Safety

I had initially thought safety was well covered. With 4 levels of safety interlocks, I never imagined I would witness a failure of all 4 systems, but I did. And even more frustrating I am not aware of any mistakes made. So while I hope you never witness such an event, I hope you can learn from this situation.

If a DC controller fails it will often fail in the full on position, or a dead short. So one must design for this possibility. I had the system designed so when one turns the key off; power is cut to both the controller and contactor. I even have a secondary cut off switch that also cuts the power. This did not work in our case. I had noticed the controller was getting hot, very hot in operation and I decided to add 1/2" Al plate with additional air space to help keep the controller cool. 3 miles into the test run the controller went full on for an exciting time. Curtis did replace the controller under warranty. It seemed like the B1 terminal was loose and heated up causing a series of failures.

	I have two circuits to the controller, the small relay in the upper right of the picture controls the low power or "on" circuit to the controller. When the controller failed this no longer worked as the controller was fried, with plenty of smoke and some nice sparks. In this event the contactor in the center of the page should cut the high power circuit but it too fused in the on position. I had swapped a perfectly good and working Albright SW200 contactor out because the specs on the Albright were 250 amps and 125 volts. With this Jeep running 500 amps and 150V I was worried we were pushing the safety limits. The Albright is back in the Jeep. The Tyco controller pictured here is rated at 500 amps and 360V, but I no longer believe the published specifications The terminals are 1/2 the size of the Albright but when I double checked with the company they said I had the right Tyco model and to trust the specifications. WRONG!! As you can see I properly had a 750 ohm precharge resistor and there is a coil suppression diode hidden from view. The power is supposed to flow from A1 to A2 and I had it right.
	Tyco maintains there must have been much more than 500 amps on the circuit for it to fuse shut. The one time emergency cut off is 2000 amps, far more than the batteries can put out. I find it difficult to believe the Tyco ratings are correct because I have two CNN 400 amp fuses, one in each battery pack in the circuit. Both fuses are still good! The fuse is in the center of the battery pack on the left. While Tyco is to replace the contactor I have lost my confidence in their product. I am switching the 400 amp fuses for 350 amp fuses for an extra margin of safety in the future.
	Here you can see the red knob, left that acts as a secondary key to cut off power. But since both the contactor and controller were fried in the on position the emergency disconnect did not work. I have now added a manual disconnect with the red lawn mower pull handle. This is connected to a manual disconnect under the hood. This is the red handle in the middle of the picture.
	When the handle is pulled inside the Jeep it pulls the manual disconnect free. So now we have a 5th level of safety in the cab.