theaveng
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Battery & motor for heat?

Sun Feb 16, 2014 12:26 pm

I was just watching Fully Charged with Kryten. Ooops I mean Robert Llewellyn (on youtube). The temperature in his Leaf battery showed 38 C which is 102F.

I imagine some heat comes off the electric motor too. Why don't EVs use this heat & inject it into the passenger cabin?

LINK: http://www.youtube.com/watch?v=eHcC65ZoyBw
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Bateman
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Re: Battery & motor for heat?

Mon Feb 17, 2014 10:03 am

I suspect for a few reasons:

1. Cost and complexity of a heat-routing system from the battery would add weight and expense to the vehicle.
2. Under cold circumstances, you would want heat on the battery anyway to improve range. (hence why newer leafs have battery heaters.)

Best to use the heat system in the car (heated seats, steering wheel, heater) for the intended purpose.
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GregH
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Re: Battery & motor for heat?

Mon Feb 17, 2014 10:12 am

theaveng wrote:I imagine some heat comes off the electric motor too. Why don't EVs use this heat & inject it into the passenger cabin?

We've been using air cooled motors in our EVs and they can get pretty toasty. I posed the same question to one of the engineers a while back and he showed me the amount of heat that could be extracted from the motor was about 1/6th of what the additional cabin heating elements could produce.. I think it was on the order of 1kW heat from the motor vs 6kW heat available for the cabin. That being said however, 1kW ain't chump change.
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Nubo
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Re: Battery & motor for heat?

Mon Feb 17, 2014 1:57 pm

I'll have to wait for the video when I get home, but I'd say it's a fairly rare circumstance to have the LEAF battery pack at 102F at any time of year where cabin heating is desired, except for maybe during/after a couple of quick charges. Properly extracting heat from the pack and moving it into the cabin would require considerable hardware and design, which is unwarranted due to how rarely it would be useful. The usefulness/propriety of a thermal management system is a larger argument.
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Smidge204
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Re: Battery & motor for heat?

Mon Feb 17, 2014 2:03 pm

Nubo wrote:I'll have to wait for the video when I get home, but I'd say it's a fairly rare circumstance to have the LEAF battery pack at 102F at any time of year where cabin heating is desired, except for maybe during/after a couple of quick charges.


The video in question features them driving from London to Edinburgh (~400 miles) using nothing but quick charges, so yeah that's something of an edge case.

I've long wondered myself why they couldn't scavenge the motor heat, though - especially now that they have heat pump units. That's heat going to waste anyway!
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JeremyW
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Re: Battery & motor for heat?

Mon Feb 17, 2014 2:39 pm

My battery here in Pasadena is anywhere from 58-78 F in the winter here in Pasadena without quick charging. Not exactly warm!
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LeftieBiker
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Re: Battery & motor for heat?

Mon Feb 17, 2014 3:16 pm

It isn't something that could just be added, but for years I've thought about using an inboard disk brake system to extract heat from the brakes. Like other approaches, it suffers from a lack of consistent heat in Winter, and would produce the most heat in Summer.
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theaveng
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Re: Battery & motor for heat?

Tue Feb 18, 2014 7:15 am

GregH wrote: I think it was on the order of 1kW heat from the motor vs 6kW heat available for the cabin. That being said however, 1kW ain't chump change.

So the motor is equivalent to a 1000 watt heater. If the engineers used that to heat the cabin, instead of a separate resistance heater that drains the battery, it would extend range.
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jsongster
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Re: Battery & motor for heat?

Tue Feb 18, 2014 11:59 am

I agree with others that the heat pump in the high end cars is likely the solution to cooling the battery also. Same idea as is used on laptop CPUs. Add some heat transferring system to the battery pack to carry away the heat evenly from each sub pack... then use the coolant from the heat pump system to carry it away. Might need a bigger radiator... Or maybe make the battery case out of aluminum and add loads of external fins to every open space to run the pipes through.

I'm hoping the engineers at Nissan are working out the plausibility of something like this. Gotta keep the cost and weight down of course.
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DNAinaGoodWay
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Re: Battery & motor for heat?

Tue Feb 18, 2014 12:02 pm

The Kia Soul EV coming this year touts a heatpump system that draws what heat it can from the motor and the inverter, since they need coolant anyway. It will also have a driver only switch, routing air only to the driver.

Would be nice if there was a switch so airflow could go through the pack, to heat or cool it as needed.
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