Cell Balancing in Leaf

[DaveinOlyWA]

active cell balancing could explain why so many are seeing the charge completed then a few hours later, another very short charge cycle as cell balancing could bring the pack low enough to kick the charge cycle back on. granted part of that could be caused by thermal cooling, but time alone should not be sufficient enough to cause the charge cycle to kick back on

 

[planet4ever]

I thought we had pretty thoroughly debunked the 30Kw rumor... It's 24Kw, period.

Can we debunk this "24 kWh, period" rumor once and for all? Jimmydreams, in My Experiments With Turtle wrote:

SOMEHOW, BETWEEN SWITCHING SCREENS I MANAGED TO SCREW UP THE ADDITION!!! FROM TURTLE-MODE (0% CHARGE), THE EVSE PUT IN 25.6kWh OF ENERGY, NOT 19.2!!!

Unless the charging process is more inefficient than we think, he should have had about 90% of that available in the battery, i.e. about 23 kWh. And Jimmy was within a few blocks of his house when he went into turtle mode, so he was not down to zero usable capacity. I think we have to believe what we have been told repeatedly. A new battery has about 24 kWh usable capacity. Surely no one who knows anything about lithium battery chemistry believes that the car would let us kill the battery by using anywhere close to its total capacity, so the total is greater than 24 kWh.

Ray

 

[evnow]

Jimmydreams, in My Experiments With Turtle wrote:

SOMEHOW, BETWEEN SWITCHING SCREENS I MANAGED TO SCREW UP THE ADDITION!!! FROM TURTLE-MODE (0% CHARGE), THE EVSE PUT IN 25.6kWh OF ENERGY, NOT 19.2!!!

Unless the charging process is more inefficient than we think, he should have had about 90% of that available in the battery, i.e. about 23 kWh.

Also, according to EPA, they used more than 24 kwh to recharge during EPA tests.

http://www.mynissanleaf.com/viewtopic.php?f=4&t=2433

 

[DaveinOlyWA]

i think the charging efficiency is no better than 85%

 

[garygid]

From Wall to the Motor Inverter, the 85% (15% loss) would be quite reasonable, even good.

Perhaps:
5% loss in the Charger
5% loss in the battery while charging
5% to 15% loss in the battery while driving, depending upon speed (current draw).

 

[TomT]

I believe that many are assuming the the charge efficiency is higher than it actually is and thus that the battery capacity is higher than it actually is. I have still seen nothing that convinces me that the total capacity of the battery is more than 24Kw... It's all conjecture and wishful thinking at this point, in my opinion. YMMV.

I thought we had pretty thoroughly debunked the 30Kw rumor... It's 24Kw, period.

Can we debunk this "24 kWh, period" rumor once and for all? Jimmydreams, in My Experiments With Turtle wrote:

SOMEHOW, BETWEEN SWITCHING SCREENS I MANAGED TO SCREW UP THE ADDITION!!! FROM TURTLE-MODE (0% CHARGE), THE EVSE PUT IN 25.6kWh OF ENERGY, NOT 19.2!!!

Unless the charging process is more inefficient than we think, he should have had about 90% of that available in the battery, i.e. about 23 kWh. And Jimmy was within a few blocks of his house when he went into turtle mode, so he was not down to zero usable capacity. I think we have to believe what we have been told repeatedly. A new battery has about 24 kWh usable capacity. Surely no one who knows anything about lithium battery chemistry believes that the car would let us kill the battery by using anywhere close to its total capacity, so the total is greater than 24 kWh.

Ray

 

[AndyH]

I believe that many are assuming the the charge efficiency is higher than it actually is and thus that the battery capacity is higher than it actually is. I have still seen nothing that convinces me that the total capacity of the battery is more than 24Kw... It's all conjecture and wishful thinking at this point, in my opinion. YMMV.

