Yesterday I loss my 3rd bar @ 26 k miles..

[QueenBee]

probably but only slightly quicker. the fastest charge happens at a low state of charge. As it fills up the rate of charge slows down. unfortunately, most of the time to charge is the slow part near the top of the pack and ALL of the loss is at the top as well. a smaller capacity only means the rate of charge slows down sooner

Dave, could you reference a charging curve that supports that "most of the time to charge is the slow part near the top"? Maybe you meant to refer to only DCQC and not level 1/2 charging? I think your guess that it's only slightly quicker is not accurate for both level 1/2 and DCQC.

Also, it's not clear what you mean by "ALL of the loss is at the top". All of what loss? The car's capacity will certainly be lost with time and use even if you never charge past 80% and there are certainly charging efficiency losses at any charging SOC.

When my '11 was down 20%, it only took about 17 mins. to QC when it used to take 27-28 mins.

sorry, my statement is for fast charging. as far as loss at the top. it is capacity I am referring to. but LEAFfan made a statement that implies that the station may only determine its charging speed based on voltage which would not indicate any measure of capacity loss. this could eventually lead to a situation where fast charging will significantly speed up degradation because the charge rate is not slowing down quickly enough. granted that level of degradation would be severe but since there is only a general guideline as to when a battery "should" be replaced, those who choose to replace a battery at 50% degradation could see a fast charge that runs at full speed almost to completion?

I don't understand batteries and charge rates enough to know how it should handle charging a pack with 50% capacity but wouldn't the BMS adjust the charging curve as the battery degrades? As the pack degrades is the 100% SOC voltage going lower and so 80% SOC is at a lower voltage as well

 

[TomT]

No, the voltage remains about the same regardless. It is the current delivering capacity (amp hours) that decreases. The cells effectively become smaller...

I don't understand batteries and charge rates enough to know how it should handle charging a pack with 50% capacity but wouldn't the BMS adjust the charging curve as the battery degrades? As the pack degrades is the 100% SOC voltage going lower and so 80% SOC is at a lower voltage as well

 

[QueenBee]

No, the voltage remains about the same regardless. It is the current delivering capacity (amp hours) that decreases. The cells effectively become smaller...

I don't understand batteries and charge rates enough to know how it should handle charging a pack with 50% capacity but wouldn't the BMS adjust the charging curve as the battery degrades? As the pack degrades is the 100% SOC voltage going lower and so 80% SOC is at a lower voltage as well

So that's the opposite of lead acid batteries right? Whereas a 100% resting charge has a lower voltage.

So I don't see the problem that Dave thinks exists? A 50% degraded battery will just get to 80% SOC quicker and at a similar voltage and the charge rate curve will basically be the same except for a shorter duration?

 

[TomT]

Well, the voltage I see on my Gid Meter for a 100% charge is about the same now as it was before degradation set in... I'll let more battery savvy minds than mine draw the conclusions...

A 50% degraded battery will just get to 80% SOC quicker and at a similar voltage and the charge rate curve will basically be the same except for a shorter duration?

 

[DaveinOlyWA]

when charging, the voltage is used to determine when charge is complete so its independent of capacity. so no matter what the level of degradation, the voltage remains the same as long as the number of functioning cells remain the same.

my issue is that when fast charging, the charger charges quickest at the lower end of the SOC then slows down as the SOC rises to capacity. so it would make sense that the larger the pack the higher the ratio of charge per unit time would be as long as there was an equal number of cells right?

so you have two packs both same # of cells so same target voltage but one pack is degraded and can only take say 16 Kwh verses the other pack with less degradation that can take 20 kwh.

so now we go to LEAFfan's statement

When my '11 was down 20%, it only took about 17 mins. to QC when it used to take 27-28 mins.

so he has 20% less capacity to charge BUT its taking him significantly more than 20% less time to charge. maybe my thinking is off but if the fast charger still slows down to a certain rate of charge at a specific SOC as it ramps up to a full charge then a 20% less capacity should be 20% slower at the most?

 

[LEAFfan]

I don't know, but the super fast charging was a surprise. So it would give me 98-99%/12 bars but only about 80% capacity.

 

[GerryAZ]

I just joined the 3-bar loss club. Silver 679 in Tony's range test dropped the 3rd bar on the way home from the airport this evening at 24,152 miles and exactly 2 years. I had 10 bars when I stopped for dinner and 9 bars when I started toward home after dinner. I am trying to compile my charging and GID meter records and will post a summary this weekend. I will add my 3rd bar loss to the Wiki later.

Gerry

 

[GRA]

I just joined the 3-bar loss club. Silver 679 in Tony's range test dropped the 3rd bar on the way home from the airport this evening at 24,152 miles and exactly 2 years. I had 10 bars when I stopped for dinner and 9 bars when I started toward home after dinner. I am trying to compile my charging and GID meter records and will post a summary this weekend. I will add my 3rd bar loss to the Wiki later.

Gerry

Assuming you can still get where you need to go in the meantime, you may well lose the fourth bar by the end of summer and can take advantage of the warranty. Still sucks.