Level III charging a Leaf

[DarkStar]

Don't worry, we have to pump our own diesel... Just gasoline is full service...

 

[PDXLeafer]

Did another test today on Level 3 charging after being disappointed that there were NO charging stations at the Auto Show (avaliable to charge at)... Any way, interesting data. I did a 7 minute video on my iPod Nano, which shows charging from 58% to 84% in 7.5 minutes and a total of 2.6Kwh. I will load that up in the morning, and appologize now for the shaking video (just holding it in my hands).

So, the question this raises is:
If the L3 (what we will call it for simplicity's sake) charger is suppose to only charge to 80% capacity, and I assume that the LEAF is the one saying 'stop, no more!', then why didn't it stop?

Here is my idea of why:
The charging started at over 70A, at 58% charge (according to the L3)
I manually stopped the charge at 84%, when the output was only at 30A-32A range. So, my assumption is that the LEAF realized that since the L3 was only putting out L2 amounts of charge, it was just fine to continue.

Thoughts?

Oh, and an O.T. - P.S. Waylan (White Zombie) and I met at the Auto Show, and we will have both our cars at the Golden Touch restaurant on Barbur Blvd in SW Portland Wednesday at 7:00pm for some EV car show of sorts.

 

[planet4ever]

According to the service manual, the display goes to ten bars when you get to 80% full, and eleven bars when you get to 88% full. As many people have observed, you never see an exact percentage in the state of charge digital display, only a number which corresponds to the number of bars lit up. 84% is the number you always see when ten bars are lit, and that makes sense, in a way, because ten bars (at least while charging) means somewhere between 80% and 88%.

Short answer: If charging stops at 80% you will see ten bars and the state of charge number shown will be 84.

Now do you see why people are wishing for a real SOC value, not just a restatement of the number of bars?

P.S. on rereading I see that Oliver was referring to SOC as reported by the charger, not the car. So much of what I said here may not really apply.

 

[LEAFer]

The 2.6kWh sounds wrong. Seems to me to charge an incremental 26% SOC you should be adding about 1/4 of the total battery capacity or slightly more due to losses. So that would be 8-9 kWh. :?: at worst ... but 6-7 kWh at minimum.

As to the 7.5 minutes: That's 1/8 of one hour. So (using the weird 2.6kWh) means you were charging at a rate of 20.8kW ... not bad. But with the more sensical # (6-7kWh), you were charging between 48-56 kW. That makes more sense at L3.

Rough check: you are supposed to be able to do 80% in 30minutes. 24kWh * 80% = 19.2 kWh. So the rate of charge would be 38.4kW.

So again the 20.8kW rate seems off.

 

[walterbays]

Here is my idea of why:
The charging started at over 70A, at 58% charge (according to the L3)
I manually stopped the charge at 84%, when the output was only at 30A-32A range. So, my assumption is that the LEAF realized that since the L3 was only putting out L2 amounts of charge, it was just fine to continue.

That's the answer I've been hoping for. I don't recall seeing anywhere that Nissan tells you you may not charge over 80% on L3, just that they quote the 0 to 80 charging time. Well that's an impressively fast time. But if the charging software slows it way down at 80% - as I think it ought to do - then quoting a recharge time to 100% wouldn't be nearly as impressive. But I'm hoping that the Leaf will always take electrons from whatever source is available, as fast as possible, without damaging the battery. And I won't have to worry about it.

 

[planet4ever]

The 2.6kWh sounds wrong. Seems to me to charge an incremental 26% SOC you should be adding about 1/4 of the total battery capacity or slightly more due to losses. So that would be 8-9 kWh. :?: at worst ... but 6-7 kWh at minimum.

100% SOC is relative to the usable capacity, not the total capacity, and AFAIK no one thinks the usable capacity is more than 24 kWh. That would suggest only 6 kWh for 25%. Since we are talking about DC input to the car, and presumably the kWh being delivered to the car, not pulled from the distribution center, there should be very little loss. I would think 6.5 kWh would be an absolute maximum.

But I agree with the rest of your analysis.

 

[PDXLeafer]

I should mention (it will be apparent in the video when I upload tomorrow) that the Amps were reducing at a linear rate from 71A when I first looked to approx 32A at the end, so the average over the 7.5 minutes would have been around 51.5A

 

[PDXLeafer]

That's the answer I've been hoping for. I don't recall seeing anywhere that Nissan tells you you may not charge over 80% on L3, just that they quote the 0 to 80 charging time.

