Fast Charge Mercedes-Benz bclass electric (B250e)

Development and discussion of fast charging systems eg Chademo , CCS etc
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smathermather
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Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

As you may see in another post, I am one of the many victims of the inevitable decline of a Tesla Large Drive Unit. In my case, as you may have surmised from this topic subject, said LDU is in a 2017 Mercedes-Benz B250e. I am fortunate enough to have had a good after-market warranty, and the car may return to me this week with a replacement motor that has been "redesigned". We'll find out soon what that means, I hope.

With that brief summary aside, I have an interest in, long before scratch building an EV, modifying this beautiful little parts box vehicle to be a little more practical for my use cases. Some mods, such as grill blocking and similar are pretty easy, and some are more interesting, like a desire to add fast charging.

To that end, I see two options: put a CHAdeMO unit in the vehicle for a slower fast charge; or take advantage of the 400 volt system as possible to CCS fast charge. My impression is that the former is simpler, and the latter is more difficult, but the potential of a 14-minute 10-80% on that tiny battery pack is a bit tempting, assuming that's even possible.

I've looked at threads on i3-based fast charging, watched a number of Damien's videos with the occasional funny cat video interuption, and am happy to hear my pipe dreams are just that or otherwise. I did, what I think is a thorough search of the forum, but forums for a new user can be a bit harder to navigate, so my sincere apologies if this isn't a novel query, or if it should somehow be lumped in with a different portion of the index.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

The car finally came home with a shiny new (refurbished motor of someone else's heartache core charge really...) LDU. New enough even that it needed a new controller board and looks a bit different to the old one, although I don't have great pictures of the old one, so I'm not too certain about that... . It's been in the shop too long.

At this point I am leaning toward doing CHAdeMO for the time being. I'll likely order the controller from EVCreate https://www.evcreate.nl/shop/charging/c ... ontroller/. Eventually, I'm sure this will escalate to CCS fast charging, but I've only got so much capacity, and it seems that CHAdeMO is the simpler solution

So: concrete question: has anyone read the CAN bus during charging of a B250e or it's predecessor the bclass electric (which is pretty much the same car)? If not, I've got an arduino hat on order, but I might need to chat here as I dive in.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by arber333 »

smathermather wrote: Mon Dec 19, 2022 5:10 am The car finally came home with a shiny new (refurbished motor of someone else's heartache core charge really...) LDU. New enough even that it needed a new controller board and looks a bit different to the old one, although I don't have great pictures of the old one, so I'm not too certain about that... . It's been in the shop too long.

At this point I am leaning toward doing CHAdeMO for the time being. I'll likely order the controller from EVCreate https://www.evcreate.nl/shop/charging/c ... ontroller/. Eventually, I'm sure this will escalate to CCS fast charging, but I've only got so much capacity, and it seems that CHAdeMO is the simpler solution

So: concrete question: has anyone read the CAN bus during charging of a B250e or it's predecessor the bclass electric (which is pretty much the same car)? If not, I've got an arduino hat on order, but I might need to chat here as I dive in.
Why would you need that? Since your car does not have Chademo you will not be able to get any such relevant data.
I have some Leaf msg on EVSE... viewtopic.php?p=44983#p44983
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

Without going full zombieverter, can one add CHAdeMO to any EV?

It’s true I won’t be able to read CHAdeMO specific messages from the BMS. I don’t know what I don’t know: how standardized are state of charge related BMS messages otherwise?
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by arber333 »

smathermather wrote: Mon Dec 19, 2022 6:16 am Without going full zombieverter, can one add CHAdeMO to any EV?

It’s true I won’t be able to read CHAdeMO specific messages from the BMS. I don’t know what I don’t know: how standardized are state of charge related BMS messages otherwise?
Hm... in theory yes.

