# Cooling thread



## brian_ (Feb 7, 2017)

If you use two entirely separate loops, you can't use waste heat from the inverter to warm up the battery more quickly for better performance in cold conditions. Maybe that's a refinement that doesn't matter in this case, but that sort of thermal management option is why production EVs have more complex valve configurations.

If the vehicle is going to use a Tesla drive unit and Tesla battery modules, why not use the rest of the Tesla cooling/heating design, or start from that and strip it down to what you need and find to be worth building? I assume that any Modell S would have at least some capability beyond just two independent cooling loops. Of course if you don't have a heat pump you would be looking at an basic early version and perhaps even omitting some of its features.


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## brian_ (Feb 7, 2017)

alexbeatle said:


> Radiator + fans - Jeep Radiator + fans, though I'm looking for bidirectional fans. Bidirectional fans will allow blowing heat into vehicle cabin or outside of the vehicle.


Sending heat to outside or to the cabin would normally be done by coolant valves directing flow to either the radiator or the cabin heater core, rather than by direct airflow. I've never heard of a bidirectional fan in a vehicle.


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## alexbeatle (Jul 28, 2020)

Thanks for the replis.


brian_ said:


> If you use two entirely separate loops, you can't use waste heat from the inverter to warm up the battery more quickly for better performance in cold conditions. Maybe that's a refinement that doesn't matter in this case, but that sort of thermal management option is why production EVs have more complex valve configurations.
> 
> If the vehicle is going to use a Tesla drive unit and Tesla battery modules, why not use the rest of the Tesla cooling/heating design, or start from that and strip it down to what you need and find to be worth building? I assume that any Modell S would have at least some capability beyond just two independent cooling loops. Of course if you don't have a heat pump you would be looking at an basic early version and perhaps even omitting some of its features.


Tesla parts are expensive. Looking to find less expensive alternatives by reverse engineering their setup.



brian_ said:


> Sending heat to outside or to the cabin would normally be done by coolant valves directing flow to either the radiator or the cabin heater core, rather than by direct airflow. I've never heard of a bidirectional fan in a vehicle.


I'm converting a vw bus. There's a pipe that goes from the engine bay straight into the cabin, from the original design. It was guiding ice motor heat into the cabin. Thought I'd use the same principal, but with the radiator, which would otherwise waste heat.


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## brian_ (Feb 7, 2017)

alexbeatle said:


> Tesla parts are expensive. Looking to find less expensive alternatives by reverse engineering their setup.


Right... but the design can be implemented with cheaper and more available parts. I was just thinking of the pattern of flows.



alexbeatle said:


> I'm converting a vw bus. There's a pipe that goes from the engine bay straight into the cabin, from the original design. It was guiding ice motor heat into the cabin. Thought I'd use the same principal, but with the radiator, which would otherwise waste heat.


But if you reverse the airflow, you get heat into cabin in one direction (good when you want it) and you suck air out of the cabin in the other direction (probably not very effective, and causes other issues). It might work...

With a radiator and a heater core, each with its own valve, you get component cooling when you need it, cabin heat when you want it (if the coolant is hot), and each can have a suitable and simple fan. The valve for the radiator doesn't need to be open (it can just bypass the radiator) when you don't want to lose the heat.


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## alexbeatle (Jul 28, 2020)

Is the heater core electric? PTC heater?


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## SWF (Nov 23, 2007)

Hi there.

I assume since you are planning to incorporate heating for the batteries that you plan to charge and use the car when it is quite cold? You would only really need to heat the batteries if you plan to charge them when the temp is below the safe charging temp (<~5C), or if you need to get the max capacity out of them when driving.

I used Model S modules in my conversion and hooked up a cooling system, but based on my calculations beforehand I did not expect to see much temp increase during use. That is exactly what I got, as I typically only see the temps increase a degree or two during driving. So designing your system to capture useable cabin heat from the batteries may be a lot of effort for not much gain. Likewise, you can do some calculations based on the efficiency of the motor/inverter to see if they would generate enough heat worth capturing. If you really need a substantial amount of heat, you will need to incorporate a resistance heater or heat pump regardless of whether you capture waste heat from the motor/inverter.


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## alexbeatle (Jul 28, 2020)

SWF said:


> Hi there.
> 
> I assume since you are planning to incorporate heating for the batteries that you plan to charge and use the car when it is quite cold? You would only really need to heat the batteries if you plan to charge them when the temp is below the safe charging temp (<~5C), or if you need to get the max capacity out of them when driving.
> 
> I used Model S modules in my conversion and hooked up a cooling system, but based on my calculations beforehand I did not expect to see much temp increase during use. That is exactly what I got, as I typically only see the temps increase a degree or two during driving. So designing your system to capture useable cabin heat from the batteries may be a lot of effort for not much gain. Likewise, you can do some calculations based on the efficiency of the motor/inverter to see if they would generate enough heat worth capturing. If you really need a substantial amount of heat, you will need to incorporate a resistance heater or heat pump regardless of whether you capture waste heat from the motor/inverter.


