Charging - SOC level differs based on prev. discharge

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nosuchthing

Well-known member
Joined
Jul 16, 2010
Messages
740
I've noticed this over the course of a few days: I drive 84 miles a day, do some charging at work. I need 54 "official" miles to make my 42 mile journey home - all freeway with crusise on. I noticed that if I discharge the batt to three blinking lines and no miles left with the last bar gone, down to about 4-6 "invisible" miles remaining before the turtle mode, and I charge overnight, in a.m. 100% charge reads 88 miles. If I bring the car back with, say 4 miles and one bar remaining and charge overnight, I get it to mid nineties in a.m. When I go short downhill with the full batt it jumps to over 100 miles. If I got it up to only 88-mile full charge after a deep discharge, it may make it to 90 downhill. It's like I'm missing almost 10 miles from the same overnight charge based on what I did the previous drive home. Weird, is it not?

Nissan, we need bigger batteries! Fast!
 
Good observations. Not strange, working as designed.

At 100% charge, the SOC is the same, but the calculated "Miles Remaining" differs, depending upon how gently/aggressively you drove during the (roughly) 5 minutes before you parked the car for charging. Drove very gently it could say 100 miles, drove very aggressively it could say 70 miles, BOTH at the SAME State of Charge (SOC).
 
As Gary says, that number you are referring to is not really mappable to State Of Charge. It is only a computer's guess at how far you can safely go if you continue driving the way you just have been. Because of that, many of us have been calling it the guesstimator, or some slight variation of that made-up word. Like a number of others, I find it best to ignore the number altogether. I do watch the twelve bars which surround it; they are much closer to being a real (albeit very low resolution with a non-zero origin) SOC gauge.

Ray
 
Has Nissan talked at all about changing to a real 0-100% SOC gauge instead of the 12 mystery bars? Have they fixed the issue with turtle mode only giving about a mile or less of range?
 
JRP3 said:
...Have they fixed the issue with turtle mode only giving about a mile or less of range?
I would't call that broken. Turtle means "pull over now!" It's the equivalent of an ICE coughing and sputtering because fuel is running out. We already have a "very low batt" warning that means there's only a few miles left.
 
Since the mileage estimate is less than accurate the low battery warning that tells you there's only a few miles left may not be accurate either, and people have been left stranded because of it. Turtle should come on sooner and allow a few miles of travel in my opinion, coupled with a more accurate SOC gauge listing percentage of charge on a finer scale of 0-100. EV's can travel a long distance at reduced speeds so there is no good reason to go into turtle mode and then be stuck after a few hundred feet.
 
JRP3 said:
Since the mileage estimate is less than accurate the low battery warning that tells you there's only a few miles left may not be accurate either, and people have been left stranded because of it. Turtle should come on sooner and allow a few miles of travel in my opinion, coupled with a more accurate SOC gauge listing percentage of charge on a finer scale of 0-100. EV's can travel a long distance at reduced speeds so there is no good reason to go into turtle mode and then be stuck after a few hundred feet.

How many miles should remain once you hit turtle mode is always different depending on one's opinion.

But AFTER the software change, I think it's fairly safe to say that no one will run out of juice without PLENTY of advanced warning. As has been said many times buy many people: ignore the miles remaining number and count the bars remaining. If you exhaust all your bars, hit turtle mode, and still feel like Nissan left you stranded, well, I don't know what to say. ;)
 
Not being a LEAF owner I wasn't aware that the software update improved the accuracy of the bar graph. Good to know.
 
Now here is another thing, going back to my original post. Again, this a.m. it showed 84 miles. Fine. I understand it was freeway 65 and over hard (ECO though) driving. This a.m. I drove 10 miles in town at 35 or so I jacked in and topped it off. The "smiley face" smiles at 100% showed -- as expected -- mid-90's. Going down my starting point hill, 101 "smiley" miles.

