Joining the 80% Club

[Caracalover]

I am in the 80% club, having only charged to 100% a few times in several months (Mid March delivery) of ownership. My commute is 30-40 miles RT and I live high enough on a hill to get some regen after I leave home, so I don't like a full charge - it feels like an ICE when it is fully charged EWWWW.

I use ECO mode to slow down only. I am drive all the time, pulling out in front of other traffic because I can, and the other vehicles are worried about $4 gas. I laughed so hard as I cut through a gas station that even with the windows rolled up (And the radio blasting), someone noticed.

Sure I go to 100% when I think I need it, but I have yet to need it.

I have found that the extra regen in ECO helps when slowing - gain back that which you lost while accelerating fast - my foot isn't gentle enough on the brake to make that work.

I would suggest Mwalsh try using ECO mode to slow the car around corners and when you see traffic slowing - I have even started to experiment with Neutral. Cruise control doesn't seem to be efficient the few times I have used it, but coasting along at freeway speeds is quite nice in neutral.

As to whoever worried about traffic jams, the slow crawl has provven to be an energy saver, unlike with an ICE. I actually smile at slower traffic and my life seems to have slowed down and gotten mellower through the electric drive experience. Freeways are boring, ugly, and too purpose driven. Getting to work on the back roads takes a little more time perhaps, but I have found some gems through the "Route 66" experience. Sometimes it even takes more energy, but that is ok too, it is cheap comparitivly.

 

[tzzhc4]

After a week of driving the Leaf to see how far she would go I set my charge timer for "Improves Battery Longevity" mode last night and charged to 80%. I still plan to charge to 100% on an as needed basis but since most of our trips are 20-30 miles 80% is more than enough.

 

[GaslessInSeattle]

I think I've boiled it down to something simple for myself: When my daily driving involves lots of short jaunts and frequent opportunity/top off charging (which is most days), then I go with 80% to avoid having the car at or near 100% (of allowed) so much of the time, if on the other hand my daily driving needs involve long distance stretches and or fewer opportunities to charge, then I go with charging to 100% and don't worry about it.

g

 

[LEAFfan]

I drove the 70 mile round trip and returned home with 3 miles to spare

When you had 3 miles left, was the '3' blinking? If you had used those 3 miles, would the turtle appear?

 

[waidy]

To the 80% club gurus: I finished reading all the posts in this thread. I went out of juice (purposely to test whether the turtle light works in my LEAF) a few weeks after I got my LEAF. I was 30 feet in reach of my charger I had to use a long extension cord to trickle charge the LEAF so it would have enough juice to move 30 feet.

Here is my question: When the LEAF is out of juice (stop moving), does it has "reserved level" of electrons in the battery pack to protect the battery or did I use that "reserved electrons"?

 

[GaslessInSeattle]

From what I've read, it seems that the consensus is that there is still a reserve, that we are essentially cut off before we would do damage to the battery. I have assumed though that it would not be good to leave it in this state for a long period.
G

To the 80% club gurus: I finished reading all the posts in this thread. I went out of juice (purposely to test whether the turtle light works in my LEAF) a few weeks after I got my LEAF. I was 30 feet in reach of my charger I had to use a long extension cord to trickle charge the LEAF so it would have enough juice to move 30 feet.

Here is my question: When the LEAF is out of juice (stop moving), does it has "reserved level" of electrons in the battery pack to protect the battery or did I use that "reserved electrons"?

 

[DaveinOlyWA]

Guessing here but we have access to about 90%the of the 24 kwh calcify. So I am guessing the total range available to us runs from an SOC. Of 7-97%....or may e 5-95%...my guess is the first

 

[AndyH]

To the 80% club gurus: I finished reading all the posts in this thread. I went out of juice (purposely to test whether the turtle light works in my LEAF) a few weeks after I got my LEAF. I was 30 feet in reach of my charger I had to use a long extension cord to trickle charge the LEAF so it would have enough juice to move 30 feet.

Here is my question: When the LEAF is out of juice (stop moving), does it has "reserved level" of electrons in the battery pack to protect the battery or did I use that "reserved electrons"?

The short answer is 'yes' - when the car coasts to a stop the driving is done but the battery is not completely discharged.

The longer answer...

Let's start with terminology so we can guarantee we're talking about the same thing. I think of 'reserve' like the 'reserve' switch on a motorcycle fuel valve or the mandatory reserve for aircraft flight planning - in other words, fuel intentionally left in the tank that should not be used for normal operations but is available for use if necessary to get to a fuel station or back on the ground safely.

Using this definition of reserve, the portion of the total/ultimate battery capacity above and below the 'consumer' 0%-100% that we see on the dashboard display is not a reserve because it is not available for our use in any situation.

