Thursday, September 29, 2011

Extending the Range:

In my home-made, all electric pickup truck, I have been able to get about 35 miles per charge driving around town. On the freeway, I am hard pressed to get 28 miles. This is discouraging considering my daily commute is 20 miles each way, 75% of which is driving on the freeway. I could ask if my place of employment would allow me to plug in and charge the batteries while at work, but that really doesn’t align well with my goal of self sufficiency and independence. Besides, my calculations show that I should be getting 50-75 miles per charge. What’s going on here?

After doing more reading online, I learned that I was not charging the battery pack all the way. My pack is 120 volts. 100% charge is 127 volts. I was charging it up to about 129 volts and calling it good. Come to find out, that is only about 80% charged. To fully charge a 12 volt lead acid battery, you need to get the voltage up to about 14.5 or 15.5 volts. Duh!  For my 120 volt pack, I shouldn’t stop at 129 volts. I need to go all the way up to 150 volts or higher. I guess I knew this all along but hearing 1200 lbs of lead acid batteries bubbling as they entered the gassing stage made me a little nervous.  Turns out, that is a normal part of charging lead acid batteries to 100%. 

Charging all the way up to full made a huge improvement in my range, buying me an extra 8-10 miles. But a range of 36-38 miles still isn’t good enough.
Initially, I thought I may have a bad battery or maybe even Costco batteries are pieces of junk (The Jury is still out on that one). After not finding anything conclusive, I decided to take a different approach. Eliminate all sources of friction! REDUCE DRIVETRAIN, ROAD AND AIR RESISTANCE.

It’s all about the bearings:
I started by replacing the front wheel bearings because they are easy to do on a RWD truck. To my surprise, they extend the max range to over 40 miles. I actually drove 46 highway miles. That about killed the pack and it’s pretty scary driving on a busy interstate when you realize you can no longer go 55mph anymore.  55, 50, 45, 40 mph.  Why must there be a hill before my exit?  Move over onto the shoulder. 35 mph, 30. Somehow I made it to my exit and onto the last main road before I arrived to my neighborhood. I pulled over to let the voltage in the battery pack recover. If you let a dead battery sit for several minutes, it will recover slightly and allow you to drive a couple more miles.

I managed to drive the truck over one last hill before rolling over the other side and into my neighborhood. Home at last. I don’t ever want to do that again and neither does my battery pack. At least now I know the limitations.

Low Rolling Resistance Tires:  
After giving the truck’s battery pack a very thorough charge overnight, I drove it to the tire store and had them replace the original tires with low rolling resistance variety. After I got the tires, I took the truck for a freeway speed test. My old speed record was 70 mph. I have tried to exceed 70 mph a few other times but each time, that is all she will do.  With the new tires, I can drive 85 mph. Wow! A 15mph improvement. At first I didn’t believe it, thinking the tires were smaller and throwing off the speedometer or something. A second run with a GPS confirmed my new speed record was accurate.  

Real Wheel Bearings:
Try as I might, I could not get the rear wheel bearings out.  After 232,000 miles, metal on metal tend to meld into one piece.  Even after over 100 attempts of using the redneck mechanic removal method (throwing down the axle shaft on some wood on the concrete as hard as you can), the bearings would not come out.  I took the truck to Big-O Tires but sadly, they couldn’t get the rear wheel bearings out either. After a day of soaking the bearings in a corrosion blocker solution, they finally got them out, replacing them with bran new ones.

New distance record:
After charging the truck’s battery pack up to 100%, I drove it into work. Amazingly, this time, the 20 mile commute only depleted the battery pack to 80% state of charge. After sitting in the hot sun all day without charging, then driving 5 miles around running errands and then driving 20 miles to home at 55 mph, I pulled into my driveway with the battery pack at 40% state of charge. If I can drive 45 freeway miles with only using 60% of the battery, then maybe the battery would carry it further still. I estimate my max range is 50 miles but I don't want to confirm it lest I shorten the lifespan of my battery pack significantly.


Not Good Enough:
50 miles is fine for now but what happens when it gets really cold outside and the batteries have a 30% reduced capacity?  Eventually I want to install a heater. Running a 1100 watt heater during my commute will reduce my range by another 3 miles.

If this truck is going to be my reliable commuter vehicle all year around, it needs to have a 70 mile range or better. That would also extend the life of my battery pack significantly on the days I only drive 40 miles depleting the pack to only 60%.  So now what?
One word!  AEROMODS!


Take it from my sexy Electric Truck's ugly sister the Tesla, Aerodynamics give you excellent range.   Tesla has almost twice the battery capacity as my truck but over 4 times the range, (200 miles).