1988 Honda Prelude conversion - fastest build log ever.

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... :?

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.

[youtube]6p6j6NdmoeY[/youtube]

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:


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:
View attachment 1

Anything I'm missing here?

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.

[youtube]LBiUo_5MDAc[/youtube]

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

Worth it.

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-airconditioning/dc-9001-12v-24v-74v-400v-dc-rooftop-air-conditioner.
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.

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.

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?

Seems legit...

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 ?

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.

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 !

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.

Quick update.

The air conditioning compressor has been powered down with a PWM generator which reduces the energy consumption down to about 2 kW while delivering the same cooling power as before, so that's a win.

The cell cooling power is awesome and works great.

Got the front-rear weight bias and total tare measured. 55-45 split front to rear. 1260 kg all up, which is about 160 kg more than original. Still getting ~150 km range on the freeway, but I need to do another long drive on a cooler day to see what it comes to.



Otherwise she's very happy with it. The master contactor inside the battery pack is stuck, which is not ideal, but it doesn't make any difference to the operation of the vehicle. I now have a manual isolation point in the back.

jonescg said:

1260 kg all up, which is about 160 kg more than original. Still getting ~150 km range on the freeway, but I need to do another long drive on a cooler day to see what it comes to.

Click to expand...

Sounds good to me! Range is comparable with an original Leaf (if not better) but over 250kg lighter.

There's too many big, heavy expensive EVs about. Some smaller/lighter/cheaper options, like you've built, would suit many people.

Quick, and sad update on the Prelude.

The battery developed a coolant leak, and that caused a pouch cell to corrode. This lead to the cell voltage dropping and flagging the BMS to take it to the workshop.

I put it up on the hoist and dropped the battery out. I pried open the lid and this is what I saw.

[tube]nh86_lf7v14[/tube]

The condensation managed to spread amongst the whole battery and at least two modules are beyond hope. The rest are OK, maybe useful for a storage project, but I would never use them in a car again.

I need to eat this big, stinking turd sandwich.

There's about $20k worth of cells here gone to waste, and I need to make this car roll again. So I need to sell the race bike, or something. I'll own it. But it likely means I'll stop building batteries for people. I just can't afford the risk.

Battery building is hard, and when you do it for other people, you take on full responsibility for it.

Pleased to report this battery was finally built and installed last week.



The owner drove it off into the sunset, and I hope I never need to look at it again.

https://youtu.be/WRPXfSc43no
[youtube]WRPXfSc43no[/youtube]

jonescg said:

The owner drove it off into the sunset, and I hope I never need to look at it again.

Click to expand...

:lol:

Great work! Did you get any relationship counseling in return...? :wink:

Finger and toes crossed for you Jonescg..

There's about $20k worth of cells here gone to waste, and I need to make this car roll again. So I need to sell the race bike, or something. I'll own it. But it likely means I'll stop building batteries for people. I just can't afford the risk.

Battery building is hard, and when you do it for other people, you take on full responsibility for it.

Click to expand...

How are you feeling about this now ?
Will you still assemble packs for others ? Or is it just too much of a financial liability still ?

Incidents like this would keep me awake at night if i were selling batteries..
https://www.news.com.au/national/nsw-act/news/chilling-pictures-reveal-devastating-damage-from-darlinghurst-terrace-inferno/news-story/20248f27449af4b66b06298c0525ba02

Well of the 8 modules, two were toast and I had one spare. They went to a friend's house where he's using them as a home storage system. Don't worry, they're well separate from the house and inside a fireproof cabinet. So far so good - no grief at all with them.

I'm not really building batteries for others any more. It's too much work for a start and I can't charge enough for my labour. Quite a few ES members have batteries that I built for them over the years and are still enjoying crazy LiPo power, but I always lose sleep over the potential for things to go very bad. In general I'm pretty confident in my work, so this failure was a blow.

At least in this case, and hopefully in any other case, the BMS did exactly what it was supposed to do and prevented a disaster. It didn't protect my wallet, but that was something I just had to wear. It was my workmanship that failed and I honoured it's repair. I still owe about $8k to the owner as she stumped up for the new cells. It was quite frustrating as I lost about 3 months trying to buy LG pouch cells out of China, but at least I got (most) of my money back.