Tarrngtn
Posts: 59
Joined: Tue Nov 07, 2017 6:32 pm
Location: Albuquerque, NM

Extending battery life

Sat Jul 07, 2018 6:25 pm

I think there is already a thread on this, but I would like an update from people who really know about electrical engineering and can comment from some expertise. I have read that battery life is extended if we: 1) use hilltop reserve so the batter is not fully charged up; and 2) recharge only after the battery is significantly discharged. Does #2 mean down by half, down by two-thirds, down by three-quarters?? Thanks for the expertise of other owners.

RickCH
Posts: 26
Joined: Sat Jul 15, 2017 7:54 pm

Re: Extending battery life

Sun Jul 08, 2018 2:24 pm

The expertise on this topic is based on chemistry, not EE, and this is the expert that Tesla contracts: https://www.dal.ca/diff/dahn/about.html

Jeff Dahn's simple recommendation is to charge up to 70%, and to 100% when needed. He hasn't said anything specifically about the low end, but that's probably because the car's management system won't let the charge to drop to the danger levels.

If you really want to go down the rabbit hole, here's his lecture, "Why do Li-ion batteries die and can they be immortal?". https://youtu.be/9qi03QawZEk

WetEV
Moderator
Posts: 365
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Location: Near Seattle

Re: Extending battery life

Sun Jul 08, 2018 3:36 pm

Tarrngtn wrote:{Does recharge only after the battery is significantly discharged} mean down by half, down by two-thirds, down by three-quarters??


With hilltop reserve on, this probably doesn't matter very much. If hilltop reserve was at 70% rather than about 90%, it wouldn't matter at all.

Charging to 100%, then discharging and recharging by a tiny amount will degrade a battery more quickly than charging to lower percentage and doing the same discharge and recharging cycles.
#49 on the LEAF 100 mile club.
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2014 Leaf SL Red
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Or perhaps a Buick version? Buick Electra 225???

SparkE
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Re: Extending battery life

Sun Jul 08, 2018 4:13 pm

My approach has been :
- do not fully charge unless it is needed (which isn't often in a Bolt, unless you have a 200+ mile commute) ; I would charge to about 80% (either manually stopping the charge, OR setting the timer to start charge so that it would be about 70% when I got up). It wasn't that difficult for me, as I rarely drive more than 30 miles a day, so plugging in for 90 minutes or 2 hours got me back to 70-80%.
- when you do charge to 100%, don't let the car sit for a long time at full charge. I would set the charge timer so that it would reach 100% about an hour or 90 minutes before my departure.
- do not charge when the battery is hot - heat kills Li-Ion batteries. Repeated hot charges (and discharges) are bad, bad, bad. I used to even wait an hour or two before plugging the car in to charge after I got home, and wait to charge late at night after the temp had dropped on really hot days - OR, plug in the 120V OEM EVSE on really hot days, so that the car would run it's battery temp mgmt system to keep the battery cooler while still not putting in juice at a fast rate - then plug the car into 240V late at night, or even skip it for a day.
- do not park in full sun for long periods (like when at work) on HOT days (over 85 or 90). The battery will get heated up over the hours that you are at work. I have a friend who talked his employer into letting him install one of those canvas-and-aluminum portable car-ports at the back of the parking lot (with a reserved for <license plate> sign) so that his EV was always in the shade. He'd put it up around June and take it down in early October.
- rarely DCFC (only when needed). DCFC heats up the battery cells. The faster you charge, the more heat accumulates in the battery, especially as you reach 80% or higher. (It also depends on how much you put in - charging from 10% to 80% will generate a lot more heat than charging from 55% to 80%.)
- let the car charge to 100% about once every 4-6 weeks to let the battery do cell balancing, if needed.

So I wasn't a maniac about it - if I needed it, I did it. If I forgot and occasionally charged to 100%, no biggie. I was just trying to set my *default* mode to protect the battery as much as possible. I figured that if I did a full charge (maybe) 2 or 3 times a month, instead of every night, that I was prolonging the life of my battery. And they are easy habits to get into - I actually bought a super-cheap kitchen timer that I always had set to 60 minutes and I stuck in to my fridge door, which I would turn on when I got home (unless I forgot - then I'd see it when I got food out of the fridge, and remember to charge anyways). When it went off, I'd hook the car up to charge.

Now some of these are "extreme" - but only in the sense that they might not be needed, so they are a 'waste of time'. But my outlook was that they are really easy to make 'the default', they don't take up much time, and just the *chance* that these actions might increase the battery life (and range) was enough for me to add an extra 30 seconds a day into my routine. Again, I didn't obsess about them, I just tried to do them most of the time.

SparkEVPilot
Posts: 91
Joined: Thu Feb 02, 2017 4:42 am
Location: Manteca, California

