Project VW Cadd-E, Leaf/Volt/Mercedes + Mk1 VW

[vwbrady]

What kind of 3d printer are you using to print those housings?

the cheap ole original Ender 3. Filament is ASA, my favorite and perfect for functional parts.


Well it fits nicely on the battery. Now just need to finish soldering on up and test it on the first module.

[RetroZero]

Neat job

[RetroZero]

Were the batteries you bought from accident Vehicules? Anyway of controlling if there are faulty cells?

Sorry for asking, re-reading your posts and found the answers. I can get my hands on a few faulty batteries. Don't know why they are faulty, so will get an icharger or something to check cell voltages before committing. I like your progress and will probably piggy back off lots of your work.

[vwbrady]

Were the batteries you bought from accident Vehicules? Anyway of controlling if there are faulty cells?

Sorry for asking, re-reading your posts and found the answers. I can get my hands on a few faulty batteries. Don't know why they are faulty, so will get an icharger or something to check cell voltages before committing. I like your progress and will probably piggy back off lots of your work.

so these batteries had a piggy-backed DC-DC converter. I believe that, or maybe the BMS, went bad and the service process was to just change out the entire assembly. So the cells are likely totally fine, I checked voltages when they arrived and all was good. i'll be cycling them in my truck as soon as i get my frankensteined Tesla/SmpBMS system finished.

[vwbrady]

BTW i still have 8x of these mercedes modules in my garage (≈7kWh). As well as just picked up 6x BMW i3 modules (≈12kWh) that were a good deal. For future projects i guess!

[RetroZero]

You're in the US from what I see, so shipping to Europe would be costly. I'm looking into how to get some MB modules here. With legalities here, I need to find the best solution for 15Kw in terms of weight (and size). Phev pack would be more space saving and less 'diy', but I would like to test at around the 380v mark and see performance etc before committing.

[vwbrady]

yeah, the Merc hybrid modules are ok but certainly not the most volumetrically efficient @ ≈7 kWh.

The BMW hybrid modules (and i3 i believe) with their native BMS boards is a great way to go for around 12-15kWh. They are compatible with Simp BMS which makes it an easy plug and play with BMS.

[m.art.y]

changing my BMS strategy. Was intending on using the Nissan Leaf BMS, but have since decided to go the Simp BMS + Tesla route.

Hi, wonder if you Tested this BMS solution already and how it is looking

[vwbrady]

Hi, wonder if you Tested this BMS solution already and how it is looking

I've just finished wiring up the secondary module boards and am just waiting for more 4p Deutsch connectors (didn't plan well :\)

I hope to take one out to the truck later today and connect to a module to see what happens. I will report back.

[vwbrady]

I got one 12s module hooked up with 2 Model S bms boards. The error was set because I had the series cell count wrong in the SimpBMS settings.

Now to make a larger wiring harness.

[Bratitude]

awsome! this is such a good budget solution.

[vwbrady]

awsome! this is such a good budget solution.

I agree!, though it's been a lot of work getting all battery modifications, soldering, and wring done.

If I was using a SimpBMS supported charger and batteries, I would be in a cleaner situation but for a lot more $$. But, I now have more custom work to integrate the cheap Gen 2 Volt charger.

For now i've left out temperature sensing, since I really don't plan on stressing these batteries. I may go ahead and wire one of the built in thermistors, then play with the Steinhart-Hart equation in the code to get them reading correctly.

Baby steps, i say.

[vwbrady]

Adding some detail about connecting to the model s/x secondary boards.

Tesla uses a board-to-board JST JL connector (pdf attached) for the cell taps on these gen 3 boards, which means simply buying the connector and wiring it up yourself isn't really a thing. Tesla does this by using a ribbon cable to a small flying PCB with the mating connector mounted to it. I guess you could make small PCBs for the connector then connect to that PCB, but that's a lot of work to make a connection. you could also potentially cram some same-pitch connector in there, but it will require cutting.