I still haven't had a chance to go through the entire manual, so thanks for that info. It was an 'assumed fact' for me at this point

 

[smkettner]

Did another test today on Level 3 charging after being disappointed that there were NO charging stations at the Auto Show (avaliable to charge at)... Any way, interesting data. I did a 7 minute video on my iPod Nano, which shows charging from 58% to 84% in 7.5 minutes and a total of 2.6Kwh. I will load that up in the morning, and appologize now for the shaking video (just holding it in my hands).

So, the question this raises is:
If the L3 (what we will call it for simplicity's sake) charger is suppose to only charge to 80% capacity, and I assume that the LEAF is the one saying 'stop, no more!', then why didn't it stop?

Here is my idea of why:
The charging started at over 70A, at 58% charge (according to the L3)
I manually stopped the charge at 84%, when the output was only at 30A-32A range. So, my assumption is that the LEAF realized that since the L3 was only putting out L2 amounts of charge, it was just fine to continue.

Thoughts?.

It may well stop based partially on battery temperature. So going from 0 to 80% it must stop. But since you started at 58% it may well go a bit longer.
Did it completely stop? I could see it just slowing way down and then going to 100% very slow.
The QC time from 0 to 80% is the zone where you will get 100% max power into the battery to show best charge time.

 

[DarkStar]

If the L3 (what we will call it for simplicity's sake) charger is suppose to only charge to 80% capacity, and I assume that the LEAF is the one saying 'stop, no more!', then why didn't it stop?

The DC Quick Charge system will charge a LEAF to 100%. The 0-80% time is right about 25 minutes and the other 80-100% takes an additional 20 minutes.

Just like Level 1 or Level 2 though, the LEAF does have full control of the DC Quick Charge system using the CAN-bus and in the event that the communication is broken and the DC Quick Charger doesn't stop supplying power, the LEAF will open a contactor that goes directly from the CHAdeMO port to the battery pack to keep things safe.

 

[garygid]

DS, I agree, about 45 minutes to QC to 100% of user.

But, if left unattended, is there some way to stop QC at 80%, or 90%, or 95% (assuming temperatures remain OK)?

 

[PDXLeafer]

The DC Quick Charge system will charge a LEAF to 100%. The 0-80% time is right about 25 minutes and the other 80-100% takes an additional 20 minutes.

Just like Level 1 or Level 2 though, the LEAF does have full control of the DC Quick Charge system using the CAN-bus and in the event that the communication is broken and the DC Quick Charger doesn't stop supplying power, the LEAF will open a contactor that goes directly from the CHAdeMO port to the battery pack to keep things safe.

Good info - thanks DarkStar
I will let it go to 100% next time, as it seemed to be operating in a responsible way (slowing as it filled), but will probably keep an eye on it any way. Looks like there are many layers of safety built in the the system though.

 

[DarkStar]

DS, I agree, about 45 minutes to QC to 100% of user.

But, if left unattended, is there some way to stop QC at 80%, or 90%, or 95% (assuming temperatures remain OK)?

Since you can only set 80% in the timed charging function, that would be the only way to do it. But I'm not even sure if the timed charging will function across the DC Quick Charge port...

Good info - thanks DarkStar
I will let it go to 100% next time, as it seemed to be operating in a responsible way (slowing as it filled), but will probably keep an eye on it any way. Looks like there are many layers of safety built in the the system though.

No problem! I definitely think that Nissan should offer options to set a maximum State-of-Charge though. For example, Nissan has stated that DC Quick Charging to 100% three times a day could be very detrimental (over time) to the battery, however DC Quick Charging to 80% three times a day shouldn't be an issue at all as most of the heat is generated in that last 10-15%.

 

[JasonT]

however DC Quick Charging to 80% three times a day shouldn't be an issue at all as most of the heat is generated in that last 10-15%.

This sounds backwards to me, but I am completely ready to be schooled by anyone who has more knowledge on this than me.

You said the 80% charge takes 25 minutes, and that last 20% takes an additional 20 minutes. I didn't think the system slowed down because of heat, but instead to ensure the batteries don't get overcharged. As I (mistakenly?) understood it, the closer you get to "full" the harder it is to tell if you are at "full". With that slower charge I thought there would be less heat generated.

Going further down this line, that's why I thought the L1 and L2 charging was no concern because of the slow speed but L3 is a concern due to the heat/stress that goes on.

Where did I go wrong on this?

 

[garygid]

Presumably cell heating is (can be) a significant problem, but Nissan has not been clear on this QC "battery damage" issue. It seems that Nissan has 4 temperature sensors in the Pack, presumably sufficient for "protection", as long as the heat is well distributed. However, with QC, the heat MIGHT not distribute fast enough.

Any QC would normally be an "immediate-charge", rarely ever "Timer-driven". Apparently there is no automatic way to stop the QC progress at anything short of 100%. So, manual control, standing/sitting there watching the progress is required?

