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Install a 4680 pack and remove the PEM?

MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
I'd like to buy a first gen Roadster.

Plan A is to get a bricked Roadster buy used 4680 structural pack from a wrecked MY, when they become available, then either wait for someone (Jason Hugh's for example) to develop something to control the Tesla BMS or purchase a third party BMS and get an inverter/controller to run the motor.

I didn't have any idea until I checked this forum that this was a possible problem. What functions does the PEM perform that I need to replicate for this to be a workable solution?

Main reason for choosing the 4680 structural packs is that I believe that dividing the pack into self-contained chunks will be relatively easy.
 

MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
Maybe consider plan B. Plan A goes south starting with trying to find a bricked roadster, and gets even worse after that.
I'll give you the benefit of my doubts and assume that you are trying ro be helpful, but if so your attempt failed. I'm hoping for a brief list of the major technical hurdles involved. I have 3 friends who I think could solve the problems but before presenting this to them I'd like to know what's involved. If they can do it finding a bricked Roadster will simple. I hoped that this technical forum would be the best place to ask. I believe that there is someone on this forum who could off the top of their head provide the information I am looking for. Will someone who knows please be kind enough to help me?

Thank you :)🙏!
 

gregd

Active Member
Dec 31, 2014
2,596
1,812
CM98
Making some guesses here... At a high level, I think the issues will be in convincing the rest of the car that what everything is ok. Those parts - the main computer, for example, are pretty opaque in their operating, and pre-date any of the modern implementations where a lot more is known about what they care about. Nobody outside of Tesla has access to the code to make accommodations for a different battery or PEM.

I also wouldn't assume the MY's 4680 modules would be even close to compatible with the original Roadster BMS. Very different charging characteristics. The Roadster uses the old LCO 18650 cells, and even Tesla (who have full access to the original design) ran into significant issues just using modern 18650s in making the 3.0 battery pack. It might be instructive to scan the threads on the 3.0 battery, their service life problem, and the work that Chrisro is doing (New Roadster 4.0 Battery developement with Model S cells)

Basically, pulling on the battery cell thread can cause the entire car to unravel. There's more to the car than just the battery and PEM, so you might be looking at completely replacing the entire system, in a car that was barely large enough to hold the original equipment. You might get the car to move, but getting it to perform safely is a very different challenge.
 

MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
I also wouldn't assume the MY's 4680 modules would be even close to compatible with the original Roadster BMS. Very different charging characteristics.
Thank you very much!

Just to clarify I have ZERO intention of trying to use the original Roadster BMS. I hope to be able to use the BMS that comes with the MY pack.

Thanks again 🙏 :)!
 

X.l.r.8

Supporting Member
Supporting Member
Feb 18, 2018
1,555
998
Toronto/Miami
You may find that the information you seek ids not here, your plan will not improve on the original car, no hot rod ever did, but then that’s not the point of hotrods. That’s 1/2 my background so I understand the desire to build concept. Head over to open inverter. That’s where we are doing exactly this. The car itself makes little difference as you will see. Using a model Y battery may not be the ideal once you read through the battery threads. The simp bms controls pretty much all BMB’s so you can use what you like. The Prius/leaf and Tesla model s and 3 have been pretty much decoded and have can codes for pretty much all the components, even DC charging. Not sure why you would subject this to a roadster, but then I had a V8 in a 924 CGT so who am I to judge,
 

Mark77a

Member
Jul 7, 2012
463
188
Poole, Dorset, UK
Its easier to convert a lotus (Elise, VX220/Opel Speedster, Elan). And then you get the choice to trade weight and range. Personally I'd loose some weight and range for more 'Lotus Like' handling, but I think at the time of the Roadsters launch an all electric sports car with 'only 120 mile range' would have given [more] ammo to all the naysayers.

I converted an Elan, because the Roadster is similar to the Elise, same steering, better acceleration, not so 'flickable', and I'm lucky to have the choice.
I wouldn't want to mess too much with a roadster as EV conversions are often frowned up by 'purists' .. and may spoil its value. Even relatively plentiful Lotus conversions get 'hate mail' (I had death threats in comments on the above video - now removed !!).

There are some good EV conversion forums and FB groups, plus check out EV West, Electric Classic cars and Zero-EV
 

MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
You may find that the information you seek ids not here, your plan will not improve on the original car, no hot rod ever did, but then that’s not the point of hotrods. That’s 1/2 my background so I understand the desire to build concept. Head over to open inverter. That’s where we are doing exactly this. The car itself makes little difference as you will see. Using a model Y battery may not be the ideal once you read through the battery threads. The simp bms controls pretty much all BMB’s so you can use what you like.
Thank you! Exactly what I was looking for.

