ChrisEV
Posts: 51
Joined: Tue Nov 14, 2017 3:47 pm
Location: GTA, Canada

Battery charging: Full versus Partial

Fri Apr 27, 2018 10:07 am

Found this article, not sure how it applies to the i-MIEV battery.

https://pushevs.com/2018/04/27/battery-charging-full-versus-partial/

Cycling from 100 to 0 % we get 500 cycles
Cycling from 100 to 10 % we get 500 cycles
Cycling from 100 to 20 % we get 1.000 cycles


Cycling from 90 to 0 % we get 1.500 cycles
Cycling from 90 to 10 % we get 1.500 cycles
Cycling from 90 to 20 % we get 2.000 cycles


Cycling from 80 to 0 % we get 3.000 cycles
Cycling from 80 to 10 % we get 3.000 cycles
Cycling from 80 to 20 % we get 3.500 cycles


Cycling from 70 to 0 % we get 5.000 cycles
Cycling from 70 to 10 % we get 5.500 cycles
Cycling from 70 to 20 % we get 6.000 cycles


As you can see it’s better to cycle your battery at lower SOC. For example, if you decide to constantly fully charge your battery (100 %) and discharge it till 20 % you can expect 1.000 cycles until reaching the EOL. However, if you charge it till 80 % and discharge it fully (till 0 %), you can expect to triple the cycles (3.000) before reaching the EOL. In both cases you’re only using 80 % of the total battery capacity. Nevertheless, this chart shows us that it’s better the cycle batteries at lower SOC.

Cycling batteries at lower SOC is great to assure that their degradation is as less as possible. However, people driving electric cars often prefer to fully charge their batteries so they can avoid range anxiety, which is understandable.


I am going to have to adjust my charging habits.
2012 i-MIEV SE Premium

Don
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Location: Biloxi MS

Re: Battery charging: Full versus Partial

Fri Apr 27, 2018 12:34 pm

We began discussing this here 5 or 6 years ago and many of us have limited our charge cycles to 75 or 80% most of the time based on reports just like this one - If you need full charge, by all means start with a full pack, but if you don't (and it doesn't give you range anxiety) the science seems to say you're better off with partial charges

"Summing up, if you really want to take care of your battery try to limit charging to 80-70 %, even if it means that sometimes you’ll need to discharge it almost till empty. Of course this is only advisable if you already know your electric car’s range limits and don’t suffer from range anxiety."

Joe has a Tesla which he's put about 35,000 miles on and unless it happened recently, I don't think he's ever charged it to 100%

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

TobyGadd
Posts: 29
Joined: Thu Jan 18, 2018 3:53 pm
Location: Fort Collins, Colorado

Re: Battery charging: Full versus Partial

Fri Apr 27, 2018 12:48 pm

It would be really nice if the car would give us the option of stopping a charge at a specified percentage. I know that we can try to use the remote to set a starting and ending time, but this is a major PITA--and pretty much a guessing game anyway...
2016 iMiev ES, Blue

kiev
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Location: The Heart o' Dixie
Contact: Website

Re: Battery charging: Full versus Partial

Fri Apr 27, 2018 1:02 pm

There is no need to worry.

Anybody can cut and paste graphs from anywhere--this is a non-technical article with no application for Miev.

Different cells: 18650 cylinder versus the LEV50 prismatic, and they use a different chemistry.

Yuasa datasheet for our cells shows cycle life data of 5500 cycles at 100% DOD depth of discharge from 4.1 down to 2.75 with a loss of only 20% over that period (i.e 80% remaining). The design life is 10 years.

Mits must believe the datasheet since they extended the pack warranty from 8 to 10 years for US cars.

Mits never charges up to 4.2, and they don't allow the pack to drain down to 2.75. When you hit turtle at "0" bars there is still 10% capacity held in reserve, so the nominal DOD range is already on the order of 80 to 90%.

My view is that there is no benefit to try to "save" your cells--they are made to be used to get you where you need to go. So what if the cells degrade over time, that's the price of not buying gasoline for 10 years.

i predict that there will be nobody with any significantly better pack than anyone else after 10 years. i use the entire 16 bars nearly everyday--i'm trying to wear my cars out as fast as possible in my lifetime.
kiev = kenny's innovative electric vehicle

Don
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Re: Battery charging: Full versus Partial

Fri Apr 27, 2018 2:33 pm

But . . . . we already have owners here with less than 80% remaining and they're all well short of 100,000 miles

Other factors come into play, especially temperature as our cells are not temperature stabilized like the ones in the Volt and Tesla are. For sure, nobody is hurting anything by only charging to 70 or 80 or even 90% when they don't need a full pack to get where they're going. For sure it's a good idea not to fully charge when it's HOT out

Me? I hope to still have useful cars after 20 years, because our 'savings' won't have completely amortized the difference in price between a $12K Kia and what we paid for the car in only 10 years

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

DBMandrake
Posts: 53
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Battery charging: Full versus Partial

Tue May 01, 2018 2:29 am

kiev wrote:Different cells: 18650 cylinder versus the LEV50 prismatic, and they use a different chemistry.

