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Discussion Starter #1
Hi guys,

I am prepared to be told that this has been discussed many times over. But I searched and searched the forums and just can't come up with threads that cover this more basic design topic.

My car 1974 BMW CSE is up and running and I've been doing more and more short drives around the neighborhood. I am now moving into my cooling projects.

I've chatted with people about drive unit cooling, and the opinions are very different. Some very conservative others very extreme. I am aware of the flaws with the large unit's cooling design, as discussed in the threads. My car is a daily driver, with modest needs (no hard track cooling needs).

So the help I am looking for is the very basics:

- What type of coolant are you guys using?
- What type of tubing?
- What type of radiator, and how small can I get away with?
- Are you adding a pump to supplement flow?
- I am using the Tesla DC/DC converter and gen2 charger, so I need to route to those as well. I assume I should split the system to route to drive unit and back, with a separate branch that routes to these devices and back.

Thanks for any help or direction to the threads that I couldn't find in my many searches. Perhaps the real help I need is in forum searching :)

Cheers,

Paul
 

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Thanks for any help or direction to the threads that I couldn't find in my many searches. Perhaps the real help I need is in forum searching :)l
It helps to use a Google web search restricted to this site with the "site:www.diyelectriccar.com" term, rather than using the internal search tools, but it can still be frustrating. If you know the username of someone who posted what you are looking for, the advanced version of the internal search is the way to go.
 

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Discussion Starter #3
Thanks Brian,

Yeah, I did discover that searching Google has brought some better results within this forum. But alas, there doesn't seem to be answers to my particular questions here.

I actually thought that a "best practices" section is very desirable. I am sure I'm not the only one who has had the same questions about this and a thousand other topics. The answers aren't found in a thread of that title. They are small comments among build threads, or totally different topics. It's made worse for those of us using Tesla, Nissan or Chevy EV parts, because when you search those terms you mostly get answers regarding repair of those actual cars.

Anyway- just my $.02.

Thanks guys,

Paul
 

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Hi Jetdexter

First run some numbers! - you need cooling to remove the surplus heat - make some estimates as to how much heat you need to remove and work out how much flow
That number give you your starting point

In most applications in cooler countries you are not so much "cooling" the battery as maintaining the same temperature for each cell - if a cell gets warmer than it's mates it becomes a slow positive feedback which is why Leaf batteries don't last as long as Tesla
 

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Discussion Starter #5
Hi Jetdexter

First run some numbers! - you need cooling to remove the surplus heat - make some estimates as to how much heat you need to remove and work out how much flow
That number give you your starting point

In most applications in cooler countries you are not so much "cooling" the battery as maintaining the same temperature for each cell - if a cell gets warmer than it's mates it becomes a slow positive feedback which is why Leaf batteries don't last as long as Tesla
Thanks Duncan. Actually my question was regarding the Tesla Motor/inverter. But I do appreciate the input as I move to batteries next.
 

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Hi Jetdexter - same issue start with some numbers

With a 90% efficient motor and 200 kw input then you need to "dump" 20 kw

If you can have a 20 degree "Delta T" then you need

water is 4.2 Joules/gram degree - so for 20kw

20,000 divided by (20 x 4.2) = 240 grams/second - 14 kg/minute

Juggle the numbers and do some flow testing of your pump
Remember the continuous power at road speeds is going to be more like 20 kw than 200 kw

In comparison a 50 kw IC engine will be rejecting about 50 kw to the water

Most electric motors are better than 90% - but that would be a good conservative number to use
 
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