I believe he is experiencing temporary capacity fade mostly. I did a recent
test after all the battery discussion we had last month.
I had some CALB gray cells 60ah in my garage. I had left them at 2.5 volts
which every one tells me is a no no. They sat in my garage over a year at that
voltage. When I check them some had dropped in voltage one down to 1.8 volts. I
became concerned the others were correct in their theories.
I charged this one cell up to 3.65 volts. Then discharged it and got 25 ah. Now
I became very concerned but not convinced. I repeated the process and each time
I was discharging at 0.5C and charging at 1/6 C or 30amps and 10 amps. The
second time I got 25ah the third I got 45ah the fourth time I got 61,75. Ah and
the fifth time I got 62.5 ah. The paperwork from CALB says it's a 62 ah cell.
I heard from another user that you can wake these cells up by slow cycling them
and the paper I shared with the group stated that this type of capacity loss
could be recovered.
Now after this inadvertent experiment I am convinced that this mechanism is
real and there can be apparent capacity loss from not exercising the cell all
the way and the speed of charge seems to matter for this particular situation.
I realize one test is not enough but as I said this is documented by
researchers in the pAper I shared before.
Sent from Outlook
_____________________________
From: brucedp5 via EV <ev@lists.evdl.org>
Sent: Monday, August 3, 2015 2:32 AM
Subject: [EVDL] EVLN: Offset Supercharging degradation w/ pack balancing
To: <ev@lists.evdl.org>
'“It’s fine to Supercharge,” she said “Just don’t do it too much.”
Tesla Service Center “pack balancing” ... they do it all the time.
“Discharge it as close as you can to zero, and then charge it as slow as
possible all the way up to 100 percent,” ... “You’ll probably get some
capacity back.”'
% Is it the pack, guessometer, or both that is reset? %
http://www.greencarreports.com/news/1099280_life-with-tesla-model-s-does-supercharging-cut-battery-capacity
Life With Tesla Model S: Does Supercharging Cut Battery Capacity?
By David Noland Jul 28, 2015
[images
http://images.thecarconnection.com/med/tesla-model-s-electric-car-road-trip-upstate-new-york-to-southern-california-photo-david-noland_100500010_m.jpg
Solar panels at Supercharger in Barstow, CA, during Tesla Model S road trip
/ David Noland
http://images.thecarconnection.com/med/tesla-model-s-lithium-ion-battery-pack-in-rolling-chassis-photo-martin-gillet-via-flickr_100481091_m.jpg
Tesla Model S lithium-ion battery pack in rolling chassis / Martin Gillet
via Flickr
http://images.thecarconnection.com/med/2013-tesla-model-s-at-supercharger-station-on-ny-to-fl-road-trip-photo-david-noland_100454642_m.jpg
2013 Tesla Model S at Supercharger station on NY-to-FL road trip / David
Noland
http://images.thecarconnection.com/med/2013-tesla-model-s-at-supercharger-station-on-ny-to-fl-road-trip-photo-david-noland_100454644_m.jpg
]
[image] Tesla Model S in Albuquerque's 'snowstorm' during NY-to-California
road trip / David Noland
Last month, my wife and I took my 2013 Tesla Model S on a day trip from our
home in New York’s Hudson Valley to Brattleboro, Vermont, a distance of 180
miles.
We picked up our daughter, charged the 85-kilowatt-hour battery up to 98
percent at the Brattleboro Supercharger, and returned home via a longer,
more scenic route of 210 miles.
To my surprise, the return trip took almost every electron the battery could
muster. We pulled into the driveway with only 5 percent capacity
remaining—roughly 15 miles of range.
At first I attributed the close call to a headwind on the way home. But the
efficiency readout for the return leg had showed a respectable 302
watt-hours per mile.
That was only a bit worse than the 290 Wh/mi of the outbound leg, and well
within my normal range for summer Interstate cruising.
Diminished battery capacity
Looking more closely, what caught my eye was the dashboard readout for total
energy used for the 210-mile return leg: 63.5 kWh.
I had started with 98 percent battery and finished with 5 percent. Thus the
63.5 kWh amounted to 93 percent of the total battery capacity.
That suggests the 100-percent capacity was 68.3 kWh.
Wait a minute: Wasn’t this supposed to be an 85-kWh battery? What the heck
had happened to the other 17 kWh?
Too much Supercharging?
There has long been speculation that Supercharging--and DC fast charging of
any electric car--can cause long-term loss of Model S battery capacity.
And there is credible research to support the general idea.
