Whacky Hacky: Adding extra DC/DC and DC/AC converters to PDU? (Gen1 Leaf)

[danielsantos]

Hello! I am intellectually gifted person, but it all seems to have come out of the "sanity" stat when my character was rolled. (Thankfully, I'm at least aware that I don't always know what's good for me!) None the less, I have a 2013 Leaf and would rather like to add:

1. a 2.4kW-ish DC/AC converter (120V),
2. an additional 500W-ish DC/DC converter with two or more variable outputs between 12V and 48V
3. a controller for both (probably STM32Fxx or Gxx -based).

And yes, of course I don't want to use the 12V circuit! Is anybody aware of such a project already? Even if it's not for the Leaf, any resuse of existing (and especially tried and tested) engineering would be most welcomed!

For simplicity, here's a quick glossary of acronyms I'm using with references to the shop manual

• VCM - Vehicle Control Module, EVC-20
• LBC - Li-ion Battery Controller, EVB-16
• PDM - Power Delivery Module, VC-12
• PDM cover - the big metal thing you with the Nissan emblem on it when you open the hood

My current thoughts on this are to:

1. Create more vertical space inside the PDM by CNC fabricating either a.) an over-sized PDM cover, or b.) an extender that the existing PDM cover would bolt to that in turn would be bolted to the PDM base. (I'm favoring the later.)
2. Either of the above will have openings to install additional connectors for power outputs.
3. Fabricate a few bus bar extensions
4. Fabricate a few support brackets
5. Find a place to break into the CAN bus
6. Put together wire harnesses for power and data
7. Install that crazy stuff!

Missing from above are two things I haven't figured out yet:

1. How I can dissipate my extra heat to the high voltage cooling system (I'm hoping I can run heat pipes to PDM base where coolant runs).
2. How, or IF, I can work with the VCM to request and report power consumption.
3. A good alloy (or pure copper?) to use for bus bars

Discussion

I believe that doing all of this inside the PDM is the way to go since I already have the open bus bars from the battery, cooling nearby, and I don't need insulation for the high voltage (just a stable support framework).

One would never want to just start using power from the batter unit, because the LBC has a current sensor and the VCM will detect an incongruency and (hopefully) panic, shutting everything down. Also, we never want to (try to) pull more power from the battery than it can safely discharge. I would also want my components to always yield to every other device that might need power (motor, A/C, PTC heater element, etc.)

I haven't yet learned the CAN messages for these systems and I hope that there's a way to tell the VCM that "Hey, I'm somebody you've never heard of before, but I want x current for x milliseconds" and it will allocate it or deny it. I think that this is the very next thing I need to figure out before moving forward much further.

As for cooling, I really do hope I can dissipate all of my heat via heat pipes or such to an appropriate surface. If not, I suppose it could be possible for a PDM cover extension to also house a coolant channel and use the inner surface for dissipation.

The extra DC/DC is related to a number of projects / hacks I'm either planning or already powering via a 120v inverter with ordinary wall-type power supplies. I just want the DC/AC converter so I can use my car for power tools or whatever in a remote location.

Any information, thoughts, criticisms, pleas for me to save myself, and especially references are MOST welcomed. Thank you!

PS: I read somewhere that another possibility is hacking the quick charger port, since it will give you direct access to the battery pack after you convince the VCM that it's really a good idea to trust you!

 

[MikeinPA]

I agree that probably the best way to hack into the main pack is at the PDM.

First thing would be to see if the car throws fault when you pull current from the DC bus bars in the PDM. Pull the traction battery fuse/plug, open the PDM, hook up to the DC bus with a 600 VDC fuse/breaker in line. Then run the DC through some power resistors. When testing the blue 2013 pack after replacing cells, I used this 16 amp breaker and six of these resistors in series to discharge the whole pack (put a fan on those) (charging was more of a pita). The point would be to make sure the car doesn't have issues with taking power at the bus bars in the PDM.

Having verified that, I would see what happens when supplying 400 volts to a DC/DC converter, if you can find one.

If I was doing it, I would look for some way to charge a 48 volt LTO or LiFePO battery bank, and then put the AC inverter on that. A proper DC/DC converter would be ideal.

 

[cornbinder89]

Why would you do it that way and not Via the CHademo? My understanding is there is two way protocol available, so you could build the right "handshake" stuff and just go from there.

 

[danielsantos]

I agree that probably the best way to hack into the main pack is at the PDM.

First thing would be to see if the car throws fault when you pull current from the DC bus bars in the PDM. Pull the traction battery fuse/plug, open the PDM, hook up to the DC bus with a 600 VDC fuse/breaker in line. Then run the DC through some power resistors. When testing the blue 2013 pack after replacing cells, I used this 16 amp breaker and six of these resistors in series to discharge the whole pack (put a fan on those) (charging was more of a pita). The point would be to make sure the car doesn't have issues with taking power at the bus bars in the PDM.

Having verified that, I would see what happens when supplying 400 volts to a DC/DC converter, if you can find one.

If I was doing it, I would look for some way to charge a 48 volt LTO or LiFePO battery bank, and then put the AC inverter on that. A proper DC/DC converter would be ideal.

