Better (reverse) SOC meter already in the car?

[RegGuheert]

Carwings showed 4h / 1:30 for me charged to 80% this morning as expected. I tried to get the car itself to show me time to 100% by turning off timers, changing my 80% timer to 100%, but for some reason the car itself wouldn't show anything but --.

O.K. Thanks for trying! That matches what I saw as far as dashes go.

So what do you make of my reading 3.5 hours to 100%? I suppose that could be due to lower capacity, but perhaps there are other explanations? It's been a while since I've let the LEAF charge to 100% and then sit for a while to balance. Perhaps the cells are out of balance? Maybe there are differences in firmware somewhere? Could it be that it takes AC voltage into consideration in its calculation (my voltage is 125 VAC)?

 

[RegGuheert]

Another charge to 80% today also yields a 3.5-hours prediction of time to trickle charge to 100%.

I suspect my pack may be quite out-of-balance since I rarely charge to 100%. Perhaps that is why mine yields a lower prediction...

 

[grommet]

Adding a few data points, from someone in the relatively mild S.F. Bay Area. (Generally Palo Alto.)

Hit LBW yesterday, time to 100% via 120V read 17 hours. (56 miles driven on 80% L2 charge, 4.4 miles/kWh average.) Later, hit VLBW... time to 100% via 120V read 20 hours.

15 month old LEAF, normally charged to 80%... low mileage, just a tad over 10K miles.

 

[GerryAZ]

I will add a few data points since I have now resorted to using this method for some indication where I am at after reaching LBW or VLBW.

15,000 miles and 2 capacity bars down and no attempts made to "calibrate" 120V charge time by using trickle charger (all charging to 100%):

Estimated charging time 8.4 miles after LBW:
240V 5:00
120V 15:00
56.1 miles total
3.9 mi/kWh dash
6 temperature bars
17.41 kWh actual power from wall
L2 charge 4:40 actual

Estimated charging time 14.4 miles after LBW (includes 2.4 miles after VLBW):
240V 5:30
120V 15:00
61.9 miles total
4.1 mi/kWh dash
6 temperature bars
18.36 kWh actual
L2 charge 4:54 actual

Estimated charging time 17.8 miles after LBW (includes 7.2 miles after VLBW) and run heater to shutdown in driveway:
240V 6:00
120V 17:00
65.4 miles total
4.0 mi/kWh dash
7 temperature bars
20.13 kWh actual
Estimated charge time was 5:30 and 16:00 before turning on heater. Turtle was reached about 1 or 2 minutes after heater was turned on and shutdown was reached a total of 5 minutes after turning on the heater. Actual L2 charging time was 5:24.

Clearly, the estimated charging times are not highly accurate in predicting actual charging time or actual SOC, but they provide reasonably accurate information to give some guidance after the other instruments just display 0 bars and dashes.

Gerry

 

[surfingslovak]

Estimated charge time was 5:30 and 16:00 before turning on heater. Turtle was reached about 1 or 2 minutes after heater was turned on and shutdown was reached a total of 5 minutes after turning on the heater. Actual L2 charging time was 5:24.

Clearly, the estimated charging times are not highly accurate in predicting actual charging time or actual SOC, but they provide reasonably accurate information to give some guidance after the other instruments just display 0 bars and dashes.

Gerry, thank you for the data! Great to see this. Would you know what the 120V charging time was when you reached the low battery warning? To be fair, I was watching the display when I drove Randy's Leaf during the range test, and if memory serves, I saw similar numbers.

 

[GerryAZ]

Estimated charge time was 5:30 and 16:00 before turning on heater. Turtle was reached about 1 or 2 minutes after heater was turned on and shutdown was reached a total of 5 minutes after turning on the heater. Actual L2 charging time was 5:24.

Clearly, the estimated charging times are not highly accurate in predicting actual charging time or actual SOC, but they provide reasonably accurate information to give some guidance after the other instruments just display 0 bars and dashes.

Gerry, thank you for the data! Great to see this. Would you know what the 120V charging time was when you reached the low battery warning? To be fair, I was watching the display when I drove Randy's Leaf during the range test, and if memory serves, I saw similar numbers.

Surfingslovak,

LBW has become so routine that I don't pay that much attention other than resetting the "B" trip odometer. I usually display the mi/kWh on the dash until I get a ways into LBW and then switch to estimated charge time. I will try to remember to check the estimated charge time when I hit LBW for the next few trips and then post them to this thread.

