Update

Quest for an Electric Porsche Boxster.

Today I will update the status of the Porsche Boxster. My personal and professional life have had many detours in recent months, so the Porsche has not been as much a priority. However, I have been driving the car lately, and have many new experiences to share, so here we go!

Batteries:

The configuration using K2 batteries in blades without forced air cooling has been a major disappointment. The batteries have degraded in capacity over time, reducing range and power. The car now goes about 25-30 miles if driven VERY conservatively. Efficiency is about 315Wh/m at best. The power is less now, putting out about 650A max, which is still enough to comfortably drive the car, but it's no racer.

When we designed the car, battery options were limited. Now, if we were choosing batteries again, we would strongly consider the CALB 130Ah cells that are relatively small and put out pretty good power. I think enough cells could fit in the car to get over 240V and over 100 miles range. A123 pouch cells are becoming available, with more potential for a supercar, but integrating them into a module is still a relative pain compared to prismatics. I have heard positive things about high power Headway cells, but CALBs would be more practical IMO, and the car would be powerful enough.

Motor:

Warp 11 has been stable since fan blew apart. We had trouble with the spindle rubbing on the adapter plate, but got that fixed by drilling into the motor crankshaft. Now it spins smooth.

Controller:

Most reliable part of car. The car would have been fine with a Z1K, and even the newer Soliton1 or Warp controllers. I can't wait to see how it will run with a more powerful pack that can get closer to 2000A.

Charger:

Sent it back and they adjusted the thermistor and added a fan to the liquid cooling. So now we get 42A for about 15 min before it throttles back to around 35A for rest fo charge due to overheating. We may send it back again to add another fan which should do it. Since the car doesn't have much range, the faster you can charge it the better.

Evision:

After discussions with Victor, he finally decided to accept the return of the eVision 1, and sent us a new eVision 2. We worked hard redesigning the install, and once done, had a similar problem... inacurrate amp measurements. This time it was also crashing sporadically. The charging shunt which is new on eVision 2 worked fine. The shunt board is mounted on side of front battery pack. So we removed the whole thing again, added some foam for support of the back of the circuit board, and rearranged the big high voltage wires nearby. To our surprise, it is working MUCH BETTER now. We just finished, so still evaluating, but I LIKE IT! Especially with a short range, the eVision allows me to keep very good track of state of charge between charges. Right now, I think the problem was installation, and not the eVision 1 since it was working until Mark took the front string out to do some work. I think he must have arranged the high voltage wires in such a way that it was causing interference. Just a guess. I would recommend installing the eVision shunt board away from crossed high voltage wires. Also, the eVision 2 is MUCH easier to see driving in the day.

BMS:

Had a bolt drop on one of the boards in the rear battery string. We were out of working boards, so the guys tried to build one from hand and finally succeeded. We decided to buy a professional run of 12 boards for back up which cost over $500. One of the boards is not giving proper temperature readings and will be replaced. Also, the front string is crashing periodically, probably related to a bad BMS board. We are still working of troubleshooting that one.

Suspension:

Seems loose in hard turns, so will need to get it aligned again. Probably messed it up taking the motor/transmission out.

Brakes:

Had problem with rear brakes on right making loud noises. Ended up needing to replace all the brakes and rotors, which on a Porsche ended up costing $1200.

Convertible top:

Had it replace with a glass rear window and then had the car ceramic tinted. Looks nice. Had to replace convertible top transmissions and cables. Bought them on eBay for a couple hundred dollars and installed them myself. Works fine now.

In conclusion, I think the Boxster makes a great conversion. Now that we have learned the pitfalls, if we can install a better battery pack the car would be outstanding. Even so, the car is great fun to drive, and I don't regret the project overall. I will probably drive the current battery pack till it is getting under 20 miles range, as that is close to round trip distance to work. Then we will do the upgrade, and probably battery prices will be much less and the loss less painful. I am also going to upgrade the speakers as Porsche was cheap on the sound system. My old Subaru had a better sound system. Good luck to all you guys out there trying to convert Porsches to electric!