A 2014 study by Idaho National Laboratory of two 2012 Nissan Leafs concluded
that, after 40,000 miles, the Nissan Leaf that used 50-kW fast charging
exclusively had 3 percent less battery capacity than the one that used
standard 6.6-kW charging.
At 120-135 kW, the Tesla Superchargers are more than twice as powerful as
the Leaf fast-chargers. It stands to reason that its effects on long-term
battery capacity might be even greater.
Was my apparent loss of battery capacity due to too much Supercharging?
[image] Tesla Model S electric-car road trip, Route 66 Museum, Elk City,
Oklahoma / David Noland
As it happens, I’ve done a lot of Supercharging in the past six months.
In January, I drove my Model S to California, using Superchargers most of
the way. During a two-month stay, we made several Supercharged road trips
along the West Coast.
Then I drove the car back to New York, Supercharged all the way along I-70.
And for the past few weeks, I’ve done some local Supercharging at a new
station that recently opened near me.
Overall, I’d estimate that of the last 10,000 miles I’ve driven the Model S,
8,000 of them have been Supercharged.
No problem, Tesla says
Has this Supercharging frenzy come back to haunt me?
Tesla says no. (In fact, one Tesla tech rep I consulted almost shouted,
“Absolutely not!”) The official company line is that Supercharging has no
deleterious effect on the battery, period.
But a funny thing: all three Tesla reps I talked to, including the shouter,
hedged their bets.
After assuring me there was absolutely no problem, each one advised me
that--all else being equal--slower charging was better for the battery in
the long run.
“It’s fine to Supercharge,” one of them told me. “Just don’t do it too
much.”
When I pointed out the thundering contradiction in that statement, she just
shrugged.
So can I just Supercharge up to the point where I start to lose range?
Sudden capacity loss
Before I left for California, I’d done a couple of quickie battery capacity
tests during long drives. I carefully noted the kWh used in running the
battery from 90 percent to 40 percent capacity, and from 80 percent to 30
percent.
In both cases, I used precisely 36.0 kWh, which implied a 100-percent
capacity of 72 kWh.
Just six months later, after 10,000 miles of mostly Supercharged driving, my
apparent capacity was down to 68 kWh—a loss of 6 percent.
Coincidence? Maybe, maybe not.
Full capacity: a mystery
Every electric car battery has built-in “buffers” that prevent it from
draining down to absolute zero or charging to absolute maximum capacity,
both of which can cause permanent damage over the long run.
The BMW i3, for example has a total battery capacity of 22 kWh, but only
18.8 is usable. My 2011 Chevy Volt used only about 10 kWh of its battery’s
16.4-kWh capacity (among the most conservative of buffers).
Unfortunately, Tesla has never published a figure for the usable battery
capacity of the Model S.
This has led to feverish speculation among owners about the real capacity
available from the 85-kWh battery. Some owners claim there’s a 5-kWh
“secret” reserve capacity, good for about 17 miles, that doesn’t show up on
the dashboard display.
In his book Owning Model S, Tesla guru Nick J. Howe makes the case that
the magic number for usable capacity is 76 kWh—plus that extra 5 kWh of
secret reserve after the battery meter hits zero.
I’ve not had the nerve to test the 17-mile theory, though I've read a few
accounts by Model S owners who did. They ended up with their cars on
flatbeds. Tesla, of course, won’t confirm the secret 5 kWh.
So, lacking the facts from Tesla, I’ll stick with Howe’s number for
non-emergency usable capacity of a brand-new Model S battery: 76 kWh.
Overall, it looked like I’d lost about 12 percent of my battery capacity,
from the presumed 76 kWh down to 68 kWh.
[image] 2013 Tesla Model S in winter, Hudson Valley, NY / David Noland
That was not good. A recent study from the Netherlands, based on data from
90 cars, concluded that the typical Model S will lose about six percent of
capacity after 50,000 miles.
But here I was with double that loss after only 34,000 miles.
Balancing the pack: salvation?
In researching my problem, I came across yet another rumor triggered solely
by Tesla’s policy of keeping useful technical information from its owners:
balancing the battery pack.
The idea is this: some lost battery capacity may be the result of unbalanced
charge levels among the 7,000-odd individual battery cells in the Model S
pack.
Lost capacity may be restored by “balancing the pack”—that is, charging it
to 100 percent to make sure that each of the cells is fully topped off.
Tesla, of course, is mum on the subject; I’ve never seen any official word
on pack balancing, and the company officially recommends against charging to
100 percent unless maximum range is necessary.
