Speed up your Zenn

Has your state recently raised its NEV speed-limit to 35 mph, but your Zenn is still limited to 25 mph by the controller setting? You CAN change the speed setting yourself.

First, a few little warnings and disclaimers.

• If 35 mph is not the legal speed limit for Zenns in your state, it's not legal to make this alteration. Don't blame me if you get a ticket.
• Your Zenn has a 5hp motor, which is a little bit lightweight for a lot of running at 35 mph - so it might heat up the motor a bit if you push it, especially on a hot day.

  If the overheat indicator light comes on, the motor will then power down to help prevent damage. This limits you to about 15 mph until things cool down, which you might find inconvenient if you were planning to get somewhere on time.

  Alternatively, if the light comes on, you can pull over and turn the motor off for 10 minutes or so.

  If you overheat your motor repeatedly, you may find yourself replacing the motor ahead of schedule. According to rumor, a very determined gentleman from Montana did manage to kill one of these Zenn motors this way; )

• Your batteries may run down more quickly, so plan accordingly. You can cut your range in half by running at 35 mph for a while, although some folks who've done this modification report very little difference in range.

  This is the Peukert effect in action - which means in a nutshell that the more amps you draw from your battery at a time, the quicker you'll drain your battery. It's not a simple one-to-one equation like a savings account, where you put in 500 amps and draw out 500 amps at any rate you like; the Peukert effect means that you put in your 500 amps, and get penalized for high-rate withdrawal; )

  The better your batteries, the less this effect will affect your range, because the Peukert number is generally lower on a high-quality battery.

• This modification may void your Zenn's warranty. Potentially. If they can make a good case that your warranty claim is directly related to your increased speed.
• Your mileage may vary. The batteries in your Zenn might not have enough zing to get you to 35 mph (except downhill, or with a strong tailwind, or behind a tow vehicle), even with properly modified controller settings.

  The important thing to remember is that these modifications LET you go 35 mph - they won't MAKE you go 35 mph. The speed you achieve, and how quickly you can accelerate to that speed, depends on other things besides the controller setting.

Okay, that's it for the caveats; you're a grown-up. (Aren't you? Maybe I should have put one more warning and disclaimer on here - if you're NOT a grown-up, don't go modifying Momma's car without her permission.)

Shall we begin?

You'll need:

• GE Sentry Software, version 4.07.00e. The forklift electronics store has created a software kit just for Zenn owners, which includes a service CD with GE Sentry software version 4.07.00e, the GE operating manual for the E1 controller, and a bunch of cables; )
  
  
• A couple of files (which I will send you for free upon request) called "35mphv2.ges" and "gl4j.mdb". These will have the settings needed to run the car at 35 mph.
• A laptop or some computer to run the software and hook into the car. Any old laptop running pretty much any version of windows should work.
• Serial connector cable and power patch cable. These are supplied to any EV dealer, so it's easiest to go with them if you can. They will also have instructions on how to hook these cables up to your laptop and your car's drive computer.

Ready...set...reset!

• Car must be turned off and key out of the "ignition" while doing the changes.
• Connect computer serial port to drive computer port and connect drive computer to power. See instructions on how & where to connect the serial and power cables.
• Open GE Sentry software. Under the configure tab, set the comm port to whatever you're using. Under the configure tab, select change user level. In the window opened & under new access level field, type OEM3. Under the file tab, select import -> control type.

  In the window opened, select GL4J from the Sentry v4.07.00e folder.

• Back up old configuration. Tempting though it may be, don't skip this step; ) You may want those old settings. If nothing else, this is a good way to assure that your connections work.

  Click the Read button to upload your current settings. Click the Save button and choose an appropriate name.

• Update drive computer. Under the file tab, select import -> function settings. In the new window opened, select 35mphfinal from the Sentry v4.07.00e folder.
  • Select the "Download" button to save the setting changes to the drive controller. You will see the progress of the download and when it is complete, you will see a popup stating you will need to reset the drive computer for changes to take effect.
  
  
  
  
  • Disconnect the power cable to the drive computer, re-hooking up the barrel connector.
  • Disconnect the serial connector and reinsert the serial connector cap.
  
  
  
  
  • Turn off the car with the red master disconnect switch on the driver's side of the car. On is pointing forward, off is pointing to the side of the car. Leave it off for at least 60 seconds and then turn the switch back to on.
  • Depending on your car version, you may not need to do the following:
  • Open the driver's side door. Do not yet put the key in the ignition.
  • If you do not hear a series of two beeps, you are done and can now drive your car.
  • If you hear a series of two beeps, you will need to close and open the driver's side door, waiting for a repeated pair of beeps each time, until they stop. This is generally a total of four sets of two beeps. There will be another set of five or more beeps approximately 30 seconds after this reset.
  • You should now be able to drive your car.

What's up with all these fields?

• Field 13 - "Rolling radius in inches". Roughly speaking, each 2 you decrease this field by gives you one more mph. For example, if you wanted 40 mph the current value of 76 would be set to 66. This was 103 in the Mar8 release.
• Field 7 - "Minimum field current". Set to 78 on our "test ZENN", it was kind of overkill with the Discover pack. On the other hand, it seems insufficient on the older packs to get to 35mph on flat ground. It's probably best to test out each car to make sure the acceleration is what you want. Take a stab at 72 or so with a weaker battery pack. This was 88 in the Mar8 release.
• Field 21 - "MPH Overspeed". This isn't as essential, but it appears to give a smoother ride. It also seems to be the field that lets feathering the accelerator work. This was 250 in the Mar8 release.

That's it! Drive 35mph, enjoy, and drop us a little note to say how it went. We're doing a little informal research; )

Need the "35mphv2.ges" file, or some help with this project?

The first key to wisdom is assiduous and frequent questioning.
- Peter Abelard

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