you want to call it that (and by using evening electricity, is less eco than it intends?). I find it odd this isn't mentioned anywhere as it's very predictable that people will use it this way?

I have found it a bit glitchy with it not connecting to my charger on some occasions. Possibly WiFi/zappi glitch I think. Car itself has handled it with 100% success.

Also totally randomly last night car charged to 88% despite being set to 80% limit (and yes it was set correctly in the both the app and car, I checked both!) Weird. Maybe it's the cold

 

[johnb80]

I'm finding Octopus Intelligent Go great, particularly whilst my solar is out of action. A couple of observations:

It seems you can (entirely legitimately) go beyond the generally recognised 6 hour window, if you need more juice. Eg. By "requesting" 100% charge at 7.30pm, the schedule generated will (in my case) be pretty much all night, way beyond the 2330-0530 perameters. I have checked this with Octopus and they said it's fine, basically whatever is scheduled is 7.5p end of story. So it's quite open to "abuse" if you want to call it that (and by using evening electricity, is less eco than it intends?). I find it odd this isn't mentioned anywhere as it's very predictable that people will use it this way?

I have found it a bit glitchy with it not connecting to my charger on some occasions. Possibly WiFi/zappi glitch I think. Car itself has handled it with 100% success.

Also totally randomly last night car charged to 88% despite being set to 80% limit (and yes it was set correctly in the both the app and car, I checked both!) Weird. Maybe it's the cold

Intelligent Octopus Go is a great tariff and as you have discovered you can make great use of the extra time available under Octopus control. On Sunday mornings we plug my wifes MG5 in to charge at 6AM, we get off peak energy all morning until usually 11:30. The house batteries, washing machine, tumble drier, Sunday roast in the oven and immersion heater are all in progress at the amazing 7.5p kWh.
If you keep the weather in mind, if it's windy or sunny youre more likely to get the additional time because they will have more surplus energy.

 

[Tim Green]

I have an old 7kW car "charger" (EVSE) which is not wi-fi controlled. So I have it controlled by a timer 00.30-4.30am and use the standard Octopus GO of about 9p/30p kWh. This suits me fine and I suspect it's not worth the extra cost of purchasing a newer charger due to the lengthy payback.

 

[Coulomb]

This suits me fine and I suspect it's not worth the extra cost of purchasing a newer charger due to the lengthy payback.

Except that interrupting a car charge at full power with a switch or relay contact (as will be found inside the timer) is a bad idea. The input of the on-board charger has an inductor; interrupting an inductor's current suddenly causes an inductive kick-back that has to be absorbed by various transient suppressing components. These have a finite lifetime, and are not designed for regular operation. When they inevitably fail (perhaps only after months of operation), then the inductor's energy finds its way into more sensitive and vastly more expensive electronics, e.g. the car's on-board charger.

I strongly suggest that you don't do this. Interrupting the control pilot signal, while nowhere near as convenient as plugging in a cheap timer, is far better for the electronics. The on-board charger will ramp the charge power to zero safely, and no inductive kick-back will occur. A fancier EVSE ("AC charger") will presumably do this for you.

 

[johnb80]

The input of the on-board charger has an inductor; interrupting an inductor's current suddenly causes an inductive kick-back that has to be absorbed by various transient suppressing components. These have a finite lifetime, and are not designed for regular operation.

The inductor will go through this process 100 times per second during operation, it wont cause it any issues at all.

When they inevitably fail (perhaps only after months of operation),
then the inductor's energy finds its way into more sensitive and vastly more expensive electronics, e.g. the car's on-board charger.

If it fails (unlikely) it wont have any energy to discharge

I strongly suggest that you don't do this. Interrupting the control pilot signal, while nowhere near as convenient as plugging in a cheap timer, is far better for the electronics.

It is a much more elegant way to control the charging process but a lot less convenient.

The on-board charger will ramp the charge power to zero safely, and no inductive kick-back will occur.

It's not a problem.

A fancier EVSE ("AC charger") will presumably do this for you.

My Zappi drops out the relays for sure and doesnt ramp down via the pilot signal.

I have an old 7kW car "charger" (EVSE) which is not wi-fi controlled. So I have it controlled by a timer 00.30-4.30am and use the standard Octopus GO of about 9p/30p kWh. This suits me fine and I suspect it's not worth the extra cost of purchasing a newer charger due to the lengthy payback.

It would depend on the amount of charging you do. Intelligent Octopus Go is 7.5p off peak as opposed to 9p for GO, you get 6 hours of more at 7.5p as opposed to GO's 4 hrs. Just taking the rate difference of 1.5p and assuming a ZAPPI could be installed for £700 ish you need to charge for 150,000 miles to break even. It's quite as bad as that because your whole house benefits for 2 additional hours or more at off peak rate and your existing charger has some sale value.

 

[Tim Green]

Well I used to work in electronics for a company making induction hobs, so I am familiar with all that stuff....
My charger has a key switch to disable the unit through the control electronics - I just have a relay across that switch. Works fine.
Actually I do agree to some extent with Coulomb that breaking the mains input is not wise. A noisy contactor could cause a series of spikes which could be large.

 

[Coulomb]

The inductor will go through this process 100 times per second during operation, it wont cause it any issues at all.

The inductor's current will ramp between two values as the potential across it varies; it will do this ramping tens of thousands of times per second in normal operation. The problem with opening a switch in series with the inductor is that there is then no limit to the voltage, and the inductor develops a potential equal to L.dI/dt, and dI/dt (the rate of change of current) is effectively infinite.

In normal operation, yes there is a 100 Hz envelope over the normal ramping between two limits. The inductor's current is essentially the mains current, and that is aimed to be close to a sine wave. The problem is in disconnection, which is very different to normal operation.

 

[johnb80]

The inductor's current will ramp between two values as the potential across it varies; it will do this ramping tens of thousands of times per second in normal operation. The problem with opening a switch in series with the inductor is that there is then no limit to the voltage, and the inductor develops a potential equal to L.dI/dt, and dI/dt (the rate of change of current) is effectively infinite.

Not really, the switch contacts are not perfect i.e. instantly on to instantly off, a small arc will develop effectively slugging the rate of collapse. Furthermore, it's highly likely that varistors will be across the input slugging further any voltage spikes.

In normal operation, yes there is a 100 Hz envelope over the normal ramping between two limits. The inductor's current is essentially the mains current, and that is aimed to be close to a sine wave. The problem is in disconnection, which is very different to normal operation.

Disconnection is absolutely normal operation and steps are taken to protect the charger from any untoward spikes etc as per above.

Not likely to cause any issues at all.

Well I used to work in electronics for a company making induction hobs, so I am familiar with all that stuff....

You would also be familiar with Metal Oxide Varistors usuaully place across the input lines to clamp any untoward voltages.

My charger has a key switch to disable the unit through the control electronics - I just have a relay across that switch. Works fine.

A much nicer but less convenient way for most.

Actually I do agree to some extent with Coulomb that breaking the mains input is not wise. A noisy contactor could cause a series of spikes which could be large.

It is highly unlikely to be an issue, my charger has been working for over 6 years, it uses a relay to switch the output and doesnt (or didnt) manipulate the pilot signal first.