High Voltage MPPT for DC-Direct EV Charger

Charge Controllers
1

I want to build a DC direct EV charger. Not because it’s practical, but because I think it’d be fun. I know people are working on commercial versions, but there’s no fun in waiting around, and they all want to lock you in to their ecosystem.

Other reasons include off-grid resilience and better efficiency by not going DC->AC->DC. Or imagine an EV charging station in the middle of some area that you can’t run big power to. Panels are getting cheaper by the day. Or even bringing your solar panels with you like the guy doing a solar cannonball right now (or The Martian).

Here’s the high-level plan:
Power board - High voltage synchronous buck/boost MPPT charge controller (e.g. 300-500v, 15a). This will make it very efficient to convert to the ~400V of most EVs (like my Model Y). I haven’t found anything like this that exists voltage-wise, so plan to design my own, starting from the mppt2420hc. I know at a very minimum, I’ll need to source components rated for the higher voltages, like the mosfets and driver ic. And probably several other components that I haven’t considered yet. It’ll be a pretty big change to be honest, but I’m down to figure it out.
Control board - Pi CM4 running Everest open source EV charger software. This will handle speaking CCS to the car and high-level communication like wifi and data logging.
The boards will talk over some protocol, to be determined between CAN, SPI, MOD, I2C, etc. I don’t know the pros and cons of them yet. This will help the power board focus on being safe and not blowing things up or starting fires since there will be a lot of power going through it.

Optional Features that should be possible but are not immediate focus:

  • passthrough to normal inverter when not charging car
  • bidirectional from car (though this should work going to the mppt input of an existing inverter, like my 18kPV)

I’ve been researching a bunch of research in the past couple of months, learning/relearning electronics, and the idea just won’t leave my brain. I took a few hardware classes in college, but I’m mostly a software guy. Still, I think the basic idea should work. Anyone who wants to help would be appreciated. This site’s designs seem to be by far the most organized and hackable as a basis that I’ve found on the internet. I’m planning on keeping the whole thing open source, and I’ll try to keep this thread updated as well.

2

That sounds very exciting. I’m not sure if a synchronous buck converter is suitable for such high voltages, though. It would definitely require a complete redesign of the MPPT 2420 HC.

In any case please keep us updated about your findings and further developments!

3

What makes it less suitable for high voltages? The voltage drop in the diodes for an asynchronous design would be less significant, and a littler simpler to get working, if ultimately less efficient.

Or were you thinking a totally different design, like something transformer based like a push-pull?

4

I am very interested in using MPPT to dump all the PV power directly the load which, as @jakepusateri mentioned can be an EV, an inverter or even a HV battery.

I think it is possible to create a software+hackable MPPT solution where there is only one DC-DC conversion between PV and DC load. This is the cheapest possible way (equipment capital) and also should have the lowest losses. The disadvantage is that in such a system each MPPT can only dump to one load.

I have had an idea in my mind for some time to create a system where the electrical path to the load can be routed using relays. The relays would be switched when the MPPTs are open (not dumping power) in order to avoid arcing. Then the appropriate number of MPPTs would be assigned to the load and start dumping power directly to the load.