[NoviceAttempts]

'69 Karmann Ghia Conversion

I posted almost 2 years ago about my conversion plan. To make this Electric:

https://www.diyelectriccar.com/forums/showthread.php?p=808817#post808817

Spent some time saving up money and looking at my options. I really liked what I was seeing out of EVWest as far as resources and builds; and selected them as our primary part supplier. We went with their AC-50 kit and we're going with 10 Model S battery modules. This completely blew the budget I was originally aiming for, but I think I'll be a lot happier in the long run.

Component list:
Motor: AC-50
Controller: Curtis 1238-7601
Charger: Elcon PFC2500
DC-DC: Elcon 500W
Battery Pack: 10- Tesla Model S Modules 2p5s 53kWh @114V

I've received essentially all the parts now and have already started with some things, so I am on my way.

We are doing some restoration work at the same time as the conversion. I've already rewired the whole car with a brand new harness. Removed an aftermarket dash and welded in a replacement donor dash from a '70. Changed all the lights to LEDs. Swapped the straight shifter with an older bent bar(we're short).

 

[NoviceAttempts]

Progress is being made slowly but surely.

Before ordering everything we made a set of mockup batteries to make sure everything will fit where we need it to. It's pretty close but 5 modules will fit both in the frunk and in the rear cargo area for a total of 10 modules giving us a 53kWh pack. The picture here works but isn't optimal, we are going to recess 1 module into the gas tank cavity with 2 more modules stacked on top and another 2 stack adjacent to it. We could not find an arrangement that allowed us to keep the spare unfortunately.

We got the motor prepped with an adaptor, and the old flywheel and clutch mounted.

Installed the motor in the car. This was so much easier than getting the old engine out of the car.

After the motor was in We cut some marine board to fill the gaps around the motor and let us mount other components like the controller cooler and dc-dc converter. We got the charger mounted above it. I've got a problem here though. I can't mount the charger any lower or it would interfere with the controller input terminals, but even where it is it prevents the deck lid from closing all the way. It's so close, I'm leaning towards shaving the aluminum fins down a bit just enough to get it closing.

Finally we've gotten the rear cargo area prepped and the rear battery pack installed. This was a huge pain as I built the box with 2 modules installed to reduce the bending required on the marine board we used to secure them, so that's over 100lbs balanced to the back that we had to shove into place before loading the rest of the batteries. I'm thinking I probably should have offset each module just enough so I could wire them after installation, but that would have probably made the box slightly less structurally sound and would have cost quite a bit more.

 

[Boxster-warp]

Hello
Wunderfull Car.
You have Place in the ghia for 10 Tesla Model s Moduls ,wow
Then the rear seats are out of the car or?
Greetings Boxster-warp

 

[NoviceAttempts]

Hello
Wunderfull Car.
You have Place in the ghia for 10 Tesla Model s Moduls ,wow
Then the rear seats are out of the car or?
Greetings Boxster-warp

I was actually pleasantly surprised at how much room there actually is in this car. 5 modules just fit behind the rear seat so that stays, and the look of the car remains stock.

The only things I lose are: ALL cargo space and the spare tire.

 

[Boxster-warp]

Hello
Great, did not think that there is so much space behind the seats.
In the front trunk also fit 5 modules? Then the ghia has more space than the Classic Beetle.
Karmann Ghia is a Wonderfull Car.
Greetings Boxster-Warp

 

[electro wrks]

I hope you've read these threads on this forum:

https://www.diyelectriccar.com/forums/showthread.php?t=175730

https://www.diyelectriccar.com/forums/showthread.php/working-tesla-packs-179361.html

The Tesla modules are not to be trifled with when it comes to stacking them, using a BMS, isolating individual modules, and in the event of a fire; directing flames and hot gases away from the passenger compartment.

Older lead acid and safer lithium battery types have much less of a fire hazard than the type of cells used in the Tesla modules. Please don't be as foolish as the DIYer in Canada, who ignored our advise. He burned his vehicle and garage down putting himself, his family, home, and first responders at great risk.

 

[NoviceAttempts]

Yep I have read quite a bit and continue to. They aren't going to be supporting each other in the stack. At the bare minimum I'll be doing periodic cell level monitoring. I've also been thinking about doing a homegrown monitoring system with audible alarms for cell and temperature level thresholding since the Tesla modules have cell level voltage taps and built in thermisters. I've also been looking at the Orion BMS but haven't committed to anything yet. I know there's inherent risks and I can't remake my own Tesla with all the safety features. Just will do my best to mitigate risks as best as I can.

 

[Russco]

Yep I have read quite a bit and continue to. They aren't going to be supporting each other in the stack. At the bare minimum I'll be doing periodic cell level monitoring. I've also been thinking about doing a homegrown monitoring system with audible alarms for cell and temperature level thresholding since the Tesla modules have cell level voltage taps and built in thermisters. I've also been looking at the Orion BMS but haven't committed to anything yet. I know there's inherent risks and I can't remake my own Tesla with all the safety features. Just will do my best to mitigate risks as best as I can.