Nothing personal, mogur, but I guess we're lost in the "in my opinion" part.

http://www.mynissanleaf.com/viewtopic.php?p=12708#p12708

At Plug-in 2010 today I stationed myself at the Leaf battery display and listened for a while as the Nissan rep manning that display answered a number of questions without a misstep that I could detect. I finally got my chance and, pointing at the board that said "24kWh total capacity", I asked, "Does that really mean total capacity, or total usable capacity?" He grinned, and replied, "The total usable capacity is roughly 24kWh. The total capacity of the pack is confidential."

How much milk is left in a gallon jug if I open a new container and drink the top 20%?

If I take one of my 10Ah LiFePO4 cells and use 80%, I've used 8Ah and left 2Ah in the can.

What if I actually NEED all 10Ah? You might suggest that I can simply take all 10Ah from the cell and I'd agree - but I want 10Ah and a long cell life. The only way to connect both those dots is to use a larger capacity cell.

It really is that simple.

As for efficiency, I'll agree with about 95% [edit] ~88-90% [/edit] for a high-frequency CC/CV charger, and about 95% for a good quality lithium cell.

 

[TomT]

Nothing personal at all - it IS my opinion - but that thread is just another of many pieces of unsubstantiated information. It's he-said, she-said. Maybe when someone has some actual hard numbers we can put this discussion to bed once and for all but until then I don't believe it is a 30Kw total capacity pack.

I believe that many are assuming the the charge efficiency is higher than it actually is and thus that the battery capacity is higher than it actually is. I have still seen nothing that convinces me that the total capacity of the battery is more than 24Kw... It's all conjecture and wishful thinking at this point, in my opinion. YMMV.

Nothing personal, mogur, but I guess we're lost in the "in my opinion" part.

http://www.mynissanleaf.com/viewtopic.php?p=12708#p12708

At Plug-in 2010 today I stationed myself at the Leaf battery display and listened for a while as the Nissan rep manning that display answered a number of questions without a misstep that I could detect. I finally got my chance and, pointing at the board that said "24kWh total capacity", I asked, "Does that really mean total capacity, or total usable capacity?" He grinned, and replied, "The total usable capacity is roughly 24kWh. The total capacity of the pack is confidential."

How much milk is left in a gallon jug if I open a new container and drink the top 20%?

If I take one of my 10Ah LiFePO4 cells and use 80%, I've used 8Ah and left 2Ah in the can.

What if I actually NEED all 10Ah? You might suggest that I can simply take all 10Ah from the cell and I'd agree - but I want 10Ah and a long cell life. The only way to connect both those dots is to use a larger capacity cell.

It really is that simple.

As for efficiency, I'll agree with about 95% for a high-frequency CC/CV charger, and about the same for a good quality lithium cell.

 

[AndyH]

Nothing personal at all - it IS my opinion - but that thread is just another of many pieces of unsubstantiated information. It's he-said, she-said. Maybe when someone has some actual hard numbers we can put this discussion to bed once and for all but until then I don't believe it is a 30Kw total capacity pack.

Let's see... X-(20%*X)=24 I guess we could do .8X=24

Or don't you recognize that lithium gives a significant life when we use 80% but will not last 8 years at all if we use 100%? Or it could be that you don't agree with the model the NREL did of the Leaf when calculating battery effects of thermally conditioning the cabin (they modeled a 24kWh usable pack, where the operator uses 84% of total capacity and charges to 95% of ultimate)?

What type of 'proof' would you recognize and accept? I'll work with you but you've got to help a bit as well!

 

[AndyH]

Nothing personal at all - it IS my opinion - but that thread is just another of many pieces of unsubstantiated information.

http://www.mynissanleaf.com/viewtopic.php?p=63786#p63786

There has been much speculation and I can tell you with a very high level of confidence after a connection to a LEAF using the appropriate tool the full capacity of a new LEAF pack is 27kw and change. I know myself and others have always believed this and now we know!

Well, last night we connected a LEAF to the Nissan Diagnostic tool and ran full tests. The AH rating is all there as well as quite a bit of data, the tool cost about $7K to buy and only works at this time on the LEAF and Murano. For those smart eggs that suspected all along it was over 24kwh, kudos for sticking to your guns!

