TexasLeaf
Posts: 68
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

Re: Using air conditioning to reduce battery pack tempature

Tue Aug 07, 2018 10:58 am

TexasLeaf wrote:There was still a lot of fresh air coming out of the vents with the vents taped up and I could not figure out where the air was going.


There is a very large gap at the bottom of the panel with the vents in the trunk. I'm pretty sure that is where the air is getting out to the relief vents behind the bumper when the trunk grilles are taped up. The gap does all the way around the edge at the bottom of the trunk.

When I go on a long trips I will try to tape this gap up to force as much air as possible through the Service Plug port. The only problem is the trunk liner that covers the gap sits under the sub wolfer. It looks possible to work around the sub wolfer but it might be easier just to remove the sub wolfer when you tape up the gap

TexasLeaf
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Re: Using air conditioning to reduce battery pack tempature

Tue Aug 07, 2018 11:19 am

WetEV wrote:
Batteries degrade. They degrade slower at 60F than at 70F. Even slower at 50F. Probably slowest somewhere near 0C/32F. This is a complex chemical reaction.

There are different reactions that happen below about 0C, and batteries probably degrade faster below about 0C. Battery heater tries to keep battery above -20C, unless you have one of the early LEAFs without a battery heater.

I'm not sure I would modify the car to add battery cooling. The possibility of getting condensation where there shouldn't be any raises the worry of battery fires at worst case. Sure, unlikely, but Li-ion batteries don't mix with moisture very well.


I was trying to avoid this topic. This thread is about cooling the battery using the air-conditioning system to improve charging speed on long trips, not about battery degradation. But I think I need to chime in to get this thread back on track.

At this time I could care less about battery degradation on my 2018 Leaf. You need an EV that can go the distance in Texas. Slow charging on long trips is a much more serious issue for me than any potential battery degradation.

One of the reasons I got the 2018 was that it has so much range I figured I could lose a little battery capacity and still be able to make the trips I needed to. And in Texas, if you don't want your battery to get hot you better leave the car in garage. My mind set on EV batteries is that they are like tires, EV batteries are going to wear out and they are going to have to be replaced eventually.

If the battery goes down to seven bars before the end of the 8 year/100,000 mile warranty then Nissan is going to be buying a new battery for the car. If the battery goes bad after the warranty ends then I will pay for a new battery. But, I figure by the time I have to pay for a new battery I will have gotten my money's worth out of the car and I would have no problem with just parking the car on the side of the road and walking away from it.

TexasLeaf
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Re: Using air conditioning to reduce battery pack tempature

Thu Aug 09, 2018 6:00 pm

TexasLeaf wrote:There is a very large gap at the bottom of the panel with the vents in the trunk. The gap does all the way around the edge at the bottom of the trunk.


I removed the sub-wolfer and taped up this gap and the grilles and ran the AC in Fresh Air mode again. I couldn't really tell any difference in air flow from without the tape. My tissue test seemed to indicate that air was going under the rear seat.

I thought there might be an air opening through the floor under the rear seat so I pulled the rear seat. It's easy enough to remove the rear seat, all you have to do is pull up on the front. There are not any air openings through the floor under the rear seat.

Even though the unit was in Fresh Air mode, I thought that air might be getting back to the fan through the return air opening in the AC unit. I found the return air opening above the drivers feet. With the AC in Recirculate mode my tissue pulled up into the return opening but with the AC in Fresh Air mode my tissue was limp.

So even with the grilles in the trunk taped up air still gets out of the car somehow. I tried the tissue test on the Service Plug port with the trunk grilles taped up. With the AC in Recirculate mode the tissue would just hang limp in the open port but when I turned the AC to Fresh Air mode the tissue really flapped away in the port.

I think tapping the grilles up in the trunk does some good in forcing more air into the Service Plug port and it's pretty easy to do. Tapping up that gap around the trunk was a chore and I really didn't see any significant gains. I don't think I'll be tapping up the gap again.

I'm not going to worry anymore about how the air is getting out of the car in Fresh Air mode with the grilles tapped up. I'm pretty sure most of the air is being forced down the Service Plug port. I am just going to assume that air gets out the door seal, window seals and the like but most of the air will seek the path of least resistance down the open port.

The next order of business will be to take a long trip with multiple fast charges and see how well I can keep the battery cool with the trunk grilles tapped up and the Service Plug port opened up.