So, you're thinking of using a Tesla pack without a BMS?

NEVER park your EV in the garage. Park it a block away.

BE SURE to have a 500K auto liability insurance policy with a 1M umbrella extra policy.

The "ION" lithium cells can be very dangerous and self-ignite unless watched over with an electronic BMS 24/7. The auto owner is NOT an electronic BMS.

Be smart.

 

[electro wrks]

This is the fire that resulted from an estimated (the full report is not out yet) 1 or 2 of the ~16 Tesla modules burning up in Tesla's carefully designed battery pack: https://youtu.be/9VtbBKnG97c


Another view: https://youtu.be/feLB1dmKcgA


The pack design (Tesla calls it their "architecture") appears to have limited the fire and kept it from spreading to the other modules.

Imagine, in your vehicle, one of your 5 module, front or back packs burning-up with 2.5-5 X the intensity of the fire in the video. The consequences of the "inherent risks", to quote you, are so great with these modules, "safety features" have to be incorporated when these modules are used. No one in their right mind would mount a fuel tank in an unsafe manner in a ICE vehicle. Think of these modules with the same kind of safety in mind.

In their builds, other DIYers have put the modules in a sturdy metal box and incorporated some kind of fire vent system. All good ideas. I probably would go further. I would isolate individual modules, for example.

And for crying out loud, get a good BMS and use it!

 

[bawfuls]

EV West now uses and endorses a BMS from Dilithium Design, though it is not yet on their website.

Bream sold me on it when I was last in their shop, and I'll be using it with my 5 Tesla S modules. For 10 modules you'd need one Master and two Slaves, which is I think $450 + 2x$250. It is possible that you'd need 3 slaves in order to properly split the two packs between BMS boards though, check with EV West.

I'm surprised you stuck with the AC50 if you're going to the trouble and expense of 10 modules. Since only 5 are needed to get the voltage for the AC50, you could theoretically add a second motor and double the power/torque with your 10 pack. But if the range is that important to you then so be it.

 

[brian_]

NoviceAttempts, could you clarify your plans a bit? Although you refer to a "box" in your second post, I don't see any evidence that you are planning for boxes to enclose the sets of modules; there seems to be no clearance for that. As you know, in a Tesla all 14 or 16 (depending on model) of these modules are enclosed in a big flat metal box which is hung under the floor of the car, and every other modern EV does something similar. Will there be additional housings (presumably one for the rear set of modules and one for the front set) that are not shown yet?

I have heard of commercial conversion providers using Tesla Model S/X modules in Beetle conversions, but details are sparse. They usually show only the motor and controller, not the battery, but at 1:41 in this video you can see a big black box behind the (missing) rear seat that presumably contains the modules in a Zlectric Motors conversion.

 

[Duncan]

To all of the BMS fans that are busy spouting
For every failure without a BMS I have seen about six failures CAUSED by BMS's

IMHO a factory BMS is a good idea - the aftermarket ones all seem to cause more problems that they cure

The normal failure mode is
(1) A cell fails - aftermarket Lithium cells seem to have a failure rate of about 4%
This kills any other cells in parallel

(2) the owner then charges the battery not realizing that there is a cell down and effectively overcharges the rest

Any of the split pack warning devices will tell you if you have a cell failure - I use the Lee Hart BattBridge

As far as I can see an actual BMS simply tells you just before a cell fails - but there is nothing that you can do - it's going to fail anyway!

That is when the BMS is not causing cell failure by discharging or unbalancing the cells

 

[piotrsko]

Can anybody tell me exactly how many Tesla vehicles have had a battery fire in the car? And social media examples don't count. Real NHTSA data showing causes / conditions.

According to what I can research, the failure rate is about the same as cell phone fires, or rather insignificant. I know that most VOLT packs flamed after some sort of impact or puncture or wiring issue.

I agree once they start, you are along for a ride until the chemicals neutralize.

 

[NoviceAttempts]

Bawfuls: Dilithium Design BMS That actually looks much more like what I was looking for in a BMS. One of the things I was concerned with in my reading was the issue with parallel strings. While this one doesn't fix all those problems it at least has logic to allow it to recognize 2 packs. I also like the centralized but modular design. Reading their documentation I could get away with just 2 slaves, but 3 is probably the way to go for my pack distribution. This one may have taken the lead in my options, thank you for pointing that out to me. As for the AC-50 with 10 modules, I don't really care about performance, I'm more interested in distance and babying the pack.

brian_: For that box I went with 3/8" marine board bolted to the body. I routed channels to lock the modules into via there tabs. I'm going to add some threaded rod to the front there to cinch the top and bottom at the front to ensure the modules are fully secure. I am considering adding other retaining measure. Zelectric works with EVWest on their conversions and the black boxes you see there are also made out of marine board. You see the same construction on their Karmann Ghia video https://youtu.be/5OK4o8gSTNM?t=55 that conversion uses the Smart Car modules with the pack split between the frunk and behind the back seat, they've got 8 or 12 of those modules in a 2sXp configuration.

