Quick Charge Mod - CH4D3M0

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Getting ready to re-check everything to make sure it's in the correct spots before I start putting power to it

[Heima]

I know that is a breadboard, but it looks like a spagetti board.
Fingers crossed!

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Garlic bread board

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Tested that circuit with one of my "new" ADM chips and saw NOTHING coming out of the CAN pins. I'm going to desolder the known good chip to test this circuit again but, given the difficulty of sourcing that chip, I've ordered high speed optocouplers to use with a regular CAN transceiver.

That ADM3052 isn't crazy special, it just has optocouplers built into it to be a single chip solution. It's pretty clear Sefs wanted as many pre-fabbed parts as possible, so I certainly don't fault the choice.

With the change away from the ADM3052, all of the components will be through-hole form factor, so it should be possible to set this up on a proto board like this one:


The shipment of components would have been here Thursday, but apparently UPS destroyed the package. I'll continue to keep you posted. That package also has a bistable solenoid to use with my EVCC to test CCS charging.

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Got my new chip and the high speed isolators. Been making progress setting up the new circuit and have learned some interesting things along the way.

If the Rx pin on the Due isn't pulled high, it will not output on the TX pin. That lead to a bit of head scratching. Basically it thinks a higher priority device has control of the bus and it's waiting for it's turn. Might actually be why I wasn't getting output from the other chips. I'll have to re-check.

The lowest speed the CAN spec supports is 40kbit/sec and that's confirmed as the lowest bitrate that still gives output from the Due. Building and testing at low speed since I'm using an Arduino as an Oscilloscope and it maxes around 15K samples/sec. I can't view the waveform in full detail, but I can at least see the frames.

I had hoped I could avoid needing to to use transistors to undo the inversion that happens through optoisolators, but that doesn't look workable. I was able to drop them from the monitoring isolators since I can invert the logic in SW, so the count hasn't changed.

Maybe, just maybe, I'll have this ready to try this weekend.

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Alright. Good news and bad news. Bad news, I don't have a final version of this circuit working.

Good news, I now truly know why. Turns out the original power supply in the circuit I documented and traced - the one that says +DC In, -DC In, Ground and +5V - is actually a 12V to 12V isolated supply. That meant the ADM3052 was getting 5V when it expects 7+, so it was never enabling CAN output to the charger side.

Only fried 1 supply figuring it out.

That means the original version of the shield could be made to work with a new rev and an updated supply chip. Not sure how I'm going to proceed.

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So, work continues. After realizing I needed to get a 12V source to drive a relay, the contactors and the CAN chip, it dawned on me just how much power that would require. The contactors alone need ~16W with the 12V relay and CAN chip adding on top of that. It's not an excessive amount of power BUT the Arduino Due has a 1A diode on the input - meaning I would either need to have some parallel 12V hookup that bypassed that or risk burning that diode out during use. Past that, 15W+ isolated 12VDC-12VDC supplies are not cheap or particularly compact.

I managed to get legitimate access to the CHAdeMO spec documentation and confirmed that pin 2 of the charger connection is required to be able to provide up to 2A of current at a nominal 12V. That gives me a budget of 24W that does not need to pull from the car at all, meaning I can get away with a far smaller supply.

But it gets better. Turns out the optoisolator components are not a strict requirement and the isolation test is actually just done between the positive and negative DC conductors to ensure it is not at risk of arcing/shorting when it ramps up current. Obviously that would be bad. The spec explicitly notes that the optoisolators shown in the reference circuit can be replaced with transistors or relays as needed. Optos are still often used to help with noise and level mismatches but are not strictly required.

So with all that said, I may be able to drastically simplify things on this design. No isolated supply, no difficult to source isolated CAN chip, no optoisolators to support a non-isolated CAN chip, no optoisolators on my control relays, no optoisolators on the monitoring pins. Conceivably, I might even be able to drop 2 of the relays, which makes this whole thing WAY easier to build.

So, keep an eye out, a new minimalist rev is coming.

[Heima]

Good Luck, Hope you can get it all optimized with minimal parts count.

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Yeah, that looks simple.

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This is further than I've ever gotten with anything but the original hardware/circuit

24 parts total. All easily sourced. Going to need to bring along my laptop and CAN sniffer to monitor what's going on. Possibly write in some extra debugs on the Arduino program to track the process. It "started" the session but didn't actually start sending current - though the current requests come from the car side.

If nothing else, I have to make sure that it's not just shutting down the CAN output - this chip will stop transmitting if it doesn't see any other activity on the CANBus. I'd hope the charger keeps sending frames but if it does not, I might need to make some more changes.

Edit: I need to remember the Due runs 3.3V I/O. I'm going to smoke my CAN1 RX pin without even realizing. So, add 2 resistors to the part count...

Edit2: Confirmed I did NOT kill my secondary CAN RX pin. I now have a voltage divider on that output from the CAN transceiver and I'm just sending raw 3.3V to the TX input since that is high enough to read as logic high for 5V.

This is what I'm working with currently: