1988 Honda Prelude conversion - fastest build log ever.

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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Nov 15 2019 1:43am

Interesting conundrum with the air conditioning. It looks like the battery coolant heat exchanger and the cabin evaporator together might end up being too big a load for the system. I can't exactly fit a new or bigger condensor, but I might be able to put a valve in where I can select between cabin cooling and battery cooling. If they go in series, it might mean the refrigerant is completely boiled by the time it makes it to the heat exchanger. I guess it just means the system won't get as cool as I like it. Not well versed on refrigerant cycles... :?

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 14 2019 8:02am

Air conditioning has been installed! What better way to test it than on a 41'C day. It's very, very noisy. And it vibrates through the chassis to the cabin, so I need some fully isolated mounts and a stack of that Dynamat to deaden the racket around the compressor.



The compressor does not sound good at all. Also, it's a fixed speed - 5500 rpm. Which means it winds up pulling 3.5 kW from the battery. Now the upshot is the nice cool air in the cabin:
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Also, I feel fully vindicated on my battery cooling system. The heat exchanger is between the discharge of the evaporator and the suction of the compressor, and it's still reasonably cool as it goes through the compressor. Meanwhile, the battery went from about 34'C down to 29'C in about 15-20 minutes. So that's great.

However similarly frustrating, the A/C only works when the Arduino tells it to, not when you press the button in the cabin. It turns out pulling 3.5 kW as you try and charge in hot weather is a counterproductive exercise. About the first 30 minutes are spent cooling the battery to 30'C. Which is good, but far out what a racket! Would almost be easier if there was full manual control...
Here's how it's currently wired up:
new Aircon wiring5.png
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Anything I'm missing here?

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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 14 2019 9:39pm

I decided to abandon the automatic A/C when charging. It wasn't working quite right, and the oscillation when you were right on the threshold was probably going to wear out the relays. So now it just works when you press the switch. When the human is hot, the battery is hot. Only thing now is that when you charge, it won't come on. So if it's really hot and you need to charge, make sure you let it run for 10 mins before switching off and plugging in.
new Aircon wiring6.png
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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 15 2019 7:43am



Liquid cooling for the win. Not bad for day four of 40'C +

Worth it.

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by Hillhater » Dec 15 2019 7:05pm

Again, i respect and admire your skills and determination.
...I am no A/C expert, But 3.5kW draw just for that A/c seems to be out of proportion to the job in hand.
I dont know how comparable it is , but these guys (DCAirco) quote a load of only 720 W @ 100% duty, (360W @ 50% duty), .. for a 2.6kW (9000 BTU) cooling output for a vehicle based , DC powered A/c unit. ??
https://www.dcairco.com/product/mining- ... onditioner.
I am not suggesting you use one of their units, but there must bee some clues as to how they achieve that efficiency.
..You may find some of their other systems,( Battery cooling, controls, etc etc) , interesting also.
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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 15 2019 7:38pm

I think the problem is that the compressor is set to run at far too high a speed. Frustratingly I can't change the speed, so it's all or none. I'm trying to get a replacement inverter unit for it so it will run at half the speed.

Also, the Prelude is a solar oven on wheels. It takes a lot of effort to get it down to bearable temperatures, and 10 mins in the sun will take it back to where you started. Hondas were notoriously hard cars to cool.

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by Hillhater » Dec 15 2019 8:29pm

Maybe $100 worth of Solartint would be a smart move ?
PS those DCairco units are used on Dozers , Graders, etc... i think they may have a decent heatload to deal with.
Do you know the BTU rating of your pump etc?
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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 15 2019 8:38pm

Seems legit...
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Hillhater   100 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by Hillhater » Dec 15 2019 9:26pm

Hmm ?... At 3.5kW /5500rpm yours seems to be 30% up on power consumption.?
But i notice the “COP” ratio stays at 2.1, whilst on those inverter drive units it is practically double that ?
So even if you can drop the speed down (??) to 3krpm, you would still be drawing 1.4kw .
...almost exactly double the 720W of the DCairco unit at the same output ?
Interesting !..is a DC inverter pump really that much more efficient ?
Last edited by Hillhater on Dec 15 2019 10:05pm, edited 1 time in total.
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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 15 2019 9:31pm

Well the rest of the plumbing is straight out of 1988, and I have added a rather large heat exchanger to the discharge of the evaporator, to it's actually pumping 'warm' superheated refrigerant. By warm, it's probably 10'C or something whereas it's normally around 0'C.
I think modern day cars use larger, and more efficient condensers too, which would no doubt help a bit.

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by Hillhater » Dec 15 2019 9:44pm

Well, if the “COP” ratio stays at 2.1, you may be pumping 7.0 kw output ? (23,000 BTU)
And, i bit of research suggests a typical car A/C is rated for 10-12,000 BTU (3.0-3.6 kw) OUTPUT.
..with a 18,000BTU ( 5.5kW) unit being extreem spec ! :bigthumb:
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jonescg   1.21 GW

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Re: 1988 Honda Prelude conversion - fastest build log ever.

Post by jonescg » Dec 15 2019 10:22pm

I have a PWM generator which I hope to set up some time soon. Might be worth dialing it back to about 1.4 kW electrical just to see what happens.

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