Gerry

 

[RegGuheert]

I had an interesting result yesterday. Due to a calamity of circumstances, I *nearly* hit VLBW twice about 3 hours apart with about 2 kWh of L1 charging and 12 miles of driving in between.

What is interesting is that after the first discharge the GOM still showed "4" and Carwings reported 18:00 hours to recharge on L1. The second time the car had just hit VLBW, and Carwings reported 16:00.

FWIW, the second discharge was at a higher miles/kWh and possibly 10F colder temperature.

Given that I got recharge numbers that differed by two hours within a three-hour period, I question how reliable that report is as a battery capacity gauge.

 

[surfingslovak]

I had an interesting result yesterday. Due to a calamity of circumstances, I *nearly* hit VLBW twice about 3 hours apart with about 2 kWh of L1 charging and 12 miles of driving in between.

What is interesting is that after the first discharge the GOM still showed "4" and Carwings reported 18:00 hours to recharge on L1. The second time the car had just hit VLBW, and Carwings reported 16:00.

FWIW, the second discharge was at a higher miles/kWh and possibly 10F colder temperature.

Given that I got recharge numbers that differed by two hours within a three-hour period, I question how reliable that report is as a battery capacity gauge.

That's really odd. Assuming that you did not plug the car into a 120V outlet, I would not expect to see this behavior. The only time I came up one hour too short, and missed my destination, was when ambient temps dropped precipitously from about 50F to 30F. On all other occasions, the gauge was very predictable, so long I constrained myself to using 240V for charging.

Here is an example of a range test I preformed this summer. My Gid meter was on loan then, but it showed a value in mid 260s when it came back. I followed the protocol outlined in this thread, and I would consider these values to be as accurate as they can get given the instrumentation we have in the car. Note that I was getting 25 hours indicated on the charging display in turtle mode earlier, when my Gid count was still a perfect 281.

 

[davewill]

I had an interesting result yesterday. Due to a calamity of circumstances, I *nearly* hit VLBW twice about 3 hours apart with about 2 kWh of L1 charging and 12 miles of driving in between. ...

That's really odd. Assuming that you did not plug the car into a 120V outlet, I would not expect to see this behavior. ...

He said he did plug into L1 for 2kWh worth of charge.

 

[surfingslovak]

I had an interesting result yesterday. Due to a calamity of circumstances, I *nearly* hit VLBW twice about 3 hours apart with about 2 kWh of L1 charging and 12 miles of driving in between. ...

That's really odd. Assuming that you did not plug the car into a 120V outlet, I would not expect to see this behavior. ...

He said he did plug into L1 for 2kWh worth of charge.

Oh, cool, makes perfect sense then. Thanks for pointing it out. I completely missed it when reading Reg's post

While still on the topic, my Leaf went 21.2 miles after LBW with 6.5 m/kWh energy economy in the range test mentioned above. This implicitly confirmed for me that the range below LBW does not degrade. I was getting about 3.3 kWh usable before, and 3.26 kWh in this particular test. Also, four hours will lapse between LBW and turtle mode. This equals 44 Gids = 4 hr x 11 Gid/hr.

If nothing else, we can use the charging display to navigate the low SOC reaches a little better.

When you see the LBW, bring up the charging time display and take a note of the number of hours to charge on 120V. Keep monitoring this value, and when it increases by 3, then you are getting really close to turtle mode and have less than 5 miles of very careful slow driving left. When the gauge adds 4 hours, you should look for a safe location to park or try to coast to the nearest charging station.

Not nearly as good as a Gid meter, but in the absence of something better this will do.

 

[RegGuheert]

Oh, cool, makes perfect sense then.

So are you saying that it simply subtracted off the two hours of L1 charging that I did but it did not subsequently add in about two hours for the 2.1 kWh that I consumed later?

If so, that would certainly explain it, but I have to wonder why in the world it would stop counting energy coming out of the battery.

 

[surfingslovak]

Oh, cool, makes perfect sense then.

So are you saying that it simply subtracted off the two hours of L1 charging that I did but it did not subsequently add in about two hours for the 2.1 kWh that I consumed later?

Yes, the plain act of plugging the car into a wall outlet will definitely affect the 120V charging time display. By how much, and in which direction, that's anyone's guess. I wasn't able to observe a predictable pattern there. The most common outcome of plugging in was a 2-hour positive offset, which means that instead of seeing X hours on the display, I would see X+2 hours. The only way to reliably reset that is to top off to 80% or 100% on 120V.

