Sunday, May 22, 2011

Building weatherproof boxes for the electronics

The standard design from EA involves mounting some sensitive electronic parts and terminal blocks out in the open in the engine compartment, subject to to water, dust and other nasty things.  Working for a solar power company, I've learned to protect this kind of equipment as best as possible to give the car the longest possible life without having to worry about electrical failure, rust and ongoing repairs.

I started with the relay board.  EA supplies a thick plastic board, predrilled for mounting the components.  I bought a NEMA4 rated enclosure sized to fit the board inside.  You can see I had to do a bit of machining to make it fit.



I mounted the relays and the terminal blocks to the supplied board.


I then followed the instructions and wired everything up.


Here's how it looks with the clear cover on the box.  I bought the clear cover option so people can see the internal workings of the system and I can keep an eye on things for moisture intrusion, discolored wires, etc.



Next I moved onto the contactor.  The contactor, a small relay and two terminal blocks are supposed to be bolted to the side wall of the engine compartment.  I wasn't comfortable with that, so I proceeded the same way as the relay board above.  Here's the contactor - it's essentially a very large and powerful relay that is wired between the motor controller and the motor.  It needs to handle 600A of current flow.


The boxes I bought did not have internal mounting plates available, so I found these pieces of plastic sheet at Lowes, and machined one to size to fit into the box.


I spent a lot of time figuring out the best position for each part inside the box, making sure there was enough space for wire bends and clearance for inserting and removing wire connectors.  Here's a picture of the final assembly.  You can't see the clear mounting plate with the protective film removed.



Then I moved on to the potbox.  Alert readers will remember that the potbox assembly wouldn't fit into the space defined by EA because the brake proportioning valve was removed before I got the car, so I had to do something.  I decided to disassemble what EA had me build, and stick it into a weatherproof box.


Here's how the potbox fits insde the box.  Just right.


Another change I had to make was to reverse the mounting of the accelerator cable pivot post.  It sticks up too high, so I'll just flip it around.


I figured the plastic sheet wouldn't stand up to the stress of the moving parts, so I made a metal plate that the potbox will mount to, which will then be mounted to some embedded nuts in the box.



I drilled mounting holes in the box and then into the firewall.  I installed rivnuts into the firewall and bolted the box into place.  I sealed around the bolts and washers with silicon sealant.


Here is the potbox in place, with the accelerator cable coming through from the left side and attached to the pivot arm of the potbox.  When I continue the build and figure out where the potbox cable needs to go, I'll drill a hole and install what we at REC Solar call a pongi - a weatherproof fitting that compresses down on a cable as you tighten it down.  I don't want anything coming into the box.


I'll do the same for the relay board and the contactor box when I mount them.  Well I'm off for a 2-week solar monitoring road trip, so the car gets to sit and wait for me to return.