To charge or not to charge?

I am going to describe what I think might be a typical situation for a lot of us. My daily commute round trip is maybe 25 miles. Add in groceries, errands, etc. and I MIGHT put 30 miles on the car per day. So now I'm in a pickle. I want to do what's best for the battery! I can easily go 2 days without recharging. I've already got the timer to go to 80%. So my question is, which is better for the battery: charging every night and never using the bottom half of the battery capacity, or charging less frequently but using more of the battery? Let's assume I will never use the "top fifth" (80%-100%) or the "bottom fifth" (0%-20%) of the battery (per the manual's recommendations).

A) Only using the "top" part of the battery's capacity (50-80%), but charging more frequently (every night).
B) Using more of the battery (20-80%), but charging less frequently (every other night or so).

I vote for option B. I think less charge cycles will make the battery last longer. But that is not based on any real science.. just my own experience.

Hopefully someone can chime in who knows the science. I see alot of these discussions going on... which is a good thing and necessary at the beginning as we learn how to use our new cars more efficiently.

-Peter

WWBD said:

I am going to describe what I think might be a typical situation for a lot of us. My daily commute round trip is maybe 25 miles. Add in groceries, errands, etc. and I MIGHT put 30 miles on the car per day. So now I'm in a pickle. I want to do what's best for the battery! I can easily go 2 days without recharging. I've already got the timer to go to 80%. So my question is, which is better for the battery: charging every night and never using the bottom half of the battery capacity, or charging less frequently but using more of the battery? Let's assume I will never use the "top fifth" (80%-100%) or the "bottom fifth" (0%-20%) of the battery (per the manual's recommendations).

A) Only using the "top" part of the battery's capacity (50-80%), but charging more frequently (every night).
B) Using more of the battery (20-80%), but charging less frequently (every other night or so).

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We are pretty much in your situation, and today was a typical 25 mile commute plus a few errands - about 33 miles total, and we went from a timer-based "80%" (83% in Carwings) to 33% (28 miles range) - we've been wanting to try what you describe (2 days between 80% charges) but until there's more charging infrastructure out there I don't think it's going to work out if we want to leave the possibility of anxiety free random errand activity on the back end of the second day. I think we're going to be hard pressed to end the first day consistently showing 50% even when it's just the commute.

WWBD said:

A) Only using the "top" part of the battery's capacity (50-80%), but charging more frequently (every night).
B) Using more of the battery (20-80%), but charging less frequently (every other night or so).

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I would say that if a 80% charge is enough to avoid going into the red (bottom 2 bars) with 2 days of driving, then charge every other day. Otherwise charge every day. This is another case where having a custom charge % level (instead of 80% or 100%) might allow one to extend the life of the battery pack more (sounds like a daily 65-70% charge would be just about perfect for you keeping the SOC between 35-70%).

You could try (b) - but I don't think it will make a big difference. How much is 5% more battery capacity in 8 years worth compared to the surity of daily charging (if you try to plug in every other day, you may forget) and possibly some cushion in case you want to drive in the evening to a place 20 miles away.

I would charge every other day. Then next week charge every day. The next week charge at least once to 100%.
I plan to mix it up and not get in a fixed pattern.

I think you're over-thinking it. Nissan didn't mean for us to fret over all this stuff. Just set the timer to charge to 80%, charge everyday and fagedaboutit.

Do you think that Nissan may be able to make some kind of adjustment to the timer in the car to offer 70% or 90%. Sound like just a software upgrade. Something to ponder

WWBD said:

A) Only using the "top" part of the battery's capacity (50-80%), but charging more frequently (every night).
B) Using more of the battery (20-80%), but charging less frequently (every other night or so).

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If you're only charging to 80% it won't make a difference... Probably less than 1% over 5 years. Battery capacity would probably decrease more if you regularly drop below 20% vs. keeping it charged at 80% on a regular basis.

Most lipo battery manufacturers recommend maintaining an 80% charge only when the battery will be left for some time without any usage (over the course of months, not days).

The best thing you could do (as long as your driving budget supports it) would be to charge to 80% every day and just drive and enjoy it! Otherwise, charge to 100%!

I've a very short commute. But I plan to charge to 80% on weekdays and 100% on weekends (actually Fri, Sat). But in Summer I'll charge to 100% everyday - so that on nice weekdays we can go out without hesitation.

evnow said:

You could try (b) - but I don't think it will make a big difference. How much is 5% more battery capacity in 8 years worth compared to the surity of daily charging (if you try to plug in every other day, you may forget) and possibly some cushion in case you want to drive in the evening to a place 20 miles away.

