SOC data: 281-based, New-Bars

[evnow]

This morning, the LEAF dash showed 12 bars, but I plugged in the CAN device and the reading was only 95% SOC. I didn't see the SOC # reading, sorry.

Is it possible the number represents the current reading (i.e. how much energy BMS thinks is in the battery) where as the voltage reading cuts off the charging, so as to not overcharge.

BTW, I think until we figure this all out, I don't think we can conclude 281 is 100%. I think we should just look the numbers instead of %.

 

[Boomer23]

I'm going to charge to 100% again tonight and see what reading I get. This time, I'll get both the % and the #.

 

[Coffee_Slurry]

I'm not convinced all cars are created equal.

Mine charges to 281. I know at least one other car does not.

 

[garygid]

We are getting both 95% (by Boomer23) and 100% by GroundLoop (on the 281-scale) reported after a full charge. Both on new firmware? I got about 98.9% on old firmware (and 82.2% for an 80% charge).

We should take both a "high" and a "low" 100%-charge-SOC car (at the same time) to a willing LEAF dealer (maybe Connell Nissan is a good possibility) for a Battery Checkup and Examination on each of them, and let the Nissan Task Force Engineers help us figure out what is different.

Maybe different equalization, cell construction, cell "lot" number, some firmware constant, battery "capacity", etc.?

 

[evnow]

I think charging to different levels, while interesting, is not a "problem".

The real problem is the non-linearity i.e. apparent low miles got out of 12th bar even when charged to a high 281.

What this means is that the SOC doesn't give the reliable indication of charge as we we hoping to get - atleast at the top (not a big problem). We need to figure out how it behaves at the lower end - where it would be more important.

 

[garygid]

Knowing how this "presumed" SOC estimator is derived would tell us a lot about what to expect at both ends. It appears now that the SOC value is NOT used to Stop the "full" (100%) charging. Something else must do it, presumably the Highest Cell-pair Voltage. So, observation of the high end (that is more easily observed/measured) might be quite beneficial.

Discovering just how and when cell "equalization" is done will be a big help, I suspect. Anybody who can record and graph Battery Voltage and Current flow, and SOC, for about 2 hours after each charging, would help considerably.

Soon, I will be able to do that, I hope. However I still need to make and package an 8-volt regulator for the 14v OBD-derived power that feeds my set of 3 AVR-CAN "capture" boards.

Measuring the low end of SOC is more difficult, and fewer people are willing to, or have the time or geography to test down into Turtle Mode, and a good "measuring stick" for taking data is not yet available to most. The "I drove about 2 miles" or "I drove about 100 yards" is all we have so far. But, good, consistant SOC readings at LBW and VLBW would tend to verify what "turbo" found, that those two Battery Warnings (and maybe Turtle Mode) are simply triggered by SOC. We do not know what actually stops the car or what makes SOC fall off "rapidly" at the end.

Recording Pack Voltage and Current, and SOC, AND the Lowest Cell Voltage will help.

However, we have not yet discovered the 96 individual cell-pair voltages in the CAN data, if they actually appear outside the BMS.

 

[DaveEV]

Knowing how this "presumed" SOC estimator is derived would tell us a lot about what to expect at both ends. It appears now that the SOC value is NOT used to Stop the "full" (100%) charging. Something else must do it, presumably the Highest Cell-pair Voltage. So, observation of the high end (that is more easily observed/measured) might be quite beneficial.

I wonder if the SOC indicator is based off the lowest cell voltage? Since SOC is ultimately determined by the charge of the least charged cell, that makes sense - and would also make sense since it should stop charging at 100% when the cell with the highest voltage reaches 100%, not the lowest.

So people with higher SOC numbers might have a better balanced pack.

 

[Boomer23]

I'm seeing a full 281 and 100% SOC this morning, after a full charge last night.

So what happened yesterday? The dash showed 12 bars but the SOC meter showed only 95%.

 

[garygid]

Strange it should vary so much, but good to know.

Was the anything noticably different about the 2 night's charges: starting charge, charging time, how soon after driving you started charging, etc.?

Do you have the LEAF's charging timers set? To what times?

Are they set for 80% and you were using the timer override to charge to 100%, so that if charging was interrupted for some reason, it would try to restart under timer control, I presume, but then not restart because it was already over 80%.

Maybe!

 

[Boomer23]

Strange it should vary so much, but good to know.

Was the anything noticably different about the 2 night's charges: starting charge, charging time, how soon after driving you started charging, etc.?

Do you have the LEAF's charging timers set? To what times?

Are they set for 80% and you were using the timer override to charge to 100%, so that if charging was interrupted for some reason, it would try to restart under timer control, I presume, but then not restart because it was already over 80%.

Maybe!

