20,000 miles

[DarkStar]

thanks for that. is there a "float charge" rating. some batteries tend to read a higher voltage just after charging is complete. this voltage bleeds off. so what would be the difference in range from driving immediately after charge is complete verses doing it 8 hours later?

Hmm... I've never had a lipoly battery with any kind of "float charge rating." You charge them up to a certain voltage, immediately stop, and they pretty much stay there. If your battery is old it might loose a percent or two, but generally they all hold the charged voltage (in my experience).

 

[DaveinOlyWA]

thanks for that. is there a "float charge" rating. some batteries tend to read a higher voltage just after charging is complete. this voltage bleeds off. so what would be the difference in range from driving immediately after charge is complete verses doing it 8 hours later?

Hmm... I've never had a lipoly battery with any kind of "float charge rating." You charge them up to a certain voltage, immediately stop, and they pretty much stay there. If your battery is old it might loose a percent or two, but generally they all hold the charged voltage (in my experience).

try measuring how long it takes to lose the first bar when charging was just completed verses when charging was completed several hours earlier. maybe it was a fluke (this opportunity does not come up often for me) but when charging to full capacity, i am usually charged by 1 am. however one time i had unexpected trip come up and had already charged to about 90% the night before so plugged in early in the morning. was done charging around 8:30 am and i took off about 9. i immediately realized that my first bar lasted much longer than the typical 3.5 to 4.6 miles. i actually went to nearly 7 miles. i think i had only hit 5 miles one time previously.

as far as the driving conditions, dont remember anything unusual. i live between two lakes. there are two ways out. the front or the back. so the first few miles of any trip are very consistent.

 

[TonyWilliams]

Rated capacity (0.3C): 33.1 Ah
Average voltage: 3.8 V

Given the provided specifications, the battery pack average voltage is 364.8 Volts and 66.2 Ah or 24.14976 kWh. Fully charged though, the battery pack voltage is 403.2 Volts which would equal 26.69184 kWh.

Great stuff. I'm not sure it makes sense that the current stays constant with an increase in voltage. Also, why are we only seeing 394 volts?

393.5v divided by 8.2v (4.1v per cell) seems to exactly equal the 48 modules. Are you saying "fully charged" is above 4.1v per cell?

 

[surfingslovak]

Rated capacity (0.3C): 33.1 Ah
Average voltage: 3.8 V

Given the provided specifications, the battery pack average voltage is 364.8 Volts and 66.2 Ah or 24.14976 kWh. Fully charged though, the battery pack voltage is 403.2 Volts which would equal 26.69184 kWh.

Great stuff. I'm not sure it makes sense that the current stays constant with an increase in voltage. Also, why are we only seeing 394 volts?

393.5v divided by 8.2v (4.1v per cell) seems to exactly equal the 48 modules. Are you saying "fully charged" is above 4.1v per cell?

I'm sorry, but I see two fundamental problems in this argument. I assumed that we will leave this thread to 20K milers, and won't make new inflated claims about pack capacity. Perhaps I was mistaken.

 

[TonyWilliams]

Perhaps I was mistaken.

:mrgreen:

 

[DarkStar]

Are you saying "fully charged" is above 4.1v per cell?

Nissan's "First Responder" manual (page 9) specifically states that the battery pack voltage is 403.2 volts, that would suggest 4.2 volts per cell, not unusual for a lithium-ion battery.

 

[TonyWilliams]

Are you saying "fully charged" is above 4.1v per cell?

Nissan's "First Responder" manual (page 9) specifically states that the battery pack voltage is 403.2 volts, that would suggest 4.2 volts per cell, not unusual for a lithium-ion battery.

Ok... maybe that's in there with internal combustion engine advice in the owner's manual. Or they changed the spec.

But, that's not what we measure; 393.5v, 4.1v per cell.

 

[surfingslovak]

Given the provided specifications, the battery pack average voltage is 364.8 Volts and 66.2 Ah or 24.14976 kWh. Fully charged though, the battery pack voltage is 403.2 Volts which would equal 26.69184 kWh.

Chris, I really don't understand how you arrived at this conclusion. I believe that you took the projected cell maximum, which you picked up from the manual, and multiplied it by the rated capacity in Ah referenced on the AESC website.

