Wait to cool first or charge spent battery first?

[surfingslovak]

For the people who voted to let the battery sit in VLBW for a long time so it's had a chance to cool down first before charging, do you have any empirical evidence that shows your choice is the lesser of the 2 evils?

As Tony said above, low state of charge has yet to produce negative results for owners. Elevated battery temperature has demonstrated that it is capable of that. Ergo, low state of charge is likely the lesser of the two evils. This is corroborated by other sources as well, please have a look at a similar thread started by abasile a month ago.

 

[LEAFfan]

Go ahead and charge it. I seriously doubt that here it's going to make much difference. It seems that the biggest problem is the high ambient heat affecting the battery's capacity. If you were in a cooler climate, like OR or WA, it probably could make a much bigger difference.

 

[surfingslovak]

Go ahead and charge it. I seriously doubt that here it's going to make much difference. It seems that the biggest problem is the high ambient heat affecting the battery's capacity. If you were in a cooler climate, like OR or WA, it probably could make a much bigger difference.

We know that temperature is a problem. When in doubt, and if I have the option, I would try to keep the battery cooler, even if it's just by a few degrees. This will likely have the highest return on investment. Charging protocols and usage patterns did not seem to matter much when you look at the sample of affected vehicles on the Wiki.

 

[pchilds]

What is worse, VLBW or 100% charge?

 

[TonyWilliams]

What is worse, VLBW or 100% charge?

100% is my vote. However, below VLB (and past the voltage "knee") would be worse.

 

[DaveinOlyWA]

i think when we examine all the "donts" most are hard to quantify. in any "dont" list some are worse than others as far as harming your battery. Nissan saw fit to not rank them (obviously to keep anyone in the southern tier from reading too much into it)

but i think we need to say that heat probably ranks high. now, i did a double QC yesterday. 135 miles of driving, got home with 20% SOC and had 6 TBs. normally see 5-6. now my choice; plug in at 5 PM. be done charging by 11 PM or let it sit.

it was already at 6 TBs and highs for the day ranged from mid 60's (in Seattle) to mid 70's in Oly. the garage was at 23.5C i left garage door open until 9 PM (temp dropped to 20.2 C.)

i started charge at 10:30. it completed at 3:49 AM. i checked it at 7 AM. temps in garage is 19.6 C. GID count 271 (was 279 yesterday) and i am still at 6 TBs.

so car should be at 5 TBs so even 240 volt 12 amp charging is enough to provide some heat to the pack.

the "guideline" for degradation states Li chemistry (no it does not distinguish from one to the other so guideline is the operative here) increases its rate of degradation at 30C (that is 84F...not very warm)

unfortunately, we are hobbled by what appears to be a huge range of temps that these bars flip on and off with along with what seems to be an inept on board thermometer

 

[evnow]

Does anyone else see why this might be a design that will never be adopted by the masses.

"Masses" are a decade or two away from buying an EV. Let us quit trying to even suggest that masses need to buy EVs now. What we need are the early adopters - 1% marketshare is still 10k cars per month. We are now at < 0.1 % of the marketshare. We are far, far from being mass market.

Afterall the masses didn't buy the computers when they first came out - but they do now. Remember how computers needed to be at an optimal 20C all the time ?

 

[QueenBee]

it was already at 6 TBs and highs for the day ranged from mid 60's (in Seattle) to mid 70's in Oly. the garage was at 23.5C i left garage door open until 9 PM (temp dropped to 20.2 C.)

Do you ever confuse yourself using Celsius and Fahrenheit in the same paragraph or are you automatically converting the numbers back and forth in your head?

 

[DaveinOlyWA]

it was already at 6 TBs and highs for the day ranged from mid 60's (in Seattle) to mid 70's in Oly. the garage was at 23.5C i left garage door open until 9 PM (temp dropped to 20.2 C.)