If this is the case, it seems to me that a software upgrade is NEEDED here.

 

[DarkStar]

however DC Quick Charging to 80% three times a day shouldn't be an issue at all as most of the heat is generated in that last 10-15%.

This sounds backwards to me, but I am completely ready to be schooled by anyone who has more knowledge on this than me.

You said the 80% charge takes 25 minutes, and that last 20% takes an additional 20 minutes. I didn't think the system slowed down because of heat, but instead to ensure the batteries don't get overcharged. As I (mistakenly?) understood it, the closer you get to "full" the harder it is to tell if you are at "full". With that slower charge I thought there would be less heat generated.

Going further down this line, that's why I thought the L1 and L2 charging was no concern because of the slow speed but L3 is a concern due to the heat/stress that goes on.

Where did I go wrong on this?

Heat is generated a few different ways, one way is the physical heating of the actual cells. As a cell reaches a 100% SOC (state-of-charge) its temperature will increase. The other way heat is generated is through the BMS (battery management system). To balance the voltage across cells, shunts are electronically created and they have to dissipate the energy as heat.

The reason why the system reduces voltage and current as it reaches 100% SOC is for both of these reasons, one is to make sure the batteries don't overheat and the second is so that the BMS doesn't have to dissipate as much heat.

The most damaging factor for this battery pack will be heat. Since Level 1 and Level 2 aren't able to "throw" as much energy into the battery pack, the cells won't get as hot and the BMS won't get as hot.

DC Quick Chargers can only charge the car at the specifications the LEAF gives it, so if Nissan has programmed it to draw 80 KWh, that's what it will draw at until otherwise told. If Nissan programmed it to only draw at 12 KWh, the DC Quick Charger would gladly comply.

 

[PDXLeafer]

VIDEO: http://www.no-url.com/LEAF/LevelIIICharging_01-30-11.html

Again, sorry for the 'hand-held experience'. I gots no tripod for my ipod

 

[AndyH]

Presumably cell heating is (can be) a significant problem, but Nissan has not been clear on this QC "battery damage" issue. It seems that Nissan has 4 temperature sensors in the Pack, presumably sufficient for "protection", as long as the heat is well distributed. However, with QC, the heat MIGHT not distribute fast enough.

Any QC would normally be an "immediate-charge", rarely ever "Timer-driven". Apparently there is no automatic way to stop the QC progress at anything short of 100%. So, manual control, standing/sitting there watching the progress is required?

If this is the case, it seems to me that a software upgrade is NEEDED here.

The info you're looking for is in the service manual and in info posted here on L3 charging. One factor is that L3 is supposed to stop after 20 minutes of use - which you complained about here: http://www.mynissanleaf.com/viewtopic.php?p=8329#p8329

 

[AndyH]

Heat is generated a few different ways, one way is the physical heating of the actual cells. As a cell reaches a 100% SOC (state-of-charge) its temperature will increase. The other way heat is generated is through the BMS (battery management system). To balance the voltage across cells, shunts are electronically created and they have to dissipate the energy as heat.

Yes - cells will heat during the later stage of charging***. Normally this is from the ~80% state and higher.

There are a number of different ways to balance cells. The method you reference uses resistors or FETs to dissipate energy from the higher-voltage cells so they don't overfill. There are other ways to balance cells, including capacitive- and inductive- charge transfer. Neither of these methods generates significant heat.

We don't yet know how the Leaf's BMS balances the pack, so it's a bit early to suggest that the BMS will contribute to pack heating.

[edit]
*** Provided the input current remains the same. Cells can continue to charge without exceeding the maximum temperature if the charging rate is reduced.

[/edit]

 

[DarkStar]

The info you're looking for is in the service manual and in info posted here on L3 charging. One factor is that L3 is supposed to stop after 20 minutes of use - which you complained about here: http://www.mynissanleaf.com/viewtopic.php?p=8329#p8329

Here's what the service manual states:

Charge mode:
Quick charge mode

Remaining charge level:
Remaining battery at the start of charging is less than 50%: 90%
Remaining battery at the start of charging is 50 % or more: 100%
NOTE: When the specified time lapses, charging stops if charge level is not sufficient.

Time required for charge (at 25°C):
Approx. 30 minutes (Charging from Li-ion battery available charge level low to 100%)
---
Quick Charge Mode

Quick charge mode performs charging with quick charger. Maximum charge level varies depending on the remaining level of the Li-ion battery at the start of charging. When charging is not completed and the charge time set on the quick charger or the time out (approximately 60 minutes) set on the vehicle elapses, charging stops.

NOTE: If charging stops before charging is complete, additional charging by quick charge can be performed again.