Charging from 80% to 100% -- What's the issue?

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mkjayakumar said:
I am planning to only charge through L1 at my home for the foreseeable future. Would that make any difference ? I am planning to not plug in until it comes down less than 50%, and then charge fully to 100%. That might mean charging every day or skipping a day or two depending on how much I end up driving that day.
That seems like an odd strategy. Even using L1, charging from 50% to 100% will take longer than charging from 30% to 80%, because charging slows significantly as you approach 100%. And especially when using L1, that extra time is going to be painful, since you would have to be talking about charge times well over 10 hours. (Remember, Nissan's 21 hour estimate is from Low Battery Warning to 100%, not from Turtle to 100%. That means it is really for only about an 83% charge.)

So why not go 30% to 80% instead, which would give you better regen, faster charging, and possibly longer battery life? I don't see what the downside would be, unless you were afraid you might need 80% or more on some days. And if you are worried about that, you are going to be in real trouble trying to restore your charge using L1.

Ray
 
Ray,

Charging time, for the most part is not an issue. I plug in at 8 pm and stays plugged in till next day till 9 am when I leave. On most days it is fully charged to 100% and some days may be around 95% depending on how low I was the earlier night.

All I am saying is, I am not going to make a conscious decision to stop at 80%, because:

- I don't see a clear consensus here that charging 100% or closer to it using an L1 on a regular basis is bad for the battery (am I right ?)

- that extra 20% gives me an extra range of 18 miles on the city streets or 12 miles on the highway. There might a day or two in a month when I would need that extra range, and I don't want to be caught off guard.

- if I restrict myself to 80% every time then essentially this is a 80 miles city/60 miles highway car.

Jay
 
mkjayakumar said:
if I restrict myself to 80% every time then essentially this is a 80 miles city/60 miles highway car.
Yeah, so what? If you only need 50 miles, who cares if it's a 60 mile, 120 mile or 1000 mile car?

mkjayakumar said:
that extra 20% gives me an extra range of 18 miles on the city streets or 12 miles on the highway. There might a day or two in a month when I would need that extra range, and I don't want to be caught off guard.
Is this extra need ever a surprise? Sure, you might need a little more extra planning if you are using only L1, but we manage this just fine by planning out our next day and switching between 80% and 100% timers as appropriate. You said yourself that you were planning on waiting until the car was below 50% to charge up anyway, so what would happen if you were sitting at 7 bars and had an unexpected (if that's a possibility) long day the next day and you didn't charge?

I think you really need to consider Ray's points about added regen and avoiding the longer charging times between 90-100%. Those are very valid points. I know he suggested going from 30-80%, but I don't see why you'd necessarily have to wait til 30% (unless you were confident that your next day's driving would fit within a 30% charge) and just go for a 50-80% target most of the time, and 100% when you knew you were going to use it.

I think the biggest issue with charging to 100% is if it sits around at 100% charge for "long". I don't really have a good sense for how "long" is, but if I'm going to charge to 100% I like to try to be in the car and driving within 4-6 hours. Maybe I'm being conservative, but I usually have no problem with this.
 
mkjayakumar said:
Reading through the posts in this topic, do I conclude there is no clear consensus that charging full to 100% all the time does some harm or no harm from the perspective of long term health and capacity of the battery ?...
Jay

I think the best statement of the "consensus", is that leaving the battery at higher rates of charge, above 80%, for a large proportion the time will have some effect of accelerating loss of battery capacity.

How much effect, is really unknown.

In addition, charging to 100% will reduce charging efficiency a bit, and driving efficiency will be reduced, and friction brake wear will be increased, depending on how much braking you have to do, before your charge is reduced, to to the point that allows the use of Regen to slow your LEAF.

So, optimal charging is really dependent on your own situation, IMO.

I drive on an irregular schedule, often leaving my LEAF parked for several days, between trips. I start almost every drive from home with a 1,500 ft descent over 7 miles. My minimum trip length is about 50 miles and have almost no public charging availability.

