evnow
Well-known member
Assuming 90% to 10% usability range -
100% = 90% (duh)
80% = 74%
16.7% = 23% (battery low)
8% = 16.7% (Turtle)
0% = 10%
100% = 90% (duh)
80% = 74%
16.7% = 23% (battery low)
8% = 16.7% (Turtle)
0% = 10%
I wish we had a chart or data from AESC that gave us SOC VS. voltage for these specific cells. I'm beginning to wonder if we have 10% at each end or 10% total - 5% at each end. If we have 5% at each end, then there may be some life improvement if we charge to less than 'consumer 100%'... Time to go back thu all the early interviews and re-remember.evnow said:Assuming 90% to 10% usability range -
100% = 90% (duh)
80% = 74%
16.7% = 23% (battery low)
8% = 16.7% (Turtle)
0% = 10%
I think 8% is very suspect. The chart from the diagnosis manual says the last bar doesn't disappear until 4%. I wouldn't expect turtle mode until that bar disappears.evnow said:8% = 16.7% (Turtle)
The only hint I've seen on this is that the steps on the capacity gauge are 6.25% except that first step is 15% and the last is 16.25%. Could this perhaps mean 8.75% reserved at the top and 10% at the bottom?AndyH said:I wish we had a chart or data from AESC that gave us SOC VS. voltage for these specific cells. I'm beginning to wonder if we have 10% at each end or 10% total - 5% at each end. If we have 5% at each end, then there may be some life improvement if we charge to less than 'consumer 100%'... Time to go back thu all the early interviews and re-remember.
We know that a module is 2P-2S - so that 7.5V nominal is 3.75V per cell - up from the old 3.6V number.Weight: 3.8kg
Nominal Voltage: 7.5V
Capacity: 66Ah
planet4ever said:But is charging to 90% less stressful than discharging to 18%? I think that is what you are really talking about. I continue to believe that the total capacity of the battery is about 30kWh with a usable charge range of 24kWh. In converting usable charge percent to total charge kWh, I contend (for a new battery at room temperature) that:mogur said:I still contend that charging to 100 percent is less stressful for the battery than discharging to 10 percent or less... This is true for almost every lithium battery ever made and I have a hard time believing that the Leaf battery would be any different.
- "100% charge" is really about 27kWh
- "10% charge" is really about 5.4kWh
- "0% charge" is really about 3kWh
- The car will never let you go below about 3kWh or above about 27kWh
Note that I don't claim to know the answer to the question I asked. I only claim that it isn't "obvious" from prior lipo experience.
I understand and agree completely - that is apparently EXACTLY what we have for our use as drivers of this car!mogur said:Everything I have read to date, and the numbers from current owners, makes me believe that the full capacity of the battery is what Nissan has always said it is, 24Kw, and there is no hidden top or bottom end. 24Kw period.
And I haven't either. But what we do have points strongly in that direction. Nissan stated that there is about 10% capacity above and below the user capacity zone. In another Q/A Nissan was asked how much capacity the owner had - the answer was 24kWh. The Nissan rep was then asked the total pack capacity - the answer: That's Proprietary.mogur said:I have seen no data to indicate a true capacity of 30Kw.
vkruger said:I have over 300 cycles on my LiMn battery pack I built for my bike. When I researched the cells I found out that discharging to 3.0 V does no harm but charging above 4.1 V does. I charge my pack to only 4.06V. I would be surprised if Nissan allowed charging above 4.1 V. Data back then showed charging to even 4.15 V cut cycle life (to 80% of original capacity) in half. Discharging to 3.0 V had no measureable impact on cycle life.
I charge to 80% weekdays (because that is all I need) and 100% on weekend and don't worry one bit about loss of cycle life. I would prefer to charge to 95% all the time until I find out that 100% is less than 4.1 V, then I'll charge to 100% all the time. I think Nissan is just being over cautious.
charlie1300 said:As a non-EE, I'm impressed with some of the technical arguments here that the Leaf's BMS will protect us from doing the battery pack damage. Yet I keep coming back to the fact that Nissan clearly recommends charging to 80% and not discharging below 20%. Given the fact that following their recommendation changes the Leaf from 100 miles/charge to 60 miles/charge, with a really negative marketing implication, I have to believe Nissan has some factual reason for the recommendation. I can't just write this off as corporate cautiousness.
Li batteries do best if kept in the middle of usable range (see Volt's usage of 10.4 kwh out of 16 kwh). It is also possible Nissan is using more of the topend than bottom end (or the otherway round).charlie1300 said:As a non-EE, I'm impressed with some of the technical arguments here that the Leaf's BMS will protect us from doing the battery pack damage. Yet I keep coming back to the fact that Nissan clearly recommends charging to 80% and not discharging below 20%. Given the fact that following their recommendation changes the Leaf from 100 miles/charge to 60 miles/charge, with a really negative marketing implication, I have to believe Nissan has some factual reason for the recommendation. I can't just write this off as corporate cautiousness.
