pbui19
Posts: 139
Joined: Tue Jan 07, 2014 12:17 pm

Re: Best charging practices for battery longevity

Wed Sep 06, 2017 3:29 pm

I just re-read this thread for the same reason as the title, but for a BoltEV application. Let's say if the iMiev has a 60kwh pack and your typical daily usage only needs 16kwh, about 60-miles, or about 25% of the pack capacity.

What is the recommended SOC % to hover around for daily charging ? some says 50% but I haven't been able to confirm. Which is better:

1. Leave at 75%, return at 50% and charge up to 75%
2. Leave at 65%, return at 40%

or am I chasing after gnats ? My understanding is that it's better to shallow charge and stay away from 100% for long duration.

Thanks

Don
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Re: Best charging practices for battery longevity

Thu Sep 07, 2017 7:23 am

pbui19 wrote:or am I chasing after gnats ? My understanding is that it's better to shallow charge and stay away from 100% for long duration.
I think so. Discharging to around 20% and then recharging to around 80% is all I would try to adhere to. Sounds like you may be able to charge every 3rd, 4th or even 5th day and be just fine. When you need a 'full' charge I wouldn't hesitate to do that - It's a good idea to recharge fully at least once every 6 weeks or so anyway

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

JoeS
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Re: Best charging practices for battery longevity

Thu Sep 07, 2017 8:13 am

pbui19 wrote:...
2. Leave at 65%, return at 40%
or am I chasing after gnats ? ...
Yes to both, as I'd personally prefer to let the car sip a bit of juice every day while keeping the SoC around the midpoint. Mostly uneducated opinion based on both reading about the subject and interacting with people working in the field... my impression is that operating at an even lower SoC is better for longevity. My understanding is that as long as the battery is kept away from either extreme of SoC, such longevity extension benefits are minor. Need to research the technical literature to see what the latest controlled test data results yield. Perhaps more significant is the battery thermal control while the car is not being driven?

<Rant>Pity that the way our society is structured that the world's experts on the subject (outside the academic lab environment) are captive to corporations and, of necessity, tight-lipped, so it is difficult to find out what indeed would be the best practice in this example. Wouldn't it be wonderful if a battery expert from LG Chem or GM would be allowed to directly answer this question?</Rant>
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

PV1
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Re: Best charging practices for battery longevity

Thu Sep 07, 2017 8:32 am

Anywhere in the 20-80% charge range should be more than fine for extending life. The I-MiEV's full charge is actually about 90% real SoC (4.1 volts per cell), so even allowing the car to fully charge shouldn't dramatically affect battery longevity (though sitting there for extended periods may). On my Dell laptop, I trimmed the charge back from a full charge of 4.35 volts per cell to 4.15 volts and this has all but stopped cell degradation (noting that laptops over-charge their batteries and that li-ion should only go to 4.2 volts max).

With the Bolt specifically, enabling Hill Top Reserve will make the car stop at 88% charge. I tend to leave this enabled and charge once a week unless I need the range, like I did yesterday. I run the Bolt between 30% and 88% charge most of the time, as my driving takes all week to drain it down that far. A side benefit for me (which is the main point of the feature) is that regen is not limited by high SoC when HTR is enabled.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

Don
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Re: Best charging practices for battery longevity

Thu Sep 07, 2017 2:14 pm

JoeS wrote:Pity that the way our society is structured that the world's experts on the subject (outside the academic lab environment) are captive to corporations and, of necessity, tight-lipped, so it is difficult to find out what indeed would be the best practice in this example. Wouldn't it be wonderful if a battery expert from LG Chem or GM would be allowed to directly answer this question?
What they disclose to the public is all marketing - They'll say whatever they think will help sell their product

For example, my gas burning Ford Transit Connect has a 6 speed automatic that Ford says is 'maintenance free' for the first 100K, despite the fact that many owners have found out the hard way that a significant number of those transmissions will need either a replacement or a major repair well before the 100K mark - They'll likely make it to the end of the factory warranty period, but that's about it. The really sad part? They didn't even bother to fill it with synthetic at the factory . . . . . synthetic lube in the engine, but not in the '100K transmission'

The wise consumer had better either pay a big bundle for the extended warranty or do some research about common sense solutions before they have to pony up $3K or more for a new transmission

EV owners on the other hand seem to be a more educated bunch and are keeping up with the latest info available on their product . . . . and we understand that much of the marketing on our cars was done in an attempt to make the car seem as 'normal' in everyday use as the gassers most of us grew up driving. Why this is being done, I'm not sure. Many of us were looking to buy something as different from the traditional ICE's as we could find and really, really wish more common sense explaining why 'different' in this case is actually 'better'

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

pbui19
Posts: 139
Joined: Tue Jan 07, 2014 12:17 pm

Re: Best charging practices for battery longevity

Thu Sep 07, 2017 2:44 pm

thanks for all replies. I did find this yesterday

"..• 75–65% SoC offers longest cycle life
• EVs use 85–25% SoC to prolong battery life
• 100–25% SoC gives long runtime, makes best use of battery, but reduces battery life."

at this web site:
http://batteryuniversity.com/learn/arti ... _batteries

in the text just below Fig 6.

====================
Joes ...
"....Perhaps more significant is the battery thermal control while the car is not being driven? "

There is indication that the BoltEV TMS will turn on, such as running the AC to cool the pack, while off and parked. Of course, then one would wonder whether there is a minimum SOC when such management ceases to prevent draining the pack too low. Imagine parking the Bolt for a month at a hot airport for a month, then coming back to a drained pack.

JoeS
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Re: Best charging practices for battery longevity

Sun May 20, 2018 1:30 pm

Found the results of a recent study over on the mychevybolt.com forum, showing that simply delaying charging until just before leaving ("As Late As Possible") can double battery life compared with frequent and full recharging.

Here's their thread:

http://www.mychevybolt.com/forum/viewtopic.php?f=12&t=8080#

Here's the study they reference - I couldn't figure out how to access it without paying -

https://doi.org/10.1016/j.trb.2018.03.016
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

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