Friday, June 23, 2017


Last summer I was complaining about the undersized cooling system in the PorschEV and how it would send the inverter into thermal limiting, usually at the most inopportune times. How does sudden loss of power at highway speeds sound? The good news is the inverter protects itself from heat damage, but it's pretty disconcerting when it happens.

The cooler was a dual core Derale with one coolant loop for the motor and charger and the second for the inverter. With two Pierburg pumps and a 10" electric fan, it was adequate for the cooler months, but this is TEXAS and in the Summer (that's 2/3 of the year) it just didn't cut it.

A bit of Googling turned up a higher capacity aluminum replacement for the stock Porsche 924S radiator that was bundled with two 10" electric fans. Unfortunately, those fans  didn't fit so I wound up ordering a pair of 9" fans that did the job. I also found silicone 90 degree Elbow Reducer hoses that connect the 1.5" radiator outlets to the rest of the 5/8" system.

Here's a comparison of the two coolers. We're clearly adding capacity with the new system.

Mounting the new radiator had its own set of challenges. Long story short, the lower 3" of the radiator support was cut off at some point in its lifetime, so the original radiator was sort of dangling, held in place by some creative application of zip-ties. I devised a more secure if equally creative support involving angle iron and eye bolts. It feels secure and at least it's all metal.

The plumbing went together fairly easily using what was already there and rerouting the hoses so the pump output goes first through the inverter, then through the charger and finally through the motor before it passes through the radiator and then back to the catch tank for the pump.

One pump and catch tank was removed (set aside for the next project) and I think I'll use the space for a windshield washer fluid reservoir. Only one change was needed to attach the inverter output to the charger input. With everything on one cooling loop, I hope there is enough capacity to keep it all cool calm and collected.

The first short test is encouraging. With ambient temperature in the low 100's F (up to 104 in the sun on the road), a short 5 mile run around the neighborhood had the inverter steady at about 46C while the motor showed anywhere from 50 to 90C. At stop lights, the temps dropped to about 43 for the inverter and 48 for the motor, well below the 55C max recommended input temperature.

We're checking off the list of annoyances little by little. Next item is to get the air conditioning charged and working. How did we ever get along without it?

Update: 6/28/2017

I had experienced some coolant overflow on charging with the old system, so I was anxious to test it on a full charge starting at 366 volts. I have the fans set to run during the charge process and the temperature held at 34C (93F) with an ambient temperature around 33C (91F) in my garage. It's noisy but cool with no coolant loss. Happy times!

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