Plug Bug: Wiring…and more wiring

Electric Bug

I’m still waiting for batteries, but i’m getting a lot of the little details done. The car could be drivable if I actually had a battery pack. I can turn on the key and hear a satisfying “click” of the negative contactor closing. Hopefully the batteries are down in LA on a big boat that is about to come up to the Bay Area. I’m crossing my fingers hoping I get them before my week long thanksgiving vacation.

Here’s a shot of a bunch of stuff wired up. I’m using 2/0 welding wire for the battery interconnects. I may upgrade to 4/0 (which is recommended for the motor connection) at a later point if they get excessively warm while driving. I’ll be using 2/0 for wiring the battery packs together.


What is in the above picture? On the right side you can see the two fans covering a small water cooled radiator that cools the controller. The pump is underneath the reservoir, as previously mentioned on other posts.


Above it is the positive side contactor. This one is hooked up to the controller, and it will turn the High Voltage (HV) on and off. (A contactor is a way of turning HV on and off by applying a 12volt power to it)


For extra safety, I have a secondary contactor on the left side for the negative side of the pack. This contactor is controlled by “key on” and is the one I first hear click when I turn on the key. By physically separating them I ensure there won’t be any accidental way of completing the circuit.


Beneath the left (negative) contactor is the IOTA DC-DC converter. It is hooked up to the battery side of the positive and negative contactors. I initially thought “hey, why not hook it up to the other side, that way it gets turned on with the controller”. It turns out that is a bad idea; the Netgain Controller says to not do it because of voltage drop (or something like that). So, instead I use a 60 amp relay that is powered on when the “key on” comes on. This will power on the back “key on” accessories and allow the DC-DC charger to start charging the accessory battery. It will also provide power to accessories. The little white thing on the top of the left contactor is a High Voltage / 20 amp fuse for the DC-DC converters power. The wires feeding it are only 12 gauge, which good enough for 20 amps. The output wires are 10 gauge to the battery, which should be enough (it was what was originally used by the alternator).


Coming out of the motor are two little wires. These are a normally closed circuit that opens when the motor overheats. It is used to wire up a “check engine” light. The bug already had a powered wire coming in the back from the oil pressure light, and the light would come on when grounded. So, I hooked up “key on” power to the motor’s wires and input it into a 12volt/20amp relay. The relay does nothing when on, but when off it grounds the oil pressure light line and turns on the warning light. I was happy I figured this out, considering I didn’t know what a relay was just a few weeks ago.

On the left side is a wiring mess that I’m going to clean up one I have everything in its final place. I have two fuse boxes; one is a “key on” power source (directly from the DC/DC converter and battery) that goes to the controller, fans, water pump and reverse lights (which hooks up to the transmission). To the right of that is a regular fuse box for fusing other things that don’t need key-on power but do need a fuse. For instance, the controller has an “always on” power directly from the battery, and this is protected with a 5 amp fuse.

I have some other wires coming in for the heater. I just cut a hole to the left of the ash tray that I’ll use for the 3-way switch:


….more later!


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Hey dood whatcha doing about weather-proofing the whole setup? IIRC, the engine cover has vents in it… things could get moist in there! At the very least, didja put dielectric grease on the connections?

I can’t wait to see the whole shebang with wiring looms and whatnot… and a neon tube lighting up the whole compartment. :)


The back area won’t get wet; it should be okay. But yeah, the connections do have no-ox grease in them :)


John C. Randolph

So, when will you make it driveable by remote control from your iPhone? ;-)


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