Re: Extending battery life

Sun Jul 08, 2018 10:28 pm

SparkE wrote:My approach has been :
- do not fully charge unless it is needed (which isn't often in a Bolt, unless you have a 200+ mile commute) ; I would charge to about 80% (either manually stopping the charge, OR setting the timer to start charge so that it would be about 70% when I got up). It wasn't that difficult for me, as I rarely drive more than 30 miles a day, so plugging in for 90 minutes or 2 hours got me back to 70-80%.
- when you do charge to 100%, don't let the car sit for a long time at full charge. I would set the charge timer so that it would reach 100% about an hour or 90 minutes before my departure.
- do not charge when the battery is hot - heat kills Li-Ion batteries. Repeated hot charges (and discharges) are bad, bad, bad. I used to even wait an hour or two before plugging the car in to charge after I got home, and wait to charge late at night after the temp had dropped on really hot days - OR, plug in the 120V OEM EVSE on really hot days, so that the car would run it's battery temp mgmt system to keep the battery cooler while still not putting in juice at a fast rate - then plug the car into 240V late at night, or even skip it for a day.
- do not park in full sun for long periods (like when at work) on HOT days (over 85 or 90). The battery will get heated up over the hours that you are at work. I have a friend who talked his employer into letting him install one of those canvas-and-aluminum portable car-ports at the back of the parking lot (with a reserved for <license plate> sign) so that his EV was always in the shade. He'd put it up around June and take it down in early October.
- rarely DCFC (only when needed). DCFC heats up the battery cells. The faster you charge, the more heat accumulates in the battery, especially as you reach 80% or higher. (It also depends on how much you put in - charging from 10% to 80% will generate a lot more heat than charging from 55% to 80%.)
- let the car charge to 100% about once every 4-6 weeks to let the battery do cell balancing, if needed.

So I wasn't a maniac about it - if I needed it, I did it. If I forgot and occasionally charged to 100%, no biggie. I was just trying to set my *default* mode to protect the battery as much as possible. I figured that if I did a full charge (maybe) 2 or 3 times a month, instead of every night, that I was prolonging the life of my battery. And they are easy habits to get into - I actually bought a super-cheap kitchen timer that I always had set to 60 minutes and I stuck in to my fridge door, which I would turn on when I got home (unless I forgot - then I'd see it when I got food out of the fridge, and remember to charge anyways). When it went off, I'd hook the car up to charge.

Now some of these are "extreme" - but only in the sense that they might not be needed, so they are a 'waste of time'. But my outlook was that they are really easy to make 'the default', they don't take up much time, and just the *chance* that these actions might increase the battery life (and range) was enough for me to add an extra 30 seconds a day into my routine. Again, I didn't obsess about them, I just tried to do them most of the time.

WISE WORDS OF WISDOM WORTH FOLLOWING!!

Tarrngtn
Posts: 59
Joined: Tue Nov 07, 2017 6:32 pm
Location: Albuquerque, NM

Re: Extending battery life

Mon Jul 09, 2018 2:19 am

OK. So we should continue without recharging until it is perhaps down to 25% or less, then recharge to 75% or so. The only exception would be if we are planning a long trip for the next day. Also, try to keep the garage as cool as possible but above freezing. Doable. Thanks for the info. The lecture on battery chemistry was very informative.

BillHowland
Posts: 24
Joined: Wed Nov 22, 2017 11:33 pm

Re: Extending battery life

Tue Jul 10, 2018 6:48 pm

Tarrngtn wrote:OK. So we should continue without recharging until it is perhaps down to 25% or less, then recharge to 75% or so. The only exception would be if we are planning a long trip for the next day. Also, try to keep the garage as cool as possible but above freezing. Doable. Thanks for the info. The lecture on battery chemistry was very informative.


I've driven my 2017 27,000 miles and haven't noticed any decrease in range as of yet, and I often charge to 100%.

That is what is great about GM products... You get a pretty good battery with them. I'd be interested in hearing from ANYONE who has noticed any loss so far under any circumstances.

GetOffYourGas
Posts: 1092
Joined: Tue Oct 20, 2015 5:25 pm
Location: Syracuse, NY

Re: Extending battery life

Tue Jul 10, 2018 8:49 pm

BillHowland wrote:
Tarrngtn wrote:OK. So we should continue without recharging until it is perhaps down to 25% or less, then recharge to 75% or so. The only exception would be if we are planning a long trip for the next day. Also, try to keep the garage as cool as possible but above freezing. Doable. Thanks for the info. The lecture on battery chemistry was very informative.


I've driven my 2017 27,000 miles and haven't noticed any decrease in range as of yet, and I often charge to 100%.

That is what is great about GM products... You get a pretty good battery with them. I'd be interested in hearing from ANYONE who has noticed any loss so far under any circumstances.


I know you don't have the DCFC option, Bill, but those that do can still only charge at up to 55kW. The Tesla fans love to brag that they charge up to 120kW. Given GM's conservative approach to things versus Tesla's very liberal, I wonder if that 2.2x faster charging causes extra stress and degradation, or if it really is just a difference of chemistry.
~Brian

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mwk
Posts: 35
Joined: Wed Oct 25, 2017 8:15 pm
Location: Massachusetts, USA

Re: Extending battery life

Fri Jul 20, 2018 6:09 pm

So I have a 5 mile commute each way to work. Typically, I'll plug my car in once a week or so, but leave it overnight so it's full the next day. I haven't really had the car discharged under 50% except for one longer road trip where it got down to around 30%.

However, 99% of my charging has been done via the 120v EVSE that came with my car. I plug it in at home, most of the time.

So, does using that 120v charger help to preserve the battery life?

Tarrngtn
Posts: 59
Joined: Tue Nov 07, 2017 6:32 pm
Location: Albuquerque, NM

Re: Extending battery life

Fri Jul 20, 2018 6:56 pm

If my intent is to wait until I am down to about 20% charge and then recharge to about 80%, can it be done remotely? My plan is to set off-peak from midnight to 4AM, and set leave time at 4AM as well. Peak time is set for 4AM to midnight. And it is set for off-peak charging. If the car is down to 20% and I plug it in at say 11:30 or so, will it begin to charge at midnight and stop at 4AM? Or will the programming preference to leave me fully charged override my off-peak charging and leave time instructions? Or would I be doing it incorrectly? The owners manual is not clear on this point, or at least I can’t find where the clarity is found. I have a level 2 charger in the garage.

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