maintaining a low SOC to preserve battery life

[thankyouOB]

this thread makes me hold my head and wonder what the reality is.

a few posts above, we get some real interesting speculation about how and why Nissan changed the software reading.
sounds good.

I am awfully interested in knowing (that is knowing not supposing) whether mid-range cycling of the state of charge -- i.e. between 3 and 8 bars -- is optimal, rather than charging to 10 bars and running down to 2 bars.

 

[TomT]

Even if it was, it would make the car unusable for me as my driving needs do not support that much of a range limitation.

I am awfully interested in knowing (that is knowing not supposing) whether mid-range cycling of the state of charge -- i.e. between 3 and 8 bars -- is optimal, rather than charging to 10 bars and running down to 2 bars.

 

[Stanton]

I'm amazed how many different permutations of "depth of discharge" we see--and not just on this thread. Let's look at this thing in terms of status: what do we know/what has Nissan stated?

1) Nissan protects the bottom and top of the battery pack (e.g. we can't really "top it all the way off" OR "run it all the way down")
2) high temperature (like 7TB and above) definitely hurts the long-term viability of the pack
3) leaving the pack at high SOC (>80%) for long periods of time is not good
4) leaving the pack at low SOC (<20%) for long periods of time is not good

Everything else is speculation without additional data. Shallow cycling, not running it below 2 bars, not charging to even 80%: we have no idea how this will help/hurt the battery pack in the long term. Personally, I try to do the following:
1) I only charge to 80% unless I know I need the range (which is rarely)
2) I never leave the car sit (as in days) above 80% or below 20%
3) I try not to charge at >6TB (which is rare) and have employed a garage fan to reduce that possibility on extremely hot days/nights

Anything else and I'm simply adding speculation to established guidelines. While I know I have lost some capacity/range, I think I'm doing pretty good for living in a hot climate (and I haven't lost a bar yet).

 

[GaslessInSeattle]

what do we know that Nissan has NOT stated?
1) we have access to nearly 100% of the pack with almost no buffer!
2) HEV's that now have a long track record and show healthy batteries after 10+ years 150+ miles of driving typically access only 60% of the pack
3) temperatures common to the summer time in many areas in the southern US cause permanent battery damage regardless of how well owners follow Nissan's charging protocols.
4) the way the Leaf's batteries are reacting to heat suggests they have the same limitations that Li-ion batteries are notorious for, therefore applying charging habits that are generally recognized as beneficial for li-ion batteries is the least risky/speculative path to follow, IMHO.

I believe that it is therefore prudent to take it easy on these batteries within reason. For folks with a short commute, cycling in the middle of the pack is easy and seems like a good idea to me until we have more information. I do not believe that cycling in the middle of the pack is likely to cause damage in some way so for those who find it convenient enough, it seems like a worthwhile precaution with minor added inconvenience.

I believe blindly following Nissan's protocol for charging at this point is more speculative than shallow, middle pack charging. Either Nissan doesn't have a handle on what is happening or they are not telling us what they know, either way, we are left with no choice but to speculate if we want to protect our investment and assure it continues to be able to perform the task we bought it for.

I'm amazed how many different permutations of "depth of discharge" we see--and not just on this thread. Let's look at this thing in terms of status: what do we know/what has Nissan stated?

1) Nissan protects the bottom and top of the battery pack (e.g. we can't really "top it all the way off" OR "run it all the way down")
2) high temperature (like 7TB and above) definitely hurts the long-term viability of the pack
3) leaving the pack at high SOC (>80%) for long periods of time is not good
4) leaving the pack at low SOC (<20%) for long periods of time is not good

Everything else is speculation without additional data. Shallow cycling, not running it below 2 bars, not charging to even 80%: we have no idea how this will help/hurt the battery pack in the long term. Personally, I try to do the following:
1) I only charge to 80% unless I know I need the range (which is rarely)
2) I never leave the car sit (as in days) above 80% or below 20%
3) I try not to charge at >6TB (which is rare) and have employed a garage fan to reduce that possibility on extremely hot days/nights

Anything else and I'm simply adding speculation to established guidelines. While I know I have lost some capacity/range, I think I'm doing pretty good for living in a hot climate (and I haven't lost a bar yet).