I find I get almost the full benefits of increased range from a 90% charge, as I do from 100%, and almost the same efficiency gains by charging to 90%, rather than 80% (calculated by watching the Regen gauge, referring to the Carwings regeneration kWh, and checking the disc brake temperature, at the bottom of the 7 mile grade).

But I don't have a 90% timer option.

So, I charge to 80% by timer every night. I try remember to start the charger about a half an hour before leaving home, in winter, and at least an hour before I drive, on the occasional day I expect to need maximum range.
 
I find the charge timer thing to be irritating. When I plug the car in, I want it to start charging in case I need to go somewhere later.

Having said that.. After reading some of the threads on here about this topic, I decided a few months ago that I would not plug the car in unless it had 80% charge or less. Often I arrive home from work with 90% battery capacity. So I'll just skip charging that night. I'm pretty sure 90% would be enough to take me somewhere in an emergency. (besides we have another car anyway)
 
Thanks guys. I am getting a couple good take a ways here :

- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

- Regen doesn't kick in at 100%, and that means I am getting lesser miles on the top 10% of power (from 100 to 90%) than I would at lower capacity.

- more wear & tear on brakes at the top 10% of capacity, due to poor regen.

- Having the car sit overnight or a day with 100% capacity is not advisable.

I never knew any of these until I read through this topic.
 
I just set my charger for 80% finishing at 6am and charge everyday - even though most days i only drive 20 miles. I don't think about it and if there ever was a power outage during one night (early morning, really) I'd still be OK for that day. i suppose if I ever planned to drive more than 50 miles in a day I might consider charging to 100%
 
essaunders said:
I just set my charger for 80% finishing at 6am and charge everyday - even though most days i only drive 20 miles. I don't think about it and if there ever was a power outage during one night (early morning, really) I'd still be OK for that day. i suppose if I ever planned to drive more than 50 miles in a day I might consider charging to 100%

This is exactly what I do, save for the one day a week I charge to 100% since I know I'll need it for lunch. I have NO timers set for the weekend: I (bypass) charge to 100% only when I know I'll need it (like this weekend).
 
mkjayakumar said:
Thanks guys. I am getting a couple good take a ways here :

- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

- Regen doesn't kick in at 100%, and that means I am getting lesser miles on the top 10% of power (from 100 to 90%) than I would at lower capacity.

- more wear & tear on brakes at the top 10% of capacity, due to poor regen.

- Having the car sit overnight or a day with 100% capacity is not advisable.

I never knew any of these until I read through this topic.


To clarify, sitting at 100% and then not diving the next morning and letting it sit another day or two is less preferable. Charging to 100% (94%) and driving the next day every time is not an issue.
 
mkjayakumar said:
- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

I don't know about inefficient (although it may be, I really don't know). But it's definitely slower. For the last 10% or so the charger tapers off the current drawn so while you normally get around 1 bar every 90 minutes hours on L1, the last bar may take 3 hours or so (I don't charge enough at L1 to know whether those are accurate, but that's the basic idea). So if you have the time anyway, that's fine, but on average you'll get more charge per hour if you start and end lower than you would if you start higher and end closer to 100%.
 
I honestly don't believe letting the vehicle sit @ 100% is determinetal to the battery. We have tons of Li-ion batteries around in so many devices. Hitting 100% and staying that way isn't optimal but degredation is minmal at best (how many of yall charge your li-ion power tool batteries almost to full to leave them sitting until the next weekend? Everyone just charges to full). Now, the longer the battery sits @ 100% the worse it is for the battery. That I can agree. But I am thinking of order of magnitude different than a few hours (if a few hours @ 100% destroyed the battery it would have been scrapped for a different chemistry - that is just not feasible, ever). Knowing a bit about battery chemistry would leave me to believe that is right.

Now leaving the car @ 100% for a week ALL the time and only driving it once a week...eh, i can see some noticable degredation happening after awhile. Leave it a long time @ 100% for a couple weeks or more (even if its just once) - that probably will hurt the battery some.

