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GMC Somona with Open Revolt

Over the past few months we have converted a 1998 GMC Sonoma that had a blown motor to electric drive. In order to keep cost low I built and have installed an open revolt Cougar controller. Last week the truck finally made its first long drive and the controller worked out great. The plan for the truck is to use it as a daily commuter with a 60 mile round trip. Since I will always be driving the same route at about the same speed this makes a perfect test bed for various efficiency mods. I want to get some data on the various mods and how they change the Wh/mile of the truck

Right now the truck is in pretty bad shape as far as efficiency is concerned. I am collecting data now so I have a base from which to compare to. Here is a photo of the truck and of the Cougar controller in the truck before a case is put on it.

http://img30.imageshack.us/img30/6817/etruck.jpg

http://img687.imageshack.us/img687/3964/openrevolt.jpg

The quick rundown on the 1998 GMC Sonoma

Batteries - 14, 6 Volt DEKA GC25
Motor - Advance DC FB-4001A
Controller - Open Revolt Cougar, 500 Amp

Using a spare Hass 300-s a current/voltage meter is measuring the voltage and current at battery pack every 0.1 seconds. Multiplying these values gives the power being drawn from the batteries and then integrating the power values gives the energy usage. From this info as well as coast down tests I found my coefficient of drag to be 0.52 with frontal area of 24 sq ft. I have a horrible CdA of 12.4 . I have not easily measured the rolling resistance but I am sure it is on the poor side. These numbers agree pretty well with the EV calculator.

The next step is to directly measure speed and temp so I can reliably get numbers on Wh/mile before I start improving the CdA and rolling resistance.

Do you have the original truck bed that you are planning to put back on?

If not, maybe that's a good opportunity for a lightweight/aerodynamic rear body for the truck!

A custom aero-cap would look great on that thing!

Thanks for the suggestions. I do plan on putting a tapered cover on the back of the bed.

I like the air dam idea. If I plan on building an full under tray for the truck will an air dam help?

Quote:

Originally Posted by AltFuel (Post 248535)

If I plan on building an full under tray for the truck will an air dam help?

I think the more you do, the better.

Less air getting under the truck, means the belly pan might not have to be so perfect. Just my opinion, other certainly will chime in.

14x 6v = 30 miles or 40 miles

I don't think you will make 60 miles round trip without a recharge in the middle.

To achieve 60 miles you would need to drive very slowly AKA 25mph or so, with a near WOT throttle position (lowest controller losses) and you still would be in the high DOD area.

Good Luck
Ryan

You are correct about the range, the farthest I got on a charge before the pack had a cell hit 5.25 V was 32 miles. I could have probably gone 1 or 2 more miles but the truck was having trouble getting past 35 at that point. Fortunately I can recharge at work so it only needs to go 30 miles between charges. I almost run dry going to work, returning I have a little bit of charge to spare. As soon as I get the cash and time I am going to put in 6 more batteries to bump the system voltage to 120 V so I don't murder the pack.

Over the past 2 days I was able to get some data for the truck at 45 mph. There is a 3 mile stretch of road that is absolutely flat near work. I have traveled it 5 times going both north and south at 45 mph while logging the battery current and voltage. Trip A and B were on 1 charge, Trip C , D and E were on 1 charge. I rounded the current to the tens place and voltage to the volt. There was wind from the south both days. Since I was going 45 mph I cover 1 mile in 1.33 mins or .022 hours. To get my Wh/mile I just multiply the watts needed to go that mile at 45 mph by .022 hours.

Trip A - Heading South - 310 A @ 69 V - 21390 W - 470 Wh/mile
Trip A - Heading North - 280 A @ 70 V - 19600 W - 431 Wh/mile

Trip B - Heading South - 320 A @ 68 V - 21760 W - 479 Wh/mile
Trip B - Heading North - 290 A @ 68 V - 19720 W - 434 Wh/mile

Trip C - Heading South - 310 A @ 68 V - 21080 W - 464 Wh/mile
Trip C - Heading North - 270 A @ 69 V - 18630 W - 410 Wh/mile

Trip D - Heading South - 320 A @ 67 V - 21440 W - 472 Wh/mile
Trip D - Heading North - 290 A @ 68 V - 19720 W - 434 Wh/mile

Trip E - Heading South - 320 A @ 66 V - 21120 W - 465 Wh/mile
Trip E - Heading North - 300 A @ 65V - 19500 W - 429 Wh/mile

This averages to 449 Wh/mile at 45 mph.

This will be my base to compare future modifications of the truck.

I would strongly recommend trying to run her in 1st or 2nd gear and definately run as long as possible in 1st, 2nd, etc.

On my EV when I want to go further I limit max current to either 50 amps, 75 amps or 100 amps depending on how far I still need to go.

I slowly ramp up speed and push the throttle in as I speed up keeping the amps constant. Then once my throttle is to the pedal I let the thing speed up slowly (and its slow) and the top speed ends up 6-8mph faster after some time and my amp draw is much lower, I then move into field reduction since I don't have extra gears.

If I were you with your paticular setup I would accelerate glacially in low gears, the odd part is (at least on my ev) the acceleration is faster than you would expect using the ammeter as a guide to accelerate very slowly at low amps slowly letting the throttle out.

Doing this along with airing up the tires to 50 or 60psi and coasting a lot will dramatically increase your range. I can double or triple my range doing this because of how FLA behaves. Literally a few seconds at 500amps is like a few miles at 200 amps and many miles at 100 amps.

Cheers
Ryan