“It lives! IT LIVES!” I screamed as I stood over my EV Truck, gigawatts of electrical energy snaking from the engine bay towards the garage ceiling. No, well it wasn’t like that…
It was more of a sequence of LEDs lighting up in the right order along with a multitude of whirring and clicking noises, all signalling that everything was wired correctly.
After all the big work was done on the truck, the past few months have been filled with high and low voltage wiring. 12v automotive wiring is a lot more complex than high voltage, high current traction wiring, at least it seemed that way to me. Wiring up the Zilla Hairball was fairly simple thanks to a great user manual with descriptions of every connection, what it does and why, and how to break it if you don’t use appropriate fuses or diodes.
The Zilla requires a coolant pump, especially operating in Arizona heat. I am quite pleased with the location and installation of the system’s radiator, right in the stock location. I am now seriously pondering how to install fans.
The other pump that began humming away was the brake system vacuum assist, which was installed in the truck over a year and a half ago. Both pumps, and most fans when they get installed come on with the ignition key. I spent a lot of time deciding what I wanted to be able to switch, and what was to come on with the ignition and stay on. All the relays for fans and pumps are fed from one relay which also feeds the Zilla “Key Input” and also the start switch relay.
I also spent a lot of time figuring out where to put the main Zilla controller and its Hairball and their orientation, trying to squeeze them into the most efficient space possible. I knew later on this space would receive more components; yet to come is a current shunt for the meter which is essential for knowing when you’ll run out of juice.
Despite agonizing over where to put the controller I still ended up with a hard lesson learned. The bottom tab on the front, Battery Positive, was a bit tricky to get to once the controller was in. Busted knuckles and sweat; avoided by no gearhead in his/her lifetime.
I got smart with the hairball, knowing that fiddling with the little screw terminals would be a pain in the butt, its location worked quite well in that regard.
I mounted the 500A fuse and 200A contactor as far back as I could and tried to take into account spacing for bending 2/0 cable between them. Let’s talk a bit about ratings. The Zilla is a 1000 amp controller, so the ratings on the two components I just described sound a bit low, not so.
The way I’m using the Zilla, it’s likely not going to see 1000 amps, but if I did manage to shove that much current through it, the fuse would likely take a few seconds to blow and is not going to see full current for that long – fuse ratings also depend a lot on temperature… hey, so maybe it will blow in the summer? Isn’t building your own stuff fun? (This kind of fuse is actually recommended for 1000a controllers.)
The contactor rating is how much current it will reliably break at 300vdc. When the motor is accelerating it might draw 400 to 500 amps for a couple of seconds. If I where to switch off power the contactor would open and an arc would be drawn accross it, pitting and damaging the copper contacts. If I where to do this a few more times it would be in danger of not opening, possibly welding and sticking closed.
The likelyhood of the contactor not being able to open in an emergency is pretty slim, but if it’s been heavily used, the probability increases. Another reason I kept the clutch for this conversion.
Learn more about contactor relays here.
So, after realizing that I’d finally done it, I had completed my project to the point where it would actually move on its own, I was understandably quite excited. I aired up the tires and backed it out of the driveway. Heres a video.
I puttered around the neighborhood in first and second gear, having to constantly remind myself I wasn’t driving a regular car – stop pushing the clutch when you roll to a stop!
Then I put my seat belt on, did I mention I was excited?
Why is it so dang slow?!
Well… a few reasons; I was being cautious, the batteries where not fully charged and, as I later found out, I had to do some reconfiguring of the controller.
Communicating with the Zilla
No, you don’t have to speak Japanese. The Zilla comes with an RJ11 input which can be hooked via a cable to a PC or Mac comport via an adapter and you can use any RS232 emulator or terminal program to communicate with it (iPad or Palm Pilots also capable).
I have an inkling that, because the Zilla was not configured to use the speed sensor I installed on the motor, it may have affected speed, although the control is simply a toggle. Is there a speed sensor or not?
I took the truck on another test drive to see if this was the case. It did have a little more pickup on the first start, but sagging voltage let it down. Old batteries are not doing it any favors (other than to help it move), and by the end of the 5 minute drive, I had to crawl back up my driveway in first gear.
Another setting I tweaked may have also contributed to the second performance hit. LBV, low battery voltage, is a setting to indicate when the controller should limit motor amps to hopefully avoid damage to batteries. I took it from its setting of 36V to 70V, thinking I was helping. Well, it turns out that voltage is sagging under load to below 70V (on this 96V pack). Oops. So the controller cuts back, pedal to the metal or no.
New batteries or even a much better charger would help, as I could give the batteries a long charge, as a pack.
Let’s talk about the future. Lots of components to come. I mentioned a meter, but another huge one is a charger. Right now I am still charging a 10 killowatt hour battery pack with a 150 watt solar panel. It’s not even your average 8 hour deal.
With regards to a charger and the description of contactor ratings earlier, another couple of purchases need to be made. The system needs a fail safe. I’ve been told that another two contactors isn’t a bad idea. Completely isolating the battery pack from the motor controller is a very good idea, not only when the vehicle is off, but especially when charging.
The Zilla is designed so that battery negative is directly passed through to the motor negative. If somehow there is a wiring short large enough, battery positive could get connected to the frame, therefore possibly the motor. It’s a good idea to have redundancy in disconnecting means also, so I will be adding two more contactors – one more in the positive lead and one in the negative lead, likely to be located in the battery box.
This will provide additional emergency disconnect to the original contactor, and also isolate the battery completely for charging, servicing, or simply parking. And yes, in the cab there will be a big red “smack” switch which breaks power to these contactors.
Where to from here?
Hopefully it’s only going to get better. The interior and battery compartment need a lot of love and work. A few large purchases still need to be made, the first of which is an actual charger, I’m going to pull for this 5kw monster.
Then, in order to be able to use it to its full potential, I’m really going to have to do some serious work on getting a 240v outlet in the garage. It should be pretty simple, as the service entrance to my house is right on the garage wall. I’m spoiled.
It’s been quite an experience to get to here but there is much more to come. Getting this truck on the road legally is going to be an adventure. Stay plugged in.