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 Safety Notes

 for working on the truck

This note began with a list of Do's and Dont's from Michael Mutch on the preparations needed to work on the EV. I've removed some personal notes from the original email and added my own emphasis where I thought it helpful.

Simply put, the electric power in the truck's battery pack can kill you if it should find a path between your hands as that path travels near your heart. If the electricity finds a shorter path, say across fingers of the same hand, it can severely burn you. The power in the batteries is way more than is needed to weld steel.

The metal of the truck is indirectly connected to the Negative side of the battery pack. If you lean on the side of the truck and touch a wrench to the Positive side of the battery pack, the electricity will try to run through your body, between your arms and across your chest. It isn't always fatal but why chance it? Even when it doesn't kill, the high currents caused by a short circuit can cause the batteries to generate a dangerous amount of heat.

Also, keep in mind that you don't want to cause a short circuit even if your body is safe. It's very easy to put a wrench on a nut and accidently let the body of the wrench touch other metal, like the frame which holds the batteries. The resultant lightning bolt can so surprise you that your hand will move at very high velocity out of the area. I have gotten severe cuts (on other projects) when something like this has happened.

Thus, there are some important rules to follow when setting up to work on the truck. Ignore them at your peril.

Most of the safety warnings I encounter are exaggerated thus I sometimes ignore such warnings. However, I consider the EV environment dangerous enough to have helped construct this document.

General Areas to Consider

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  1. Knowledge
  2. Work environment
  3. Yourself
  4. Other people
  5. Electric Vehicle Prep


Work Environment


Other People

Electric Vehicle Prep

Initial check list:

The bulk of this section describes how to disconnect the battery pack such that you can work on the controller etc. The sequence described here is just run in reverse to restore the EV to its driveable condition.

The main traction pack voltage is isolated from the chassis, BUT there is ground available through the dc-dc converter. If you short the pack to chassis ground there will be sparks!

I will refer to the truck from the front looking back.

  1. Disconnect the long cable that lies across the rear battery bank and connects to the rear right battery (in the rear pack). This will create two banks. One of 5 batteries (front) and one of 15 (rear).
  2. Disconnect the cable that connects the shunt in the grey plastic junction box in front to the pos on the front left battery in the rear pack.
  3. Disconnect the cable from controller neg to battery neg. Front pack - left rear battery.
  4. The traction pack is now isolated from the controller and the dc-dc converter; however, there is still 120 volts in the capacitors inside the controller box! Use a jumper from controller B+ to a good ground (metal fence? hose bib?) to discharge the caps. (you may have to scrape off a little of the protective coating on the controller terminals to accomplish this) Repeat this with the M terminal to make sure.
  5. Check the terminals for voltage before proceeding! The shock from the undischarged caps is definitely jarring! It is now safe to work!

When you reconnect the battery pack, do so in the opposite order. Negative first, positive last. I like to connect the long cable across the rear pack last. Expect a small spark, it is normal and fine.