Do you ever confuse yourself using Celsius and Fahrenheit in the same paragraph or are you automatically converting the numbers back and forth in your head?

i have a thermometer that ONLY has Celsius. i am simply "reading" either that thermometer or the Car's Thermometer which is in Fahrenheit. i use both scales simply because some people dont have a good grasp of the relationship between the two.

 

[gbarry42]

I'm confused by all this. Is 7 bars on the temp gauge considered high? That is well within the "white" area and still several bars below "red," which I thought was the high temp indicator.

The uses and indications of the bars may vary. What Nissan has done by marking some of the bars red, is to tell you that it will actively limit the performance (and charging) available when the battery is that hot. The rest of the scale is for reference. Bars 5 and 6 are so wide, that I interpret them as "we didn't much care what what was going on at these temperatures, but we had to fill in something between the cold range and the hot range".

Beyond that logic, it's fairly apparent that in the white bars 7 and up, they considered it relevant, but not particularly alarming. And it's true, in the now fateful observation, that elevated temperatures are no big deal unless they are sustained for days or weeks at a time. The Phoenix Phiasco has now got everybody rethinking that strategy. But it doesn't appear that they were designed with that intent. They were put there for informational purposes, so if you wanted to, you could modify your behavior to keep the temps where you wanted. "Waiting to cool" is one example.

 

[LEAFer]

The uses and indications of the bars may vary. .....
.....

The Phoenix Phiasco ...

Term of the day ... I like it

 

[gbarry42]

As to the original discussion, I have read that some lithium chemistries, at some low SOC level, at some charge rate, is endothermic--the battery actually gets colder. I don't expect we get this effect anywhere with our LEAFs, but it does suggest that battery heating at low SOC is going to be minimal to nonexistent. This is supported by the QC behaviors we've seen, where charging below 50% was maximized and heating was minimized.

For these reasons, if I were considering the question, I would choose to bring the battery out of VLB immediately, up to maybe 20%, and then leave it sit until later. The downside to this sort of thing is the extra attention required. But there's a timer in my EVSE and in my car, and I might even be able to automate the whole thing.

 

[DaveinOlyWA]

If 7TBs I would wait

I'm confused by all this. Is 7 bars on the temp gauge considered high? That is well within the "white" area and still several bars below "red,"

**disclaimer** my response was to someone who has options. if you are in a situation where its 7TBs and wait, then ignore the recommendation. he can wait... other than that;

not sure why you would be. its a gauge. it is happy in the middle, not so much on the outsides. the only other option would be to have 3 white bars (4,5 and 6) and have gradient colors for the rest until you hit red (1,2, 11 and 12) but then again, we already knew that the farther from the middle we get the more implications we have.

everything has compromises. Li generally increases its rate of degradation "starting at" 30 C which is an easily achievable temperature in all parts of the country. but if it amounts to say 1% additional degradation over 20,000 miles are you going to lose sleep over that?

red is like anything else. it is a signal for "immediate action" iow, stop whatever you are doing to create that additional heat. period. this renders the car inoperable. not a good thing.

 

[wsbca]

We're in a mild climate (San Diego), and normally charge to 80%. Lowest usage days are one 9 mile round trip commute, so if that's all that happened and we have nothing major planned the next day some nights we skip charging. Busier day will get us down to 40-50%, and less frequently we might get down to 2 bars. Car is garaged at night, garage is usually not particularly hot, but it does generally get somewhat cooler as the night wears on.

Right now I have a 9pm-5am timer. Charge usually finishes anywhere between 10pm and 1am. We have no TOU constraints, we're on a fixed rate with solar net metering. (We do have line noise while charging which is most evident during daylight when the solar inverter is up, but not limited to that device - I can actually hear it on things like laptop power supplys if I listen closely, so I tend to avoid charging during daylight since it seems at least potentially not good for the inverter.) We own the car, and really hope to get 100K+ miles out of it (which will probably take a good 10 years.