Li-ion chemistry is fairly forgiving. No memory loss, quick charge and discharge. Li-ion batteries degrade for three reasons:

1. Time. The second they leave the line they start to degrade evetually the battery will no longer hold a charge, its just inherit in the structure of the battery. There is no way to change this. The battery will have a max set life the second it leaves the factory.

2. Heat. Heat is killer for Li-ions. Thats why the DC chargers stop. If you DC charge as much as I have, the % charge varies quite a bit from 80% - 100%. Its the heat that shuts the system down (to prevent battery damage). In the winter, the DC charger would want to go all the way to 95%+, in the summer, the second that sucker hits 80% it shuts off. This is also why the manual stats "don't plug in unless you have used x %). Li-ion batteries have no quals with "topping off", in fact, under use, they LOVE it. Its the heat generated by the resistence at the top end that is hurtful. As the battery charges, once you hit the top end, its slower and generates more heat byproduct. Its just nissan making sure that the battery doesn't get any heat damage. If you do this once it awhile, I wouldn't worry about it. But, if you find yourself doing it every day...not good.

3. Storage capacity. Have you read treatment of Li-ion batteries you purchase wholesale? Everyone comes with a care of battery storage. ALL say the same thing. If storing for multiple months (some say a month or more - but its always months) keep the battery at 50-60% for optimal life. That % is the sweet spot for Li-ion. Notice the time length. Arguing that leaving the car @ 100% over night is bad and your battery will die in 5 years is ludicrious. It takes a long time for the battery to sit at a high capacity for damage to be done. Also, never leave the car fully discharged, that will brick your battery, plug in as soon as possible!

If you notice all these issues (#2 and #3) talk about abudnant of over exposure and such. The damage done is all exponential. So the difference from a few hours to a few days is minutely small. But get to a week or so its start climbing that curve. The damage still occurs even on the short time frames, but its so small its hardly noticable. If you are shooting for the longest lasting battery record in the guiness book, then by all means follow everything to the T - always 80%, never store at 100%, never top off, don't DC charge, etc. You could probably squeeze maybe a couple of more years out of it before you reach the Time guage, maybe good for 11, 12, hell 14 years! But, lets face it. Few of us are going to try and shoot for a 14 year Leaf. Hell many won't carry it beyond 3 years and get something else. I wouldn't worry about battery degredation unless you hit the extreme times (i.e. leaving it for multiple weeks) or are shooting the car lasting you over 10 years.

My advice: If you can do 80% comfortably, then do it, every bit helps! Don't freat if you can't. The car is still built for 100% capacity and should last you plenty of years, more than you probably will keep it. And don't leave it at full for more than week untouched (I would say 2 weeks). And don't leave your car at 0%! ever!
 
mkjayakumar said:
Phil, where do you read the SOC % value and the stored capacity ? Does the car provide that data in the Nav windows, or do you get that using your own device which you had designed and installed in your car ?

thanks
Jay
Yes, See this thread.

-Phil
 
lpickup said:
mkjayakumar said:
- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

I don't know about inefficient (although it may be, I really don't know). But it's definitely slower. For the last 10% or so the charger tapers off the current drawn so while you normally get around 1 bar every 90 minutes hours on L1, the last bar may take 3 hours or so (I don't charge enough at L1 to know whether those are accurate, but that's the basic idea). So if you have the time anyway, that's fine, but on average you'll get more charge per hour if you start and end lower than you would if you start higher and end closer to 100%.

Also the slower charge time reduces efficiency since the coolant pump is running the whole time
 
Why is it that when I charge to 100%, the GOM says, 105 miles range

When I charge to 80% it is only 78 miles ? I would have expected around 82.
 
There are three different % values being used, and sometimes being confused:

1. The Car's "80%" or "100%" charge levels. These are charge limit points most likely derived from the highest cell-pair voltages, near 4.10 volts. Presumably charging to "100%" (only about 94% True SOC) will take less time after the Pack loses 25% of its Capacity.

