some quick data on charging

i was driving to work this morning when the low battery warning came on. to be clear, this was the first warning so not the "very low battery" warning and obviously not turtle mode. i had around 3 bars left and GOM said something like 15 miles.

the light came on about 1 mile from work.

I charged at work and it has been 4:11 (so a bit over 4 hours) of charging on L2 and it is 100% full.

At 3 hours the charge started to dip from 6kw to 5kw and below.

Total energy charged is 20.256kwh. At this point I am only drawing .002kw so it's done.

Since the Leaf has a 24 kwh battery and my Leaf is pretty new (about 2 weeks old), does this mean that I had around 3+ kwh left on my battery? With my normal city driving I would estimate that at around 12-15 miles?

RVD.

There's only about ~20 or 21 kWh usable on a new Leaf battery and there are some charging losses.

LBW sounds at about 17 or 18% on the % SoC meter. VLBW sounds at 7 or 8%. I believe turtle comes on at 1 or 2%. I've never taken mine to turtle. I also don't know how accurately calibrated % SoC is.

The range chart at http://www.mynissanleaf.com/viewtopic.php?p=101293" onclick="window.open(this.href);return false; might help. It was generated before the '13 Leaf, which was the 1st year to actually have a % SoC indicator built in.

Lesson learned from me. If you do not charge completely to 100% (stop it early) ths cells will not be balanced resulting in soc not being completely accurate. Cold Weather makes it more pronounced. I learned this on my Christmas marathon last year. I'd stop the charging 10-20 minutes before it was done and while I was driving 2 different times it went from around 13% to -- in literally 10 seconds. If you need the full range of the leaf you must start off with a completely charged and balanced battery.

IraqiInvaderGnr said:

If you do not charge completely to 100% (stop it early) the cells will not be balanced resulting in soc not being completely accurate. Cold Weather makes it more pronounced.

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Newbie question. If you have it set to 80% and let it do it's thing does it do the balance when it gets to 80% instead of 100%? Or do we need to occasionally charge to 100%?

i am a newbie too so take this with a grain of salt.

i don't think it will balance your batteries at 80. i have had lipo chargers before and if you set it to stop at 80% or whatever, it just stops.

i used other tools to balance batteries once it hit 80% (or whatever) but i don't know of tools like that for EVs.

if you want to balance your batteries, i would say that you should charge up to 100% periodically but if you are ok with just charging up to 80% for battery longevity they probably won't get that far out of whack anyway so you should be fine just charging up to 80% and letting the batteries get out of balance a bit.

RVD said:

i am a newbie too. So take this with a grain of salt.

i don't think it will balance your batteries at 80. i have had lipo chargers before and if you set it to stop at 80% or whatever, it just stops.

i used other tools to balance batteries once it hit 80% (or whatever) but i don't know of tools like that for EVs.

if you want to balance your batteries, i would say that you should charge up to 100% periodically but if you are ok with just charging up to 80% for battery longevity they probably won't get that far out of whack anyway so you should be fine just charging up to 80% and letting the batteries get out of balance a bit.

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Spot on RVD. Charging to 100% occasionally won't hurt anything so long as you drive it as soon as it gets finished (I'd say within the hour). Letting it sit at 100% is very harmful to the battery. Charging to 100% in and of itself is not harmful. It's mainly the side effects like heat generated (mainly a issue when temps consistently above 80°F) and time spent at 100%.

In the summer I charge at night to 80% when it's cooler out and I park my car outside as my garage retains heat. Sundays I always charge to 100% to balance the battery year round.

You probably had 3kWh left, but only because you were measuring energy going into the car, and charging isn't 100% efficient. 18 or so probably made it to the battery, and you had 3 left to the 21 useable.

New guy here...I am very confused about this thread.

Why is charging to 100% bad? How do you set it to charge only to 80% and why? Is that through Carwings? or the charging unit or whatever you call the 240v wall station I bought and installed.

I live in Maryland, I have had my Leaf for two months now, and have put on about 2000 miles! It has been very cold here since I got the car. Just now starting to warm up. I have noticed that after a full charge, the "range" remaining indicator has gone up from 84/85 to 94 and today saying 100, but those top numbers drop even before I am out of the driveway, without the heater on.

Only issue with the car, is It had a problem with the water pump and took a week to get replaced, and reprogrammed.

Also in this thread talk about summer and heat….so this summer when its 100 deg and high humidity, I again shouldn’t charge to 100%.