Given that the consensus is 1) cooler is better for charging and 2) idle time spent at higher charge states is less good than time spent at lower charge states (but > 20%), I'm wondering if I should shift my timer to start around midnight so as to charge under slightly cooler conditions and spend a bit less time at 80%.

Or, is a temp swing from, say, 80 ambient down to 65 and 3+ fewer hours sitting at 80% instead of 50% in the completely trivial range and not even worth worrying about?

Maybe a more significant reason to shift the timer would be to avoid the car immediately starting to charge when we get home near or after 9pm - not frequent but it does happen.

Am I being too nitpicky?

 

[DaveinOlyWA]

i would definitely shift it. granted different locations means different temps seen but there is a huge difference for me whether i leave the garage door open or closed.

we will be getting our 2nd "heat wave" of the season (first one was mild and temps never got beyond the mid 80's) starting today. tomorrow its expected to be near 90. it is still early in the season so Sun will be out until after 8 PM so i plan to keep the garage door open until just before bed time.

now, we live in a pretty secure area and cant tell you how many times i have come home to see garage door wide open because "someone" did not bother to insure the garage door shut when they left. She uses garage door although Prius is not parked in garage because its easier for her but my Son has habit of moving stuff around and if its in the "eye", the door will start to shut then reopen.

in your case with minimal charging needs you really dont need a session more than 3 hours usually i am guessing so i would set an end timer for like no later than 6 AM or something a few hours before your planned departure time if taking off with the Sunrise

 

[WetEV]

As Tony said above, low state of charge has yet to produce negative results for owners. Elevated battery temperature has demonstrated that it is capable of that.

Do these interact? Is low state of charge at high temperature is worse than low state of charge at moderate temperatures?

 

[wsbca]

in your case with minimal charging needs you really dont need a session more than 3 hours usually i am guessing so i would set an end timer for like no later than 6 AM or something a few hours before your planned departure time if taking off with the Sunrise

Thanks - yes, fairly rare to go over 3 hrs. Now that you mention it, end-only timer is obviously the way to go for all the reasons (ambient temp, time spent 'full', no charge immediately post drive), I just didn't really pay attention way back when it was first determined that an end-only timer would work automagically. I've had the same start/stop timer in place since we got the car.

Maybe I'll try a 4am target and see how that goes. Earliest departure is normally no earlier than 6.

 

[DaveinOlyWA]

As Tony said above, low state of charge has yet to produce negative results for owners. Elevated battery temperature has demonstrated that it is capable of that.

Do these interact? Is low state of charge at high temperature is worse than low state of charge at moderate temperatures?

i doubt that anything above VLB is not an issue. imho; i think anything above turtle is ok

 

[DaveEV]

Maybe I'll try a 4am target and see how that goes. Earliest departure is normally no earlier than 6.

Yes, end-timer only does seem to be the best way to go. On my car at least with an 80% timer, it seems to finish 30-60 minutes before the scheduled time (it varies), so if you never leave earlier than 6am, I would go ahead and set it for 6am.

Not only for the potential benefits of keeping the battery at a lower average SOC which should result in increased battery life, but from the grid's perspective, demand is lowest between 3-5am - shifting the bulk of your charging to that time period in theory will reduce strain on the grid and promote lower electricity prices long-term.

As Tony said above, low state of charge has yet to produce negative results for owners. Elevated battery temperature has demonstrated that it is capable of that.

Do these interact? Is low state of charge at high temperature is worse than low state of charge at moderate temperatures?

All else being equal - higher temperatures will also result in faster battery capacity degradation.

 

[DaveinOlyWA]

i dont know if i would set the end timer that near the departure time. its rare that you have the luxury of leaving later due to work or whatever, but i find it common that i have to leave a half hour earlier for a laundry list of random reasons.

less of a concern; 6 AM is early and before the heat of the day so less likely to have issues with warmer pack that has just finished charging but if you have the time, i think it best to put that extra few hours of cooling during the coolest part of the day...