80% Charging; Why I Don't Miss It And Why You Shouldn't Either

Guess what? Unless you want to do the math EVERY NIGHT and mess with the timer on your LEAF, you can't do 80% charging any more.  So why did Nissan decide to remove "long life charging" mode?  Well, maybe they figured out what I did.

Some background for the two people not familiar with my story. I work for an Marketing/Audit/Inventory company.  We do our work at our client's location and my district's territory covers Western WA from Seatac, WA South to Centrailia and West including the entirety of the Olympic Peninsula and South to Long Beach WA on the coast.  That is a LOT of territory!

We generally only have a choice of company vehicles when the one way commute is greater than 100 miles. After that its our POV so my driving need is beyond the norm.  FYI; my 15,000 mile annual lease limit is now been exceeded by 890 miles and I still have almost 2 months to prepare for my LEAF's Birthday...

So needless to say, even if I had 80% charging, I would never use it. Had it on my 2011 and never used it there either but there are other benefits to fully charging your LEAF such as conditioning your LEAF to better address your driving needs.  Sounds confusing? let me explain.

Based on my lease mileage issues and the start of the rainy season, I have to drive the Corolla more.  It sits outside under a tree and if I don't drive it regularly (unlike the once every 4-6 weeks this past Summer) it will become a haven for mold, mildew and other things I am guessing I won't appreciate. So the LEAF has spent the last 6 days mostly sitting the nice dry garage unplugged.

I actually went 3 days not plugging it in at all with the rest of the time just plugging it in for an hour or so here and there never getting past 11 charge bars. So what happened?

Well, as expected, my battery stats plummeted. I have blogged previously about how battery stats can be manipulated which was really more of a curiosity than anything else but the results did suggest that top end balancing was a good thing that should be done on a regular basis.

ahr went from 66.37 to 63.56
kwh available from 22.0 to 21.4
GIDs from 284 to 276
Hx from 102.58 to 97.58

So what does all this mean? probably not a whole lot.  There is NO evidence whatsoever that top end balancing or lack thereof causes any permanent damage.  So whether you do it every day like I do or once a month, you are probably ok.

But this does bring up some interesting observations.  I have contended from day one that my 2013 LEAF has more range than my 2011 and it was not a popular idea at first. Now that a lot of people have claimed the same thing, its now "somewhat" accepted to be true. And to be fair; its only a few miles more like about 4 or 5 so easy to miss, ESPECIALLY if you have not properly "trained" your battery to do a range test.

Tony Williams does a great job of testing ranges of various EVs by going thru great lengths to insure the testing conditions are as similar as possible but the one thing he has not done is conditioned the LEAF by charging it to full for several days in advance of the test and this is likely why his tests show only 21ish kwh (FYI; My LEAF when new showed 22.7 kwh available... wondering just how big my LEAF's pack is nowadays?) available and that is EXACTLY what mine shows as available when I don't do any top end charging.  In Tony's defense, he is testing cars that are not his so he has no control over the charging habits of the tester car and realistically, its a few miles; not really that important in the overall picture.

But the question remains; Should you charge to 80% (or any level below full) or 100% and what is the best thing to do?

Well, a few things to think about.  Pack balance is important. Only a well balanced pack can give you the chance to get the full range from your LEAF and sometimes every little bit can help. I am pretty certain this fact kept me from walking one day!  Now batteries are pretty flexible so they can take a lot but there is a breaking point and that happens when you charge too much or discharge too deeply. Now, Nissan has taken care of the "charge too much" thing limiting us to no more than a 97% SOC on the top end but the bottom end is a bit of a different story and the reason is an unbalanced pack means its possible a single cell could be overly stressed leading to a premature end.

Now a well designed BMS is supposed to protect against that and I have no doubt Nissan has addressed this issue but the delta in an unbalanced pack is greatest at lower SOC.  Normally my voltage delta is 20 mV or less.  10 or 11 mV is normal but when the SOC gets low...

 
So the potential for damage is MUCH greater.  So its 328 mV variance or  this.  You decide.

The other thing to think about is... well getting there! We all know the LEAF's range is limited but then again is it? Despite my "slightly" greater than normal need, I have only been forced to gas it 6 times in 10 months.  I have actually driven the gasser more times just to keep it active.  But is it better to run the SOC from 80% to 15% or  100% (or whatever) to 35%?

I think its the latter and not because of the screen shots above.  "Experts" say we drive 38 miles a day but do we really?  We may commute that much but some of us have lives! My "unexpertise" analysis says Life adds another 20 miles to the equation making "want" needs to be more like 60 miles.

So charging to 100% really just allows you more options, less stress, more ready to EV it! So how can that be bad?