2. True SOC (TSOC): reported by Ingineer's LEAFSCAN device. Apparently this is just over 94% when the car has "charged to 100%". Most of us do not YET have access to this figure. After the Pack loses 25%, will a "100%" charge still indicate about 94% TSOC? If so, it is essentially useless (without an additional Capacity value) for computing Range.

3. The LEAF's "GID" value: GIDs generally indicate a value closer to "Usable Energy", not "True SOC". At 80 Wh per GID, this might be "Applied" (for charging) Energy, but Stored Energy is less, and Recoverable (Useful) Energy is even less. Since a typical new (full capacity) battery can show 281 GIDs when charged to "100%", a percentage of 281 is shown on the GID-Meter (SOC-Meter) as a percent of new-full Charge (not TSOC). If a Pack has lost 25% of its Capacity, we are likely to see this value, after a "100%" charge, indicate something like 75%, a useful indicator for estimating Range.
 
How do you guys calculate the GID values after a charge ? Is that off the wall from an L2 EVSE unit, or have you installed something specific to get this ? Currently I am using only 120V L1, Nissan supplied unit.
 
The GID value in internal to the LEAF, and not visible without special electronics to read the value from the car's OBD connector.

No, a typical OBDII reader will not help.

The "Leaf CANbus" sub-forum has threads that describe the "SOC-Meter" project that will display the GID value, along with other values, like Battery Pack voltage, current, and power.

This SOC-Meter (GID-Meter) project can be entirely DIY, but is also available as a Kit, or fully Built and Tested.

Also, see more info at:
http://www.wwwsite.com/puzzles/socmeter/" onclick="window.open(this.href);return false;
 
Gary's meter reads the Battery ECU's "Current Battery Level" as expressed in watt-hours when multiplied by 80. Therefore a typical number (my most recent "full" charge) is 22240 which Gary's meter shows as 278 "Gids". This is a useful number, but it's limited to a rather low resolution of 80 watt-hours. There is also much higher resolution data available. Here are some other parameters from the Battery ECU after that "full" charge on my Leaf:
Code:
SoC: 94.591%    (Current State of Charge)
Lvl: 22.240kWh  (Current Level, i.e. 278 Gids)
Ful: 67.568Ah   (Full Capacity)
Tmp: 72.3f   	(Battery Temp)
Vlt: 393.23v 	(Battery Voltage)
CLC: 1.030   	(Grad Cap Loss Coef)
CLM: 1.005   	(Grad Cap Loss Mtr)
CPL: 92.3kW  	(Charge Power Limit)
RPL: 41.6kW  	(Regen Power Limit)
DPL: 110kW   	(Discharge Power Limit)
Last time I checked, my car opened it's main contactor after turtle mode at around 2% SoC. That means about the bottom 2% and the top 5% are not normally usable.

Using these numbers, I can calculate that if I were able to charge to 100% instead of ~95%, and discharge to zero, I'd actually have 23.512kWh total capacity. (Pretty close to 24kWh) Nissan does not allow the full use of the battery in order to ensure a long life.

The Battery ECU reports the full capacity on my Leaf is 67.568 amp-hours which means that the average voltage would be about 348, which sounds right to me.

All of this data comes from my new LEAFSCAN instrument that simply plugs into the Leaf. It's currently in development and I'm working as best I can on getting it out to everyone that wants one.

The Diagnostic connector located under the driver side dashboard gives access to the Leaf's internal networks which connect to it's various computers and modules. This connector is called a DLC3 (Data-Link Connector type 3), which is the same physical connector used for the OBD II system on cars with engines. Since the Leaf does not have an engine, it is not required by law to be OBD II compliant, and therefore it is not. This is why only devices specifically developed for the Leaf will work. The only one available now is Gary's meter, soon to be followed by LEAFSCAN.

-Phil
 
Values may have higher precision (more digits),
but that does not mean that they are more accurate.

For example: a value of 94.013% (high precision) could
still be wrong by 5% in some circumstances (low accuracy) !!!

A GID value of 50 could easily be "wrong" by 5% or 10%, so showing it as 50.123 GIDs does not increase its accuracy.
 
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