Thanks for the info…I am finding this site to be very insightful.

As was said earlier... charging to 100 is not in and of itself, a problem. It is leaving it at 100% is.

I use the end timer to set the charge to end at about 10 minutes before my usual departure in the morning. The car knows how to do the math and starts itself in the very early AM such that the car will be at 100 on time.

I also use the climate control timer to turn it on before departure. This way the heating or cooling of the car can be done before you even get in. It runs off house power if you are plugged in. Saves a bunch of range if you take the chill off before driving. Liberal use of the seat heaters and wheel heaters is also more effective than heating the air while driving.

When you hit defrost make sure you turn off AC and Heat to maximize range... fresh air will often do the trick. Turn up the fan before turning heat and AC back on...

on really cold days make sure that recirc is off... or the icy air will make you turn up the heater more often that you would need to otherwise.

Some of this is only possible with CarWings... some only with 2013 and newer cars.

When you first see LBW, you have ~3.6kWh useable energy left (=(50gids@LBW-5gids@turtle)*0.08 kWh/gid).

RVD said:

i was driving to work this morning when the low battery warning came on. to be clear, this was the first warning so not the "very low battery" warning and obviously not turtle mode. i had around 3 bars left and GOM said something like 15 miles.

the light came on about 1 mile from work.

I charged at work and it has been 4:11 (so a bit over 4 hours) of charging on L2 and it is 100% full.

At 3 hours the charge started to dip from 6kw to 5kw and below.

Total energy charged is 20.256kwh. At this point I am only drawing .002kw so it's done.

Since the Leaf has a 24 kwh battery and my Leaf is pretty new (about 2 weeks old), does this mean that I had around 3+ kwh left on my battery? With my normal city driving I would estimate that at around 12-15 miles?

RVD.

Click to expand...

CUBldr97 said:

New guy here...I am very confused about this thread.

Why is charging to 100% bad? How do you set it to charge only to 80% and why? Is that through Carwings? or the charging unit or whatever you call the 240v wall station I bought and installed.

I live in Maryland, I have had my Leaf for two months now, and have put on about 2000 miles! It has been very cold here since I got the car. Just now starting to warm up. I have noticed that after a full charge, the "range" remaining indicator has gone up from 84/85 to 94 and today saying 100, but those top numbers drop even before I am out of the driveway, without the heater on.

Only issue with the car, is It had a problem with the water pump and took a week to get replaced, and reprogrammed.

Also in this thread talk about summer and heat….so this summer when its 100 deg and high humidity, I again shouldn’t charge to 100%.

Thanks for the info…I am finding this site to be very insightful.

Click to expand...

If you have a '14, you don't even have an 80% mode, so for sure don't worry about it; Nissan doesn't seem to think it's an issue... or they just wanted to get their EPA numbers up.

jsongster said:

As was said earlier... charging to 100 is not in and of itself, a problem. It is leaving it at 100% is.

I use the end timer to set the charge to end at about 10 minutes before my usual departure in the morning. The car knows how to do the math and starts itself in the very early AM such that the car will be at 100 on time.

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I would check to see when you car actually finishes charging, the on board timer/estimator isn't the best. Depending on the charger you're using it can be off by several hours. On my 2013 S w/Charge package and the Bosch 30amp EVSE I have my charge time set for 10am, to leave at 7:10am. I have yet to have it below 100% when I get into the car in the mornings. I started this process first doing 10 or 20min later than my normal departure time, thinking I would charge to just below 100%, over several weeks of adjustments I've finall got it about spot on..... with a nearly 3hr delay.

just another data point:

i was running on (battery) fumes this morning...

yesterday i got the "low battery warning" coming home around 3 miles or so from my house. once home, the GOM said 15 miles left and i was down to the last 2 bars. SOC said 15%. since my commute to work is only 9 miles i decided to risk it.

so this morning, i was driving really really cautiously...like i was barely pressing the gas, etc. i went up the hill from my house to the street really slowly, etc. i didn't put the car in eco mode but i was more or less driving that way. i did have the car in B mode. i was cautious but not enough to be annoying...i kept up with traffic but didn't race anyone on the mean streets of the Seattle suburbs.

with around 2 miles left, i got the "very low battery" warning.

when i got to work, i was at 8%. when it got down to the very low battery warning, it said 8 miles left on range but then it went to "---" when the warning came on. those last 2 miles didn't decrease the SOC at all.

anyway, i don't know if i'll take it this close again. i got to work where we have free chargepoint chargers and there was 1 bar remaining and the estimate to charge full is 5:30. i'm a little interested to see how many kwh get pumped back in today.

