I want my 281!

[EdmondLeaf]

I appears that after 7 mo and 7.2 KM in I have my perfect GID score. My highest battery temp so far was 89F for very short time and now is in the range of 77- 82F. I am not driving Leaf now, and I was thinking to do so till temp drops to max of 85F. My friend that got his car about a month ago will be driving, his Leaf battery temp yesterday on the way home reached 108F. Our temp monitoring systems are not perfect but reasonable. Looking for your input if worthy to continue doing what we doing and measure temp and battery capacity. Cars are in the same temp zone and reasonably similar to start with. What do you think, summer time in full swing today we started with 84F and will reach 106F and same or similar for many days to come.

 

[DaveinOlyWA]

well after 3 straight 280's i only got 275 this morning. i chalk it up as a fluke for now

 

[garygid]

Edmond...
How are you measuring the Battery Pack temperature?

I considered putting a temp. sensor on the upper surface
of the Battery Box, near the rear, probably in the center,
possibly accessed through the Emergency Off hatch in the
rear-seat foot-space.

However, I have not yet done that.

Thanks, Gary

 

[garygid]

Maybe some are suggesting that the 100% capacity point should be
270 GIDs rather than 281, so that a "new" car (at 281) would read 104.0%?

 

[EdmondLeaf]

Edmond...
How are you measuring the Battery Pack temperature?

I considered putting a temp. sensor on the upper surface
of the Battery Box, near the rear, probably in the center,
possibly accessed through the Emergency Off hatch in the
rear-seat foot-space.

However, I have not yet done that.

Thanks, Gary

That is exactly where my sensor is and the way you described. IMO this is best spot because so many modules in very close proximity. I only have 1 reference point which is 74.3F from 5 to 6 TB on the way up, I know is not perfect but....

Gary thank you for GID info I will be disconnecting my 12V and my car is a reference so no GID measurement while not used.

 

[surfingslovak]

Maybe some are suggesting that the 100% capacity point should be
270 GIDs rather than 281, so that a "new" car (at 281) would read 104.0%?

Gary, it's certainly something to consider, but I don't believe that there is enough data to support such a decision yet. Perhaps Phil will weigh in on this at some point, and if 281 Gids was an overcapacity recorded only on new cars, then what you suggested would make complete sense. I will try to te-read his old posts if I get a chance. I believe that he talked about that before, and Leafscan will use 281 as 100%.

 

[garygid]

For consistancy, I will also continue to use 281 as 100%,
since switching to a new reference point accomplishes little.

I am now working on setting the Date/Time in my new
2x16 LCD "Black-Box" CAN-Recorder for the LEAF.

 

[Stoaty]

Maybe some are suggesting that the 100% capacity point should be
270 GIDs rather than 281, so that a "new" car (at 281) would read 104.0%?

Well, that would fit with the fact that loss of the first capacity bar (15%) seems to correspond very closely to 20% Gid loss, which would be around 84%. I asked in an earlier post on a different thread how one could make sense of 15% loss (one capacity bar) being a 20% loss of Gids and suggested (jokingly at the time) that would require 104-105% as the orginal battery capacity.

 

[TickTock]

Gary,
Where did this 270 come from? I did a search and your comment was the first I saw suggesting it.

 

[DaveinOlyWA]

Gary,
Where did this 270 come from? I did a search and your comment was the first I saw suggesting it.

Good question. If we assume that 90% of the pack is accessible and 300 gid its 100% that still does not account for the fact that we don't see 1gid.

The 270 had thrown me because my batteries are not new bit read 280 on a regular basis

 

[garygid]

Boomer and I think that it is possible that "new" Packs often have a "usable" capacity OVER a minimum acceptable capacity (of perhaps roughly 270 GIDs).

Then, as they "age", the "usable" capacity "gradually" decreases from maybe a high of 295 GIDs, BUT while only being charged to about 280 or 281 GIDs. The diminishing "excess" capacity is not noticed, because it is never actually used.

Finally, the "excess" capacity is gone, and charging can no longer reach 281 GIDs, because the charging becomes limited to the (diminished) "usable" capacity.

That would explain why some of us are "suddenly" seeing (after a year) reducing 100%-Charge GID values, below 280.

A thought ... at least ... that fits some of the data.

 

[Boomer23]

I do? I didn't think we had discussed it to that quantitative a level.

I do think that aging might be a piece of the picture, and that's why some of us are seeing dropping Gid counts beginning around the early May time frame. My thought was that perhaps our packs were manufactured around the same time, and even though they have been charged and driven differently, some of us are seeing Gid reductions of 10 or more Gids at full charge beginning in early May.

As I read all of these threads, I'm coming to the opinion that pack aging, temperature, and number of charge/discharge cycles are the chief factors in Gid reductions. Mwalsh and xtremeflyer live close to me and Gary. Mwalsh's car is a few months older, than Gary's and mine. Xtremeflyer's car is a few months newer than ours. But those two guys have similar commutes, and though xtremeflyer's car is newer, he commutes more often than mwalsh does. It is well known that these batteries have a limited number of charge/discharge cycles in them, and Gary and I don't use the full range of our packs' capacity like these two guys do. Hence we have fewer pack cycles, and we have less of a Gid capacity degradation.