Wow! What a wealth of helpful information. THANK YOU!

So you just stuck a 120Ω dummy load and drained it right down. I'm presuming that the car was off during this? Otherwise, I would really hope that VCM would tell the LBC to shut off power, since a current leak could mean very bad things.

As far as DC/DC converter, I haven't done much shopping yet and was considering just making my own, as I do a fair amount of electrical engineering for my job as a firmware engineer (but it's all low voltage stuff). I've got a lot more learning to do, but was hoping there is (or a way to make) a DC/AC (bucking) converter without going to DC first so that there are fewer power transistors to reduce both cost and efficiency loss.

What I don't prefer about going down to 48V DC first is that it increases complexity and decreases efficiency because we're first bucking down to 48V and then boosting back up to 120V.

I think I need to do a lot more reading on this part, but again, I don't really need to use off-the-shelf components. If you do a project as open hardware, https://oshpark.com will do your circuit fabrication as a very nice price, and I have no desire to build almost anything without sharing it.

 

[danielsantos]

Why would you do it that way and not Via the CHademo? My understanding is there is two way protocol available, so you could build the right "handshake" stuff and just go from there.

Thank you. I've read a tiny bit about this and I understand that it's a two-way street. But this would also mean that it could only be used while the car is parked. I also recall that CHademo means that you are the charging controller, and I presume this means you become responsible for monitoring a lot of stuff related to battery stability. Again, I'll need to read a lot more.

But if I can't work with the VCM to pull from the main bus bars, then I'll be forced to use CHademo for stuff while parked and the 12V circuit for the rest, which won't make me happy. Also, I'll need to discover the maximum current the for the "12V" (actually 13-14V) DC/DC converter.

 

[cornbinder89]

What the heck do you need 2.4 kw of 120 power while driving? And can you afford the loss of range if you did have it?
If all I needed was a few hundred then I would invert from the 12 volt side of things,

 

[danielsantos]

What the heck do you need 2.4 kw of 120 power while driving?

Well that's not really the question, is it? Not that I mean to be rude.

None the less, I'm feeling like your idea has a lot of value as it could be reusable on many different cars and wouldn't require modifications to the vehicle. It would need settings so the user can dictate a maximum amperage draw, a minimum battery level (where it cuts off) and has a warning when it begins to get close to that value.

But it's a 20A circuit. I'm going to mount a large table saw to the side of my car and run it while driving down the highway to keep other cars from getting too close.

Look, I'm not like "normal" people. I look at a platform and see what it's capable of and THEN I find out about all of the limitations the manufacture artificially imposed upon it and I get agitated -- or some times damned angry, like with "smart phones" demanding all of your goddamn private information. America is stupid as hell for allowing this to become a norm!

Anyway, I see WAY more possibilities for things than most people do so I'm not going to turn this thread into a "why" discussion.

Thanks for your suggestion

 

[cornbinder89]

The thing about using the Chademo, is it leave the car stock, and as you pointed out, could be used on any Chademo vehicle.
I wasn't trying to be rude, just a practical question as to why it would be needed while driving.
If I were going down this road, I would want to keep the car stock, and still achieve my goals. That way, if the car got totaled and/or replaced for any reason, my hard work could be transferred with minimal effort.

 

[BillAinCT]

Just my 2 cents. You can't just throw this together. Engineer it. What are the requirements? Goals? Error conditions? Safety concerns? (If it shuts off HV while driving you're in danger a best!) What things it must do? A wish list is nice but most designs add them only if it's low cost and easy to implement. Then do the design. Check the limiting issues (you mentioned a couple - good!). What else are or could be the showstoppers? Check them. If you design for the maximum that you don't need or will ever use (2400W 120V while driving) why design it that way? For fun? When you could impact your own safely or kill a perfectly fine EV. Especially if it over complicates or adds excessive cost to the design. And yes, this too isn't really the question, so do what you wish and please don't kill anyone!

 

[danielsantos]

The thing about using the Chademo, is it leave the car stock, and as you pointed out, could be used on any Chademo vehicle.
[...] if the car got totaled and/or replaced for any reason, my hard work could be transferred with minimal effort.

Nearly impossible to argue with! Further, this could be a handy product -- makes me wonder if anybody's already making one. I guess the main thing is that you set a min battery level so you don't get yourself stranded.

I used to work construction and pretty much nothing happened until we got power to a pole -- where upon we often cautiously rigged up own own connection to it -- standing on a pallet and with a coworker standing by ready to whack us with a 2x4 in case something went wrong -- ahh, those were the days.

 

[MikeinPA]

So you just stuck a 120Ω dummy load and drained it right down. I'm presuming that the car was off during this?

The pack was out of the car with the lid off while I was replacing some bad modules. Charged all cells to 4.000 +/- 0.003 by paralleling them, and then cycled the pack a few times to make sure that at low SOC the cells all look good. One snuck past me anyway, costs about 2 miles range.

 

[Jsprinkle]

Well that's not really the question, is it? Not that I mean to be rude.