 

[Stoaty]

what do we know that Nissan has NOT stated?
1) we have access to nearly 100% of the pack with almost no buffer!
2) HEV's that now have a long track record and show healthy batteries after 10+ years 150+ miles of driving typically access only 60% of the pack
3) temperatures common to the summer time in many areas in the southern US cause permanent battery damage regardless of how well owners follow Nissan's charging protocols.
4) the way the Leaf's batteries are reacting to heat suggests they have the same limitations that Li-ion batteries are notorious for, therefore applying charging habits that are generally recognized as beneficial for li-ion batteries is the least risky/speculative path to follow, IMHO.

Short, sweet and to the point.

 

[bytrain]

I've driven about 16,000 miles in Sacramento over the last 17 months. I charge only to 80% Monday through Thursday at work and then to 100% on Friday so that it carries me through as much of the weekend as possible. I seldom go below two bars and have only seen the low battery warning about four times. I never top off. The result is that my battery evaluation last month came in at five stars.

bytrain

 

[TEG]

...Personally, I try to do the following:
1) I only charge to 80% unless I know I need the range (which is rarely)
2) I never leave the car sit (as in days) above 80% or below 20%
3) I try not to charge at >6TB (which is rare) and have employed a garage fan to reduce that possibility on extremely hot days/nights
...

I have been doing the same thing with mine since I got it in April, 2011. Coming up on 15K miles.
Full 5 stars 1 year battery check (but I don't read much into that), and still have all 12 bars.
I have a relatively long commute.
I have a timer to charge to 80% by 5AM at home, so the usual routine is like:

Start out in the morning at 80% soon after it has 'filled'.
Drive to work where I get down to about 50% SOC by the time I get there...
No opportunity to charge at work, but that is OK, since letting it sit at 50% may be a good way for it to spend much of its' time.
Drive back home where the SOC drops down to about 30%.
Then I plug right back in, but it sits at 30% until late a night when the timer figures out it needs to start charging to get back to 80% by 5AM. That way all the charging happens at the coldest time of day/night, and the average SOC for the 24 hours is about 45%...

I think the LEAF works best as a 'pure commuter car' where you have a very predictable schedule, and can plan charging around routines to prolong battery health.

 

[GaslessInSeattle]

Sadly, it appears the battery evaluation tells us next to nothing about battery health and is rather an evaluation of your habits based on what the computer stores... Leaf's with early capacity loss, already missing capacity bars are getting an excellent "5 star" rating. the battery evaluation is worthless to me if it doesn't also reflect the health of the battery.

I've driven about 16,000 miles in Sacramento over the last 17 months. I charge only to 80% Monday through Thursday at work and then to 100% on Friday so that it carries me through as much of the weekend as possible. I seldom go below two bars and have only seen the low battery warning about four times. I never top off. The result is that my battery evaluation last month came in at five stars.

bytrain

 

[TonyWilliams]

The result is that my battery evaluation last month came in at five stars.

bytrain

And I ran my battery to Turtle over 20 times, and guess what? Five stars !!!

The guys in Phoenix missing 1, 2, 3, and 4 bars could all get five stars.

 

[EatsShootsandLeafs]

the way the Leaf's batteries are reacting to heat suggests they have the same limitations that Li-ion batteries are notorious for, therefore applying charging habits that are generally recognized as beneficial for li-ion batteries is the least risky/speculative path to follow, IMHO.

This is highly likely.

However, when I was a kid I knew another kid who used to obsess over repackaging his toys. He'd buy a toy, keep the box, and box it up after every play session. I remember thinking how much time he was wasting with it. It was technically being kept in better shape, but surely he was losing some enjoyability thinking he had to do this. This anecdote of mine is real, btw

I would be very surprised if it's not ideal to keep this thing around 50% as much as possible; the closer the better, which means drive little and don't charge much, so that it's always around the mid-way. But, if you're spending much effort aiming for that goal you'll necessarily be losing driving range, since you're targeting just the middle of the pack as your usable buffer.

Even though mine is leased I can't rule out the possibility of buying it, and I'll treat the battery kindly, primarily through 80% max charge except probably once/week (I drive a lot on Saturdays) and I'll not let it hit low charge points.

There may be little reasonable that people in Arizona can do anyway to be frank. We've all seen what heat does to lithium batteries in our consumer devices and though not all are equal, my main laptop chews through batteries like mad. I don't unplug it much, but just the gross heat from it and being at 100% all the time it bricks the battery in about 18 months.

