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.