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Tesla Powered BMW E31 8 Series

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jackbauer

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Discussion Starter · #1 ·
So some of you might already know about my E31 conversion as it's been going on 3 years now! Currently running a Siemens 1pv5135 motor and DIY inverter and 6 speed manual gearbox. Has been running very well the last few months but with the Tesla components becoming available and my work on the open source control boards progressing nicely I've decided to convert the E31. Again.

I had originally thought to use the small high efficiency drive unit but decided to go all in and put in the Large rear unit for 450hp+ :D

Going to be getting some help and the use of a workshop and vehicle lift for the drive unit install as it will need some serious work done to the rear subframe and boot floor. Once the drive unit is in then I can start putting some batteries into that nice big empty engine compartment. Should make quite a fun car and test bed for the open source control board. Stay tuned:)
 

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C

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#3 ·
Kevin Sharpe said:
I'm really looking forward to this build... my money is on 600HP which it will hit just before the motor melts :p
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Keep in mind that even a "real" Tesla with dual motors won't do more than around 500HP because the batteries won't provide more power than that. A lot of people were bummed because the total HP should have been over 600HP between the front and rear drivetrains but you can't actually get that. So, one of the biggest hurdles in such a project is figuring out how to get that much power out of the battery pack itself. 500HP is about 373kw or right around 1000A. There aren't too many packs that'll handle 1000A for very long. Racing people have them but then they use packs with high surge capacity and not quite as much longevity.

That's a long way of saying: I'm looking forward to seeing how he plans on getting that much power out of a battery pack. That'll have to be some pack!
 
K

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#4 ·
CKidder said:
That's a long way of saying: I'm looking forward to seeing how he plans on getting that much power out of a battery pack. That'll have to be some pack!
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Agreed, it's a system wide challenge, but given Sasha's Evora has already hit 450HP with a single motor and Volt pack, I'm confident the open source system will deliver a lot more when coupled with a suitable battery :D
 
Duncan

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#6 ·
I'm hitting 1200 amps and 340 v with my "most of a Volt" pack

I expect that

(1) Jack will be able to pull a lot more out of the Tesla pack - for a short time and the pack probably won't last 200,000 miles being treated like that

(2) Jack will be able to get a LOT more than 600 Hp out of that motor - with the same provision - for a short time and the motor probably won't last 200,000 miles being treated like that

Tesla has to be careful - they are expecting 999 out of 1000 people to be able to get 200,000 miles

We - as "Enthusiasts" are willing to accept much worse results - in exchange for more power
 
C

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#8 ·
Duncan said:
I'm hitting 1200 amps and 340 v with my "most of a Volt" pack

I expect that

(1) Jack will be able to pull a lot more out of the Tesla pack - for a short time and the pack probably won't last 200,000 miles being treated like that

(2) Jack will be able to get a LOT more than 600 Hp out of that motor - with the same provision - for a short time and the motor probably won't last 200,000 miles being treated like that

Tesla has to be careful - they are expecting 999 out of 1000 people to be able to get 200,000 miles

We - as "Enthusiasts" are willing to accept much worse results - in exchange for more power
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You're right, you can get 1200A out of the average battery pack. The issue with that is twofold. One, the battery has some effective resistance itself and this will cause the pack to sag when you draw a lot of power. And two, its not particularly good on the battery to draw it too heavily (chemical and mechanical damage may result). I've seen plenty of graphs of the Tesla battery pack when doing hard accelerations. They sag that pack pretty heavily when drawing 1000A. So, I wonder what your "most of a volt pack" does when you draw 1200A. There's no way I'd believe you're still seeing 340V when you do that. It's pretty likely it sags by many 10's of volts. I wouldn't even doubt it if you said it sags to 280V or less. To some extent that's OK. Like I said, Tesla packs sag *heavily* when you draw on them hard. It isn't as heavy a sag as you see with lead acid batteries but lithium cells certainly do sag.

I'd be interested to hear how those volt cells hold up in the long run. It's always a bit of a gamble but maybe they'll do fine and I'll be surprised. ;)
 
A

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#9 ·
CKidder said:
You're right, you can get 1200A out of the average battery pack. The issue with that is twofold. One, the battery has some effective resistance itself and this will cause the pack to sag when you draw a lot of power. And two, its not particularly good on the battery to draw it too heavily (chemical and mechanical damage may result). I've seen plenty of graphs of the Tesla battery pack when doing hard accelerations. They sag that pack pretty heavily when drawing 1000A. So, I wonder what your "most of a volt pack" does when you draw 1200A. There's no way I'd believe you're still seeing 340V when you do that. It's pretty likely it sags by many 10's of volts. I wouldn't even doubt it if you said it sags to 280V or less. To some extent that's OK. Like I said, Tesla packs sag *heavily* when you draw on them hard. It isn't as heavy a sag as you see with lead acid batteries but lithium cells certainly do sag.

I'd be interested to hear how those volt cells hold up in the long run. It's always a bit of a gamble but maybe they'll do fine and I'll be surprised. ;)
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I had experimented with Kokam LiPo 85Ah and they sag for cca 8% at 225A when charged to 4V/cell, which is the max i dare to load them. I think that is quite good for such a small cell!
Also i have made one cell of 48P1S panasonic NCR18650PF. So some 134Ah cell in effect. They show 13% voltage drop at same load. I put it in my car in series with kokams. Liions have more Ri and it shows with load. When i remove my foot however they bounce back to 3.9V/cell without significant effect. No significant temp increase too. They are just softer...


A
 
K

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#13 ·
arber333 said:
Also i have made one cell of 48P1S panasonic NCR18650PF. So some 134Ah cell in effect. They show 13% voltage drop at same load. I put it in my car in series with kokams. Liions have more Ri and it shows with load. When i remove my foot however they bounce back to 3.9V/cell without significant effect. No significant temp increase too. They are just softer...
A
Click to expand...
Tesla's 100kWh packs in the P100D are producing 1500A at max discharge.
That means about 17a from each of the 8256 cells.
With a DCIR of 40 mOhm each, a volt sag of 0.68 v per cell , or 65 volts on the full 96S pack...so 335 volts theoretically !
..which would mean 500+ kW , or 670 bhp !
 
jackbauer

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Discussion Starter · #15 ·
Panzer and Tesla large drive unit delivered to my friend Dave's workshop today. The hard work starts tomorrow but having access to a vehicle lift and other equipment is amazing.
 

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jackbauer

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Discussion Starter · #17 ·

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jackbauer

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Discussion Starter · #19 ·
Mega progress today with the E31 Tesla drive unit swap. Both the modified E34 subframe and the drive unit fit with only needing to cut out the spare wheel well. Custom subframe mounts will allow us to bolt up to the exisiting factory mounting points.

this thing might just work:)
 

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