A lot of times im attempting to do something that's actually contrary to my goals . in this case I stopped trying to source connectors and just jumped straight to cutting and soldering 176joints. This makes the most sense because it's free, and I don't need a connector in this location at all - in fact it's kind of a bad idea considering my implementation; connector to wire to connector to wire to cell all within 10" makes no sense.

my soldering setup which made this relatively easy.

final product:

[vwbrady]

and the jst connector for the temp sensing:

Part number: PAP-04V-S

[vwbrady]

BMS boards mounted and cell taps connected. Next is power and comm harness. Im currently top balancing all the cells so i'll need to get this thing out on the road soon and burn off some energy to empty the battery a bit and so i can start testing charging.

reminder: 8x Mercedes 12s 875Wh hybrid modules. 2x Model S BMS boards on each.

[RetroZero]

Looking great, well done for a good effort.

[vwbrady]

Looking great, well done for a good effort.

thanks Retro!

I'm liking your Prius implementation . I have a gen 3 prius inverter sitting on the side for some unknown reason . imagining an awd system of some sort using Mitsu differentials. But i don't have access to those over here in NA

I also have a full model 3 rear drive unit and subframe sitting around...

Here is my cabby:

[RetroZero]

Thanks, I love what you are up to. I am trying to source 6 mercedes modules for a first attempt into battery management etc, with hopefully your bms setup . In the meantime, teething problems getting this running is frustrating but worth it.

[vwbrady]

Were the batteries you bought from accident Vehicules? Anyway of controlling if there are faulty cells?

Sorry for asking, re-reading your posts and found the answers. I can get my hands on a few faulty batteries. Don't know why they are faulty, so will get an icharger or something to check cell voltages before committing. I like your progress and will probably piggy back off lots of your work.

So I did purchase the batteries not knowing why they were warrantied by Mercedes, so it was a little bit of a risk. But of the 16 batteries that I got, they were all at 3.86V/cell. So it had to be something with the BMS or DCDC that was part of the little assembly that went wrong. Granted, I haven't cycled any of them yet, so I could still yet find a problem.

[RetroZero]

Think it's to do with the bms, let's hope those cells are all good. Next is a cell reader of some sort.

[vwbrady]

I wish the SimpBMS had a screen that showed individual cell values. I may try to create one. would be nice to actually see a histogram and voltage of all 96 cells like LeafSpy does.

[vwbrady]

Been doing some shake-down drives in the Cadd-E. Need to burn some energy out of the pack so I can start testing the charge system.

Had a chance to get most of the Radwood fleet (+wife photobomb) in one image. ❤

[vwbrady]

We have BMS success!

After frustratingly replacing 2 tesla module boards, it's all working

now to get a current sensor input so i can actually count Wh

[RetroZero]

Bravo vwbrady!! Looking good.

[vwbrady]

BMS notes:
Using 16 model S/X module BMS boards was actually kind of a lot of work. I would say it's only something you should consider if you need a battery form factor that you can't get with a compatible BMS. I'll say this was my case to make myself feel better

Here is a summary of the work required:

Batt side: cut out all native BMS content, design and order busbars, sand each cell tab so I could solder a cell tap, then add a 12p connector (leaving main + for a ring terminal). This added up to about 12 hours of my free time over many months.

BMS side: find and order 16 model S/X boards from a source that doesn't want insane money for them. my V3 boards had the weird JST board to board connectors so I went ahead and cut all those off - which caused a blister on my hand!. then cut 4+7x16 = 176wires, strip them, set up a soldering station and add all wires to the BMS boards. Then design and print 3d enclosures for 2x boards for each 12s batt module. add 12p connector to battery cells and HOPE you connected everything correctly. In my case I had a 2 boards that were just not right. one wasn't communicating at all, and the other was reading a cell 700mV low! All this was easily 20-30hours of work.

Finally after running RX/TX and power wires to each module I was "done". Still need to integrate my charger somehow.

I have another 8 of these batteries, so would I do it again? ... maybe.

Costs
batteries: $100/ea + shipping = $900
custom copper busbars: $300
BMS boards: $24/ea = $384
Simp BMS: $500
Wire/Connectors: $80
printer filament: $15

Total $2180 for the complete 350V 7kWh system.