Yes, starting charge for night 1 (the 95% full charge night) was 25%, 1 bar. For the second night (100% full charge) starting charge was 54%. Charging start times were the same, midnight. Started charging pretty similar amounts of time after driving, about 9 hours.

LEAF's charging timers set for all days, start at midnight, no end time, 100% charge. No timer override used.

 

[mwalsh]

I'm seeing a full 281 and 100% SOC this morning, after a full charge last night.

So what happened yesterday? The dash showed 12 bars but the SOC meter showed only 95%.

What message did you get yesterday - charging complete or charging stopped? I'll be willing to bet the latter.

Edit: Scratched the last bit about me not getting any message on yesterday....that was actually on Monday.

 

[Boomer23]

I'm seeing a full 281 and 100% SOC this morning, after a full charge last night.

So what happened yesterday? The dash showed 12 bars but the SOC meter showed only 95%.

What message did you get yesterday - charging complete or charging stopped? I'll be willing to bet the latter.

Edit: Scratched the last bit about me not getting any message on yesterday....that was actually on Monday.

I haven't enabled messaging. The thought of lots of emails and texts from my car just leafs me cold. :lol:

 

[garygid]

When using a LEAF Timer with just a Start time (no End time),
if charging was interrupted, ... after the interruption, will charging resume,
or will it wait until the next Start time to begin charging again?

Presumably, an interrupted charge (or a charge to 80%) sends a "Charging Stopped" message, while a completed full charge sends a "Charging Completed" message. Both messages include the number of Bars (presumably New or Old, depending upon the LEAF's firmware).

I just charged to full, and the SOC displays 99.2% on my SOC-Meter (with 12 Old-Bars).

I do not "text" messages, but do enable emails which I auto-filter to a special folder for only those messages. It helps me understand what the LEAF and Carwings are doing.

 

[evnow]

I just charged to full, and the SOC displays 99.2% on my SOC-Meter (with 12 Old-Bars).

279/281 = 0.992882562

280/281 = 0.996441281

Are you truncating instead of rounding it up ?

ps : In classical engineering showing 99.2% when the precision is not as good as 0.1% would be frowned upon

 

[davewill]

I just charged to full, and the SOC displays 99.2% on my SOC-Meter (with 12 Old-Bars).

279/281 = 0.992882562

278/281 = 0.996441281

Are you truncating instead of rounding it up ?

ps : In classical engineering showing 99.2% when the precision is not as good as 0.1% would be frowned upon

278/281 = 0.98932384 on my calculator, BTW. He's probably using integer math (common in embedded programming), (279*1000)/281 = 992 which does make the mistake of truncating.

 

[evnow]

278/281 = 0.98932384 on my calculator, BTW. He's probably using integer math (common in embedded programming), (279*1000)/281 = 992 which does make the mistake of truncating.

Yeh ... I meant 280/281.

 

[garygid]

I truncated on purpose so I would not show a too-high number, like showing 2 Bars when you only have 1.05 Bars.

In classic engineering, we try to not throw away useful information.

 

[TonyWilliams]

Measuring the low end of SOC is more difficult, and fewer people are willing to, or have the time or geography to test down into Turtle Mode, and a good "measuring stick" for taking data is not yet available to most. The "I drove about 2 miles" or "I drove about 100 yards" is all we have so far.

I'd be happy to do a mostly controlled experiment. Here's what I posted on this thought earlier:

Dyno Testing For Calibrating Battery

I'm going on a trip until 11 July.

 

[garygid]

ALERT:
Boomer's SOC Meter lash-up apparently uses 279 (instead of 281) as 100% SOC.

So, his % readings are about 1% high, but his Raw-SOC are correct, I think.

By the next Gathering, I hope to have at least one of the next-version SOC-Meter models.

 

[tbleakne]

I'm seeing a full 281 and 100% SOC this morning, after a full charge last night.

So what happened yesterday? The dash showed 12 bars but the SOC meter showed only 95%.

It is hard to keep up with you guys, but I am going to jump in here. My first thought: is it possible the temperature during charge was different for the two nights ?

In colder weather, I have noticed that the charge time estimates are way too high, as the battery appears to be at a lower SOC than it actually is. After charging for a while, the car seems to figure out the actual SOC even though the indicated battery temperature remains low.

600+ pounds of battery represents a lot of heat capacity, so the history of battery usage in the hours before and during charge might be relevant. Even if you don't recall much temperature difference (less than abasile experiences in the mountains), the temperature dependence might well be more sensitive near the top of SOC (i.e 12th bar). The 100% charge cutoff seems likely to be determined by the first cell pair to reach a cutoff voltage. If so, very slight variations would be magnified.

You might want to see how much variation you get on several different nights charging to 80%. At this level there should be no need to shutoff because one cell-pair is slightly ahead of the others.