It appears that this is incorrect for two reasons. The report I referenced earlier postulates that maximum capacity for a cell with nearly identical chemistry was reached at 4.17V. If the report applied to the Leaf, then there would be no reason to charge raw AESC cells to 4.2V. Certainly not to get more energy storage out of them.

Secondly, you assume that the AESC cell is capable of storing 139Wh of energy, which then translates to 26.7kWh on the pack level. This is represented by the orange rectangle in the graph below. I picked it up from the AESC website and added the bottom area between 0 to 2.5V for scale.

As Tony already mentioned, the cell voltage is not constant when we draw energy from it. On the contrary, it declines steadily. If we were to discharge the AESC cell with a constant 11A current (1/3 C), then the blue curve would represent declining cell voltage. Because of this, we have to deduct the blue shaded area from the orange block you claimed for total cell capacity. This is just an approximation, but this area seems to represent about 13Wh.

Because of this discrepancy, your calculation overestimates the full rated capacity by about 10%. The average voltage you mentioned is what we are supposed to use together with the rated capacity in Ah to save ourselves this trouble: 3.8V * 33.1Ah = 125.8Wh or 24.15kWh on the pack level.

I'm very surprised to see this and it could be just an oversight on your part, and not lack of knowledge. Be it as it may, what I don't understand is this obsession with pack capacity. Nissan engineers have stated off the record, that the rated capacity information is correct and that there was no padding.

Yes, if you bypassed the BMS, heated Leaf's battery to 100F, charged all cells to 4.20V, stood on your left foot and held your right ear, you might be able to store 26 or 27kWh in the pack. But then, the same thing could be done with other batteries as well. Be it the Volt, the Tesla Roadster or any other EV. We can take any battery, expose it to abnormal conditions, measure 10 or 15% more capacity than what the spec sheet says and declare victory. While at it, let's don't forget that it works the other way around as well. Someone could cool the battery and measure 10% less capacity and say that Nissan was not telling the whole truth.

I'm not clear about is the purpose of this exercise. While it might be interesting from a technical standpoint, it's not OK to tell folks looking for information on Leaf's battery pack that the actual capacity was 26 or 28kW. This is irrelevant at best, and misleading at worst.

 

[DarkStar]

Given the provided specifications, the battery pack average voltage is 364.8 Volts and 66.2 Ah or 24.14976 kWh. Fully charged though, the battery pack voltage is 403.2 Volts which would equal 26.69184 kWh.

Chris, I really don't understand how you arrived at this conclusion. I believe that you took the projected cell maximum, which you picked up from the manual, and multiplied it by the rated capacity in Ah referenced on the AESC website.

The AESC website states that each cell is rated at 33.1 Ah. In the series/parallel configuration that would equal 66.2 Ah. Yes, this is a very simplistic (or some would say crude) way about calculating things, but is generally regarded as an acceptable way to estimate things.

As Tony already mentioned, the cell voltage is not constant when we draw energy from it. On the contrary, it declines steadily. If we were to discharge the AESC cell with a constant 11A current (1/3 C), then the blue curve would represent declining cell voltage. Because of this, we have to deduct the blue shaded area from the orange block you claimed for total cell capacity. This is just an approximation, but this area seems to represent about 13Wh.

Because of this discrepancy, your calculation overestimates the full rated capacity by about 10%. The average voltage you mentioned is what we are supposed to use together with the rated capacity in Ah to save ourselves this trouble: 3.8V * 33.1Ah = 125.8Wh or 24.15kWh on the pack level.

I'm very surprised to see this and it could be just an oversight on your part, and not lack of knowledge. Be it as it may, what I don't understand is this obsession with pack capacity. Nissan engineers have stated off the record, that the rated capacity information is correct and that there was no padding.

I agree, the only way to know for sure would be to put the actual battery through an analysis, until someone does so we are all just guessing with the information we've been provided.

Also, other Nissan engineers have stated to design DC Quick Chargers with the intent of charging a 27 kWh battery pack, and others have viewed diagnostic data reflecting a capacity of around 27 kWh. I don't know which is right, however until someone takes out their battery and finds out, we can only present data based on the "public" figures available.

I'm not clear about is the purpose of this exercise. While it might be interesting from a technical standpoint, it's not OK to tell folks looking for information on Leaf's battery pack that the actual capacity was 26 or 28kW. This is irrelevant at best, and misleading at worst.