The Model S fan site Teslarati, however, recommends charging the pack to
100 percent every three months or so.
When I asked at my local Tesla Service Center about “pack balancing”, I was
told they did it all the time.
“Discharge it as close as you can to zero, and then charge it as slow as
possible all the way up to 100 percent,” I was told. “You’ll probably get
some capacity back.”
It works!
So, after a week-long abstention from charging and a bit of judicious
planning for the last few miles, I pulled into my driveway with the battery
meter reading 1 percent and the projected range readout at 2 miles.
I plugged into my regular NEMA 14-50 outlet, but set the charging rate to 20
amps, half the normal level. The full charging process would take about 18
hours, the longest I could manage to do without the car.
[image] 2011 Chevrolet Volt [pih] and 2013 Tesla Model S [EV] / David
Noland
Long story short: During those 18 hours, the dashboard readout told me that
I’d pumped 74 kWh worth of electrons into my battery.
I had apparently regained not only the capacity I’d lost from the
Supercharger binge, but also an additional 2 kWh that got me all the way
back to 97 percent of Howe’s number for full new capacity.
Not so fast….
Was this apparent 6-kWh capacity gain after balancing the pack real or
imaginary?
During the subsequent week of local driving, the numbers didn’t add up.
When the battery hit 50 percent, I had used only 31 kWh and had traveled 105
miles. That implied a full capacity of just 62 kWh and a max range of 210
miles. I seemed to be losing even more capacity.
Oddly, though, the “rated range” display told me I had 125 miles remaining
from the last 50 percent.
I chalked up this 20-percent discrepancy to “vampire” power drawn while the
car was parked, which Tesla puts at about 1 percent per day.
Long-distance test
Fortunately, I had another long trip coming up, this time to visit friends
in Maine. It would be the true test, untainted by any vampire losses.
The round trip had four legs—two each of 160 and 200 miles.
On the first leg of 160 miles, I started at 100 percent and finished at 32
percent, using 48.0 kWh in the process. That worked out to a theoretical
100-percent capacity of 70.6 kWh.
Results for the other three legs were similar: 70.3, 69.9, and 70.0 kWh.
Call it 70 kWh.
That was better than the 68 kWh before the pack-balancing, but well short of
the apparent 74 kWh capacity immediately after the pack-balancing process.
It still looks like I’ve lost about 9 percent of my battery capacity after
35,000 miles—a lot more than the projected losses in the Dutch study.
Conclusions
Based my experience, it seems to me that Supercharging probably does
somewhat degrade the long-term battery capacity.
And as for balancing the pack, it seems to work ... a little bit, sort of.
But how long does the pack-balancing benefit last? That remains to be seen.
Tesla, of course, could easily clear up all this confusion by simply
revealing a few basic facts that it certainly knows:
What is the usable capacity of the battery when new?
Is there any reserve capacity after the battery meter hits zero?
What is the effect of pack-balancing?
(Its failure to reveal such basic information continues to baffle me.)
Finally, I'd also like to see Tesla provide some actual data to back up its
claim—in my opinion, now rather dubious—that Supercharging does not affect
long-term battery capacity.
[© 2015 Green Car Reports]
...
http://www.greencarreports.com/news/1098658_life-with-tesla-model-s-local-supercharger-joys-frustrations
Life With Tesla Model S: Local Supercharger Joys & Frustrations
...
http://www.greencarreports.com/news/1098831_teslas-contradictory-messages-is-supercharging-unlimited-or-not
Tesla's Contradictory Messages: Is Supercharging Unlimited, Or Not?
For EVLN posts use:
http://evdl.org/evln/
http://gas2.org/2015/07/27/why-is-gm-only-planning-30000-chevy-bolts-per-year/
Only 30k/yr of GM's 200mi EV Planned>scared of Tesla-3 & LG's limits
http://cleantechnica.com/2015/07/28/2-potential-reasons-gm-is-only-planning-30000-chevy-bolts-per-year/
http://www.newshour.com.bd/2015/07/29/wireless-charging-for-electric-vehicles-inches-closer-to-reality/
Wireless charging for plugins inches closer to reality
http://evfleetworld.co.uk/news/2015/Jul/Tesla-Superchargers-now-live-at-three-UK-motorway-service-areas/0438020908
Tesla Superchargers now live at three UK motorway service areas
+
EVLN: Renault tips to maximize EV range (v)
{brucedp.150m.com}
--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Offset-Supercharging-degradation-w-pack-balancing-tp4677025.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.
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