Now here is the thing. I DROVE TO WORK TODAY THE SAME WAY I ALWAYS DO AND ARRIVED WITH 6 BARS AND 46 SMILEYS, WHILE DAY BEFORE 5 BARS AND 35 SMILEYS. So what I'm concluding here is the following: Deep discharge prevents the batt from accepting a truly full charge. And topping it off after a minor discharge does the trick. It's as if I need to do some minor driving and topping off before my 42 mile freeway commute, than just charge overnight and do the 42 miles, because I start with less SOC than with the former. I'm thinking of it as having pissed the batt off by deep (almost turtle) discharge and it's making it not properly recover from the event. And the smiley miles 84 vs. 101 attest to that at least on the face (pun not intended) value.
 
JRP3 said:
Not being a LEAF owner I wasn't aware that the software update improved the accuracy of the bar graph. Good to know.

It didn't improve the accuracy so much as built in a larger 'reserve' buffer. Now, you're down to your last bar before you get your first warning. The last bar should already have you thinking about finding a charge, so the warnings aren't catching people off-guard any more.
 
JRP3 said:
Not being a LEAF owner I wasn't aware that the software update improved the accuracy of the bar graph. Good to know.

Tony posted a really good chart on here showing the actual number of miles you have remaining depending on your speed at the time. For instance, when my guess-o-meter said '10' with one bar left (and low battery warning), I actually had 22 miles left at 38 mph. Thanks again Tony!
 
Jimmydreams said:
ILETRIC said:
And the smiley miles 84 vs. 101 attest to that at least on the face (pun not intended) value.
What the heck are 'smiley miles'?
I think they're the guessometer reading.

Anyway, ILETRIC, The higher guessometer reading may just be the low speed drive, and the difference between 5 bars and 6 bars can be just a tiny bit of charge if the readings were close to the bar boundary. I suppose it's not impossible that you managed to get the system to charge the battery a little more that way, but I wouldn't keep doing it. The owner's manual mentions not recharging unless you run it below 80% as one way to preserve battery life.
 
davewill said:
JRP3 said:
...Have they fixed the issue with turtle mode only giving about a mile or less of range?
I would't call that broken. Turtle means "pull over now!" It's the equivalent of an ICE coughing and sputtering because fuel is running out. We already have a "very low batt" warning that means there's only a few miles left.
I agree with Dave. You get a "low battery warning", then a "very low battery warning" and finally turtle mode. Based on my experience, if you get off the freeway shortly after getting "low battery", you will have 12-15 miles left before the turtle comes on. That's about 15% of your total range, and quite adequate in my opinion. You should not count on going very far in turtle mode. It's purpose is to let you get to a safe place to stop, and that is also important.

Ray
 
LEAFfan said:
Tony posted a really good chart on here showing the actual number of miles you have remaining depending on your speed at the time. For instance, when my guess-o-meter said '10' with one bar left (and low battery warning), I actually had 22 miles left at 38 mph. Thanks again Tony!


This data might help your range estimates:

Range Estimate Chart Thread

Use of the digital mile remaining "Guess-O-Meter" is futile. I recommend just covering it up with a sticker.

With the current, post April 2011 firmware in the car, the moment that the last fuel bar disappears closely corresponds to 10 miles of range remaining at 38mph, and 5 miles at 70mph.

Also, one bar remaining should closely associate with the first battery low warning, and zero bars should associate with the "very low" warning. These two warnings are based are measured "hard" values of battery power, and not on your recent previous driving, like the Guess-O-Meter numbers are.

Speed in MPH......38...50...60....70...Battery Value / Percent Charge
.............................Range in miles.................................................
Fully charged.....130..91...78....65..........281..................100%
Battery Warning...20...14...12....10..........48......................17%
Very Low Warn....10.....7.....6......5...........24......................8.5%
Turtle mode........about 1 mile...................5......................1.7%

Obviously, up hills, extreme outside temperatures (hot or cold), significant wind, snow on road, use of climate control (particularly the heater), etc, will all decrease the range estimates.
 
