DC-DC Overcurrent Malfunction

It's good to get the extra transmissions out of my garage. I guess it's poetic justice that the guy who bought my side shifter from the original car is going to give it to Jeff at Rothsport systems for a rebuild, the same guy who didn't work on it for 2 1/2 months when I gave it to him.... The buyer of the tail shifter transmission is also in the process of doing an electric vehicle conversion, so he asked a bunch of questions about my project.

I've been noticing that my auxiliary battery seems to drop in voltage significantly as I commute to work. After some experimentation today, I found that under a moderate load of 8 amps or so, the DC-DC eventually stops working and fails to charge the 12V battery. I was misled a few times because when I turn off the key for awhile and turn it back on, the DC-DC starts working again for about 30 seconds before stopping.

At light loads the DC-DC keeps working, so I can charge the 12V battery if I just turn on the key (to close the DC-DC relay), but don't turn on any accessories or start driving (thereby pulling current from the motor controller). For the moment, I charge the main pack at work and turn on the key for about an hour before I have to drive home to recharge the 12V battery.

Here are some current values I measured coming from the 12V battery (without the DC-DC in operation) from various accessory loads:

• key off - 10 mA
• key on (motor controller idle) - 700 mA
• parking brake flashing light - pulses of 300 mA
• parking lights - 3.7 amps
• parking lights and headlights - 9.4 amps
• parking, headlights and fog lights - 17.3 amps
• left and right turn signals - pulses of 3.3 amps
• backup lights - 3.1 amps
• parking, headlights and backup lights - 12.3 amps
• brake lights - 3.3 amps
• CD player - 1.0 amps
• climate control fan (low) - 2.8 amps
• climate control fan (med) - 4.5 amps
• climate control fan (high) - 6.7 amps
• defroster (hair dryer) relay - 200 mA

As you might suspect, I'm irked by the DC-DC still not working, but it's probably my own doing given the modifications I made to the controller. I guess it's back to taking the thing apart and adding an increasing load to see when it fails. Argh.

Watt-Hour/Mile ratings and Selling the Trannies

I dropped off the 914 with Alan at A&P today to upgrade the brake cylinder and do a front end alignment. Brett, a local guy, is going to purchase my two leftover transmissions and Curt from Salem is visiting today to see the car (hopefully back from the shop).

In the meantime, I took some approximate readings from my ammeter and voltmeter as I drove on flat roads this past week. Overall driving at 20mph tends to pull 30 amps at 140 volts. Driving at 60mph (flat road only) pulls 90 amps at 135 volts. This averages out to around 205 Watt-Hours per mile. Paul Jorg asked for this info, so hopefully this is what you were looking for. I suspect that the fluid resistance in the transmission consumes quite a bit of power.

Although I hate to admit it, there's still a faint screeching sound that comes from the transmission when I spin the input shaft with the electric motor. The sound goes away after I drive a block or so, which leads me to believe that the transmission fluid isn't getting into all the bearings it should. The rather frigid mornings probably aren't helping the situation either.

First Day Commuting with the New Tranny

Today was the first day on the freeway with the new transmission. Other than watching my amperage, I didn't have any issues and the car drove just fine.

Many thanks to all the people who have offered their support during this long wait to get a working transmission. I'm happy to see all the other 914 EVs out there.

On Friday I'll be re-aligning the front end for better steering and replacing the brake cylinder. I have some machined BMW 320i calipers coming in a few weeks to upgrade the stopping power. I'm also thinking about replacing all the rear bulbs with LED lights to save on 12V current. I might possibly purchase a 12V 20Amp heater for the cockpit, but I don't want to stress out the DC-DC converter too much and a 300 weight polar fleece jacket seems to work fine.

The hair dryers do very well in defrosting/defogging the front windshield. The only thing I forgot to do initially was to open the windshield vents by moving the fan lever halfway to the right. Otherwise, the hot air from the hair-dryers doesn't make it up to the windshield (oops).

I might splurge over the next year and purchase an EVision system from Metric Mind to really get a grip on the battery state of charge, but the installed PakTrakr might do just fine. I need to be careful of "feature creep when installing a bunch of new toys on the EV.

I'm in the process of figuring out if there are any tax breaks at the federal and state level for the car. I also still have two leftover transmissions sitting in the garage that I'm trying to get rid of.

I'm really happy to get the 914 on the road given rising gas prices and the economy tanking at the same time. 2008 will prove to be a very interesting year. Best wishes to all.