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Agree. In my case, at least, there is one component of the charging system which is far less reliable than all the others. And that component has a strange attribute called "habit" which makes it much more reliable.

i would look at other charging systems.

the Prius is probably the current battery management king. it runs its SOC from 40 to 80%. based on that and that alone, i would do A

DaveinOlyWA said:

i would look at other charging systems.

the Prius is probably the current battery management king. it runs its SOC from 40 to 80%. based on that and that alone, i would do A

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I'd at least look at cars that use a similar battery chemistry, and not NiMH.

DaveinOlyWA said:

i would look at other charging systems.

the Prius is probably the current battery management king. it runs its SOC from 40 to 80%. based on that and that alone, i would do A

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Dave,

The 40-80% depth of discharge is nearly across the board for hybrid use. Hybrids and EVs use the battery very differently. Hybrids are subjected to very sharp/abrupt high-rate charge and discharge 'spikes' and can have many thousands of these spikes in the time it takes an EV to go thru one full charge/discharge cycle. Hybrid service is harsh - EV service is relatively easy by comparison. And hybrid car companies are required to warranty the battery a long time - because it's a vital part of the emissions control system for the vehicle.

Yes - 40-80% (of absolute capacity) does give the absolute longest life. But the 'gain' (actually 'reduced rate of degradation from cycling') will be lost in the noise of 'time based degradation' that happens to any battery that's simply sitting unused.

The battery is going to degrade one way or another. Park it and swap the pack in 10 years with 10 miles on it, or drive it and swap it in 10 years with 150,000 miles.

Andy

Batter University.com has a great table about various battery chemistries and how to best treat them. A couple relevant items this is thread:

Should I use up all battery energy before charging?
Lithium: No, it is better to recharge more often; avoid frequent full discharges.

Should I charge my battery partially or fully?
Lithium: Does not matter. Charging in stages is acceptable. Full charge termination occurs by reading the voltage level and charge current. Charging a full battery is safe and does not cause harm.

http://batteryuniversity.com/learn/article/how_to_charge_when_to_charge_table

Is there a simple way (i.e. through Carwings or the charging systems, etc.) to track the history of my charging habits? I am wondering because if I maintain my battery between 40-80% charge for 3 years, and then decide to sell my LEAF, I want to use that as a selling point relative to other used EV's that could be for resale. I could keep a daily log, but I would think there is a simple way to track this. Any advise from the experts in the crowd?

Thanks,

Brad

cdub said:

I think you're over-thinking it. Nissan didn't mean for us to fret over all this stuff. Just set the timer to charge to 80%, charge everyday and fagedaboutit.

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I agree. Your already staying away from the end with the 80% so just fill er up every night to 80%.

bsavall said:

Is there a simple way (i.e. through Carwings or the charging systems, etc.) to track the history of my charging habits? I am wondering because if I maintain my battery between 40-80% charge for 3 years, and then decide to sell my LEAF, I want to use that as a selling point relative to other used EV's that could be for resale.

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Nissan issues report cards when they do the battery inspection, you could keep them and show them to the prospective owner. I'm more interested in the opposite point, how does a purchaser know if the battery has been abused with frequent 100% charges and daily 70 miles commute?.. the Leaf should have a display of remaining battery capacity just for that, the BMS knows exactly what the actual capacity is at any time.

Herm said:

Nissan issues report cards when they do the battery inspection, you could keep them and show them to the prospective owner. I'm more interested in the opposite point, how does a purchaser know if the battery has been abused with frequent 100% charges and daily 70 miles commute?.. the Leaf should have a display of remaining battery capacity just for that, the BMS knows exactly what the actual capacity is at any time.

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Isn't that what the small bars on the side of the "charge" gauge mean (batt capacity remaining page 2-10 of owners manual)?

-Matt

Lopton said:

Isn't that what the small bars on the side of the "charge" gauge mean (batt capacity remaining page 2-10 of owners manual)?
-Matt

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I want hard numbers, 24kwh when the car is new, 23kwh by the 3rd year and so on.. the BMS knows. There has to be way to deal with the used car market, batteries are expensive. If you are a conscientious Leaf drive you should be rewarded when it comes time to trade it in.