That's my story and I'm stickin' with it!

 

[surfingslovak]

Interesting read! I found Ingineer's old post on a similar topic, which might be worth revisiting in this context.

Reg brought up another interesting point, the Gid count, or the level in Nissan's vernacular, might not be an expression of natural battery capacity. Instead, it's likely an expression of a BMS behavior. If this was not the case, then these batteries would have less than 0.3% difference in total capacity. Given that the pack consists of 192 individual cells, that's quite unlikely, even with very tight manufacturing tolerances.

If you accept this rationale, the 281 value will suddenly appear as something imposed on the pack by the BMS. It's likely a synthetic value or perhaps a result of the balancing algorithm, and not a true representation of your battery's storage capacity.

 

[TickTock]

Boomer and I think that it is possible that "new" Packs often have a "usable" capacity OVER a minimum acceptable capacity (of perhaps roughly 270 GIDs).

Then, as they "age", the "usable" capacity "gradually" decreases from maybe a high of 295 GIDs, BUT while only being charged to about 280 or 281 GIDs. The diminishing "excess" capacity is not noticed, because it is never actually used.

Finally, the "excess" capacity is gone, and charging can no longer reach 281 GIDs, because the charging becomes limited to the (diminished) "usable" capacity.

That would explain why some of us are "suddenly" seeing (after a year) reducing 100%-Charge GID values, below 280.

A thought ... at least ... that fits some of the data.

Wouldn't the measured voltage at 100% for a new car with this excess read a lower voltage (<394V) at 281 until capacity drops to the point that the max gid begins to drop?

 

[garygid]

Yes, that would seem likely, but the voltage difference might be
small, maybe 10 mv per cell (x96 = 0.960 volt for the Pack).

Since the Pack voltage data is only to 0.5 volt (the SOC-Meter
averages 20 readings to get a pseudo-resolution of 0.1 volt),
the small Pack Voltage difference MIGHT be difficult to see.

 

[TickTock]

Agreed. If you extrapolate on the curve, it looks like 15 gids would only result in ~2V difference which is small but may still be noticeable. Anyone report reading 392V & 281G regularly for a full charge?

 

[garygid]

That curve tends to indicate that the cells are "full" (about 394 volts) but that they have a smaller capacity (about 244 GIDs).

However, the charge might just appear low due to a faulty current sensor ... but I think you checked that by measuring the energy from the wall, right?

So, if the energy-in rate (power), after charger losses and circuitry power usage, matches the GID rate x 80 Watts, the conclusion would be that less energy went in, and the Pack current sensor is about correct ... leading back to smaller "effective" capacity.

So, something (like an out-of-balance cell) might be terminating the charge early ... but one most likely needs to read and monitor all the cell-pair voltages to get a better handle on that issue.

A frustrating situation, indeed!
Cheers, Gary

 

[Boomer23]

I have more Gid losses to report. I'm now down to 257 Gid on a 100% charge and 217 Gid on an 80% charge.

EDIT: Current mileage is 14,143, delivered 15 months ago. I have not lost a capacity bar. Charges to 80% still give 10 charge bars. Car was delivered within 2 days of arriving at dealer. I did 100% charges more than 90% of the time until this issue arose. I've been doing 80% charges when planned driving allowed, since mid-May 2012.

In the first week of May, 100% charges were 280 and 281 Gid, and an 80% charge was 232 Gid. Starting in the second week of May, I started seeing 100% charges resulting in mid to low 270s.

Here are my June Gid counts in chronological order. I'll add the voltage on the last charge on each list:

80% charges: 223, 223, 223, 223, 222, 222, 221, 221, 221, 221, 220, 221, 220, 220, 219, 217, 217 (June 29 early AM, 387 Volts (EDIT, fixed error, I originally said voltage was 357))

100% charges: 268, 270, 265, 268, 270*, 269, 265, 266, 260, 257 (July 1 early AM, 393 Volts)



(* the 268 and 270 were on the same morning, the 270 was after topping up at a ChargePoint while waiting for Tony in Laguna Beach, then driven almost immediately)

 

[TickTock]

Was that May of this year? Or last year when you received your Leaf?

 

[DaveinOlyWA]

I have more Gid losses to report. I'm now down to 257 Gid on a 100% charge and 217 Gid on an 80% charge.

In the first week of May, 100% charges were 280 and 281 Gid, and an 80% charge was 232 Gid. Starting in the second week of May, I started seeing 100% charges resulting in mid to low 270s.

Here are my June Gid counts in chronological order. I'll add the voltage on the last charge on each list:

80% charges: 223, 223, 223, 223, 222, 222, 221, 221, 221, 221, 220, 221, 220, 220, 219, 217, 217 (June 29 early AM, 357 Volts)

100% charges: 268, 270, 265, 268, 270*, 269, 265, 266, 260, 257 (July 1 early AM, 393 Volts)



(* the 268 and 270 were on the same morning, the 270 was after topping up at a ChargePoint while waiting for Tony in Laguna Beach, then driven almost immediately)

ok, so as i expected the first loss comes on rather quickly and in a big chunk. it sounds to me that the BMS is holding back info until it reaches a certain parameter since this happened in a span of less than 2 months