 

[evnow]

I've been monitoring the total energy pumped at the wall. Thanks to the new Blink firmware I can do that while plugged in now.

I charge to 100% on weekends. The first charge completed mail from Leaf came last night - and Blink showed 55.18 kwh (for this month). In the morning I got another charge completed mail from Leaf and Blink shows 55.51. I'd have to guess Leaf drank some more power after some rebalancing - to the tune of 0.33kwh.

 

[DaveinOlyWA]

I've been monitoring the total energy pumped at the wall. Thanks to the new Blink firmware I can do that while plugged in now.

I charge to 100% on weekends. The first charge completed mail from Leaf came last night - and Blink showed 55.18 kwh (for this month). In the morning I got another charge completed mail from Leaf and Blink shows 55.51. I'd have to guess Leaf drank some more power after some rebalancing - to the tune of 0.33kwh.

what is charge efficiency as compared to energy reset on Leaf?

 

[DeaneG]

I called Nissan this morning to ask whether occasional 100% charging is helpful or required, or is it OK to use 80% charge every day.

The CSR said that it is a good idea occasionally to run the battery fairly far down and then give it a 100% charge. I assume this helps the battery controller software better understand the battery state (to avoid a 10 miles remaining then sudden turtle then sudden shutdown scenario), but probably ages the battery a bit.

 

[DaveinOlyWA]

Some times it amazes me how much lasting damage NiCad barre have done considering how briefly they were in our world.

 

[palmermd]

Some times it amazes me how much lasting damage NiCad barre have done considering how briefly they were in our world.

It seems the support person was referring to the, fully discharging and then charging fully, allowing the software in the car to reset, not doing anything for the battery. It does make some sense in that regard.

 

[DaveinOlyWA]

Recalivrating the meter is something done on cellphones because there was a fraction of a penny spent to insure its accuracy. I would hope tha Nissan spent a bit more than that

 

[palmermd]

Recalivrating the meter is something done on cellphones because there was a fraction of a penny spent to insure its accuracy. I would hope tha Nissan spent a bit more than that

hece my underlining "some".

 

[Herm]

Some times it amazes me how much lasting damage NiCad batteries have done considering how briefly they were in our world.

Very true Dave, from the 60s into the late early 90s?.. people still are worried about the memory effect.

 

[DeaneG]

Some times it amazes me how much lasting damage NiCad batteries have done considering how briefly they were in our world.

A lot of high-current hand tools still use NiCd. But I think the Nissan rep was referring to software "calibration" of the battery's charge level. Who knows.

 

[AndyH]

Exactly guys - it's definitely not about battery memory (which doesn't exist in lithium cells and wasn't that much of a problem for NiCD) but about recalibrating the computers.

I hate to draw a comparison with other electric tech but we have to do this process in our laptops as well. Laptops have the battery, the BMS in the battery box, and (for MS at least) the Windows power management software. Short cycling allows the BMS and software to get out of sync - and the computer reports shorter and shorter run-time. It says the battery is losing capacity - but what's really happening is that the software only 'thinks' the capacity is dropping (or thinks it's degraded more than it has).

http://www.brighthub.com/computing/hardware/articles/50844.aspx
http://ftp1.us.dell.com/diags/R66243.htm
http://books.google.com/

Although LiIon batteries do not form a chemical memory per se, they do suffer from irreversible life-robbing oxidation. When the battery has a significant charge, this oxidation is exacerbated by heat, such as that generated by the laptop in which the battery is installed or by leaving the battery in a car exposed to ambient heat. There is no cure for this effect, and the battery has a finite life expectancy; but the effect also has a bearing on how Windows' battery gauge interprets the battery's remaining charge. Calibrating the battery, which really means calibrating Windows' gauge or synchronizing the gauge with the battery, involved allowing the battery to discharge completely once in every 30 charging cycles until the laptop loses power. Doing so keeps the gauge more accurate, and users who watch their gauge vigilantly will not be caught off guard.