Duncan: I agree, although I like the idea of charge/discharge safety cutoffs. I haven't been convinced about BMS cell balancing, but that's something I continue to read about especially because the major manufacturers seem to top balance.

piotrsko: I couldn't find much data specific to Teslas or Tesla batteries, but here is a doc with some results from a study the nhtsa commisioned. I only read the executive summary, and it's good info even is most of the data is a few years old: https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/documents/12848-lithiumionsafetyhybrids_101217-v3-tag.pdf
The NFPA also lists total US highway fires, they don't seperate EVs from ICE but there is an interesting decreasing overall trend: https://www.nfpa.org/News-and-Research/Fire-statistics-and-reports/Fire-statistics/Vehicle-fires/Highway-vehicle-fires

Thanks everyone for the comments, I think all input is helpful. Does anyone have more info on parallel strings of packs? I've read the doc from Orion and it's interesting, but I've looked and haven't seen any statistics. It seems that a well balanced pack and slightly lower top end cutoff mitigates most of the concerns, but does anyone have some anecdotal data of running parallel strings/packs and how the cells drift over time, especially for 18650 type designs?

 

[electro wrks]

Sounds like you're on top of the info for using the Tesla modules. Please let us know what happens. The Canadian DIYer misusing Tesla modules had Duncan pull the plug on his thread. For liability reasons? Maybe, he was embarrassed by his sheer stupidity? We had to piece together and speculate how he burned down his vehicle and garage.

It's hard to learn from other people's mistakes when important information is removed.

 

[brian_]

brian_: For that box I went with 3/8" marine board bolted to the body. I routed channels to lock the modules into via there tabs..

Thanks for the details , but I'm still confused : in the rear the photo shows a stack of modules (on edge) on a board, but no sides or front, so there's no box, just a base... and now I realize that there's a top as well. Am I correct in assuming that the modules are really in a box, and the other sides have just not been shown yet?

I assume that "marine board" is a high-density polyethylene sheet such King StarBoard®.

 

[boekel]

use the factory bms!

https://www.diyelectriccar.com/forums/showthread.php/fs-tesla-vw-outlander-bms-master-198263.html

 

[NoviceAttempts]

electro wrks: I am sure there's a lot of things I can be doing better, but I will let people know if anything happens and thoughts on what I should have done.

brian_: It's not a full box. It's a c shape with a top, bottom, and back. The top and bottom have channels routed in them to socket the modules into, on edge. I'm hopeful that being on edge will help in the event of a fire to slow propagation from one module to the next instead of just burning straight up through the column. We put a couple of all-thread rods in the front to squeeze the top and bottom together to lock the modules in place. After looking at the all-thread and where we managed to locate them I'm going to drill further and run those rods through the parcel shelf and the floor of the cargo area to add a bit more rigidity and a couple more points of connection to the car itself. If the box still seems to need a bit more stability I may add a panel to the right hand side, but I really don't think that will be necessary. The left had side is going to remain open for wiring. King StarBoard® is what we picked up for this purpose.
The front box will be a stack of 3 next to a stack of 2. We will use the same marine board type construction with routed channels to suspend each module so they're not resting on each other. This box will be fully encased as it's more exposed to the elements. and I need to come up with a way to support the 3 module stack as it will be recessed into the gas tank cavity. I may weld together a bar stock tray, or a full sheet metal box and will utilize the gas tank holes to secure it.

boekel: I considered this. I even picked up an Arduino Due and the components to make my own BMS shield from the hackaday project, that's what I was referring to when I mentioned making my own BMS. I think I'm gonna go with the Thunderstruck system though.

 

[brian_]

brian_: It's not a full box. It's a c shape with a top, bottom, and back.
...
The front box will be a stack of 3 next to a stack of 2. We will use the same marine board type construction with routed channels to suspend each module so they're not resting on each other. This box will be fully encased as it's more exposed to the elements...

My concern wouldn't be exposing the modules to the elements of the outside world, but rather potentially exposing people to the both the high-voltage electrical connections and the consequences of a cell failure within those plastic module cases. Maybe it's not a problem, but EV manufacturers don't build cars this way.

 

[NoviceAttempts]

We are going to have the back seat preventing most access to the rear module when we are done. I expect we will do some sort of locking system on the seat, maybe heavy duty zip ties, as a review of EV fires indicated that access to the battery was the biggest factor of success when putting it out. There shouldn't be a danger of exposing people to high voltage accidentally. As for fire, the smoke created from that plastic is an extra warning system .