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Hyundai Ioniq 28
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Discussion Starter #1
When a car is pre-heating, does it draw its power from different ‘pins’ in the charging cable or is it just the same as charging?

the reason I ask is that I can set a ‘don’t charge if over XXp/kWh’ and the charger won’t charge the car if the rate is above that threshold however when the car goes into pre-heat mode, it ignores the max cost per kWh and just heats the car up.

I’m curious as to how the charger knows the difference.
Thanks.
 

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Ampera aka IGOR
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AFAIK same pins will supply the power. I don't know if you would be able to set a secondary higher threshold during the pre-heat session?
 

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Discussion Starter #3
To be clear, it’s ALREADY doing it. It pre-heats absolutely fine at the higher rate. And I want it to do so even though it is above the max threshold.
I’m just curious how it knows to let it pre-heat but not to charge.
Thanks.
 

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There is a nice simple answer to the question posed - a wall charge point (EVSE) cannot know whether a car is charging the battery or just pre-heating. :)

There is nothing in the J1772 protocol that would allow this to be distinguished. In short, the EVSE advertises to the car the maximum amount of power it is allowed to draw (this can change dynamically during the charging session which is handy for things like load sharing between adjacent EVSE's, or varying the amount the car is allowed to use based on solar generation) and the car tells the EVSE when it wants to draw power, which causes the EVSE contactors to close and supply AC voltage.

Once this happens the car is free to draw anywhere from zero watts to the maximum the EVSE says is allowed, at its discretion. Whether that goes into the battery or heater or both is incidental and the EVSE has no way to know, nor does it care, as long as the car doesn't draw more than the EVSE says it is allowed to.
 

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Discussion Starter #6
Thanks.
I set the max cost per kWh in the app.
It’s the EV.energy app to control my Rolec Smart charger.
In which case it ‘may be’ that when I also say have my car ready by X o’clock, the app applies logic that in the half hour before X o’clock, it will let the car have power as it knows it will probably be pre-heating.
I can’t think of any other explanation whyit lets power get to the car when it’s above the maximum allowed cost.
 

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More likely that it thinks that it has failed in its job to achieve the desired charge and gives the car as much as it asks for up to the cable/car limits.
 

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Discussion Starter #8
But that doesn’t make sense. The car would be asking for charge all the time if it wasn’t full but the charger won’t supply any power as it’s over the max cost threshold.

It’s only come pre-heating time will it supply any power and exceed the threshold.

If the car can’t tell it that it’s for pre-heat, it must be logic in the app that allows it to exceed the cost threshold based upon the app knowing when to have the car ready.
 

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You say you've set ‘don’t charge if over XXp/kWh’ and also 'have my car ready by X o’clock' If I've understood right.
What exactly do you mean by "ready" ? If you mean "fully charged" than that sounds to me a much higher priority requirement than the first one, which is more-or-less saying "try not to charge if it's expensive, but go for it if the price is less". The cost saving by keeping off he highest price leccy is only going to be a few quid at most, but the cost of not having your car charged could be huge, if you miss that interview/concert/operation as a result.
 

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Discussion Starter #10
You set car ready by X.XX and it will do that. In this scenario it will charge to 100%.

You can then add another (in the advanced settings) setting stating max cost of Xp per kWh. This is absolute and if the price is above that, no charge given. On Octopus Agile that means some 1/2 hours you get charge and some 1/2 hours you don’t (prices change every 1/2 hour).

Lots of disclaimers saying if you set this, the car will not charge if price is above the threshold you set.

Therefore it’s all about user choice. I set max pence per kWh. Worst case, it it ever went t*** up, I’m 10 miles away from a Rapid.
??

Below is tonight’s setting.
128653
 
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