I have added a "chademo pod" to my conversion. This pod should be self sustaining. A small AC-DC LED driver makes 13.6V 3A supply for electronics and contactors. My pod integrates ISA shunt and Leaf VCU with 2x contactors. Good GND connection to a car is mandatory.
You need a way to connect to main DC cables. Is there a way on your car? I used VW Golf GTE cable and socket to connect to DC.
https://leafdriveblog.wordpress.com/202 ... ademo-box/
https://leafdriveblog.wordpress.com/202 ... o-exhaust/

Caution! The only thing my pod is lacking is charge disable function. There is a risk i could drive away from EVSE and pull a cable behind me. :twisted:

EDIT: There is another thing, BMS related. On my wifes Ampera i pulled DC cables from battery into the trunk so i can have direct access to battery. I tried to fast charge directly and indeed i could fast charge OEM car!!! Its just that BMS would throw a fit. Next time when i wanted to start the car BMS would not let me. I had to access main VCU and erase the errors there to be able to drive.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

Ok, this gets me closer (and a fun blog to read and return to). Thanks!
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by asavage »

Smather, your MB B250e has the same Tesla-supplied LDU (more or less) as my 2014 RAV4 EV -- your DU has one different PCB than mine on the inverter side, but otherwise it's pretty much the same.

As my battery pack is also a Tesla-supplied unit, with the contactors inside the pack are controlled -- sorta -- by the Tesla BMS that also resides inside that pack assy., I do not yet know how to instruct the BMS to energize the main contactors aside from sitting in the driver's seat and pressing the "Start" button. That brings up the HV system (closes the Precharge and Main contactors) and then I have access to HV outside of the pack, which in typical Tesla fashion is an 860 lbs metal box that has its lid glued on, and then is bolted to the bottom of my vehicle: not a lot of fun to open up, and not really useful to open up anyway . . . read on.

The reason for this preface is that I am in process of going the BMW i3 LIM route and adding CCS to my vehicle, and I think you'd face the same issues retrofitting DCFC (either CCS or CHAdeMO) to your B250e, as the salient parts are Tesla Model S-era in both cases.

If your Tesla-supplied battery pack is engineered similarly to mine -- and I think it's a good guess that it is -- then you will not have easy access to the contactors to add-on your own DCFC wiring, and as you need the Tesla BMS up and running anyway when charging, you may consider that the straight-line route is as I described above: you can only DCFC when the vehicle is in "Ready" mode -- the BMS is working, the battery heating/cooling system is active, circulation pumps can operate, radiator fan control is active, etc., and Tesla handles it all.

The obvious downside is that you can't easily lock the car and walk away whilst charging. How do I know this?

There's an outfit whose name I will not mention, that since 2015 has made a CHAdeMO aftermarket add-on "kit" to add CHAdeMO charging to both the Gen2 RAV4 EV and the US-version of the MB 250e. It was/is nicely built to near-professional standards, runs USD$3k to buy, can be installed in a day, has an instruction manual for installation, etc. Unfortunately, the company is run by a jerk, the firmware cannot be field-updated, and the early firmware did not enforce a 125A current limit that its wiring required, which wasn't a problem when all the available CHAdeMO stations only supplied 50kw, but then higher-power CHAdeMO stations became more commonplace, and suddenly we had melting wiring, fire hazard, etc. And that company stonewalled fixing it for a looong time. Old units can have their firmware upgraded if you mail it back to them . . . not a trivial task, and the way they handled the situation makes me think I'd not spend money with them, period.

That is only the most egregious example of their behaviour.

And all of THAT is preface to say: the way that that company's "kit" works is precisely the way I've described: you "start" the car, then initiate DCFC, and it works. But you can't lock a "running" car from the outside (so far, anyway).

Whether CHAdeMO or CCS, the same problem exists for you and I, with our Tesla-OEM EVs: we can either work with the existing system (ie let Tesla's hardware and software control the contactors, battery conditioning, fans, etc.) OR we can hack it so that we do the control, and that means a lot more wire, and probably adding our own BMS.

See the problem? For an EV conversion or from-scratch vehicle, these problems and decision points don't exist, but we have niche vehicles.

I'm about USD$1k into CCS hardware here and am still skirting the issues, circling around them, but I have to say . . . letting Tesla manage the non-charging stuff is definitely the straight-line solution. And, whether you go CHAdeMO or CCS, I don't think one is "simpler" than the other.

---

I have a fantasy of being able to get the Tesla bits to turn on, via hardware trickery plus CAN, and have the rest of the car "off". We know it can be done, because it does exactly that when we AC charge now. I have not begun actually looking into that, because for me that's a "nice to have", and not a dealbreaker feature. I will be happy to have the DCFC parts in place and working first . . .