I'm only presenting the publicly available information to assist people with making their own determinations. Nissan has stated that the battery has a 24 kWh "consumer usable" capacity, but they also have a very aggressive warranty that suggests that more capacity could be present to protect the cells from being damaged. Some owners have reported only being able to charge about 21 kWh into the batteries too and that is way below the advertised 24 kWh that Nissan has stated and that the EPA/DOE tested the Nissan at. My information isn't anywhere close to misleading.

 

[surfingslovak]

Yes, this is a very simplistic (or some would say crude) way about calculating things, but is generally regarded as an acceptable way to estimate things.

I'm sorry, but this is not true. You cannot take the maximum projected cell voltage and multiply it with the rated capacity in Ah. The manufacturer provides the average or nominal voltage for that purpose. If you intend to use this method when nominal voltage was not available (it is for the Leaf), then apply a 5 or 10% fudge factor to account for declining cell voltage if you care about accuracy at all. Speaking of which, there is little value in providing five decimal digits for rough estimates, although I'm still at a loss as to what exactly you were estimating and why.

The discharge characteristic provided by AESC takes a fully charged cell down to the cutoff voltage of 2.5V. This is the rated maximum energy the cell can supply when following an established test protocol at 70 F ambient temperature. The cells are cycled more conservatively in the Leaf, roughly between 3.0 and 4.10V. This accounts for the difference between rated (or full) and usable battery capacity. There is no gray capacity anywhere, that's wishful thinking.

I agree, the only way to know for sure would be to put the actual battery through an analysis, until someone does so we are all just guessing with the information we've been provided.

Yes, absolutely. And until that day, could we please agree not to spread unfounded rumors and wild speculation? We all have our theories and beliefs, but we should at least have the common sense to put a disclaimer in our posts and clearly separate fact from fiction. The rated battery capacity is not 26.7kWh. Not even close, and none of the verified and publicly available information supports that statement. The calculation you presented is fundamentally wrong and misleading.

I don't know which is right, however until someone takes out their battery and finds out, we can only present data based on the "public" figures available.

Yes, I agree 100% with this view.

I'm only presenting the publicly available information to assist people with making their own determinations. Nissan has stated that the battery has a 24 kWh "consumer usable" capacity, but they also have a very aggressive warranty that suggests that more capacity could be present to protect the cells from being damaged. Some owners have reported only being able to charge about 21 kWh into the batteries too and that is way below the advertised 24 kWh that Nissan has stated and that the EPA/DOE tested the Nissan at. My information isn't anywhere close to misleading.

No, this is incorrect. Nissan has stated that the Leaf had a 24kWh battery, full stop. They never said how much of it was usable, and I believe that the exact number is proprietary. There was an older quote from Mark Perry about 95% of the pack capacity being usable. From what I understand, this is a pretty high figure for an EV, and there was a lengthy debate on that topic last year. Honda made a similar statement recently. They claim that 19 out of 20kWh will be usable in their upcoming Fit EV.

The EPA measured wall-to-wheels energy economy and it made no determination about battery capacity, either usable or rated. If I recall correctly, they measured 24.8kWh from the wall to recharge the Leaf from turtle to full. If you factor in average L2 charging efficiency of 85%, we end up with about 21kWh net into the battery. I hope that you understand that charging is an imperfect process and heat and other conversion losses are incurred. There are well-established metrics for this, in the event that you don't want to take empirical data at its face value. We discussed this topic a little while ago, yet don't seem to want to listen.

Empirical energy economy and odometer data shows that most Leaf owners with post-April firmware can recover about 21kWh from the pack as well. This suggests a 87% ratio of usable to rated capacity. I believe that while aggressive, this ratio is not too high for an EV application and it would be consistent with the projected battery life and capacity degradation figures. The Mini E for example, which according to my research used similar battery chemistry (NMC) and usable to rated battery capacity ratio (86%), fared extremely well with regards to battery longevity.

To sum it up: any statement insinuating that the Leaf had 27 or 28kWh of battery capacity is patently wrong, and if you wish to do so, please at least include some form of disclaimer that it's speculative data based on your personal beliefs. I hope that you agree; I would like to leave this tangential topic and let the 20K mile reports roll in.

