Joining the 80% Club

[DaveEV]

when referring to charge cycles, they always mean "full cycles". now if a battery is rated at 24 kwh. then 6 charging sessions of 4 kwh each would be one cycle.

Except that 6 4 kWh charge cycles (assuming the SOC is kept near the middle of the pack) is going to be a LOT easier on the pack than 1 full 24 kWh charge cycle. I would expect the pack to handle at least twice as many "cycles" using partial charge/discharges rather than full charges.

 

[Herm]

3000 cycles for the Leaf's current battery is optimistic, its probably 1000-1500 full cycles.. you need a different chemistry to achieve a longer life. You will get a longer life if you follow Nissan's recommendations, charge to 80% only.. perhaps thats were the 3000 cycles came from.

 

[DaveinOlyWA]

Drees; that is why they always state a "range" of cycles

as far as how long the Leaf pack is supposed to last, i thought it was 2000 cycles to 70% and dont ask me where i got that from...but that has been in my head for a long time.

but then again, that would be 200 cycles a year over a 10 year period which would be on the high end of usage. most would be in the 150 cycle or 14-15,000 miles a year range. my problem is that i have read soooo much about vaporware that i dont remember if this 2000 cycle figure is the Nissan pack, another pack or simply for a product that does not currently exist

 

[AndyH]

3000 cycles for the Leaf's current battery is optimistic, its probably 1000-1500 full cycles.. you need a different chemistry to achieve a longer life. You will get a longer life if you follow Nissan's recommendations, charge to 80% only.. perhaps thats were the 3000 cycles came from.

Depends on the specific chemistry and definition of a cycle.

EIG's Li(NiCoMn)O2 cells provide 1000 cycles to 80% capacity. But that's not enough information, is it? It's 1000 cycles to 80% capacity when cycled with 1C charge/1C discharge to 100% depth of discharge. http://www.eigbattery.com/eng/product/3.jpg

We know from other lithium testing that dropping from 100% to 90% has a significant positive effect on cycle life - and the Leaf is only using about 84% of total capacity. In addition, we know that the focus of the auto battery industry has been to increase high and low temperature response and cycle life to meet USCAR battery goals that include 1000 cycles to 80% and a 10 year life span. http://www.uscar.org/commands/files_download.php?files_id=27

If the Leaf's current battery can only return 1000 cycles, and can travel 100 miles on the battery as configured, that's 100,000 miles of travel to 80% capacity loss - and many more miles at slowly decreasing ranges. (The battery will likely gain capacity over the first 100-300 cycles, so that slight range increase will offset some of the range loss in later life.)

If 100,000 miles to 80% works for the owner. there is ZERO 'need' to charge only to (consumer!) 80%.

 

[TonyWilliams]

but its like free refills of soda at a fast food joint. now why anyone would order a large when they plan to dine in is beyond me unless they are so fat and lazy they do not want to get up to make multiple trips to the soda fountain.

I'm gunna use that one !!!

 

[Herm]

Sure, it might calculate a 87.1% SOC from a 3.52v reading, but the actual SOC is probably +/- 5% of that "calculated" value.

Shhhh ! Didn't you read how important it is to display the soc to 0.1% ?

Lol, very true!. Coulomb counting is the best way, but yes it depends on setting a baseline.. charging to full based on voltage and temperature is a good way to do it, but it means you may have to charge it to 100% every couple of months or so for a refresh. The Ah reading in the canbus is probably based on this.

 

[Herm]

Polishing my crystal ball. When the new battery comes out in Leaf V2 (2015?), Nissan will offer a Leaf Classic and a Leaf 200. The Classic will be lower cost than now (hopefully, inflation adjusted) and lighter.. thus city range should increase if you are not a proficient hypermiler*. The Classic will be a jackrabbit.

*Proficient hypermilers dont use brakes, stick to the posted speed limit or less and keep their tires at high pressure to minimize drag.. no drafting either, thats dangerous and stupid.

 

[TomT]

But NOT higher than the maximum listed sidewall pressure, because that is unsafe!

and keep their tires at high pressure to minimize drag.

 

[rclams]

... no drafting either, thats dangerous and stupid.

I have found that following AT THE RECOMMENDED MINIMUM OF 2 SECONDS SEPARATION makes a noticeable reduction in drag for my 2009 Plug-In Prius, as measured in real-time MPG improvements of 10-30% by my ScanGauge. I believe that our LEAF also benefits from this legal/"reasonably safe" drafting distance.

Especially when following trucks (which beneficially, cannot stop faster than you, tend to be going slower than the leadfoots and are in the rightmost lanes) or better still, a truck followed by a car or SUV (which seems to smooth out some turbulence from the truck).

Oh, and the best kind of truck to follow is a TANKER, maybe because of its tubular shape?

One risk factor is that a truck can straddle and clear an object in the center of the lane that you will not see in advance (something I always keep in mind when on my motorcycle).

So "situational awareness" (knowing if you are hemmed in by other vehicles) is mandatory when drafting.

As always, your mileage (and your reflexes) may vary.