ILETRIC said:
So what I'm concluding here is the following: Deep discharge prevents the batt from accepting a truly full charge. And topping it off after a minor discharge does the trick. It's as if I need to do some minor driving and topping off before my 42 mile freeway commute, than just charge overnight and do the 42 miles, because I start with less SOC than with the former. I'm thinking of it as having pissed the batt off by deep (almost turtle) discharge and it's making it not properly recover from the event. And the smiley miles 84 vs. 101 attest to that at least on the face (pun not intended) value.
There are no physics of lithium battery charging to support your conclusion, what you are seeing are the vagaries of the Nissan software. Even a turtle event does not take the battery low enough to cause any issues with it's charge acceptance, though obviously you don't want to do that on a regular basis since shallow cycling is best for longevity.
 
running a small charge off a full battery then topping the charge and driving right away probably (at least it does with lead acid and i doubt that LI is different in this respect) creates a "float charge" situation.

this practice is not good and strongly discouraged as it is the #1 way of reduce battery longevity.

when looking at battery management, we need to look at convenience, need and cost.

your cellphone battery which is not a lot different than the Leaf batts are designed to last 300-500 charge cycles. iow, 2 years if real lucky, just over a year if normal. (now you know how cellphone companies determine upgrade cycles? :? )


but the biggest reason is the cellphone battery has a very small charge along with a very small cost, so longevity is not the point. so they recommend you top it off all the time or whenever convenient. it simply is not worth having a dead battery verses a $35 battery replacement. communication is simply too important.

transportation is almost as important ( i know many people who would give up their car first before their cell phone. only a few that would go the other way... pretty tough decision either way) but the logistics is different.

a dead battery in a car will almost always mean no transportation for an extended period of time. it takes an hour to replace a cellphone battery or even better get a car charger. in a car if you need 60 miles of range and your car is only doing 50 miles, you are screwed. the charging infrastructure simply aint there yet.

so battery management for longevity in a car is much more important. i think you need to realize that you can drive to work and back. you have done it several times. i would stop topping off your battery. if you are concerned about range, you are better off to time it so the battery completes charging just before you have to leave in the morning.
 
As I've previously stated in other posts. The numerical mileage remaining is for entertainment purposes only. I like the term "smiley miles". The charge bars, complimented by the miles per kwh reading, give you the most accurate indication of juice left in the battery. You just have to do a little math in your head. I find this "brain exercise" slows down the onset of dementia... :shock:

My trusty LEAF is up to 2,858 miles now.... I still can't wipe that grin off my face every time I jump in a light things up! :cool:
 
DaveinOlyWA said:
running a small charge off a full battery then topping the charge and driving right away probably (at least it does with lead acid and i doubt that LI is different in this respect) creates a "float charge" situation.

this practice is not good and strongly discouraged as it is the #1 way of reduce battery longevity.
Lithium is different and you really cannot compare the two chemistries as they operate quite differently. Frankly I'm not sure where you get the idea that taking a small charge out of a lead acid battery then quickly recharging it is a bad thing, it's exactly what every starter battery goes through in a car, and most starter batteries can last 5-10 years. Lithium lasts longest if shallow cycled in the middle of SOC, but if you charge up and then drive away it's better than charging up and letting it sit, and better than deeply discharging if you end up pushing your range.
your cellphone battery which is not a lot different than the Leaf batts are designed to last 300-500 charge cycles. iow, 2 years if real lucky, just over a year if normal. (now you know how cellphone companies determine upgrade cycles? :? )
My cell phone is probably 5 years old at this point, still working well. Of course I almost never let it go dead and usually don't leave it on the charger.
so battery management for longevity in a car is much more important. i think you need to realize that you can drive to work and back. you have done it several times. i would stop topping off your battery. if you are concerned about range, you are better off to time it so the battery completes charging just before you have to leave in the morning.
I'll agree with the timing but I doubt he's hurting the battery much by topping it off then driving as opposed to not topping off and discharging it more deeply. If he can do his entire drive in the middle of the SOC range and isn't deeply discharging then yes skipping the top off charge is probably better.
 
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