 

[cwerdna]

There may be little reasonable that people in Arizona can do anyway to be frank. We've all seen what heat does to lithium batteries in our consumer devices and though not all are equal, my main laptop chews through batteries like mad. I don't unplug it much, but just the gross heat from it and being at 100% all the time it bricks the battery in about 18 months.

FWIW, I'm still on my original (and only) battery on my Lenovo T61p that I've had since late 8/2007. The Thinkpad Power Manager (mentioned at http://web.archive.org/web/20091002082144/http://lenovoblogs.com/insidethebox/?p=52" onclick="window.open(this.href);return false;, images are busted though) is no doubt a help. I generally have my laptop set to only charge when down to 35% and only charge to 65%. I only charge to 100% if I need it (not often).

I don't recall that capacity numbers claimed by the utility (when at 100%) vs. design capacity, but IIRC, it's still over 80 or 85%. I know I can run it cordless for over 3 hours still, w/fairly heavy usage and high brightness.

In contrast, my Dell Inspiron 4000 series from 2001 went thru 4 batteries. It came w/1 and I ordered an extra. When those hardly held a charge after a few years, I ordered 2 more. All of them either totally failed (became unusable) or held very little charge. The laptop was always plugged in w/at least 1 battery in.

I can't speak to current Thinkpads but as I posted at http://forum.notebookreview.com/lenovo/658824-current-lenovo-lines-models-let-you-either-set-battery-charging-thresholds-have-best-battery-health-option.html" onclick="window.open(this.href);return false;, it seems even el-cheapo consumer non-Thinkpads Lenovos have at least rudimentary battery management. They have two options: optimize for battery runtime or optimize for battery health. This is better than nothing and better than many other laptops.

So, I prefer Lenovo laptops now, even if they cost a bit more. Might result in not needing to buy new batteries as often.

 

[ksnogas2112]

I'm considering making a transparency to put over the white part of the bars to have this colorization.

Jeremy

that's actually quite tempting. wish there was a 60% charge timer option

 

[Herm]

This thread would not help in the sales of the Leaf ..
I bought this car to save on gas from my long drives to work and back,the 2 bar rule would never work with me..

Its not the long drives but the temperatures.. reducing SOC high charge level to improve battery life is the only thing you can do in Phoenix.

 

[pchilds]

I have been charging to 60-65% for two months, except the few times I need more range. I still lost another 4%, battery capacity, down to 85%, on a gid meter, for a 100% charge. IMO The LEAF is not viable anywhere the temperature exceeds 90F.

 

[Herm]

I have been charging to 60-65% for two months, except the few times I need more range. I still lost another 4%, battery capacity, down to 85%, on a gid meter, for a 100% charge. IMO The LEAF is not viable anywhere the temperature exceeds 90F.

Is that 4% measurement repeatable?..

 

[DaveinOlyWA]

I have been charging to 60-65% for two months, except the few times I need more range. I still lost another 4%, battery capacity, down to 85%, on a gid meter, for a 100% charge. IMO The LEAF is not viable anywhere the temperature exceeds 90F.

i also charge manually frequently to the 60-70% level. i found that it takes SEVERAL 100% charges to get a true reading of my pack capacity.

i would not take anything less than 3-4 repeatable results

 

[pchilds]

Four 100% charges three days in a row all in the low 240s gid. It's 3.5% loss not 4%, in one month, I got a 250 gid on 8/5/12.

 

[JeremyW]

Just bought a sample pack of Rosco color gels. They're used in theater and movies for changing the color of lighting for mood and artistic appeal.

It's basically a dye impregnated polyester film. It should be a good way to change the color of the bars by cutting up sections of different colored gels and placing them on the gauge face.

 

[smkettner]

I would suggest 2-yellow, 7-yellow, 10-red. Head for a drive in fridge if it is 11 or 12, yikes.

 

[JeremyW]

I'm going to do the "charge" bars first since I can actually control my SOC much better then the temp. I am venting the garage pretty well, but I can't shake my 6th temp bar in the morning, even with ambient temps at 68 and rarely charging at home. For the time that I had only a carport up here (and charged exclusively at work and in public), I would regularly see 5 temp bars in the morning, but I'd be back at 6 in a few miles. If I do the temp bars, bottom 5 would be green, 6 would be yellow, and 7 and up would be red. :? That sixth bar is way too large, 70 to 100 degrees? Gimme a break. :roll: