Tuesday, June 26, 2012

Six Month Checkup

Interim Instrument Panel
I've been driving my EV truck for about 6 months now and thought I'd give an update.  The short version is, it's great! The best part is driving by the gas station every day.  I put aside all interior finish work while working on the power train.  For the first few months I was driving around with a very austere interior including the minimalist instrument panel shown here.  It consisted of just the state or charge indicator and the multifunction motor display.  Without my dashboard and traditional instrument panel I had no odometer or speedometer.  However I quickly learned that, in second gear, my speed, in mph, was roughly equal to the rpm divide by 100.

BMS programming

Typical Discharge Data
I spent a lot of time during the first month or so of driving monitoring my charge and discharge cycles and adjusting my BMS settings.  Gotta give a big shout out to the technical support at Elithion, originally Robert Helvestine and now Steve Van Buskirk. They were very helpful in getting my BMS properly setup and programmed. I'm very pleased thus far with the performance of the Lithiumate BMS.  I can't over emphasize the importance of collecting and carefully evaluating charge and discharge data during the first month of driving.  I had to collected data from a number of charge and discharge cycles to determine exactly what was going on with my battery pack and to properly set all the parameters for my BMS.  Initially I thought that I had a bad cell that was not fully charging.  That can be seen in the figure to the left when green minimum voltage line drops off quickly at the end of the discharge cycle.  However, after monitoring the pack for many cycles I found out that the cell was fine.  The problem was my failure to do an initial balance of all the batteries before installing them.  I skipped this step assuming the BMS would do the balancing for me once the pack was setup.  This did happen but it took the BMS quite a few cycles to balance out the pack since they started well out of balance.  Another lesson learned.

Making it look nice

Dash Cap Installation
Once I got all the guts of the system working, I was able to turn my attention to fixing the interior.  I spent a good deal of time looking for solutions to repair the cracked vinyl dashboard.  This is a common problem with older dashboards.  I turns out there are a range of solutions from crack fillers on the cheap and ineffective end to professional removal and refurbishment on the beautiful and expensive end.  I opted for the middle ground--the dash cap.  A dash cap is a vacuum formed plastic piece designed to fit over the old cracked dashboard.  It's simply glued on top of the old dashboard with silicone adhesive.  Sounds simple, but is actually a lot of work to install properly.  The final product looks a lot better than the cracked dashboard but it's obvious that it's not the original dashboard--sorta like a Maaco paint job--much better than that an old oxidized finish, but nothing like first class paint job.
Integrated Instrument Panel
I really wanted the EV gauges integrated into the original instrument panel.  I don't like the look of gauges hanging off the bottom of the dashboard or mounted on top of the dash. I opened up the existing instrument cluster and mounted the state of charge meter in place of the now unused gas gauge, hooking the low battery warning to the old low fuel light.  I was able to put the Curtis multifunction display in the location of the tachometer, since I didn't have an analogue tach in the vehicle.  You can see the results on the left.  Finally I had the interior upholstery, door panels, and headliner replaced by a local shop.  They did a nice job, except for the speaker covers which I redid myself.  So far the only work I've subbed out on the job is the transmission rebuild and the interior upholstery.  I'm really pleased with the overall look of the vehicle now.
Completed Interior
The truck's big coming out party was at an EV car show last month on the Cal Poly Pomona campus.  My truck was there representing DIY EV conversion. The show included all the big boys, Nissan Leaf, Chevy Volt, and Tesla roadster.  The Reverend Gadget, of Revenge of the Electric Car fame, was also there representing the commercial EV conversion market.  You can see his EV speedster next to my truck.  That guy is definitely a character.  All in all the show was a lot of fun.

Driving Stats

My First Ever Car Show
One of the biggest lessons I've learned over the past six months is difference in energy use between conservative driving, normal driving, and unconservative  driving.  If I'm very careful about minimizing energy use I can get 70 miles out of a single charge of my battery pack. If I drive normally, not being particularly cautious about energy usage, I'll get about 55 miles out a charge.  If I just ignore my energy use and floor the vehicle at starts I'll get around 40 miles per charge.  I find when I have a limited energy supply and an ammeter constantly showing my energy use, it really leads to a lot of energy savings.  So, the stats
  • Range city driving: 60 miles
  • Max speed: 85 mph +
  • Acceleration 0 - 25 mph: ~3.5 sec
  • Acceleration 0 - 40 mph: ~ 9 sec
  • Charge time from empty: ~ 4 hrs using 240v source
This is now my regular commute vehicle.  I'm really enjoying it.  I still have several things left to do including: installing gas shocks to aid in lifting the bed, installing a cable disconnect for the main breaker, and making a sheet metal shield to protect the front battery pack from water during the few rainy days we have here in SoCal.  Those will be some nice summer jobs.