You don't believe that putting a modern pack in a bricked Roadster can improve it? The 3.0 pack improves it. The PEM's are clearly a weak link.

Thanks @Mark77a and @X.l.r.8 (again)!
 

X.l.r.8

Supporting Member
Supporting Member
Feb 18, 2018
1,555
998
Toronto/Miami
I don’t know what the saturation point is for a roadster motor is, but the fact they are hand wound for the sport and the temperature it climbs to on 200 mile drives, showed it’s pretty close to max. If you could push the max voltage rather than increasing the amps, then find a way to get some better cooling. Again, at that point I think a M3P motor would be a much better option. Built in inverter, throw a Gen 2 48A charger, a volt 12v DC converter and you could have quite a package. Again stopping it may be problematic. The weak point of the roadster is the brakes, it was a primary reason I went to the Porsche platform for my model S performance motor.
To your point the 3.0 gives more range, that’s it, the 3.0 does not charge quicker so the range is hindered by the increased charging time, something model 3 owners fail to understand. If you are charging for 6 hours for a 2.0, the 3.0 will take 9 hours. So unless you can reach your destination in one go, the 3.0 is basically bragging rights. The modern pack will need cooling? And that’s controlled via the PEM. There goes the HVAC, I’m not seeing any improvement, it’s no longer an jntergrated package. You may improve range, but that’s one metric, knowing the roadster is one of the most efficient vehicles, period, you are going to have to do something amazing to ‘improve’ on the original in all areas, making it go faster is easy.
 
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MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
@X.l.r.8 Thanks again!

So my idea to ditch the PEM isn't crazy? My goal is to get an inexpensive reliable Tesla Roadster. The 10 year old PEM are not reliable, unless you think reliably bricking the pack is a feature. Without the PEM CCS charging should be doable?
 

einhalv

Member
Aug 2, 2019
88
66
Horten, Norway
Perhaps not crazy, but is the idea right?

Even if you can get your hands on a bricked roadster, it will hardly be inexpensive. The only time I have seen one for sale, the asking price was about 60% of the typical asking price of a fully functioning one and probably 75% of the lowest asking prices at the time. Roughly the price differences in this example correspond to the cost of a remanufactured battery pack from Tesla. It doesn't seem reasonable to expect significantly lower prices than that.

It is difficult to see why you expect higher reliability on your build, and I don't understand how you are going to assure it.

The current PEMs have their flaws, but the flaws are well understood and can be dealt with.
 

miimura

Well-Known Member
Aug 21, 2013
6,678
6,511
Los Altos, CA
Taking apart a structural battery pack will be inherently challenging. The whole point is that there is structural adhesive holding all the cells together so that they act as a solid structure. Take a look at the Model 3 modules and how hard they are to take apart without damage. Now imagine that there are no modules and the whole pack is bonded together.
 

MitchJi

Trying to learn kindness, patience & forgiveness
Jun 1, 2015
3,989
9,173
Marin County, CA
@miimura Thanks! I think a sawzall or a bandsaw might work. Depends on if the cells are touching.

@X.l.r.8 "I think a M3P motor would be a much better option. Built in inverter.."
Would that be easier to control than the OEM motor? How difficult to mount? The most fun would obviously be either one new MS carbon wrapped motor that weigh 30 lbs. and are can put over 400hp or the complete dual motor drive system with torque vectoring. Be nice if Tesla offered that as a Plaid 1st gen Roadster upgrade.

"brakes were a primary reason I went to the Porsche platform for my model S performance motor."
Do you have a link to a description of your Porsche build?

I'm not planning to do this project myself. I'm trying to come up with a plan that EV-West or some close friends can implement for about 30k that will be better than the 3.0 package.

Cross posting:
Question asked and answered on this Gruber video live this morning!
David Jones Do you know if new 3.0 battery pack has new PEM or just a new board for the original PEM? We get different answers from Tesla?
 