We appear to have a full 24kWh of usable energy available for driving. Once we've moved thru the fuel gauge bars and warnings and turtle light and finally coast to a stop on the side of the road, we're done.

The battery management system will protect the battery from us. The car will not let us charge too quickly, overcharge the battery, or drive enough to hurt the battery.

While we do know the voltage limits the car uses to protect the battery, we don't yet know the actual limits of the specialized battery Nissan uses in the car. There's enough similarity across the lithium cell family, though, to strongly suggest that Nissan is not allowing us to use more than ~80-85% of ultimate battery capacity. Using more costs battery life. A racer will gladly use nearly all of the capacity because they're going for total performance and a trophy. They're fine with rebuilding the motor or battery regularly - sometimes after every race. But this is not acceptable performance for passenger vehicles with warranties and company reputations on the line.

The only situation I can come up with that could possibly hurt the battery as a result of our choice (normal operations - not parking over a campfire!) would be driving until the car stops completely, and then parking it for months with the 'empty' battery. Lithium tends to self-discharge about 3% per month. Eventually - like over 5 months - the last ~15% of capacity should bleed off and cells could drop to 0 volts. They should come back to life when recharged, but will likely lose some cycle life due to the 'abuse.'

 

[NosqueakMouse]

Nissan has said that we can expect about 80% charge capacity after 10 years if we do primarily Level 1 or Level 2 charging, and that if we use QuickCharging as our primary charging source, we would expect something under 70% after 10 years. There has been much talk here about 80% charging vs. 100% charging, but other than the fact that Nissan "recommends" the 80% level, I have seen no information that tells me what kind of tradeoff I am making if I charge to 100% each time. Would I expect to see less that 80% capacity after 10 years? Would the battery die before 10 years? Would it be worse than level 3 charging? (You can ignore level 3 charging - there is not a solitary level 3 station here in Northern CA!)

 

[surfingslovak]

There has been much talk here about 80% charging vs. 100% charging, but other than the fact that Nissan "recommends" the 80% level, I have seen no information that tells me what kind of tradeoff I am making if I charge to 100% each time.

There is some indication that when the Leaf is charged to full 12 bars, the battery is about 90% full. Likewise, when the Leaf stops dead after crawling in turtle mode, the battery likely still holds about 10% charge. These are approximations, since Nissan does not publish actual numbers, but this would roughly correspond to a 80% depth of discharge cycle (DOD). Should that be the case, then anyone charging from 0 to 12 bars is already doing pretty well. However, it would be better to shallow cycle the battery. How shallow a cycle you ask? As shallow as your usage patterns allow. A 50% DOD cycle, often referenced in the literature and achieved by keeping the battery between 2 to 10 bars, can prolong battery life by a factor of three when compared to a full 100% DOD cycle. It's roughly a difference between driving 50K miles or 150K miles on one battery pack. This is well worth doing.

There was a really nice post on this topic on the Tesla forum. I believe that it originated with Dan Myggen at Tesla and a lot of what's been said there is directly or almost directly transferable to the Leaf:

http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Care?highlight=battery+warranty

 

[NosqueakMouse]

"There is some indication that when the Leaf is charged to full 12 bars, the battery is about 90% full. Likewise, when the Leaf stops dead after crawling in turtle mode, the battery likely still holds about 10% charge."

In which case, according to the Myggen page you directed me to, what I call a "full charge" is just about what he is looking for. However, this page did not tell give us any further indication of the level of degradation over time that true full charging, whatever that is, will do. All any blog or page that I have found so far has satisfied itself with saying "to maximize lifespan", which tells me bloody little.

 

[surfingslovak]

In which case, according to the Myggen page you directed me to, what I call a "full charge" is just about what he is looking for. However, this page did not tell give us any further indication of the level of degradation over time that true full charging, whatever that is, will do. All any blog or page that I have found so far has satisfied itself with saying "to maximize lifespan", which tells me bloody little.

Yes, that's my understanding as well and all the data points I found so far seem to confirm this assumption. I'm pressed for time right now, but please have a look at the following link. Table 2 is of particular interest, it shows how the depth of discharge pattern translates to shorter or longer battery life. In the Leaf, one cycle corresponds to roughly 100 miles. This means that 500 discharge cycles translate to about 50K miles and 1500 cycles are the equivalent of 150K miles. Nissan is giving the Leaf the gift of a 80K mile battery by limiting DOD to 80%. However, we should be able to eek out 150K by shallow cycling and charging to full and going below two bars only when we have to.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

[thankyouOB]

near turtle, with dashboard blinking, my Red took 15.95 to charge to 80% in 4 hours 15 minutes.

 

[surfingslovak]

near turtle, with dashboard blinking, my Red took 15.95 to charge to 80% in 4 hours 15 minutes.