Friday, January 6, 2012

It's Running!

New motor mount with isolation dampers
I found enough time over the holidays to get all the essential things completed.  First I had to redo the motor mount to include rubber isolation dampers.  Thanks to those of you who pointed out I needed these.  Since I already had the motor mount welded without the dampers, it took a little ingenuity to figure out how to add the dampers without starting over from scratch. In the end I cut the original loose from the mounting brackets and installed a new structural element under the original with spacers to make room for the dampers.  Kinda of a Rube Goldberg solution, but it works.

Acrylic battery cover
I also built some acrylic covers for the batteries.  I'd never worked with plastics before and was worried about how hard this would be.  Fortunately for me my son recently learned some plastic skills and he helped me with the battery covers.  It really was a lot easier than I thought it would be.  The material is pretty pricey.  But it will keep fingers, tools, and other junk away from the battery terminals and still allow people to see them.  (I already like showing off my EV).  I still need to fab the acrylic cover for the main electrical board with motor controller, contactor, & DC/DC converter.  Just got the plastic for this cut today, so I should be able to get it done this weekend.

Bed reinstalled on its hinges
My friend, Chris, came over just before New Years and helped me reinstall the truck bed.  This too was easier than I had envisioned.  I welded some stiffeners at the ends the frame's c-channels and then tack welded hinges on the frame.  Chris and I then picked up the bed, set it place and aligned it properly.  The bed weights only about 220 pounds so two people can handle it easily.  I then tack welded the hinges to the bed.  We removed the bed, finished all the welds and reinstalled it.  Now I have a dump truck! 

Pin securing bed
At the suggestion of performance car enthusiast, I used a couple hood pins to secure the front of the bed.  I welded some tabs to the frame and the bed just in front of the wheel wells. The pins are accessible through the wheel wells so it's easy to lift the bed and display the battery packs and charger in the rear. (Please don't comment on the quality of the welds on the tabs for the pin.  I know I've still got a lot to learn about welding.)

I drove around the neighborhood and up and down some big hills to discharge the pack while Chris rode shotgun with the PC hooked up to the BMS.  After a couple of discharge cycles and some tweaking of the BMS parameters, I felt confident that the low voltage warning and the state-of-charge meter were both working properly.  So last week I started my EV commutes to work and back.  My commute is 20 miles round trip and I can make two trips on a single charge with about 10-15% charge left in the battery.  So I can get 40+ miles round trip.  This is a bit below my 50 mile design range, but it also included some highway driving.  Speaking of highway driving, I took it out on the freeway yesterday and today and no trouble keeping up with the average speed on the freeway.  My dash still isn't installed, so I don't know precisely how fast I was going, but I'm guessing about 65 mph and I had not maxed out the system.  I do a peak speed check when I get the dash and instrument panel reinstalled.

Still have a lot of stuff left on the todo list including:
  • Finishing battery and motor controller covers
  • Getting the interior reupolstered
  • Installing gas shocks to aid in lifting the bed
  • Putting a dash cap over the old cracked vinyl dash and reinstalling the dash
  • Installing the EV instruments in the instrument panel
  • Put a 220v outlet outside the garage so my wife can have her parking space in the garage back (I think I'll put this at the top of the list.)
A happy EV driver
I love driving it! It's so quiet.  The loudest noise is when the vacuum pump comes on.  Today guy in another Nissan D-21 followed me off the highway, pulled up next to me at the stop light and said,"Hey is that an electric vehicle?"  When I acknowledged it was he said "I new it.  I new it! I saw your batteries under the bed and knew it must be an electric vehicle."  We held up traffic at the stop light while he took photos on his smart phone.  That was even better than driving by the gas station on my way home.  I love my EV.  Now I need to think of a name for it.