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X.l.r.8

Supporting Member
Supporting Member
Feb 18, 2018
1,555
998
Toronto/Miami
I’m going to say 30k will not get you close. 8 grand barely gets you a DC forklift motor and an adaptor plate in a VW. The problem with throwing out the PEM is that the inverter that’s usually mated to the later Tesla motors is now gone, so you need an inverter, probably open source, add a controller, a charger, a DC converter, programming, actually fitting the components, hoping that they work together, you could take the whole of a model 3 and graft in the whole system but where are you going to fit the battery. Will it work without all the additional sensors. The model 3 runs one can bus, the roadster runs 3 on different frequencies, you cannot emulate that. So you will end up with a roadster shell. Fitting a later Tesla motor to the roadster will not be an issue, that’s the inverter and motor, still not sure where you are going to fit the batteries and be able to cool everything. The later model electronics will have a fit when the powersteering pump is not there, along with the charge port door. The basic concept really is simple, but the original roadster is wickedly complicated on simple systems. If you plan on paying EV-West by the hour to sort those systems out you are going to be working a lot of overtime. And I fear that you will probably the most unreliable car that no one can diagnose, or be willing to touch. I’d love to be proved wrong but watching a lot of people build around systems rather than cherry pick and build complementary systems always leads to disappointment.
I don’t have any build blogs or pictures, I just don’t have that kind of time, I’m only online between patients if nothing crazy is happening at work.
 

TEG

Teslafanatic
Aug 20, 2006
21,967
9,194
Some other thoughts:

* Many people have contemplated what it would take to fix a bricked roadster and put some other kind of cells in there. Easier said than done!
* As much as Elon/Tesla like the idea of disrupting the establishment and re-engineering everything, they don't really like it when people try to mod their vehicles and throw all kind of roadblocks in your way.
* There are improvements to all sorts of systems between Roadster & 3/Y, so it might be better to just take a whole Model 3/Y drivetrain and put that pack/charger/inverter/motor into some kind of Roadster shell instead of trying to Frankenstein in certain replacement components.
* Tesla firmware assumes all sorts of things about the vehicle it is in and if you tried to put Model 3/Y parts into a Roadster you would end up in a minefield of systems detecting incompatibilities and shutting down with error codes.
* I don't want to rain on anyone's parade and suggest what you propose is impossible, but I think it is fair to say the us old timers watching from the sidelines can say history is littered with armchair engineers that came in thinking something was doable only to be defeated by the complexity along the way.
* I would say there are 0 shared parts between original Roadster and 3/Y. Tesla basically started with a blank sheet of paper and didn't carry anything forward, so don't assume that there would be some compatibility due to them both being Tesla vehicles.
* Be very careful if you mess with lithium battery packs. A lot of smart people started fires by accident because they didn't do the cell charging perfectly.
* The PEM does AC->DC (all the charging), and DC->AC (inverter for the motor.) So if you thought to replace the PEM with a Model 3 charger you would be missing the inverter for the motor! (Car would charge but not go!) [ For Model 3/Y the inverter is in the motor housing. ]
* The PEM is basically hard coded to do charging for the original 18650 based ESS and would probably require some massive re-engineering to be able to charge other cell types. The 3.0 pack still uses 18650s and the 3.0 PEM has some mods to support the voltage range of that chemistry. I think the 3.0 pack uses 18650s that are closer to original Roadster cells than the model S cells, I think they had to use some older style cells because the PEM wasn't really suitable to recharging newer model S cells. So, don't assume that the 3.0 pack upgrade means that the PEM is all that flexible.
* Some of the PEM constraints have to do with the DC voltage ranges it can output to the ESS for charging. You would need to build an ESS that fit within the original voltage range of the original Roadster pack, or else redesign the PEM.
 
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TEG

Teslafanatic
Aug 20, 2006
21,967
9,194
The most fun would obviously be either one new MS carbon wrapped motor that weigh 30 lbs. and are can put over 400hp or the complete dual motor drive system with torque vectoring. Be nice if Tesla offered that as a Plaid 1st gen Roadster upgrade.
Yeah, Tesla wants you to buy their new Roadster to get that new plaid drivetrain. They have little interest in retrofitting original Roadsters when their job is to sell new vehicles.

Rather than butchering up a bricked Roadster (that might get a 3.0 pack someday), how about converting a gas Lotus to electric?

 
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bart513

Active Member
Feb 27, 2013
1,350
96
East Hampton
Yeah, Tesla wants you to buy their new Roadster to get that new plaid drivetrain. They have little interest in retrofitting original Roadsters when their job is to sell new vehicles.

Rather than butchering up a bricked Roadster (that might get a 3.0 pack someday), how about converting a gas Lotus to electric?

Hi TEG. Long time no speak. There is a lotus sitting at a local gas station for quite some time How dificult/expensive it that to convert? Thanks and all the best!
 

TEG

Teslafanatic
Aug 20, 2006
21,967
9,194
Hi TEG. Long time no speak. There is a lotus sitting at a local gas station for quite some time How dificult/expensive it that to convert? Thanks and all the best!
Might want to contact those guys in the video and see if they are willing to do another, and what they would charge.
That was a custom job they did. Some other EV conversion companies could probably tackle the job as well.

EVwest converts a lot of old sports cars to electric...

You could talk to them about putting a Tesla motor in a conversion:
 

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