Thanks. The plan is to use the heat majorly produced by inverter.
Regarding the battery inline heater and battery temps. Per https://www.evcreate.nl/ideal-battery-temperature/, the batteries perform best between 15C and 35C temps. I'm planning to rapid charge (CHAdeMO and CCS) also, so keeping batteries in the ideal temps is important.
Curious to learn more about your setup though and what kind of temps you're experiencing.


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## SWF (Nov 23, 2007)

You mentioned a 6.6kW charger in your opening post, so I did not know you were planning on fast charging, where warmer temps are needed. I don't drive my car except in the summer and didn't plan on long drives so I did not bother with battery heating or fast charging capability. My current draw when driving on the highway is roughly 70-100A, which is <0.5C for a Tesla module. As I mentioned, I have rarely noticed any temp increase above the ambient temperature, and this aligns with estimated heat generated from internal resistance at these discharge rates. I have glycol circulating through a small 6"x12" radiator, but did not expect it to do much heat exchange. Here is a link that has some specs on flow rates and pressures you may find helpful.

Using heat from your inverter/motor to warm the batteries may make sense in your case, but you still may want to think more about the extra effort and complexity of trying to heat the cabin this way, if you will need to install supplemental heat anyway. Do some calculations of total BTU/hr output and the temperature delta of air passing over a radiator that has various temperatures of fluid flowing through it and you may be surprised at how little you would gain.


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## ev-swap (Jan 31, 2020)

If you go the traditional radiator route, look for Kawasaki radiators, most have 19 mm inlets and outlets, the same as the Tesla drive cooling outlets. That jeep radiator has outlets that are almost twice that big.


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## alexbeatle (Jul 28, 2020)

ev-swap said:


> If you go the traditional radiator route, look for Kawasaki radiators, most have 19 mm inlets and outlets, the same as the Tesla drive cooling outlets. That jeep radiator has outlets that are almost twice that big.


Can you suggest a specific one with fan(s)? 

Trying to also understand how does one calc the size needed....


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## ev-swap (Jan 31, 2020)

alexbeatle said:


> Can you suggest a specific one with fan(s)?
> 
> I got an after market unit from Mishimoto, its made for a 700cc bike, which makes a lot of power (and heat). It does not come with a fan, but there are a lot of used ones on ebay.
> 
> ...


Yes, so that is the sixty-four thousand dollar question, and not one that is easy to answer. Invertors and batteries are very efficient, meaning that they don't put out a lot of heat under normal circumstances. But when pressed for big power, they also produce a lot of heat. So the amount of cooling you need varies on 1) your power output, 2) your cooling pump flow rate, 3) the size of your radiator, 4) ambiant temperature, and probably a few other factors that have slipped my mind since Thermodynamics 1. You may have to approach it the DIY way with trial and error. As long as your MBS keeps an eye on your battery temp for you and declares an ALL STOP when the temp gets too high, you can prevent major damage. 

One last thought, check out the size of a Tesla Model s radiator (there are several on ebay) They are about 12 inches tall and maybe 40 inches wide. That would be the worst case scenario, size wise, I would think. 

Good luck! Have you stared a build thread?


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## alexbeatle (Jul 28, 2020)

ev-swap said:


> Yes, so that is the sixty-four thousand dollar question, and not one that is easy to answer. Invertors and batteries are very efficient, meaning that they don't put out a lot of heat under normal circumstances. But when pressed for big power, they also produce a lot of heat. So the amount of cooling you need varies on 1) your power output, 2) your cooling pump flow rate, 3) the size of your radiator, 4) ambiant temperature, and probably a few other factors that have slipped my mind since Thermodynamics 1. You may have to approach it the DIY way with trial and error. As long as your MBS keeps an eye on your battery temp for you and declares an ALL STOP when the temp gets too high, you can prevent major damage.
> 
> One last thought, check out the size of a Tesla Model s radiator (there are several on ebay) They are about 12 inches tall and maybe 40 inches wide. That would be the worst case scenario, size wise, I would think.
> 
> Good luck! Have you stared a build thread?


Gotcha...

Don't have the progress thread, but you can see my progress on the Instagram - Get EVfied


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## alexbeatle (Jul 28, 2020)

Has anybody tried active cooling via Peltier coolers?


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