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Discussion Starter #1
I have made my own charger for my leaf using a microbit , an A to D convertor and EVSE wallbox controller to maximize usage from my solar panels

I measure the time between pulses from my FIT meater to calculate wattage available, this in turn generates the required voltage to the EVSE to charge the car at the appropriate rate to match solar generation.

At the moment I have set the minimum charge current at 6amps

The question is what happens if i set a lower level, will the car pause charging or will it switch off

I dont want it bleeping and clicking every time a cloud comes out
 

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No doubt you've looked into the J1772 spec - there's an ancient-but-presumably-basically_ok version knocking around on the web, e.g.
https://www.sae.org/standards/content/j1772_201001/
and I think you can get the J1772_201710 for free. Or hunt for finalsaej1772.doc .

If you cut the frequency below that for 6A then I think the car's entitled to regard that as an error, and throw a wobbly. Expect it to say something like "Unable to charge" on the display.
What I think you have to do is stop the oscillator signal, i.e. cut out the square wave, while maintaining the CP voltage at the 6V (or 3V if fan reqd!) level showing everything's connected up. Then, when the sun comes out, & you judge you have enough free leccy, or have to charge anyway coz you're in a rush, then set the oscillator to 6A, and slowly crank that up over say 5 secs to whatever amps you're letting through.

Agreed you don't want to completely stop & restart the entire charge session; that's going to put more wear on the contactors I think, plus in my car, it beeps every time a fresh charge session is started up!

The J1772 also allows for 120V charging, presumably all the other signal stuff remains as-is, so whether it's possible to optimise solar even more by switching to a 120V AC supply I don't know. Maybe Evs won't like this if you try it on the fly, but could be fun finding out!!!
 

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Discussion Starter #3
Thank you, i remember now, looking in the manual instructions for the EVSE it does have this mode, will have to try it and see how it behaves.
 

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FWIW I've today had a play with the Viridian Mainpine fitted into my Rolec 32A charger. I'm able to use an AD8400 digital pot to set the allowable current anywhere from 6 to 32A in steps of about 0.2A. CPU I'm using is a NodeMcu ESP8266 board with built-in wifi, and I also have a current sensor input which I intend to use to measure actual current being drawn by the car - this will be useful info if I ever want to have 2 cheapo chargers each nominally 32A, working together to charge 2 EVs but the house can only supply max 32A between them. So lots of scope to prioritise/share etc without spending a fortune on fancy new chargers.

The mainpine doesn't have, as far as I can see, a "pause charging" mode, so I've intercepted the CP line and using a DPDT relay can redirect the car end, and the ECU end when I want to pause charging. For the car end, I feed the car with a 12V through a 1k Ohm resistor, just as if it was the ECU connected but not yet supplying a pwm signal to indicate the amps allowed. For the ECU end, I connect the CP to a diode + 2740 Ohm resistor,simulating an EV that's plugged in, but hasn't yet signalled that it wants some current please.

My Ampera charges at about 14A. If I apply my "pauser" circuit while at 14A, the car abruptly stops charging, and lights up the "Unable to charge" message & gives me an EML engine warning light! So this is obviously rather a brutal thing to do, and should be avoided!

If instead I set the Mainpine to charge at about 6A (I used a 200 Ohm control resistor), and then apply the "pauser", it works much better! The Mainpine doesn't open the contactors in the Rolec, which are noisy clunky items, so that part stays nice & quiet & well-behaved. But the Ampera obviously doesn't expect the charger to pause the supply of current, so thinks the entire charge session has come to an end, and it stops the charge at its end. I'm pretty sure the contactors in the Ampera end do open, as there's a bit of just-audible clicking under the bonnet somewhere. Then when I stop my pauser circuit & switch the CP to go straight back from Mainpine to the car to resume the charge, the car sees this as a new charge session, starts charging, and beeps the horn to tell me it's just started charging!

This is a bt of a bummer. I was hoping the car wouldn't open its contactors & stop completely, as it's the restart wih the accompanying horn-beeps that will drive me up the wall! So I'll now have to investigate how to isolate the horn. I think someone's done this for the Ampera, somewhere in these threads; will be a hunt to find it again.

But the good news is that in principle it's possible to add a simple circuit + logic to the CP line of a charger, at least one that you can control the output current to, as you want to ramp the current down from wherever to 6A before doing the pause-charge stuff.
 

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Discussion Starter #7
I guess different cars will behave differently, iv not tried my EVSE wall in pause mode yet on the leaf, i may get time later when the sun goes down, I think the instructions say at 5a the EVSE wall box it will go into pause mode , we will see.
Be interesting to know if anyone has the zappy what happens when charging is paused ??
 

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I've now made up a Horn_12V_Fuse interceptor circuit, so the horn in my Ampera isn't going to do the annoying beep-beep at start of charge any more. Circuit will be installed & tested this evening I hope. The fuse in question is in the very rear of the car, presumably as that's where the 12V battery is, and the horn control stuff has to be powered up the whole time, as it might be needed for warning toots if someone tries to nick the charging cable etc. My son suggested finding something in the boot that's only powered on when the car is properly on, and we found the DAB radio decoder box in the back as well. This has 12V permanently just like most of the car, but rather nicely there's a 2.5V pin on the edge that's switched by the ignition. So that's going to be my trigger to turn on a small mosfet, which in turn powers a relay, which in turn is in series with the the 15A fuse for the Horn circuitry. Job done I hope!

Once that's tested ok, with my pauser circuit fitetd to the Mainpine, I'm ready to start hacking the code to interact with the rest of the home energy monitoring & control stuff my son's cooked up! :)
 
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