Up and Running Again!

My friend Rick and his girlfriend Holly were gracious enough to come over and help me finish putting the transmission back into the car. We worked from 7pm-10:30pm and finished the job.


Here's Rick and I under the car re-attaching the CV joints and getting covered with grease.


Here's Rick and Holly in the working vehicle. We drove the vehicle around the block and the transmission was very smooth. I'm very grateful to Greg Robbins for shipping a transmission in such good shape. No vibration up to 5400 RPM. Big thanks to my friends for all their support during these frustrating times with the transmission.

Tomorrow is my day off and I plan on testing different RPM values above 5400, logging some data with the Pak Trakr and seeing how the car handles.

I'm rather tired to show my relief and enthusiasm in getting the car back up and running. I still need to upgrade the brake cylinder to 19mm and get a front end alignment to help with the tough steering.

Things are looking up. If it works well over the weekend, I'll commute to work on Monday. Hopefully the cold weather won't kill the car. Cheers and Good Night.

Yay! Less Vibration!

Rather serendipitously, my friend Jonathan dropped by this evening and we joined the transmission to the electric motor and spun it up. I was quite relieved that spinning up the new transmission to 5400 RPM produced little, if no vibration.

We were a bit nervous when we heard a minor squeal inside the transmission case. We then put the transmission into first gear, allowing the fresh transmission fluid to flow from the bottom shaft onto the gears on the top shaft. That caused the squealing to subside.


Here's the transmission mated to the motor. Note the rubber bands on the clutch fork to prevent it from crashing into the spinning flywheel. Jonathan is holding a piece of cardboard over the license plate because the reflection really screws up the light measurement system in my camera, especially when taking pictures at night.

Tomorrow, my friend Rick will help me re-attach everything. For now, I came home exhausted from lack of sleep over the past few nights and I don't want to risk putting this baby back together with only half a brain. I'm "cautiously optimistic" at this point that things might actually work.

Next up: hooking things back together. Good night.

New Tranny Here - Salvaging Cracked Parts

The newly rebuilt transmission from Greg Robbins showed up via UPS today at 95 pounds.


Here is the plastic tub that it was shipped in. The tub doesn't look like UPS treated it very well.


Another view of the tub. The fiberglass straps are broken, the lid is totally cracked in pieces and most of the corners are dented in.


Here's the transmission removed from the plastic tub in my front hallway with plastic peanuts everywhere. At first glance, everything looks to be in order.


Another side view of the transmission. Pretty clean! The gears feel good and solid if I rotate the input shaft and output couplings.


Oh no! Upon closer inspection, the side-shift support looks like it suffered a rather harsh fall. Note the large crack near the upper left of the picture. The bottom edge of the support looks pretty beat up too, possibly from dragging on the ground. The material inside the crack is very clean, leading me to believe that this was probably caused by UPS, although there was plenty of padding in the bottom of the plastic tub.


Another look at the crack on the side-shift support. I didn't want this liability on the transmission, so I replaced the cracked support with the one from my existing tranny.


I never thought I would have three transmissions in my small garage. I've moved several necessary parts from my original transmission to the newly rebuilt one (on the left), to make it functional.

Tomorrow, I plan to fill it with transmission fluid and see if it bolts to the motor reasonably.

Man, I reallllllly hope this works....

Rebuilt Transmission Coming Tuesday

I just received an e-mail from Greg Robbins that he shipped a rebuilt transmission to me via UPS and it should arrive next Tuesday! The UPS tracking number concurs with this.

This will be a good time to get back into the swing of things since my girlfriend Krista is starting classes next week and the holidays are winding down. Working in the garage is a bit slow since it's cold and rainy, but I should be able to get things put together.

I want to issue a big thanks to all the folks at 914world.com that expressed support and advice in my pursuit to fix the transmission. The electrical plug-in station at work has been lonely over the past few months and I'll be psyched to get the car back on the road.

About a month ago, I sold my old '94 gasoline Saturn wagon and purchased an '03 Subaru Outback. It's much more comfortable and handles the snow quite well (went snow-shoeing twice), but it's got significantly lower gas mileage (about 26 instead of 32). With gas prices going up, I'm even more eager to fire up the 914.

I'm glad to see Ross Cunniff and Matt Kneipper get their AC 914 conversions on the road as well.

May all have a Happy New Year.

Cheers,
Tim