Yuasa datasheet for our cells shows cycle life data of 5500 cycles at 100% DOD depth of discharge from 4.1 down to 2.75 with a loss of only 20% over that period (i.e 80% remaining). The design life is 10 years.

Just to be accurate - you are quoting the specifications of the revised LEV50N cells, not the original LEV50 cells that are in cars prior to about mid 2012, like my 2011 Ion.

Mine is currently at 37.1Ah or about 81% of original capacity after 7 years and only 41k miles, so there is no way that it will reach the target claimed for the later LEV50N cells.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

JoeS
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Re: Battery charging: Full versus Partial

Tue May 01, 2018 11:43 am

Over the years, it's been interesting hearing from members of this forum regarding their personal approach to battery management when charging.

At one (conservative) extreme is someone like myself who tries to keep the charge level between four and twelve bars, has never seen turtle, and, after charging fully, drives the car immediately and doesn't let it sit fully charged. My i-MiEV capacity reads 39.4Ah after around 30K miles on the battery which had been replaced on this used i-MiEV after I bought it (its past life was spent in Bakersfield heat fully charging). Yes, Don, after two years and 50,000 miles I still have never fully charged my Tesla and as best I can tell at 80K miles it has no capacity loss at all.

At the other extreme is someone like mradtke in Phoenix who had a battery replacement at 2000 miles after keeping it always plugged in and fully charged with the car sitting outside. His failure occurred after he had been gone for a couple of weeks and the car sat outside plugged-in in temperatures of 117degF (47degC). His point was that the manual did not tell him not to do that and he had no interest in babying his car, even after battery replacement. If anyone's interested, here's a link to this thread representing that perspective.
http://myimiev.com/forum/viewtopic.php?f=23&t=2301&start=10#p18653
kiev wrote:...Mits must believe the datasheet since they extended the pack warranty from 8 to 10 years for US cars.
Mits never charges up to 4.2, and they don't allow the pack to drain down to 2.75. When you hit turtle at "0" bars there is still 10% capacity held in reserve, so the nominal DOD range is already on the order of 80 to 90%.
No question, Mitsubishi has added conservatism to their battery management system; not only that, for the US market they limited the peak current draw to 150A (155A?) whereas we've seen a European versions' CaniOn video show a draw of upwards of 175A peak.
kiev wrote:My view is that there is no benefit to try to "save" your cells--they are made to be used to get you where you need to go. So what if the cells degrade over time, that's the price of not buying gasoline for 10 years. i predict that there will be nobody with any significantly better pack than anyone else after 10 years. i use the entire 16 bars nearly everyday--i'm trying to wear my cars out as fast as possible in my lifetime.
Oooh, I should do that, as in the near future our selection of electric cars will dramatically increase... :D
Hey, it's been six years and it's been mostly good news on the battery front (unlike the Leaf). Time will tell...
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
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Re: Battery charging: Full versus Partial

Tue May 01, 2018 12:46 pm

Chevy goes the ultra-conservative route with the Volt and they recommend you leave it plugged in 24/7 so it can manage the battery as it sees fit. The battery is liquid cooled (and heated) and the car will only let you use about 14.2 Kw of the 18.4 Kw advertised capacity. They did ease up just a bit on the Gen 2's beginning in 2016 and the advertised range went up from 38 to 53 miles. Having come from 6 years with the iMiEV, I got 73 miles from the first full recharge and am pretty consistently between 65 and 75 miles

Always keeping 20% or so of the battery in reserve allows it to get great ICE mileage, as it uses some battery power to aid the ICE on the uphill portion and recovers that on the downhill side. 42 to 45 mpg is about the norm for a conservative driver

IMO. the 'secret' to long life is to never charge it above 4.0 volts. It would be nice if they left that decision to the owner (select whatever top number you like) but I understand why they don't. Still, if the owner wanted to reduce the factory preset number from 4.1 to 4.0, I don't see where it would hurt them to allow a reduction if the owner chose to do so

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

Phximiev
Posts: 1178
Joined: Thu Jan 15, 2015 7:25 pm
Location: Phoenix

Re: Battery charging: Full versus Partial

Tue May 01, 2018 5:59 pm

Don wrote:Chevy goes the ultra-conservative route with the Volt and they recommend you leave it plugged in 24/7 so it can manage the battery as it sees fit. The battery is liquid cooled (and heated) . . .Don


For the high side, the Volt manual says plug it in when its over 90 degrees. If its below that, one doesn't need to plug it in. I'd have to look for the cold side, but then its never that cold here in Phoenix! :D
2012 iMIEV ES
2014 Chevy Volt

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