BrockWI
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Re: Using air conditioning to reduce battery pack tempature

Thu Aug 09, 2018 6:16 pm

I am likely wrong but I thought the service port in to the battery was the only opening in to the battery pack? Where is the air escaping from the pack? Are there relief port on the pack somewhere?

I thought there was another thread about someone fan forcing air in the service port, but using a fan at that location and just forcing in to the pack?
3 kw solar pv - XW6048 - eight L16's
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2003 VW TDI 180k miles - 52 mpg lifetime
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2013 S model with QC package Mar of 2013
@70k miles - 56.56Ahr - 86 SOH - 82.55 Hx - 245 GID

TexasLeaf
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Re: Using air conditioning to reduce battery pack tempature

Thu Aug 09, 2018 6:31 pm

BrockWI wrote:I am likely wrong but I thought the service port in to the battery was the only opening in to the battery pack? Where is the air escaping from the pack? Are there relief port on the pack somewhere?

I thought there was another thread about someone fan forcing air in the service port, but using a fan at that location and just forcing in to the pack?


The Service Plug port we are talking about is in the floor board of the car in front of the rear seat; not in the battery pack itself. There is a gap about a half inch deep between the battery pack and the floor board over the entire top of the battery pack. Cool air from the cabin can be forced down the port and spreads out through that gap cooling the top of the battery pack.

I don't know what thread you are talking about but I don't see the point in using another fan when the cabin fan seems to do a pretty good job of pushing air down the Service Plug port.

BrockWI
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Re: Using air conditioning to reduce battery pack tempature

Thu Aug 09, 2018 6:41 pm

So basically the air is going through that port and then down around the pack itself. I agree a positive pressure from the HVAC system will force air out that location.

Here is that other thread

http://www.mynissanleaf.com/viewtopic.php?t=17682
3 kw solar pv - XW6048 - eight L16's
4 ton GSHP
2003 VW TDI 180k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013
@70k miles - 56.56Ahr - 86 SOH - 82.55 Hx - 245 GID

TexasLeaf
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Joined: Wed Mar 21, 2018 5:37 am
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Re: Using air conditioning to reduce battery pack tempature

Fri Aug 10, 2018 7:05 am

BrockWI wrote:So basically the air is going through that port and then down around the pack itself. I agree a positive pressure from the HVAC system will force air out that location.

Here is that other thread

http://www.mynissanleaf.com/viewtopic.php?t=17682


I read through all the posts on that thread. There didn't appear to be any posts discussing using cabin temperature and cabin air to cool the battery pack. I think what this thread discusses is different approach that deserves consideration and further investigation.

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Nubo
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Re: Using air conditioning to reduce battery pack tempature

Fri Aug 10, 2018 9:17 am

TexasLeaf wrote:...
Using the Service Plug port for additional battery cooling was very easy to do. It worked so well that it makes me think that the Service Plug port is actually intended to be used for supplemental battery cooling. ...


It's meant as a means to disconnect power in the event of an emergency. There is a high-voltage warning which I would take very seriously.
I noticed you're still working with polymers.

TexasLeaf
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Joined: Wed Mar 21, 2018 5:37 am
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Re: Using air conditioning to reduce battery pack tempature

Fri Aug 10, 2018 9:36 am

Nubo wrote:It's meant as a means to disconnect power in the event of an emergency. There is a high-voltage warning which I would take very seriously.


Nobody is proposing doing anything with the Service Plug. The Service Plug is already weather proof, a little cool air blowing over it shouldn't hurt anything. If you are worried about something dropping down the opening then you can always put a screen over it.

One way I have thought of screening the opening is to drill holes in the cheep plastic cover. You always go buy a new cover for when you don't want to vent or if you want to sell you car. Sure, take the warning seriously, but until Nissan comes up with a way to cool the battery using the Service Plug port for ventilation is one of the best options we have.

agt
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Re: Using air conditioning to reduce battery pack tempature

Fri Aug 10, 2018 10:12 am

Nobody is proposing doing anything with the Service Plug. The Service Plug is already weather proof, a little cool air blowing over it shouldn't hurt anything. If you are worried about something dropping down the opening then you can always put a screen over it.


Are you suggesting removing the plastic cover plate, or also the metal plate secured with 10mm bolts?

If only the former, the HV components would seem well-protected; but without the metal cover, what would prevent a spilled drink (or a water from a firefighter's hose) from infiltrating and shorting the 400V DC fuse assembly?

At the very least, some sort of splash-resistant cover would seem in order.
2016 S - San Diego (Mira Mesa), CA

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