Capacity Loss on 2011-2012 LEAFs

[DaveinOlyWA]

what is the cell reversal voltage for Li?

 

[gbarry42]

If I understand the meaning of "reversal", that would be at 0 volts You are probably asking at what voltage we see significant non-reversible damage. Going by what drees just told us, if they spec it down to 2.5v, that's probably a really good place to stop. In a precisely balanced pack, that would be 240 volts.

 

[edatoakrun]

quote="derkraut" I'm a Christian...

Do all LEAFs in heaven, have 12 capacity bars, and an accurate GOM?

And think how fast those lost souls in the fiery pits below, lose capacity bars on their LEAFs.

Maybe even faster than in Phoenix...

In Heaven, we don't need no stinkin' GOM, there won't ever be battery capacity loss; and in Hell, everybody has to drive a Hummer,and refuel it @ $10USA per gallon. :twisted:

And it follows, of course, that in purgatory, you have to drive a Volt...

 

[JRP3]

If I understand the meaning of "reversal", that would be at 0 volts You are probably asking at what voltage we see significant non-reversible damage. Going by what drees just told us, if they spec it down to 2.5v, that's probably a really good place to stop. In a precisely balanced pack, that would be 240 volts.

Remember that 2.5V is resting voltage, it will and can sag below that under load and be OK. I've taken my LiFePO4 pack down to 1.77V under load a few times and when resting it sprang back to 2.45V and climbing, with no noticeable damage. Not that I recommend doing it on a regular basis.

 

[EdmondLeaf]

With current temps in 110F, I think I have reasonable solution to keep battery in reasonable temp using AC window unit that blow cold air under the car. Using about 5kWh (cost $.25). I managed to lower battery temp from 83 to 70F. This is the best way so far (labor and cost) that I tested. Looks like Nissan is serious about battery capacity issue, I should be receiving recommendations how to maintain battery during hot weather from special team established for that purpose. It looks great to see 5TB during this heat wave.

 

[1932highboy]

My Leaf lost a bar on 7/28/2012. The car has 11,212 miles and I had its since 5/5/2011. Its never been OC. I called Nissan to report it. My case number is 9074806. The case worker told me to take it to the dealer to have them check it over and also to document it.

 

[vegastar]

If I understand the meaning of "reversal", that would be at 0 volts You are probably asking at what voltage we see significant non-reversible damage. Going by what drees just told us, if they spec it down to 2.5v, that's probably a really good place to stop. In a precisely balanced pack, that would be 240 volts.

Remember that 2.5V is resting voltage, it will and can sag below that under load and be OK. I've taken my LiFePO4 pack down to 1.77V under load a few times and when resting it sprang back to 2.45V and climbing, with no noticeable damage. Not that I recommend doing it on a regular basis.

I think I remember seeing in the Service Manual that if any cell falls to 2.5V a DTC is generated and the main contactor is opened regardless if the cell is resting or under load.

 

[DaveinOlyWA]

If I understand the meaning of "reversal", that would be at 0 volts You are probably asking at what voltage we see significant non-reversible damage. Going by what drees just told us, if they spec it down to 2.5v, that's probably a really good place to stop. In a precisely balanced pack, that would be 240 volts.

Remember that 2.5V is resting voltage, it will and can sag below that under load and be OK. I've taken my LiFePO4 pack down to 1.77V under load a few times and when resting it sprang back to 2.45V and climbing, with no noticeable damage. Not that I recommend doing it on a regular basis.

in a balanced pack you can do that. in an unbalanced pack what you typically see is the weak cell voltage drop being significantly greater than the rest where you might see 3 volts on the pack of cells but one cell at 2 volts. as the SOC lowers, the gap widens to the point the weak cell will swap polarity essentially making it a resistor in the pack lowering overall pack voltage. this swap is permanent and cannot be fixed.

now, from what i read; Li is resistant to this phenomena but it is possible. the reason i ask about this is the concern over how low an SOC the pack can "rest" at. i personally feel that anything above 10% is fine. VLB is normally what 8.5 % more or less. i feel that anything above that is ok. keep in mind; the detailed battery report tracks Turtle sightings, but no VLB...

but that depends on what the cell reversal voltage is. unfortunately, i have not found a good # to base it on. guessing that the reason is that the more balanced the pack; the lower the "safe" voltage can be which tells me that all this concern on this thread about leaving the car at low SOC is groundless

 

[EdmondLeaf]

My Leaf lost a bar on 7/28/2012. The car has 11,212 miles and I had its since 5/5/2011. Its never been OC. I called Nissan to report it. My case number is 9074806. The case worker told me to take it to the dealer to have them check it over and also to document it.

Sorry, can you elaborate how your car was/is maintained day and night during high temp. Your miles are not that high.

 

[LEAFer]

My Leaf lost a bar on 7/28/2012. The car has 11,212 miles and I had its since 5/5/2011. Its never been OC. I called Nissan to report it. My case number is 9074806. The case worker told me to take it to the dealer to have them check it over and also to document it.

Since you've had it more than 12 months ... did you do a battery check at 1-year (in May 2012) ?

 

[Herm]

With current temps in 110F, I think I have reasonable solution to keep battery in reasonable temp using AC window unit that blow cold air under the car.

Did you rig up a duct to channel the cold air under the car?.. 5000 BTU window AC consume about 500Wh or so when the compressor is running.

 

[Stoaty]

My Leaf lost a bar on 7/28/2012. The car has 11,212 miles and I had its since 5/5/2011. Its never been OC. I called Nissan to report it. My case number is 9074806. The case worker told me to take it to the dealer to have them check it over and also to document it.

Added to Wiki. We just need your city and VIN number (last 5 digits) to complete your entry.