  • Charge port
  • DCFC contactors
  • HV cables to DCFC contactors
  • HV cable from DCFC contactors to battery pack HV point
  • BMW i3 LIM
  • Voltage sense board that LIM requires
  • ISA IVT-S current shunt that ZombieVerter board requires
  • ZombieVerter to run the LIM -- or possibly port the ZV code to other hardware
. . . and, once DCFC actually works, then I can move to the next phase.

Your MB B250e would need that same list if adding CCS; for CHAdeMO, substitute Johannes' CHAdeMO board, and drop the LIM/V-sense/ZV, and maybe the ISA IVT-S . . . but it will still not be "easy", IMO.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

Sorry for the delay in response. Traveling when this came in.

This is a fantastic summary and answers that fundamental question I couldn't wrap my head around.

> we can either work with the existing system (ie let Tesla's hardware and software control the contactors, battery conditioning, fans, etc.) OR we can hack it so that we do the control, and that means a lot more wire, and probably adding our own BMS.

It sounds like your route is the only real route. I've been trying to understand how the CHAdeMO adapter that shall not be named works: now I get it. Other than vehicle lock, it seems quite sensible. Also, my son managed to lock my car while it was on a few weeks back. Took a physical key to get back in. I'll have to find out what he did... .

And if the complexity is the same in our case to swap in CCS or CHAdeMO, then CCS it is. This is amazing. Thank you.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by arber333 »

smathermather wrote: Tue Mar 07, 2023 12:12 pm Other than vehicle lock, it seems quite sensible. Also, my son managed to lock my car while it was on a few weeks back. Took a physical key to get back in. I'll have to find out what he did... .

And if the complexity is the same in our case to swap in CCS or CHAdeMO, then CCS it is. This is amazing. Thank you.
I think lock is not a problem as you wont spend a long time on ccs. 28kwh in like 20 minutes as you dont usually charge totaly empty.
Real problem with oem cars is to immobilize it for charging. Here i would recommend to add a simple line from charge socket PP pin to CCS add on chip which would then pull it down. In effect the same as with L2 evse.
This way you prevent your wife/daughter driving off with CCS plug connected. It happened before you know.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by asavage »

Yeah, our packs are not so large that DCFC at ~50kw is going to take a long time (the RAV4 EV pack is ~38kwh).

While locking the car whilst charging would be nice, it's not a deal-breaker, and I'm thinking this can actually be fixed; it's just not high on my list right now.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by asavage »

arber333 wrote: Tue Mar 07, 2023 2:57 pm Real problem with oem cars is to immobilize it for charging. Here i would recommend to add a simple line from charge socket PP pin to CCS add on chip which would then pull it down. In effect the same as with L2 evse.
I've started a Wiki page about the Tesla GEN1 OBC, which is the unit our RAV4 EV and MB B250e vehicles use.

Of note, I've identified the "drive inhibit" pin on the OBC.

https://openinverter.org/wiki/Tesla_Model_S_GEN1_Charger
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

asavage wrote: Wed Mar 08, 2023 5:24 pm
Of note, I've identified the "drive inhibit" pin on the OBC.

https://openinverter.org/wiki/Tesla_Model_S_GEN1_Charger
Ahh, the last little piece falls into place... . That's excellent, thank you.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

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asavage wrote: Wed Mar 08, 2023 5:24 pm I've started a Wiki page about the Tesla GEN1 OBC, which is the unit our RAV4 EV and MB B250e vehicles use.

Of note, I've identified the "drive inhibit" pin on the OBC.
Yeah . . . no.
With that line disconnected, I can both charge OK (and cannot drive away) and when not charging can drive. While the voltage level on that wire does change when an AC nozzle is inserted, mimicking that manually does not prevent drive-away (in my driveway testing). I put a 'scope on it, and it's not PWM, just level shift.

ATM, I've no idea what that wire is doing, at least in the RAV4 EV.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by smathermather »

Wacky. Glad that somehow an accidental drive-off isn't possible anyway.

I haven't gotten time to get back to this project yet. The car is too busy being a daily driver to return to project car status, in combo with a since acquired '22 IONIQ 5. But it does have excellent new tires that are not run-flats.
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Re: Fast Charge Mercedes-Benz bclass electric (B250e)

Post by asavage »

I've left the wire disconnected, and I've actually driven several errands since, over 100mi., and no errors, no problem charging, nothing.

I have no idea of this wire's purpose.
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