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Old 09-28-2014, 12:19 PM   #32 (permalink)
Master EcoModder
Join Date: Sep 2010
Location: Saskatoon, canada
Posts: 1,478

ChargE (not yet running) - '92 Mazda MX6 LX
90 day: 33.89 mpg (US)

Ford Prefect - '18 Ford F150 XLT XTR
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Originally Posted by Astro View Post
Vacuum pump if needed for brake assist.
Electric power steering pump unless you use the original pump driven off the rear shaft of the drive motor or have a manual steering rack.
Yes - I did miss those. I have the power steering pump and was thinking about using a separate 12V motor to run it. But it ends up being QUITE heavy. I'll find out how badly I need the vacuum pump when I get it rolling in my driveway. If my wife cannot get the brakes to function, I will add the vacuum pump.

You listed 50lbs for liquid cooling.
Is this for cooling the controller?
This seems like a lot to me. Of course i have no idea what would be involved in cooling a controller but i would have thought a few of litres of coolant at the most with a nice fan assisted aluminium radiator to cool it down. Like the after market ones they sell to cool transmission fluid.
Yes, the controller is liquid cooled. I kept the original rad with the original fan. There's a few liters of fluid, the pump, and some piping. The controller is happy up to about 55C so I was considering using the coolant to feed the original heater core. I'd still need a ceramic element to keep the windows clear until the controller warmed up ... and I'm not sure how the plumbing would work. I may need to add a shutter on the rad for cooler weather.

I should be high on the 50 lbs. I forgot, until I started typing this message, that the rad and fan and fill bottle were not weighed coming out of the car.

IGBT controllers, which is most controllers that allow voltages above 200V, have a voltage drop across the transistor. I've seen specs as low as 0.6V but they seem to be around 0.8 - 1.0 normally. When you get above 1/3 to 1/2 of the rated amps (which should be into your design factor or just for acceleration) the voltage drop increases - 1.0V - 1.8V. Since Power = Volts * Amps, a 1000 amp start at 1.8V drop is 1800W. Getting 1800W away from your controller is difficult. So the heat sink is designed to absorb much of that for a few seconds of acceleration and then the liquid cooling takes it away while you are coasting/cruising to the next light.

MOSFETS have a much lower voltage drop, but they can't pass as much current. So the MOSFET controllers have a bunch of MOSFETs in parallel to allow 1000 amps or 500 amps. But if you have 1000A at 0.2V, that's 200W and an air-cooled heat sink can do it (you still need to fan cool, and the heat sink has to be big, but you can do it)

I'm planning to use a mineral-oil coolant, like they use in large industrial transformers. It is not conductive, so if it leaks my controller won't be damaged. The coolant WILL BURN, but if the temperature is that high, my cables and all of the plastic under the hood is ALREADY on fire.
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