Smidge204
Posts: 940
Joined: Wed Nov 24, 2010 1:42 pm

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 10:18 am

Here's how I'd do it:

Image

It's exactly identical to the presumed system the manual seems to describe, except there is a bypass and 3-way valve which has the ability to divert flow from the motor cooling loop into the cabin heating loop. The valve only opens when the fluid in the motor cooling loop is hot enough to contribute and only when heating is required. You wouldn't even need particularly fancy controls on the valve either: simple min & max setpoints (no modulating) would suffice for this.

It would add maybe $150 to the cost of the vehicle but would help in cold climate driving where heating would be a significant factor in power consumption. Provided, of course, the motor/inverter gets hot enough, soon enough. As turbo2ltr mentioned, the coolant system seems capable of running while charging, so that may help "pre-warm" the system.
=Smidge=

edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 10:27 am

Smidge204 wrote:Here's how I'd do it:

Image

It's exactly identical to the presumed system the manual seems to describe, except there is a bypass and 3-way valve which has the ability to divert flow from the motor cooling loop into the cabin heating loop. The valve only opens when the fluid in the motor cooling loop is hot enough to contribute and only when heating is required. You wouldn't even need particularly fancy controls on the valve either: simple min & max setpoints (no modulating) would suffice for this.

It would add maybe $150 to the cost of the vehicle but would help in cold climate driving where heating would be a significant factor in power consumption. Provided, of course, the motor/inverter gets hot enough, soon enough. As turbo2ltr mentioned, the coolant system seems capable of running while charging, so that may help "pre-warm" the system.
=Smidge=

Are you sure this is not already in use?

One of the few things I find objectionable in LEAF design is using precious battery storage capacity to heat the cabin.

Seams to me a heat pump using the main coolant system as the heat source, backed up with resistance, would greatly expand cold weather range.
no condition is permanent

kmp647
Posts: 1136
Joined: Tue Jul 27, 2010 4:00 pm
Delivery Date: 11 Nov 2011
Location: Northern Virginia

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 10:43 am

edatoakrun wrote:"it uses a pump, resivoir and heater core and is a seperate system from the inverter-charger-motor coolant circuit."

And there is no heat exchange between the two systems?

the owners manual lists 2 seperate capacities for the main traction cooling system and the heater circuit

1.8 qts for the heater circuit (something close)

seems like combining them could help but I guess they didnt for some reason
2012 SL Leaf
order 07/28/2011
took delivery 11/11/11
47,000 miles 10 bars 211 gids
Turned back into Nissan 12/31/14 @ 50,000 miles
BMW i3 rex 24 month lease
2017 BMW X540e phev
Tesla model 3 reservation

smkettner
Posts: 7501
Joined: Mon Aug 09, 2010 10:13 pm
Delivery Date: 26 Feb 2014
Location: Orange County, CA

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 10:58 am

If it was hot out there is no need to circulate the motor coolent through the cabin.
When it is cold out there is no need to warm the motor.

There is not a circumstance to share the heat.
I speculate the engine coolent may not get more than 20 degrees over ambient.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV
RAV4 traded in for I-Pace Dec 2018

GroundLoop
Posts: 1725
Joined: Mon Sep 13, 2010 9:31 pm

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 11:15 am

If you look at the cutaway pictures of the Leaf motor, you can clearly see water cooling channels.

The manual specifically mentions:
"Water pump noise while charging"
EV-8

Combining the cabin heater and inverter/motor coolant seems like a really bad complication of two individually simple systems.

Unlike an ICE, the motor has no real need to warm itself for efficiency, and no guarantee of prompt surplus heat.

Smidge204
Posts: 940
Joined: Wed Nov 24, 2010 1:42 pm

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 11:20 am

smkettner wrote:If it was hot out there is no need to circulate the motor coolent through the cabin.
When it is cold out there is no need to warm the motor.
Agreed. A 3-way valve and injection loop prevent both of these scenarios from occurring.

smkettner wrote:There is not a circumstance to share the heat.
Disagree. After ~10 minutes of steady driving I'd wager the motor and inverter have generated enough heat to be worthwhile. Similar to an ICE, but an EV would probably have significantly less thermal mass. Add to this the speculation that heat is generated during the charging process - which would mean there is less warming up to do.

smkettner wrote:I speculate the engine coolent may not get more than 20 degrees over ambient.
Maybe not with a radiator, but even if that is the case (and I speculate otherwise) heating water that is already +20 above ambient is better than heating water that is at or close to ambient.

The viability really depends on how much waste heat the motor/inverter generates, and the max temp the components are allowed to reach. Heat would vary considerably with speed, but if we assume 90% efficiency that's still several kW on average. Max temp is likely up around 200F so that's plenty hot. Throw in supplemental resistance heat and call it good I say.
=Smidge=

edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 11:33 am

Does seem to be a lot of heavy battery energy to waste.

Particularly if it were possible to use the ac compressor (in heat pump mode) to utilize a coolant heat exchanger , to use the heat when the coolant was below the temperature for cabin heating.
no condition is permanent

GroundLoop
Posts: 1725
Joined: Mon Sep 13, 2010 9:31 pm

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 12:45 pm

If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..

Smidge204
Posts: 940
Joined: Wed Nov 24, 2010 1:42 pm

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 1:07 pm

GroundLoop wrote:If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..
If only we had perfect engineers who worked in a perfect world where every possible idea could be thought of and no compromises ever had to be made... :roll:

If they didn't set it up to use motor coolant for cabin heating, there is obviously a reason why. "They didn't think of it" is among the possible reasons, right alongside "They didn't think it was worth it" and "Technicalities prevented it." Only the actual engineers know for sure so let us have our fun, k? :D
=Smidge=

edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Re: Does the Leaf have a radiator?

Mon Dec 20, 2010 1:08 pm

GroundLoop wrote:If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..
And introduce it with the "cold climate" option...
no condition is permanent

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