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Discussion Starter #1
Hi, Im looking into options for making the standard Chargemaster unit a little smarter. I have one that was fitted in 2017 which has been working fine, I am now however considering getting the octopus agile tariff and would like to have a bit more control. I have read elsewhere on the forum of mods to add openevse functionality, does anyone have any feedback or suggestions.
Thanks
Anthony
 

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Kia Soul EV 2020 64KWh
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Is it tethered or untethered?

If the latter then you could just replace your cable with the one from Ohme with the same connector, discounted price via Octopus - instant smart functionality.
 

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Thanks @DSLRed Its untethered, and the discount with octopus does make it more attractive (I had forgotten about this product).
I do seem to be drawn to an openevse solution though after seeing an example from @andyfras in another thread (didn't want to hijack that thead)
The modified charger is now working with its new circuitry.

View attachment 39553
As can be seen from the top picture, I removed the redundant contactor, 2 connector blocks, current sense transformer, the brown and blue wires (for front panel power) and C132 as it was a suitable place to pick up power. All of the circuitry directly above my 2 boards is unpowered.

View attachment 39561
On the underside, I removed U16 (3.3V regulator feeding processor and associated circuitry), Q7 (bridged to provide mains power to energising relay NO contact), RN7 and U9. Notice the pink wire (about 25mm below the bottom right corner of the (now unused) processor); it goes through a hole (which I drilled) in the board and is the feed directly from the Arduino (via a 2.2K resistor) to the base of Q8 which powers the energising relay (5V), which in turn feeds mains to switch the contactor. Wires soldered across the removed contactor contacts; the lower one also bypasses the current sense chip. Near the top left is a 100k resistor added across R132 in the voltage sense circuit to reduce the 6.4V down to just over 5V, suitable for the Arduino circuitry. The only active circuitry in the middle section is Q8 and D16, both associated with the energising relay.

I wanted to use the front panel LEDs, and found that conveniently they are connected directly to wires in the red loom shown. Unfortunately, I discovered that they were connected common anode, where the Arduino software is set for common cathode. I looked at changing the programming, but decided that it was easier to unsolder the LEDs and reverse them. No other mods were done to the front panel. apart from removing the brown and blue wires, and providing an earth for the LEDs down the red loom.

The Arduino Pro-Mini clone was programmed with Open EVSE software (slightly modified by @yoh-there for the granny cable project). The CP sensing circuit was built on strip-board. Both boards were mounted using sticky pads. For circuit see:

https://cdn.instructables.com/FJY/SU20/GYVDJL3N/FJYSU20GYVDJL3N.LARGE.jpg

I installed the main and front panel boards in my charger for testing purposes, and was very pleased with the results. It boots from mains off in about 3 seconds. It starts charging (ZOE) in about 7 seconds at the full 30A rate.
 

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You could make the Chargemaster smarter simply by adding a wireless switch to the CP connection. You could also add a 16A / 32A switch to Link2, if that would be useful to you.
 

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Discussion Starter #5
Thanks Andy, having a another think about it the simpler approach would probably suffice. The main things I am trying to achieve are to be able to have some sort of automatic charge scheduling and measure the current.
I had thought of using the key switch originally, are there any advantages/disadvantages to either approach being used regularly to suspend the charge?
 

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Oilytin, I suggets you get yourself a copy of the J1772 spec on the net. There's an early version for free, newer ones need payment. Google for "finalsaej1772.doc" should find it; msg me if not, I can email u a copy.

Switching the 16/32A option will probably only get tested by the ECU (brains bit) at the very start of a charge, when the ECU needs to know the capacity of the cable plugged in. As the cable won't change, it's unlikely that swapping 16<->32 will be noticed in the middle of a charge.

Putting an on/off switch in the CP line is being a bit brutal tbh, you're emulating (probably) a sudden power-cut scenario. The nice way to reduce the EVs charging rate is to alter the mark-space ratio of the square wave superimposed on the CP line, ramping the current down to the 6A minimum allowed, then you remove the square wave completely, and that should pause the charge. Resume the square wave to restart charge. This way the contactors may well not open, and if they do, current=0 so minimal wear. Simply chopping the CP at some high-current stage is asking to wear out the contactors & cause a lot of arcing, if the Ev doesn't electronically stop the charge pretty bloody quick.
 

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Discussion Starter #7
So many helpful people called Andy😀
That was my thought, effectivly pulling the plug mid charge.
Will have a look at the doc you suggested and do a bit of further testing to see what effect turning the key switch to off mid charge has (i wonder if that initiates a softer shutdown).
 

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I change the charge rate by switching the PP resistor on my modified plug (detailed elsewhere on the forum); it can be done on-the-fly with no ill effect, so I see no reason why it wouldn't do the same by changing the rate at the charger end.

Switching the CP would signal the car to stop the charge, so should not cause any issues with the contactors in the charger IMHO. The keyswitch on the Polar charger interrupts the CP connection.
 

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Trouble with tweaking the PP resistor is it's a big jump is charge rate, and almost useless if you can only 3.3 kW charge (most Phevs) It's not guaranteed to alter the charge rate during a charge, so if it does change then, this is a bonus! It's there to select max current that the cable's ok for, and the values it gets to choose are something like 13A, 20A, 32A. That's it. There's no super-low setting like 6A that would be great for solar charging, which I'd like. (At least not officially, there was a 6A value kluged in by some mfr, dunno the details, but not generally understood by most EVSEs). My Ampy maxed out at 14A anyway, so reducing to 13A was pointless. I think the 13A setting is for 10A "granny" portable EVSEs, the 20A gets used by 16A EVSEs, and the 32A one by the 32 EVSEs. It's the CP line with the square wave that gives you guaranteed real-time response and infinitely-fine current control right across the range.

The J1772 spec (I think, may be somewhere else) recommends stopping a charge by ramping whatever current you're at down to 6A, then shutting off the square-wave signal on the CP line. The contactors will be left contacting, as the CP voltage is at a steady 9V DC, and at this stage the car can open the contactors at it's leisure, well, I think it has 3 to 5 secs to obey the instruction! What will actually happen is the Ev sees the square-wave disappear = 0A charging commanded, it will then turn off the inverter transistors to kill the charge, and when happy it will then open the contactors at 0A (if it feels so inclined) so minimum wear & tear. If at some stage the plug gets pulled out of the car, the CP line voltage rises to 12V, telling the EVSE the car's gone, and at that point the EVSE will open it's contactors. Again at 0A.

Simply cutting the CP line connection while, say, a 32A current is flowing, is doing all the above, but asking the car & EVSE to do this instantaneously. Yes the kit will survive, coz it's like a total power-fail, but it's generally not a good thing to do to kill a 32A current in full flow by opening the contactors as your first action! Which is what the EVSE end might do; I'd hope the EV will see CP go open-circuit & shut down the inverter immediately. Renault Zoes especially use the motor windings as part of their inverter; suddenly cutting current in highly inductive coils is exactly the best way to generate massive voltage spikes, if you like kilovolts around! Got to be best to do this stuff gently.
 
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Discussion Starter #10
I tried operating the key switch (first time in 3 years) and there is definitely a delay of a few 10ths of a second between the opening the switch and the main contacts dropping out. There also seems to be a similar delay when pressing the button in the car to release the charging cable.
 
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