LBW as an indicator of total battery capacity

[bernie82]

If I start out with a 100% charge, unplug and recharge to get a total 100% charge, and then do a 4 hour battery balancing, is the amount of remaining miles on the GOM when the LBW comes on, taking into consideration the current KWH / miles %, a reliable indicator for total remaining battery capacity?
It's my understanding that the LBW will come on when the battery is low regardless of the amount of capacity bars showing on the GOM. Is the following statement correct? A LBW with 2 bars remaining is indicative of substantial battery capacity loss. Ideally, there should be no bars showing on the GOM when the LBW comes on.

 

[KJD]

Do not rely on the Guess o meter for anything other than a poor guess.

The Low Battery Warning will appear at 49 GID's or about 17% State Of Charge. Tony and others have documented this many times.
http://www.mynissanleaf.com/viewtopic.php?p=101293#p101293" onclick="window.open(this.href);return false;

If you want to detailed range testing I would highly recommend buy a GID meter. It is a very useful tool.
http://www.wwwsite.com/puzzles/socmeter/" onclick="window.open(this.href);return false;

 

[surfingslovak]

The Low Battery Warning will appear at 49 GID's or about 17% State Of Charge. Tony and others have documented this many times.

Please note that LBW appears at 4 kWh nominal energy remaining and VLBW at 2 kWh. These are fixed thresholds that just happen to correspond to about 18% and 8% SOC respectively when the battery is new.

 

[planet4ever]

We use the term "GOM" to refer to the "Distance to Empty" number showing, not the blue and white bars. They are not directly correlated. Typically LBW will appear with one bar still showing, not zero bars. LBW with two bars showing could mean a degraded battery due to the reason surfingslovak stated, or could happen with an early 2011 model that has not had the March 2011 change applied which remapped the bars. It might also be a one-off event due to variability in measurements the dash computer is using for it's bar drawing calculations.

Ray

 

[LEAFfan]

The Low Battery Warning will appear at 49 GID's or about 17% State Of Charge. Tony and others have documented this many times.

Please note that LBW appears at 4 kWh nominal energy remaining and VLBW at 2 kWh. These are fixed thresholds that just happen to correspond to about 18% and 8% SOC respectively when the battery is new.

LBW is always at 17.4% and VLBW is always at 8.5% no matter the battery capacity.

 

[DaveEV]

You sure about that LEAFfan? I was under the impression that LBW always happened at 49 GID and VLBW at 27 GID regardless of capacity loss.

 

[surfingslovak]

You sure about that LEAFfan? I was under the impression that LBW always happened at 49 GID and VLBW at 27 GID regardless of capacity loss.

Yes, LEAFfan's ScanGauge will continue to show these percentages. That much is sure. This does not mean that they accurately reflect the traction pack SOC.

My understanding is that the ScanGauge reads Gids off the CAN bus, and divides them by a fixed value (281). Perhaps you recall a recent discussion about true SOC on the CAN bus. It's doubtful that the ScanGauge is using that, since it was a recent discovery. Of course, the battery gauge on the dash is likely using this true SOC to render battery segments. So it should possible that it will display more than one bar at LBW. This assumes that the pack degraded far enough to be at approx. 25% SOC with 4 kWh remaining (49 Gids).

 

[DaveinOlyWA]

You sure about that LEAFfan? I was under the impression that LBW always happened at 49 GID and VLBW at 27 GID regardless of capacity loss.

its 49 ( a few times at 48) and 24. but a GID is not always the same value so to say VLB is 17.4% is not really correct either. like all things battery; its mostly likely temperature dependent.

now it VLB be 17.4% for "current" battery conditions? that might be but that condition would be variable.

 

[LEAFfan]

You sure about that LEAFfan? I was under the impression that LBW always happened at 49 GID and VLBW at 27 GID regardless of capacity loss.

Yep! That's the percentage. It's the same EVERY time, all conditions.

 

[LEAFfan]

You sure about that LEAFfan? I was under the impression that LBW always happened at 49 GID and VLBW at 27 GID regardless of capacity loss.

its 49 ( a few times at 48) and 24. but a GID is not always the same value so to say VLB is 17.4% is not really correct either. like all things battery; its mostly likely temperature dependent.

now it VLB be 17.4% for "current" battery conditions? that might be but that condition would be variable.

Sorry Dave, but it never varies no matter the ambient temps or battery conditions. LBW and VLBW are always those percentages.

 

[mkjayakumar]

Does that mean, how much I can drive after I hit LBW decreases as the battery degrades ?

In other words if I was able to drive 15 miles from LBW to Turtle when new, would only get me only around 12.5 miles after a 1 bar (15%) degradation (with the same driving efficiency) ? Correct ?

 

[surfingslovak]

Does that mean, how much I can drive after I hit LBW decreases as the battery degrades ?

In other words if I was able to drive 15 miles from LBW to Turtle when new, would only get me only around 12.5 miles after a 1 bar (15%) degradation (with the same driving efficiency) ? Correct ?

Jay, these thresholds appear to be constant and fixed in terms of how much usable energy is remaining. This means that you will likely continue to see LBW at 49 Gids and VLBW at 24 Gids, and you should be able to travel the same distance after you received one of these warnings like before.

What will change is the SOC percentage this energy reserve represents relative to the remaining pack capacity. For example, if you lost a capacity bar and the pack indicates 220 Gids on a full charge, then LBW is very roughly 22% SOC. In LEAFfan's case, the ScanGauge will continue to display 17.4%, because it uses a fixed value for total battery capacity (281).

 

[mkjayakumar]

George, thanks. That makes sense.