Alan 91 C2

Very great project.

It looks like you are using the Porsche drive line and trans axle. Is that correct?

I looked into using the direct drive wheel motors. Can have 4 wheel drive, with regeneration for braking.

What size electric motor did you choose? I had estimated that I would need around 20 HP to make highway speeds. What voltage did you choose, 200 VDC?

SCEV

Yes, I'm using the factory torque tube and transmission. Was much easier to just connect to the existing drivetrain. You can check out my blog (very outdated) at 951EV.blogspot.com for more info on how I connected if you want.

I've always heard wheel motors are very reliable due to the fact electric motors are able to take vertical pressure on the drive shaft.

20hp sounds awfully low. My pack voltage is 60*3.2V for 192V nominal. I'm using a Netgain Warp11 and my peak should be 170V (what I limit my motor voltage too) * 1000A for 170kw or 228hp. However I'm not currently getting that because my batteries are sagging to ~130V when pulling 1000A...I've got to track down why, may have used too small of cable at 1/0.

Alan 91 C2

Hi, the 20 HP is just the running load at highway speed. Say at 60 MPH you are estimating 250 KWh per mile or 15KW ~around 20 HP.

The trade off is total power versus efficient power at cruise. That is why I looked at multiple motors for scale and keeping the power close to point of use. With one motor only in cruise mode. Using the 911 front axle stubs from all wheel would yield 4 motors possible.

What is the internal impedance of your batteries? You may consider bus bar front to rear, 2 x 1/4 or3/8". And re-look at the chassis for grounding. The individual battery jumpers will need to be larger, parallel conductors. Data logging the voltage drops at full load will provide better input as to how you can improve power to the motor.

The 200 hp acceleration (from the electric motor) will be incredible.

I ran the numbers years ago, but the technology; motors and battery was not there.

I will check out the blog. Again, nice work.

I checked out the batteries. The internal impedance is 0.9 milli ohms, so at 1,000 amps the internal V drop is .9 volts, per battery or 54 volts aggregate for 60 batteries. So at 300-400 amps the internal and external (wire loss) could approach 60 volts. The other consideration is the internal power dissipation in the battery. So at 1,000 amps we are at 900 watts. Given we have a cycle time of say 10 seconds then we heat the battery by 8.5 BTU. The vendor does not list the battery critical power curve, the curve showing time vs amps allowable before internal damage. Usually this curve starts with actual battery temp (family of curves). You will need this curve, as you are well outside the nominal 200 amp rated discharge rate. (to avoid a fire)

The normal solution to internal impedance is to start with the max open circuit voltage allowable for the electrical equipment) and work to minimum needed volts. Basically more batteries. There are other solutions, also.

Alan 91 C2

I emailed the battery vendor to ask for the ampere discharge damage cures.