 

[Herm]

My Leaf lost a bar on 7/28/2012. The car has 11,212 miles and I had its since 5/5/2011. Its never been OC. I called Nissan to report it. My case number is 9074806. The case worker told me to take it to the dealer to have them check it over and also to document it.

How often do you charge to 100% or 80%?. What part of Texas are you in?

 

[zarwin]

With current temps in 110F, I think I have reasonable solution to keep battery in reasonable temp using AC window unit that blow cold air under the car.

Did you rig up a duct to channel the cold air under the car?.. 5000 BTU window AC consume about 500Wh or so when the compressor is running.

I have a 10k BTU window unit mounted in the wall of the garage, mainly for when the temp is up in the triple digits and I come home with 7TB on the display (or when I need to work on things in the garage). No duct, I just run a cheap fan to blow the cool air under the car, which seems to work fine. I can feel the heat billowing out from under the car when the fan is on. Always goes from 7TB to 6TB within an hour, though I have no tool to determine what the exact high temp of the battery actually was.

Having a duct go directly under the car would be a great idea to lower the cost of running that AC. Cool the car and not the entire garage. Think I'll see about doing that.

 

[EdmondLeaf]

With current temps in 110F, I think I have reasonable solution to keep battery in reasonable temp using AC window unit that blow cold air under the car.

Did you rig up a duct to channel the cold air under the car?.. 5000 BTU window AC consume about 500Wh or so when the compressor is running.

Power consumption was somewhere in .8kWH range, I made the duct using pieces of foam and blocked air under the car, car is parked very close to garage door so AC is placed under partially opened garage door insulated with foam whenever possible. Temp at 7 am in garage was 80 but under car and battery 70. Will do it again tonight temp at midnight about 95F.

zarwin are you in PHX area?
edit I have temp logger located in emergency disconnect area close to rear battery stack, as well as calibrated that battery casing is good spot to measure indirectly battery temp (calibrated with 74F bar 5 to 6 change).

 

[QueenBee]

Highly unlikely, and that it would only damage packs in warm areas makes it even less likely.

unlikely yes. impossible? ooooh no. any computer novice will tell you that heat is a killer. what protects the Nissan pack? computers do. how do computers protect the pack? they monitor various parameters of the pack and provide operations to keep those parameters within predesigned guidelines.

excessive heat can mess up the computer's circuitry to the point that it may no longer measure accurately or respond accurately.

your blanket statement needs a much closer examination

This is true... which is why most datacenters blast the ac at 73 degrees. But since cars have computers in them these days, I would think that the computer isn't the issue. I would think that auto manufacturers have the heat figured out when it comes to the computer, since it has been sitting under ICE hoods for years now. But then again, I may be giving Nissan too much credit. It could be that they needed more processing power to run the LEAF and didn't take into account needing a bigger heatsink. This would be a huge blunder for something so "electric."

AFAIK ECU's are generally located inside the cabin, not to say that they don't get hot though. If the LEAFs microprocessors/etc. were getting too hot I would expect random glitches, error codes being thrown, rebooting, lock ups, failed components, etc. Not batteries degrading quicker than expected.

If you want to start speculating on software being the cause of the battery issues a more likely scenario is that either the the design parameters themselves did not protect the battery from heat enough or bug(s) in the software caused things to not operate as designed and thus failed to protect the battery.

Also, modern advice on data centers is to raise the thermostat: http://www.datacenterknowledge.com/archives/2008/10/14/google-raise-your-data-center-temperature/" onclick="window.open(this.href);return false;

 

[RegGuheert]

I have a 10k BTU window unit mounted in the wall of the garage, mainly for when the temp is up in the triple digits and I come home with 7TB on the display (or when I need to work on things in the garage). No duct, I just run a cheap fan to blow the cool air under the car, which seems to work fine. I can feel the heat billowing out from under the car when the fan is on.

Is it important to blow the air from the front of the car (or pull the air out the back) so that flow is from front to back? I'm thinking perhaps the LEAF is designed for flow from front to back to give the best cooling while driving, but I don't know. Anyone know?

 

[DaveinOlyWA]

does the battery casing underneath the car actually get hot? that might be a way to transfer coolness to the pack. just allow a fan to blow across it to cool it quicker. set up a mister to allow evaporation to accelerate the transfer of heat...

wow!! that is too much. forget i said that

 

[EdmondLeaf]

I have a 10k BTU window unit mounted in the wall of the garage, mainly for when the temp is up in the triple digits and I come home with 7TB on the display (or when I need to work on things in the garage). No duct, I just run a cheap fan to blow the cool air under the car, which seems to work fine. I can feel the heat billowing out from under the car when the fan is on.

Is it important to blow the air from the front of the car (or pull the air out the back) so that flow is from front to back? I'm thinking perhaps the LEAF is designed for flow from front to back to give the best cooling while driving, but I don't know. Anyone know?

I have three reason to blow cold from the back:
main battery stack is in the back of the car
if you blow against natural design then cold air will stay longer in battery area
my car is parked like that and I do not have desire to move it

As of fan only I do not think it make much sense with temp gradient so little, we are talking about cooling 600lb. I ran fan only when I am sure that outside air is colder than battery. I give up on local cooling using small chiller that is using .25kWH

 

[1932highboy]

Followup to the questions about my post.

I am in Wichita Falls, Texas. Last summer it was over 100f all summer. My car sat in a parking lot for over 8 hours everyday at work. Then it sat in my garage. I changed to 80% on work days, every day. My commute was 30 miles. On weekends I charged to 100% due to more driving. My battery check was preformed on 5/9/2012 and I got 5 stars for every item , except for "frequent charging when battery state is already high", I got 4 stars. Prehaps this with the heat did the pack in.

The last 5 numbers of my VIN are 01112.

Hope this helps