I guess my wording was not the best.

“However, remember that as you climb, you need more power. As you decend, the regen brakes return energy to the battery pack.”

All I am trying to say is that in typical driving cycles you don’t just climb. Obviously, it takes more power and energy to climb a hill than driving on a level surface. By the same token, as you decend a hill, your regen braking is returning energy to the battery pack.

So granted, if you are on the east side of the Rocky Mountains, and head west over a mountain pass, you could use up your electric range before reaching the highest elevation. However, on the way back down, you would actually charge your battery pack and perhaps have a 40 mile AER once you return to plateau level.

Why do you need more power as you climb with an EV? I would think you need less power because the air density decreases and so does drag.

One scenario we occasionally have in Florida is high wind. 45 mph headwind @55mph would require 23 kW and reduce single charge range to 18 miles.

My model accommodates variable SOC for recharge. I have heard that the Volt has a separate 12V battery for accessory power. A 200 Ahr @ 50% SOC 12V battery is enough to supply all accessory power during a single 320V battery (50%SOC) discharge cycle. Therefore, I will have to eliminate accessory power drain from my single charge 320V battery range calculations. I don’t know if there is any significant drain/switching losses at idle speed from the 320V battery.

Indeed. This is the number Raymond asked for (actually 55 mph), not the 25/29 kW number you gave him. I was just trying to make that clear.

I haven’t looked in great detail at your model as of yet, but it appears to be correct (my calc’s indicated a need for an additional 5 kW power of power for every 1% in grade, based on a fully loaded 4000 lb Volt traveling at 60 mph). See more here:

http://gm-volt.com/forum/showthread.php?t=133

However, remember that as you climb, you need more power. As you decend, the regen brakes return energy to the battery pack. For the 17 mile electric range while climbing a 3% grade, your elevation is increasing about 160 feet per minute. After 17 minutes of steady climbing at 60 mph, you will have increased altitude by 2700 feet. Not something you will do in Florida or Kansas.

As far as 146 miles or 2.5 hours of climbing, this equates to an elevation change of 23,400 feet. Unless you are driving in the Himalayas, I don’t see this scenario playing out in the real world.

Also, based on nasaman’s latest info that the Volt’s AER may exceed 65 miles when the battery pack is new, would obviously change some of these results as well.

You are correct in your statement about range (under the assumed conditions). If you look at the attachment “EV_Car_Volt 3a” in Forum, Engineering, “Requested Modified Model Parameters – Thanks for the feedback”, at the very end of the attachment, the number for Cruise Power at 60 mph is 14.9 kW. The higher number for cruise power you mentioned in your post is for a road grade of 3%. The range with 3% grade is about 17 miles. With about 8.5 recharges per tank with the single 6 gal gas tank, the range per tank @60 mph with a 3% grade is about 146 miles or 2.5 hours.

One of the reasons I did the model is to be able to ask “what if?” questions. I would hate to drive on a steep grade only to get stuck after 2.5 hours.

The cruise power @55/60 mph with a 500W accessory load is about 25/29 kW.

This looks to be high by a factor of two. At 29 kW/60 mph Volt EV range would be only 16 miles. Similar vehicles such as Prius run around 12-14 kW at 60 mph. Furthermore, your own comments in and graphs in the Forums indicate more like 12-14 kW.

See Forum, Engineering, “EV Model for Simulation: GM Volt. Design your own EV.” It has the model and all the design parameters. I used a very aggressive value for Cd: 0.22. Much better than the Prius 0.26. After reading about all the GM wind tunnel work, I thought that they would try to best Prius. The body stylists probably have other ideas. If anybody has technical input on Cd or frontal cross sectional area let me know.

Van,

A123 Systems is claiming 1000 cycle life @10C for 100% DOD.

Tom