Prepare to be surprised. Nissan's using a lithium-manganese variant and the numbers I reported in my diagram modifications (95% SOC 4.0-4.2V) comes directly from Nissan's service manual.vkruger said:I have over 300 cycles on my LiMn battery pack I built for my bike. When I researched the cells I found out that discharging to 3.0 V does no harm but charging above 4.1 V does. I charge my pack to only 4.06V. I would be surprised if Nissan allowed charging above 4.1 V. Data back then showed charging to even 4.15 V cut cycle life (to 80% of original capacity) in half. Discharging to 3.0 V had no measureable impact on cycle life.
I charge to 80% weekdays (because that is all I need) and 100% on weekend and don't worry one bit about loss of cycle life. I would prefer to charge to 95% all the time until I find out that 100% is less than 4.1 V, then I'll charge to 100% all the time. I think Nissan is just being over cautious.
Can you reference the 20% recommendation? I don't recall reading that. Thanks!charlie1300 said:As a non-EE, I'm impressed with some of the technical arguments here that the Leaf's BMS will protect us from doing the battery pack damage. Yet I keep coming back to the fact that Nissan clearly recommends charging to 80% and not discharging below 20%. Given the fact that following their recommendation changes the Leaf from 100 miles/charge to 60 miles/charge, with a really negative marketing implication, I have to believe Nissan has some factual reason for the recommendation. I can't just write this off as corporate cautiousness.
I think that Nissan is using more of the 'top' of the charge. This is common practice for other lithium variants that carry more of their energy higher in the discharge curve, like LiCo. This 'top bias' seems to be confirmed by a number of government lab papers, including your recent find documenting the affect of HVAC on range.evnow said:Li batteries do best if kept in the middle of usable range (see Volt's usage of 10.4 kwh out of 16 kwh). It is also possible Nissan is using more of the topend than bottom end (or the otherway round).
Either way, ambient temperature and miles driven will have more of an impact than100% charging.
We should assume Nissan used their best engineering and economic judgement to pick the high and low hard boundaries beyond which the car will not push the battery pack. This judgement also figured into the warnings Nissan has placed in both the manual and the car itself to encourage us to use the extreme boundaries of the battery sparingly to avoid premature loss of battery capacity.mogur said:As an EE, I have to adopt the position that if charging to 100 percent or discharging to "zero" was really such a significant consideration, they would never have allowed it in the first place.
charlie1300 said:As a non-EE, I'm impressed with some of the technical arguments here that the Leaf's BMS will protect us from doing the battery pack damage. Yet I keep coming back to the fact that Nissan clearly recommends charging to 80% and not discharging below 20%. Given the fact that following their recommendation changes the Leaf from 100 miles/charge to 60 miles/charge, with a really negative marketing implication, I have to believe Nissan has some factual reason for the recommendation. I can't just write this off as corporate cautiousness.
It might even be 95% at the top and 10% at the bottom.AndyH said:I think this also allows us to use all the numbers we've been quoted - 80%, 95%, 24kWh, etc. It's clear that we have 24kWh of usable energy on the 'consumer side'. Top bias would fit well with 'consumer 100%' being 95% ultimate SOC. We'd still be using 80% of capacity by leaving 15% on the bottom.
Could be, but the cells with cobalt tend to have their power near the top, so there's not much reason to work near the bottom. Plus, dropping to the last 10% would 'violate' that we have 80% to work with. (yeah, I know - like that's an absolute maybe at this pont. )evnow said:It might even be 95% at the top and 10% at the bottom.AndyH said:I think this also allows us to use all the numbers we've been quoted - 80%, 95%, 24kWh, etc. It's clear that we have 24kWh of usable energy on the 'consumer side'. Top bias would fit well with 'consumer 100%' being 95% ultimate SOC. We'd still be using 80% of capacity by leaving 15% on the bottom.
So, we get Battery Low at 25% and Turtle at 17%. The total battery size would be some 27.5 kwh.
The reason the SOC display sometimes changes when you switch to/from charging/driving is the battery's intrinsic hysteresis. Below is a graph which displays battery voltage vs SOC for both charge and discharge cycles for Li-ion chemistry.smkettner said:I thought this was a typical way to engineer indicator lights to avoid flickering back and forth when close to between the levels.Smidge204 said:In other words, the bars have no strict relationship to SOC.
The 10th bar (third one down) will come on when the battery SOC crosses from 79% to 80% - but will turn off when the SOC crosses from 85% to 84%. So the meaning of the bars is relative to the direction.
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