Interesting, thank you for posting that! Assuming 90% charging efficiency, which is a number I heard somewhere on this forum, I'm getting (15.95 kWh x 0.9) / 24 kWh = 59.8%. This means that going from near turtle to 80% full roughly corresponds to a 60% DOD cycle. Looking at this from the other end, and assuming that the battery holds about 10% charge at turtle and the full indicator corresponds to 90% charge, I'm getting (0.9 x 0.8) - 0.1 = 62%.

Although our numbers won't be 100% accurate, I think that we are getting somewhere. It would be nice if Nissan came forward and published some of these numbers and put together a clear, concise and authoritative battery care guide.

 

[TomT]

From dead to 100%, I took 26.6 Kw (documented in another thread on this forum).

 

[GaslessInSeattle]

Great Link, thanks!

Does anyone know of a battery charger that works as described below for residential small battery use. And do similar principles apply to NMH batteries?

I have several cordless Ryobi power tools, including a weed whacker and for the most part have been quite satisfied with them, enough to invest in the $90 LI-ion batteries for them which are vastly improved over the NMH POS's that have been coming with them. I suspect there is little, if any real battery management going on with the devices and would think applying an 80% long life charging option would improve things substantially. I have enough batteries that I simply don't need to charge them to 100% and have a substantial amount of $$ invested in them and would love an easy way to prolong their life but not being able to set the charger to 80% makes this very challenging.

g

"The voltage threshold of commercial chargers cannot be changed, and making it adjustable would have advantages, especially for laptops as a means of prolonging battery life. When running on extended AC mode, the user would select the “long life” mode and the battery would charge to only, say, 4.05V/cell. This would get a capacity of about 80 percent. Before traveling the user would apply the “full charge mode” to bring the charge to 4.20V/cell. This saturation charge would take about an hour and would fill the battery to 100 percent capacity."

 

[surfingslovak]

From dead to 100%, I took 26.6 Kw (documented in another thread on this forum).

Interesting, I think I found that thread. Assuming 90% charging efficiency, you would have pumped 23.73 kWh into your pack (26.37 kWh per TED). I wonder if perhaps the air conditioning in the Leaf was on.

There is some indication that Nissan is charging each battery cell to 4.1V, which corresponds to a roughly 90% charge at full. Likewise, there is indication that about 2 kWh remain in the pack when the car stops dead. Given the type of battery chemistry Nissan went with, it would be nearly impossible for them to warranty the battery for 8 years and 100K miles if they allowed access to 95% or 100% of total pack capacity.

 

[TomT]

No, the car was completely off while it was charging... Some think the charging efficiency is closer to 85 percent though...

Assuming 90% charging efficiency, you would have pumped 23.73 kWh into your pack (26.37 kWh per TED). I wonder if perhaps the air conditioning in the Leaf was on.

 

[NosqueakMouse]

"Have a look at the following link"

Thank you, surfingslovak.

The referenced table is looking at the depth of discharge, not the level of charge, which it assumes to be "full" (and I guess we should assume that this is roughly equal to "full" on a Leaf, as well). A 50% cycle appears optimal. My Leaf is a commute car, and my daily commute is 56 miles. According to Carwings (and in a later post I shall express my extreme doubts about the accuracy thereof) I use just about 10 kWh, or roughly half the total capacity, for that daily commute. Therefore I could expect about 1500 commute cycles. If I were to also charge at work - which is an option for me - I would only be discharging 25%, but doubling my cycles, and therefore would get only about 1250 commutes. This table is telling me to charge fully, and don't "top off" at work. The table does not say what would happen if I only charged to 80% full.

There is no date on the experiment. Table 4 in the same site stems from 2002, and there has been development since. More importantly, Nissan has done their own development, and it is possible that assumptions we are making do not apply. For that reason, I think it is HIGHLY DESIRABLE that Nissan engineering help us out by giving specific DATA guidance, rather than just "recommending". We need to know, for example, what voltage level "Full" represents, and what voltage level 80% represents, etc., along with studies they have done of battery lifetimes. A recommendation without a reason is an opportunity to gravely misunderstand. (For example, they also "recommend" level 2 charging, but they do not give their reasons for preferring it to trickle charging. I strongly suspect their reasons are convenience and the ability to time charging to low-cost hours, and have nothing to do with the effect on the battery. I only use trickle, but I might change if I found out it was bad for the battery.)

 

[QueenBee]

(For example, they also "recommend" level 2 charging, but they do not give their reasons for preferring it to trickle charging. I strongly suspect their reasons are convenience and the ability to time charging to low-cost hours, and have nothing to do with the effect on the battery. I only use trickle, but I might change if I found out it was bad for the battery.)

Another possible reason is the efficiency of trickle charging is much less than that of level 2 because of all the static overhead required to charge is running for much longer.