High voltage battery cooling

[Beaver]

Looking through the handbook, I note the air intake for the cooling of the high voltage battery is internal.   Situated on the right side, just aft of the rear seat, it puzzles me how this intake works.

If you have the internal temperature high, only that hot internal cabin air can go into the intake.   If you have the windows closed and the heating/cooling system switched off, there is minimal moving air in the cabin, and nothing is likely to enter the intake.   There's a warning on page 17 of the manual not to obstruct the intake as the HV battery can become too hot.

I can't figure out how it receives cooling air from this intake.   The technicians at my main dealership couldn't explain it either!   Any theories?

[sportse]

It’s similar to the Toyota system they have been using for many years.

A fluid system would be best but has extra cost and weight so the air system is used instead.

Even with the climate control off, there will still be airflow through the car - it’s not a completely sealed box. The other end of the vent could be open, so it could pull air through suction as you drive.

The idea is that using cabin air helps the battery.

They must have modelled the flow of air into the rear of the car in typical usage. They also likely expect you to have heating on in winter and cooling in summer.

In winter when you have the heating on, it warms the battery to keep it operating well. Batteries don’t like the very cold temperatures and are inefficient.

In summer with air conditioning running, it keeps the battery cool. Batteries have a shorter life when very hot, and can also get damaged.

On Prius/etc if the vent was blocked by a coat/etc and the temperature got too hot the car would operate in reduced power mode until the battery cooled down.

Prius/etc also has a fan in the cabin battery vent to pull air through as well.

It’s more important on a full EV as the battery pack in a hybrid is smaller.

[Jazzik]

Here a lot of information in the American Honda Media Newsroom about the Honda CR-V Hybrid (in Europe the e:HEV).
The HV battery and the entire powertrain are larger, but identical in technology to the Jazz e:HEV powertrain.

"The air-cooled battery pack is fed by a fan that draws cabin air from vents located to the right of the rear seatbacks. This arrangement allows for optimal battery cooling even with the second-row seats folded down, and cooling performance has been extensively tested in severe real-world conditions, including in the deserts of Nevada and Death Valley.
The battery pack is covered by the High Voltage Battery Limited Warranty that covers excessive loss in battery capacity for eight-years/100,000-miles."

This means that when power is on, any battery temperature that may be too high is cooled by a fan.

What is unfortunately NOT talked about is that parking for hours in the blazing sun on a hot summer day WITHOUT that cooling is not good for the HV battery and it is better to find a place in the shade.

PS
This can be interesting: https://clubjazz.org/forum/index.php?topic=13197.0

[Kremmen]

A timely reminder for me.

I'll be going to the tip in the next few weeks and I have a large cotton sheet I put in to completely cover the rear area to protect the perimeter and a dedicated boot cover on top as a backup.

I need to find the vent as I'll likely cover it.

[sportse]

It can’t be seen clearly unless you drop the driver side rear seat:

[Kremmen]

Ah, there it is, thanks.

Been out and found it. Because it faces forwards I doubt that'll get covered ....... I'll make sure it doesn't.

[John Ratsey]

What is unfortunately NOT talked about is that parking for hours in the blazing sun on a hot summer day WITHOUT that cooling is not good for the HV battery and it is better to find a place in the shade.

However, the battery is shaded by the vehicle and will be cooler. In hot countries the truck drivers sleep under their vehicles. We who live in temperate climates can be assured that the battery's thermal management system won't be challenged.

[richardfrost]

I’ve driven and hiked in Death Valley and the Nevada deserts. I can assure you, if the batteries are ok there, they’ll be fine in our climate!

[Lord Voltermore]

Its likely Honda are satisfied that the temperature regulation of this battery can be met by using the temperature of cabin air.    As long as its tolerable for humans it should be ok for the battery.   

Only problem I can see is if the the occupants are particularly stoic and dont have heating or cooling  in extreme  conditions  ,  or if the air conditioning  is faulty.   When a car is approaching end of life some owners dont bother with expensive air con repairs.  But this could lead to problems with EV's and hybrids.

[John Ratsey]

Only problem I can see is if the the occupants are particularly stoic and dont have heating or cooling  in extreme  conditions  ,  or if the air conditioning  is faulty.   When a car is approaching end of life some owners dont bother with expensive air con repairs.  But this could lead to problems with EV's and hybrids.

If the aircon isn't working then people tend to open the windows when the car is moving.

[Lord Voltermore]

Only problem I can see is if the the occupants are particularly stoic and dont have heating or cooling  in extreme  conditions  ,  or if the air conditioning  is faulty.   When a car is approaching end of life some owners dont bother with expensive air con repairs.  But this could lead to problems with EV's and hybrids.

If the aircon isn't working then people tend to open the windows when the car is moving.

I am guessing in extreme conditions the occupants would die of heat stroke  before the battery does. 

The following article is very interesting. Contains lots information about the challenges and special equipment  requirements for  heating and cooling EV's.

    It lists the three basic  thermal management options for batteries.  1) what the Jazz has , using cabin air.     2) A battery cooler plumbed into the air conditioning  system , 3) full bells and whistles with heating and cooling  heat exchangers.      The Jazz method is the simplest and cheapest, and although it has some disadvantages  is probably the best option for a hybrid.  It would probably still function well enough without working heating or air con.  The others require fully functioning aircon.
 
My wife has never been a great  fan (excuse pun) of air conditioning, and prefers fresh air and tweeting birds with an open window.  .So thats still an option.  But until now all our cars have been manual air con.  She seems to like the set it and forget it of  climate control, . In fact she learned how to do that before anything else.

https://www.hella.com/techworld/uk/Technical/Car-air-conditioning/Thermal-management-in-electric-and-hybrid-vehicles-1725/

[Kremmen]

I'm sure Honda will have driven in extreme temperatures during testing.

[sportse]

I had my Auris hybrid parked outside in the British summertime sun all the time.

Although it did have the standard tinted windows on the rear, I never heard the fan for the battery going.

It’s really only desert conditions that set it off and  also the very high temperatures that reduce the battery life significantly.

There are reports of people driving hybrids in Las Vegas where the car runs fine in the morning but struggles in the afternoon as the car has switched off the hybrid battery due to excess heat.

Jazz/etc should be completely fine in the UK.

One thing I did notice is that the Jazz fan intake is open, on Toyota’] there is a dust filter/screen.

[Beaver]

Thanks for the replies.

[PaulC]

  there is a dust filter/screen.

Early Toyota Priuses did not have a dust filter but later Priuses had the dust filter added because some early Priuses had batteris fail from overheating due to a buildup of dust on the battery surface which acted as a heat insulator.

before I collected a pile of firewood logs this morning in the Jazz with the back seats folded down, I made sure the plastic tarpaulin lining the rear was set up to prevent dirt and bark falling into the outlet while also enabling good air flow.