Prelude conversion project - some questions

Technical discussion on converting internal combustion to electric
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jonescg
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Re: Prelude conversion project - some questions

Post by jonescg »

So this definitely highlighted a need for cooling, especially when fast charging. It's probably not an issue in daily operations where it does no more than 90 km a day and is charged at a low rate, but it's giving me ideas for the CRX conversion where I hope to have two chargers installed more or less permanently and take it on the odd long trip. But the hard part is making the cooling plates - nobody does vacuum brazing and I'm a bit gunshy with adhesives. But I'll keep looking into it.
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Re: Prelude conversion project - some questions

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I really want to experiment with the E fluid total cell immersion idea and Lexan walls on the battery pack behind the backseat so I can see if there are any bubbles indicating hot spots etc ....
The problem is, I can find a heap of technical data ..... but it seems it's a bit like buying a new Rolls Royce, if you have to ask the price then you clearly can't afford it ......

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Re: Prelude conversion project - some questions

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I'd avoid the likes of 3M products such as Novec - they are effectively PFAS. It leaks like a sieve due to its very low viscosity too.
And yeah, very expensive...
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Re: Prelude conversion project - some questions

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Quick temperature check on the coolant as it leaves the heat exchanger:

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Re: Prelude conversion project - some questions

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Also, some boring photos from my trip.
Trust me, hanging around for 4 hours in Williams while the car charges as 3.5 kW was pretty boring...
Charing in Mt Barker:
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Double-charging in Kojonup:
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Obligatory Albany Wind Farm photo:
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The New Tesla Destination charger in Albany finally works on all cars. If it works on the Prelude, it will work on anything!
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Quick - get onto it!
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The new WA Electric Highway / Tesla supercharger site is at the bottom of the hill near the old gaol.
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Re: Prelude conversion project - some questions

Post by brendon_m »

jonescg wrote: Thu, 03 Nov 2022, 17:42 Quick temperature check on the coolant as it leaves the heat exchanger:

I thought you didn't have battery cooling on this battery?
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Re: Prelude conversion project - some questions

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I don't but I'm willing to install it again and give it a go. My challenge is to get two 12 mm thick cooling plates which *dont* leak... Something like @necrogt4 has done on the Mazda, or even a cheaper laser cut plate sandwich with better leak-proof-iness.
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Re: Prelude conversion project - some questions

Post by brendon_m »

It's probably not as thermally effective but what about just a big flat coil of copper pipe, that way there are no joins/seals to fret about.
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Re: Prelude conversion project - some questions

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I guess that's what these products are, but I can't seem to get a price of any indication of custom dimensions.
https://www.amstechnologies-webshop.com ... ct-6074292
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Re: Prelude conversion project - some questions

Post by brendon_m »

That's basically what I was thinking, but I was leaning more ghetto. Just go to Bunnings and get an 18m roll of copper and bend it into a zigzagging pattern and plonk it on the bottom of the battery pack
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It's almost already in the right shape
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Re: Prelude conversion project - some questions

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jonescg wrote: Thu, 03 Nov 2022, 12:57 I'd avoid the likes of 3M products such as Novec - they are effectively PFAS. It leaks like a sieve due to its very low viscosity too.
And yeah, very expensive...
The E Fluids I'm looking for are the type used in Formula E battery and motor cooling as well as the Pikes Peak electric vehicle. If they found a way to contain the heat tranfer fluid in those environments, I reckon I should be able to contain the fluid in a road car ....

I'm looking avoid that high temperature spot/s that can occur in a cell when fast charging or discharging, including the connections.
The copper tube idea won't work because the body of each cell is connected to the negative terminal, so touching each cell results in this sort of thing
Burn marks from 5mm rod shorting across cells.jpg
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resulting in destroying 4 brand new LTO cells.

I'm looking for that change of state where the dielectric fluid boils at a certain temperature and that change of state will absorb a lot of heat energy without the actual surface temperature or fluid temperature rising significantly. As soone as the E Fluid vapour cools, it returns to a liquid, this could even be achieved using a loop pipe above the cells but still in the fluid that chills the fluid causing the vapour to return to a liquid.

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Re: Prelude conversion project - some questions

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Hmmm..... Something I should have thought about from my motor mechanic days, micro erosion caused by the liquid change of state.
https://www.engineeredfluids.com/for-da ... oMQAvD_BwE
Time for a rethink .....

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Re: Prelude conversion project - some questions

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Might see how this goes. 3.3 mm diameter threaded holes through the maze, tapped to M4. 3 mm sheets to go either side, countersunk. And some of the stickiest Sikaflex money can buy...
At least the CNC cutting will be (relatively) cheap. $700 for the parts, and a lot of tapping.
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Re: Prelude conversion project - some questions

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I gave up on Sikaflex on my boat years ago. I now use Butyl tape. More sticky, more robust, easier to apply, lasts much longer.
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Re: Prelude conversion project - some questions

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Not sure I could make the tape work in this instance. I used butyl tape on the flashing of my patio - I think it works fine but the person applying it could have been a bit more careful :oops:

I have placed an order for some thermal pads, 580 mm x 350 mm x 2 mm from U-Sheen. @necrogt4 how did you find them to apply? Easy? Hard? The ones I ordered have a thermal conductivity of 2.0 W/mK which isn't great, but apparently the really high stuff (10 W/mK!) is very easy to tear and it's not much fun to apply. Also far more expensive.

I will have leftovers, so hopefully they can find a home on the CRX project. About $80 a sheet... minimum order 10 :roll:
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Re: Prelude conversion project - some questions

Post by necrogt4 »

I ended up using the 10W/mK thermal pads. They're VERY tacky, do tear pretty easy (but roll on easy enough from their protective cover) and once they're on that's it. I had to adjust a battery cell pack on one of them and it was most difficult to get it off and reapply.

I used Loctite 598 sealant for the cover to my chill plate. But this plate was CNC machined so I only had to cover one side. A benefit of this is the lid is actually on the bottom and if there is ever any leak the water will be outside of the battery box with no chance of internal ingress. A second benefit is that you won't have any sealant insulating the actual chill plate channels and mass majority from the heat source. It's certainly a pricier route though 😬
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