None the less, I'm feeling like your idea has a lot of value as it could be reusable on many different cars and wouldn't require modifications to the vehicle. It would need settings so the user can dictate a maximum amperage draw, a minimum battery level (where it cuts off) and has a warning when it begins to get close to that value.

But it's a 20A circuit. I'm going to mount a large table saw to the side of my car and run it while driving down the highway to keep other cars from getting too close.

Look, I'm not like "normal" people. I look at a platform and see what it's capable of and THEN I find out about all of the limitations the manufacture artificially imposed upon it and I get agitated -- or some times damned angry, like with "smart phones" demanding all of your goddamn private information. America is stupid as hell for allowing this to become a norm!

Anyway, I see WAY more possibilities for things than most people do so I'm not going to turn this thread into a "why" discussion.

Thanks for your suggestion

Wow. Really know what you are worth don’t you?
Well. I am also an arrogant SOB so maybe we’ll get along fine.
Our firm deals in solar power backup and our lab purchased a 2023 LEAF to use the big battery to run whole house backup and related good projects.

The solar industry has many good charge controllers which will take 400vdc and charge 48 vdc battery systems which are at this point pretty standard for many whole house inverters.

Our problem is the handshake needed to convince the LEAF that we are a friend and just want access to the big battery via the Chademo port.

It seems that lawyers in the USA see a real problem with allowing us access. Overseas there is not a problem in many countries but the USA programming seems to disallow such operations even using a 4000$ device purchased from a supplier who sells into Europe and Australia with success.

There were two USA companies promising devices last year and then this year but no results I am aware of yet.

I will gladly partner with a knowledgeable someone to safely hack this lab car if that worthy partner shows up.

Good luck!

 

[cornbinder89]

It seems that lawyers in the USA see a real problem with allowing us access. Overseas there is not a problem in many countries but the USA programming seems to disallow such operations even using a 4000$ device purchased from a supplier who sells into Europe and Australia with success.

There were two USA companies promising devices last year and then this year but no results I am aware of yet.

Could you explain a little more? Are the US cars made (programed) in such a way that prevents two way Chadmeo? or are you saying something else? I am trying to understand. I believe someone here experimented with a V2L system, not sure where they were.

 

[MikeinPA]

The solar industry has many good charge controllers which will take 400vdc and charge 48 vdc battery systems which are at this point pretty standard for many whole house inverters.

These are MPPT charge controllers? Like this https://www.midnitesolar.com/pdfs/hawkes_bay_frontBack.pdf ? Is there a battery input setting for some of these controllers? This would solve the DC to DC converter problem handily, assuming your house system is running at a nominal 48 volts DC. One still needs to protect the EV battery from over discharge, either by accessing the pack through Chademo or possibly in the PDM or the PTC.

An EV battery pack would be a good adjunct to an off grid house, assuming there is already an off grid system in place, and still fulfill its normal function of powering a vehicle. Able to provide 10 or 20 kwh if needed to bring the house battery up. Or being able to dump some excess solar in, although that would likely be best done through L2 charging.

 

[BillAinCT]

Wouldn't one expect that MPPT controller have a minimum input voltage setting to shut down when the input battery is at that set voltage?

 

[MikeinPA]

The MPPT controllers are designed to work with solar panels and find the "maximum power point" of the array at any given moment. A MPPT controller would not be worried about a low input voltage unless it had a specific battery input setting. Some of Midnite Solar's controllers can be modified to work with wind and hydro. Some people have also hooked up batteries to Enphase microinverters to feed AC power into their local grid.

Now, ~400 volt batteries are routinely connected to 400 volt inverters to provide AC power. Several brands out there and of course Dala and friends are connecting these inverters to used EV batteries. But the combination of a ~ 400 volt DC battery going into a solar charge controller, and then charging a ~48 volt DC battery is not something I have heard of.

 

[Jsprinkle]

Could you explain a little more? Are the US cars made (programed) in such a way that prevents two way Chadmeo? or are you saying something else? I am trying to understand. I believe someone here experimented with a V2L system, not sure where they were.

The concept of using the internal battery to power the house or other loads is quite common in other countries and I’ve been looking at it since 2016. We had a LEAF back then and everybody was promising V2H v2g V2l and it happened overseas but not in the USA and I am told it’s because of certain codes and safety regulations and of course lawyers

My understanding is that yes, the internal canbus codes on the American bought leafs are different than the overseas to disallow that very thing again because of lawyers

Nissan probably knows that you turn American white boys loose on something like that we’ll probably kill ourselves and then sue the pants off of them

Not me, though we really want access to that great big battery it cost less to buy the whole car then some brands of off grid batteries of that size a great back up system or delivering water in an emergency charging on Solar back at home and running the night with your car battery.

 

[Jsprinkle]

When Nissan is on board, the devices that are made to interface with that big battery through the Chademo port, use the internal battery gauges and safety protocols provided by nissan in the car

 

[Jsprinkle]

The problem seems to be that they won’t let the USA market have the canbus firmware that is provided overseas

 

[cornbinder89]

I'm fairly sure someone had that working on this board, and I believe it was in the USA. I could be wrong, but I thought he sold the V2L to someone else here.