A day in the life of a Phoenician Leaf Battery

[TomT]

The battery pack is sealed and at positive pressure so there is no venting from it of any kind. What you are likely feeling is simply some air flow forced through that area by the pressure differential produced when the CC is on and/or convective temperature difference. It has nothing to do with and no affect on the battery and is likely outside air.

There is probably a controlled hatch that opens only when the temperature of the battery is above ambient.

 

[vegastar]

I think other people should test it.

The space around the fuse is filled with fine dust which is consistent with outside air. And I had no flow with 5 temperature bars, only with 6.

 

[DaveEV]

It is not convection. Too much flow and it stops when the CC fan is off.

Probably airflow caused by the AC condenser fans running.

 

[vegastar]

Ok, just tested again. The absence of flow with 5 bars was just a coincidence. The flow stops when the windows/doors are open. The air probably only passes to the battery compartment when the emergency hatch is open.

It is very easy to test:

- open the emergency shutdown hatch
- close all doors and windows
- turn on the CC fan
- put your hand inside the hatch

 

[TickTock]

Cool. So put a grill and a cloth filter on the hatch cover and start the climate control when you start charging.

 

[DaveEV]

Ok, just tested again. The absence of flow with 5 bars was just a coincidence. The flow stops when the windows/doors are open. The air probably only passes to the battery compartment when the emergency hatch is open.

Makes sense. There's typically rubber flaps in the hatch of vehicles to release positive pressure. Of course, these flaps provide some resistance so with the HVAC blowing fresh air into the car the easiest route for air to flow is through the battery disconnect hatch.

 

[Nubo]

I thought I had read that there is an internal fan to circulate air inside the pack -- not to cool with ambient air but simply to maintain more even temperature within the pack.

 

[DaveEV]

I thought I had read that there is an internal fan to circulate air inside the pack -- not to cool with ambient air but simply to maintain more even temperature within the pack.

I've heard that rumor multiple times, but the service manual doesn't appear to have any mention of it that I'm aware of (I don't have a copy of the service manual myself, going off what others have reported - would love additional confirmation!)

 

[GerryAZ]

I had the battery disconnect cover off yesterday. It was clean inside except for a fine layer of dust consistent with outside air flow for a year in the desert. I used a flashlight last night to verify that area is open to the front of the car (and toward the rear). Airflow through that area flows over the top of the battery case so it probably helps cool the battery a little. Temperature of that air is about ambient unless the A/C is running, in which case it is warmer. It is about 5 to 10 degrees above ambient with A/C on high after driving on the freeway for a while.

Gerry

 

[TickTock]

Cool. So put a grill and a cloth filter on the hatch cover and start the climate control when you start charging.

Never mind... I hapened to be a couple hours into a charge when vegastar posted and thought, I'd test this. I opened the hatch and propped the floor mat open, took a reading of the battery case with my Raytech IR thermometer, got 104F. Then I turned on the AC (using the phone app). 45 minutes later, I took another read on the same spot. 109F. Hmmm maybe it's hotter due to charging but still cooler then it would have been without the AC. So I turned the AC back off and left. When chargin was complete, I read 105F. I then downloaded the data from the logger I have in the hatch and was surprised to see that turning on the AC actually increased the temp significantly. See the chart below. I think turning on the AC dumped heat into the hatch cavity. Even though the hatch was open (and all dors/windows closed) not enough cool air made it into the hatch to combat the impact from the ac. Since the hatch was open, once I turned off the AC the hot air was allowed to rise and get replaced by the cooler cabin air and no longer fighting the heat source from running the AC. At least that is my interpretation of this result.

BTW: the reason the IR temp is lower is because I was taking a read off metal. These devices work best on a flat black surface - reflective surfaces are particularly prone to error, but the relative measurements are still useful.

 

[EVDRIVER]

I thought I had read that there is an internal fan to circulate air inside the pack -- not to cool with ambient air but simply to maintain more even temperature within the pack.

There is no fan and no electric door. You can read the manuals it does not exist. No forced cooling from any fans anywhere. This was established a long time ago.

 

[GerryAZ]

TickTock,

I think the higher temperature you see with A/C running comes from heated air flow through the condenser because that tunnel area is wide open to the front of the car.

Gerry

 

[surfingslovak]

It is not convection. Too much flow and it stops when the CC fan is off.

I confirmed this today. There is definitely a draft between the top of the battery pack and the underbody, and it increases with higher fan speed. I don't believe that this was documented anywhere, and perhaps it's one of the things Nissan did to help condition the pack. There was fine dust inside the hatch when I opened it the first time, which would be another indicator pointing to the presence of regular airflow. I suspect that this might help explain the good results GaslessInSeattle was getting with prolonged preconditioning last winter.

 

[ydnas7]

add another lines for context
the outside ambient minimum temp

 

[mwalsh]

add another lines for context
the outside ambient minimum temp

Haiku?

 

[Herm]

Good techno Haiku

 

[ydnas7]

Nice work on the data collection with your car. A couple of observations.

The Temps at night on your battery pack are about 15 or 20 degrees higher than the overnight low for Queen Creek.

During the morning drive the battery temps drop significantly.

During the evening drive home the battery temps go UP significantly.

Could you park the car outside for a couple of nights and then compare the temp charts again?

What about putting a fan next to the car to circulate cooler air under the car at night while parked. The idea being if you could lower the battery temp at night enough it might lower the max temp the pack sees during the day and this might prolong battery life.

Here's a chart, i hope TickTock doesn't mind my amateur additions to his work.

http://www.accuweather.com/en/us/queen-creek-az/85142/june-weather/346863" onclick="window.open(this.href);return false;

 

[RegGuheert]

Here's a chart, i hope TickTock doesn't mind my amateur additions to his work.

Interesting. So it appears that the average temperature of TickTock's battery is about 5F higher than the average of the day's min and max temperatures.