If so, that would certainly explain it, but I have to wonder why in the world it would stop counting energy coming out of the battery.

That's a fair question, and I wish I had a good answer. There is so many idiosyncrasies when it comes to dash instrumentation that I stopped wondering about the reasons. That said, I certainly wish that the charging time display did not exhibit this behavior. It would be much more useful that way.

 

[EvansvilleLeaf]

I tried this with surprisingly disappointing results.

Leaf with 3800 miles in warmer but seasonal S. Indiana climate that has triple digit temps but not even close to the desert SW in either extent, frequency or duration. Never been close to a QC, charged almost always to 80%, always at home and was on dealer lot for < 24 hrs so no chance of abuse there. Very little high speed use. All 12 bars still showing.

120v full charge showed 113 GOM miles (didn't expect that to mean squat, just a reference) and obviously -- -- hrs to 100%. Reset tripmeter and avg m/kw readout on dash

Ran usual mostly non-highway, very limited elevation change commutes averaging displayed 4.6 m/kw on dash, then switched to charge timer view as I got low. No significant climate or wind issues.

Hit LBW with 9 miles showing at 17 hours to 100% with 73.4miles on trip

Hit VLBW (dropped from 4 on GOM straight to _ _ _) with 19 hours to 100% and 79.2 miles on trip.

Drove around another few miles to 83.5 miles on trip. Never saw turtle but had to get home. Highest number to 100% on 120V never exceeded 20:00 and was obviously very close to turtle after more than 4 miles post-VLBW. 4.6 m/kw stayed overall average, which is about my norm.

Unless I'm missing something basic, implication is I have have fewer electrons than I should expect with such low-stress use, or my charge time gauge is suspect at best.

 

[surfingslovak]

120v full charge showed 113 GOM miles (didn't expect that to mean squat, just a reference) and obviously -- -- hrs to 100%. Reset tripmeter and avg m/kw readout on dash

That's a good start! You have covered all the bases.

Hit LBW with 9 miles showing at 17 hours to 100% with 73.4miles on trip

This is 4 hours below book performance (21 hours). If we assume 11 Gid per hour, and 75 Wh usable per Gid, we get ~ 14 kWh usable energy per the charging display. Multiplying that with your energy economy implies 64 miles of range.

A quick backcheck says that the display is missing about 2.5 hours. That could be an offset, but it's surprising to hear, since you charged the car to full on 120V. That should reset the gauge. Did you plug it in after it was charged again or did you precondition (use the climate control)?

Hit VLBW (dropped from 4 on GOM straight to _ _ _) with 19 hours to 100% and 79.2 miles on trip.

Drove around another few miles to 83.5 miles on trip. Never saw turtle but had to get home. Highest number to 100% on 120V never exceeded 20:00 and was obviously very close to turtle after more than 4 miles post-VLBW. 4.6 m/kw stayed overall average, which is about my norm.

OK, based on VLBW at 17 hours, you would have hit turtle mode at 21 hours. Something to keep in mind, and the performance of the car was more predictable in this respect. I'm calculating 79.7 miles at the 21-hour mark, which means that we are missing a few:

21 hr x 11 Gid/hr x 0.075 kWh/Gid x 4.6 miles/kWh = 79.7 miles

Unless I'm missing something basic, implication is I have have fewer electrons than I should expect with such low-stress use, or my charge time gauge is suspect at best.

I think the most plausible explanation is that your display gauge had about 2 hours offset. It's reasonable to assume that it might have incremented another hour if the car was driven all the way to turtle, but we cannot be certain. Either way, I'm getting about 19 kWh of usable energy at the most, which is on the low side for a vehicle with your Leaf's parameters. Was it cold out?

Another possibility is that the energy economy gauge is not displaying correct numbers. We had that with some Leafs. Did you ever have a chance to measure how much energy the Leaf takes from the wall on level 2 when charging from turtle to full?

 

[GerryAZ]

I purchased a Revision 1 (12 ampere) EVSE Upgrade to have for backup of my AV unit at home, use with my generator, and use at my workshop/garage. I charged the Leaf at L2 with it last night from LBW to 100% and it worked great. As I was driving around today, I noticed that the estimated time to charge for 240V was about half of the time for 120V (instead of approximately one third) so the Leaf must use the last charge of each level as the basis for its charging time estimation. My estimated charging time display should return to normal tomorrow since I am using the AV unit to charge tonight. I may try to do a complete L1 charge next weekend to see if it improves the estimated charge time accuracy.

Gerry