 

[EdmondLeaf]

can we resurrect most total miles?

 

[LEAFfan]

To sum it up: any statement insinuating that the Leaf had 27 or 28kWh of battery capacity is patently wrong, and if you wish to do so, please at least include some form of disclaimer that it's speculative data based on your personal beliefs. I hope that you agree; I would like to leave this tangential topic and let the 20K mile reports roll in.

Actually, DarkStar is close! It's 28.8. The ECOtality techs, who have been testing the LEAF's battery packs for several years, told me that Nissan told them that the total capacity was 28.8 kW hs. So there is much more in reserve than we previously thought. This is how Nissan can offer an 8 yr/100K warranty.

 

[smkettner]

can we resurrect most total miles?

12,400 here and glad to hear 20k is an easy ride.

 

[EVDRIVER]

To sum it up: any statement insinuating that the Leaf had 27 or 28kWh of battery capacity is patently wrong, and if you wish to do so, please at least include some form of disclaimer that it's speculative data based on your personal beliefs. I hope that you agree; I would like to leave this tangential topic and let the 20K mile reports roll in.

Actually, DarkStar is close! It's 28.8. The ECOtality techs, who have been testing the LEAF's battery packs for several years, told me that Nissan told them that the total capacity was 28.8 kW hs. So there is much more in reserve than we previously thought. This is how Nissan can offer an 8 yr/100K warranty.

Really, they told you and "Nissan" told them. Funny stuff. That's like when Nissan CS told me all the modules are parallel. So we have some very HV modules. It's not 28.8kw, that has already been established unless the Nissan firmware is lying. Nissan can offer that warranty because it only covers defects not capacity. You could offer that warranty and allow 100% use of the pack and if it died in 3 years it would not be a defect if it only lost capacity. A defect warranty is not of great value on a battery pack as it is very subjective.

 

[TonyWilliams]

10 months, 12 days. The car did sit for several weeks while I was out of town.

 

[EdmondLeaf]

Great job Tony, you driving much more than 2.5KM/mo.

 

[DaveEV]

10 months, 12 days. The car did sit for several weeks while I was out of town.

Nice - that's a lot of EV miles!

Is your dash correct - drove 61.8 miles at 3.9 m/kWh and still have 3 bars remaining? Looks like freeway driving at 65-70 mph?

 

[KeiJidosha]

10 months, 12 days.

Way 2 go Tony

 

[Nubo]

10 months, 12 days. The car did sit for several weeks while I was out of town.

Tony, if I may ask (off topic) -- did you notice any appreciable self-discharge while gone, or was it left plugged-in? I was gone for 10 days, stored at about 65% charge unplugged and lost only 1 mile range (per CARWINGS). People keep asking me about the Tesla "Bricking" and I give them what I know about the LEAF's discharge rate, which was tiny for me but I only have the one data point.

 

[TonyWilliams]

10 months, 12 days. The car did sit for several weeks while I was out of town.

Tony, if I may ask (off topic) -- did you notice any appreciable self-discharge while gone, or was it left plugged-in? I was gone for 10 days, stored at about 65% charge unplugged and lost only 1 mile range (per CARWINGS). People keep asking me about the Tesla "Bricking" and I give them what I know about the LEAF's discharge rate, which was tiny for me but I only have the one data point.

Sorry, but I don't use the GoM or CarWings. If you note in the picture, I actually cover the GoM. I haven't noticed anything unusual after relatively short week periods. The bricking thing is obviously real, as I'm sure folks have bricked zillions of AA batteries, usually when you absolutely need the flashlight that they're in! I don't think the LEAF has the same issues as the Tesla, however. I think our BMS is just a teeny bit smarter, and the cells are different chemistry.

Obviously, the car uses power after you turn it off. Within an hour, it tops off the 12v battery, and again at 5 days (not sure if it's every 5 days). CarWings still works for 2 weeks, before it shuts down.

So, my advice is to leave the traction (main) battery at 50%, plugged or unplugged, but with the charge and climate timers off. Then, I'd put a tender (trickle charger) on the 12v battery. It will sit that way for a LONG time. If you're gone more than two weeks, you won't be able to charge it remotely, because, again, CarWings goes dormant, so it really doesn't matter if it's plugged in or not.