ldallan
Posts: 23
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Fri Sep 07, 2018 2:01 pm

Is the following a helpful or flawed analogy regarding the way an EV Li-Ion battery is stressed by being charged to high percentages near 100%.

Consider a balloon that is repeatedly filled to different levels of fullness.

There is minimal stress to partially filling the balloon, such as to 70% to 80% capacity. It will handle many fillings without the skin of the balloon failing with a "POP".

However, if the balloon is filled to capacity ... 95% to 100% ... then we might expect the balloon to fail with significantly fewer fillings. Like the EV battery, it is relatively hard on the balloon/battery to be filled to capacity.

Note that this non-scientist is ignorant about what is actually going on inside the battery from the perspective of physics and/or chemistry.

LeftieBiker
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Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Fri Sep 07, 2018 8:21 pm

The main problem with that analogy is that it implies catastrophic failure (bursting), when what in fact usually happens is simple loss of battery capacity.
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2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
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Thick8
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Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Sat Sep 08, 2018 1:15 pm

I’m curious about this as well. I charge my Leaf every day to 100% and drain it down to about 35% every day. Some days it’s as low as 10%. Is this more than the battery can handle? It’s also been over 100F just about every day since I bought the Leaf a week and a half ago.

ldallan
Posts: 23
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Sat Sep 08, 2018 2:41 pm

LeftieBiker wrote:The main problem with that analogy is that it implies catastrophic failure (bursting), when what in fact usually happens is simple loss of battery capacity.


Good point. Thanks for the clarification.

baustin
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Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Sat Sep 08, 2018 3:31 pm

Thick8 wrote:I’m curious about this as well. I charge my Leaf every day to 100% and drain it down to about 35% every day. Some days it’s as low as 10%. Is this more than the battery can handle? It’s also been over 100F just about every day since I bought the Leaf a week and a half ago.


Charging to 100% every day is not a problem. Letting it sit at 100% for extended periods of time, especially in high heat, speeds up battery degradation. Use the charge timer so that it finishes charging just prior to your departure. If it is not yet hot at the usual departure time, set the charge timer so it charges during the coolest part of the night. I have mine set to start at 2:10am, using a 16amp Level 2 EVSE.
2013 Leaf SV - Cayenne Red - QC Port - LED Headlights

flydiver
Posts: 21
Joined: Sun Mar 11, 2018 9:14 am
Delivery Date: 20 Mar 2018
Leaf Number: 337789
Location: Seattle, WA

Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Sun Sep 09, 2018 9:19 am

[Charging to 100% is not a problem].

This is a pack, which has issues with balancing as well as simple charging so it's not quite that simple. But, there is ample evidence that over time you get superior longevity keeping the battery in the 20-80% charge window.
Absolutely agree that if you need the range, charge the battery fully. Also agree that one of the worst things is to fully charge and just let it sit, especially if the ambient temps are high.

https://batteryuniversity.com/learn/art ... _batteries

The Leaf already does some of that automatically by limiting the absolute limits of charge and discharge of the battery.
Last edited by flydiver on Mon Sep 10, 2018 8:30 am, edited 1 time in total.

ldallan
Posts: 23
Joined: Mon Jan 16, 2017 10:15 am
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Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Sun Sep 09, 2018 11:36 am

flydiver wrote:Absolutely agree that if you need the range, charge the battery fully. Also agree that one of the worst things is to fully charge and just let it sit, especially if the ambient temps are high.
Agree. I cringe and/or roll my eyes when I read people coming close to advocating the routine charging to 100%.

Example: today I've got a 70+ round trip that could be at the outer envelop of my battery range on the 2015 S with 36,000 miles and still with 12 bars. I fully charged and "cell-balanced" the battery to minimize the chance of problems. But that is less than one day per month.

If I have long'ish trip without reasonable access to Level-2 or Level-3, I'll rent an entry level Nissan Versa

FWIW:
However, about once a month I do intentionally charge to 100% plus cell-balance (about 3+ hours at 6.6/hr). I do schedule things so the car is only sitting with 100% charge for a relatively short time. And it stays relatively cool here in Colorado at 6500'.

I suppose if you are leasing a Leaf, then you could rationalize not taking the trouble to "baby" the battery. However, that seems flawed to me.

Thick8
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Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Mon Sep 10, 2018 2:44 pm

Good idea charging it at night. Start at 11 pm and finish around 6 am. Leave at 6:45. If the power should go out at night for a short period of time will the charge continue when power is restored?

baustin
Posts: 644
Joined: Tue Feb 24, 2015 1:23 pm
Delivery Date: 09 Mar 2015
Leaf Number: 402162
Location: North Las Vegas, NV

Re: Helpful analogy? Think of EV battery filled near 100% like a stressed balloon?

Tue Sep 11, 2018 3:36 am

Thick8 wrote:Good idea charging it at night. Start at 11 pm and finish around 6 am. Leave at 6:45. If the power should go out at night for a short period of time will the charge continue when power is restored?


It depends on the EVSE being used, but usually charging will start again after a power outage.
2013 Leaf SV - Cayenne Red - QC Port - LED Headlights

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