Wednesday, September 8, 2010

Trunk Ventilation

One issue I frequently dealt with was the charger shutting down due to over heating. I would finish work and come out to find a car with less than full charge. Luckily most of the time it had charged enough to still get my home, but I found myself a couple of times sticking around work another hour or more. The temporary solution was to leave the trunk slightly cracked during non winter months and this did the trick.

I plan to ensure adequate ventilation this time and have installed two 120mm fans. They will connect directly to the 240v charger source and run continuously during the charge cycle. The fans are quiet (30 dB), low speed (1900 RPM), move up to 67 CFM and take 7.5 watts of power each.

Here is a shot of the mounted fan. The trunk is big ugly at the moment but I plan to reinstall the carpeting after the modifications are complete.

Here is a shot from the bottom of the trunk. I've installed a vent which will deflect water spray while driving. They are angled to take the incoming air which should close the vents as well during speed.

Thursday, September 2, 2010

Motor Cooling

One area I found that needed improvement was the motor cooling. There is an internal fan which does a decent job, but on longer commutes like mine the temperature of the motor just continues to rise. On really hot days I found the motor would cut out a little from time-to-time. My theory is this is the springs that hold the brushes down becoming too hot and allowing the brushes to float briefly.

My plan is to install four small fans directly above each set of brushes that turn on when the motor heats up using a thermostat. The thermostat is basically a temperature driven switch that will trigger a relay to turn on the fans. I selected 40C or 105F as the turn on. This will keep it from turning on during short trips but will ensure it starts cooling as soon as possible.

Here are the fans I used. They are 2" fans that do 20 CFM and draw .25 amps.

Here is one of the mounted fans and the thermostat. I made a bracket that attaches to the old temperature sensor and the thermostat bolts to the bracket.

When I manually enable the system I can feel a good breeze coming out the back the motor so that's a good sign. We'll see what happens after I get it back on the road.