My area is mostly flat land (central Ohio) and my 2007 Zenn (model 2.22) has been upgraded to 35 MPH - with Regen turned off. I always drive my car between 30 and 35 MPH, and my summertime mileage after a full charge is invariably 26 miles. I am not complaining though. Twenty six miles is a lot of errands, and more mileage is available during the day by taking advantage of “opportunity charging”.
My batteries are six sealed Discover 12 volt lead/acid AGM batteries, for a 72 volt system. For the Zenn, these batteries are housed in two battery boxes. The forward box contains two batteries, and the rear box contains four.
During cold winter days the range can drop drastically. Last January I was lucky to get 8 miles between charges. So I started reading up on ways to improve low winter range. The answer is - keep the batteries warm. This led me to one solution described in a document I wrote, entitled “Extend Zenn Winter Range with Battery Warmers”. In this Microsoft Word 26 page document with pictures, I described the steps taken during my installation of the 110 volt electric battery warmers and the insulation.
To see or to download this document, click on:
http://groups.google.com/group/zennowners/subscribe?note=1
Then click on FILES on the right side of your screen, where you will see the document title. Click on the title and choose OPEN or SAVE. OPEN will display the document. SAVE will download it to your computer. The SAVE option is, by far, the fastest option - and you will then have a copy on your computer, ready to print out or whatever.
The photos are in color, and some of the annotation I added will be hard to see if you don’t use a color printer to print the document out.
Also, when you bring up the document, give it a couple of minutes before doing anything. There are 24 graphics (photos and sketches), so it will take that long for all of them to appear.
The file size for this document is 1.73 mb. 
I just realized that before you can access this document, you must first JOIN the forum where it resides and then login. It is a free Google forum called “ZENN Owners”. Sorry about that.