CUBldr97 said:

Why is charging to 100% bad?

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Li-ion batteries work by intercalation, which is the process of physically stuffing ions into an electrode and then pulling them out. Li batteries are not 'chemical' batteries in this sense.

The steadier the population of Li ions you leave stuffed in the electrodes, the more mechanically robust they remain. The electrodes physically expand a little as they are stuffed with ions, and shrink again when they are pulled out. The physical structure of the electrode may actually collapse if you pull too many of the ions out, and will force the electrode to swell when you stuff them back in. It should therefore be clear that the less charging and discharging, the longer the battery electrodes will last because they are under a more regular mid-range of stress in those circumstances. Imagine that the springs of your car are regularly extended and compressed to their limits on every bump, then you can imagine they would fail long before springs that ride over a road with gentle oscillations.

Of course, you cannot fear to charge up your battery to 100%, it is designed to do it. But there is no question that it will last longer if you avoid doing so*. You should charge to 100% every so often, though, and this is because of battery management rather than life expectancy. Charging to full will allow the battery to recalibrate its various function, and will 'level' the cells because following repetitive part-charges the cell voltages will begin to drift and some can end up significantly higher or lower than others, which is an issue not usually corrected unless and until all the cells are taken up to their maximum nominal voltage. (You might also note an excess of power drawn while the battery is cell-levelling, because what it is doing is 'shunting' (bypassing) the cells that have hit their full cell voltage, while the others with lower voltages get charged up further. This shunting will waste some of the charge current, so the battery will heat up during this phase, so you might notice a significantly lower 'wall-to-wheel' efficiency during such charges.)

*The exception to not charging to 100% is when you first get the battery, because, as you may gather from the description above, charging to 100% physically stretches the electrode. Within reason, a little bit of extra 'stretching' will therefore improve capacity, but there is no particular reason to do this deliberately as you will, inevitably, need to charge to 100% enough times in normal use that this will happen anyway as a matter of course.

When the battery is drained then if any cells started off quite low then they'll be the first to hit the minimum allowable voltage. I do not actually know what strategy Leaf has for dealing with one defective cell/module, but possibly (?) it only takes one low cell to tell the BMS that the battery is flat? Does anyone know how the BMS deals with this? Are the low cells shunted, and if so how many get shunted before the battery is regarded as 'flat'? Tesla run a 'battery conditioning' process - is this just warming the cells up, or perhaps do they have a way to charge up the low cells from the remainder?

i've dealt with other similar batteries and when you have one cell in a module (hooked up in parallel) go bad, your entire module has shorter life.

for example, in a 6s (6 cells in series) module, if you have one cell that is bad so even at full charge it goes up to say 3.0v and the other 5 at 4.1v, your total will be lower than the other modules which are all at 6 at 4.1v. when drained, the 4.1v will go down first but the overall module will drain faster since it doesn't have that 1 cell in parallel to use.

you can run a battery balancer but that won't help that much either because the bad cell (if truly bad) will be stuck at 3.0v (or lower) and can't go up.

of course replacing the single bad cell is the best solution but that's not always easy to do (it might be really deep, de-soldering it might be hard, etc.).

the BMS doesn't have much of a solution for this one.

but that's just my opinion...not sure about the facts so please correct me if my understanding is incorrect.

according to the chargepoint website, my charge today put in 22.381kwh.

RVD said:

according to the chargepoint website, my charge today put in 22.381kwh.

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Assuming that you charged at about 84% efficiency, then:

0.84 * 22.381 = 18.8kWh stored in the battery.

Assuming you have a new battery at room temperature, you should have about 21.3kWh usable, so that would suggest about 2.5kWh usable remaining in your battery.

That first battery warning is "50 GID", which is frequently quoted as .080kWh per GID equals 4kWh remaining.

Approximately 0.48kWh (6 GID * .080kWh) of that is not usable at the bottom of the charge. In addition, to extract that energy doesn't give us the same .080kWh per GID. I use a value of .077kWh per GID, to get a calculated usable energy content at the first Low Battery Warning of 50 GID - 6 GID unusable = 44 GID * .077kWh per GID = 3.388kWh usable.

So, you can see the variations in the end results; 2.5kWh or 3.388kWh usable? I'll suggest that the latter is more accurate.