Charging Strategy - Short Shopping Trip Leaf?

[baumgrenze]

I searched the terms in the 'subject' above and did not find much. If I opened a 'forbidden' thread, mods please move it to an appropriate thread.

I am retired. I no longer commute. Most of the time I cannot predict when or how far I will drive on any given day. Most of my driving is 1-5 miles, one-way. My community owned utility charges top dollar for electricity usage above 600 kWh/month and offers no off-peak charging advantages. It will be a while until they adopt 'smart meters' because 'community consensus' is not easily reached. I am trying to understand the best strategy for charging my Leaf. I took delivery in early December. I have had meter issues with my EVSE Project Blink charger. It was finally replaced early this week. In 2 months I've seen 2 sets of data for a single charge posted on the Blink. Today the install of new firmware wiped out data on a third, ~3 hour long charge.

My reading of the posts I've found thus far led me to this strategy:

1) Set the timer on and the start and stop times to the same time of day.
2) Set the maximum charge to 80%.
3) Watch the dash and plug in the car when the predicted charge time exceeds 2.5 hours.
4) Use the 'override' button to force an immediate charge.

I am not certain I really understand what is meant by 'charging cycles' and their impact on battery pack lifetime. We have accumulated 875 miles since late on 12/7/11. Experience suggests that I need to charge 5-6 times a week based on these 'rules.'

Are there other factors I need to consider? I live in Palo Alto. CA. where winter is chilly but seldom far below freezing, July is marginally warmer (see Mark Twain about summer in San Francisco) and September is sometimes hot enough to wish for central AC for a few days before an onshore flow brings in the fog and things cool off. My garage is shop/storage space and has not been used for car storage since 1980. Do I need to supply any other parameters?

 

[Herm]

I am not certain I really understand what is meant by 'charging cycles' and their impact on battery pack lifetime.

With your short drives, you should never charge past 80%, that and your moderate weather will give you many years of Leafing.

Usually these lithium batteries have a limited number of times that they can be cycled.. many people think the chemistry used by Nissan can take 1000-1500 full cycles before it starts to deteriorate, under moderate conditions. A "charging cycle" or "cycle" is just discharging the battery 100% and fully recharging it again.. that counts as one cycle. If you only discharge the battery 50% before recharging then that counts as half a cycle and so on. Short shallow cycles preserve the life of the battery longest, these batteries tend to heat up when used at the extremes of their storage.. near 100% or 0% of charge. Heat will prematurely age the battery and so will leaving it at a 100% of charge for a long time.

My guess is that each full cycle costs about $1 in wear-and-tear of the battery, plus the cost of the electricity.

 

[planet4ever]

1) Set the timer on and the start and stop times to the same time of day.
2) Set the maximum charge to 80%.
3) Watch the dash and plug in the car when the predicted charge time exceeds 2.5 hours.
4) Use the 'override' button to force an immediate charge.

1. Check. Good strategy if you have no TOU rates.
2. Check, I expect that will be satisfactory most of the time, unless you get a hankering to go some place like Sausalito or Santa Cruz.
3. Now, that's a rule I hadn't thought of, mostly because I always have the trip computer on Energy Economy rather than Charging Time. 2½ hours sounds low to me, but I'll have to watch it a while to be sure.
4. With the timer set as you indicate, I don't believe you need to override to get immediate charging. For you, override would be used only to get 100% charging.

Ray

 

[garygid]

Right, note the answer to #4.

As you get more experience with your next-day expected range, and the number of e-fuel "Bars" you use, you will get better at knowing when to "skip" charging. Then, you will be able to get down under 6 bars with confidence.

Welcome to LEAFing.

You might want to consider a PV system to supply a large portion of your energy usage?

 

[curtegg]

I'm sort of in the same boat as you. For a week an a half I charged 100% and drove some long trips to break the batteries in. Since I retired, I run only 80% charge levels and plan all my trips to minimize the times I charge the car. I usually get about 2 weeks of use out of my Leaf between charges. For long trips I ride my Harley

From the span of usage between the forum members in a couple of years we will have a good spread of Leaf usage profiles on the batteries. I hope this forum will gather the data in a survey every year after the first five years. I'm probably in the extreme end of maximizing the duration between charging cycles. I'm hoping to keep the car over 20 years and see how well the batteries last with my utilization profile.

Looking forward to taking the Leaf in for its first annual battery checkup in another month and a half.

 

[saywatt]

For a week an a half I charged 100% and drove some long trips to break the batteries in.

Correct me if I'm wrong but Li-ON batts don't require breaking in as the old Ni-CADs did. :?:

 

[DaveEV]

2) Set the maximum charge to 80%.
3) Watch the dash and plug in the car when the predicted charge time exceeds 2.5 hours.

Personally, I wouldn't stress #3 much since you are charging to 80%. Just charge whenever you feel like it. Keep in mind that shallow discharge/charge cycles are easier on the battery, but the battery will also be spending more time at a higher state of charge which is harder on the battery. My bias would be that the hotter your climate the more I'd favor less frequent charges so the battery spends more time at low SoC at the expensive of deeper cycles.

It's situations like these where it'd be nice to be able to set the charge stop level in 5% increments from 60-100%. Of course, without actual data on how battery SoC changes storage life and DoD affects cycle life, it's hard to say if the additional complexity is worth it.

For a week an a half I charged 100% and drove some long trips to break the batteries in.

Correct me if I'm wrong but Li-ON batts don't require breaking in as the old Ni-CADs did. :?:

Lithium batteries can "break in" a bit over the first 10 full cycles or so and pick up some additional capacity. But we don't know if Nissan already does this at the factory as part of QA testing or if the cells used in the LEAF have this behavior. I certainly wouldn't worry about it much either way.

 

[abasile]

It's situations like these where it'd be nice to be able to set the charge stop level in 5% increments from 60-100%.

Yes. Unless we need more charge, we try to stop charging at roughly 65-70% on most days, when we're not driving more than about 30 miles at a time. We set a charging timer for 80%, with an end time of 8:30am and no start time, and unplug around 7-7:30am. By doing this, we get more regenerative braking on our mountain roads, and are a little gentler on the battery.

 

[Stoaty]

Yes. Unless we need more charge, we try to stop charging at roughly 65-70% on most days, when we're not driving more than about 30 miles at a time. We set a charging timer for 80%, with an end time of 8:30am and no start time, and unplug around 7-7:30am. By doing this, we get more regenerative braking on our mountain roads, and are a little gentler on the battery.

For those who don't want to watch and unplug, there is another easy way to do a partial charge which I always use:

1) Decide how many bars of charge you want to add (for example, 3 bars when get home, want to charge to 8 bars for next day = 5 bars of charge needed)
2) Multiply by 25 minutes per bar for L2 charging (= 125 minutes in my example)
3) Set charge time to closest available--only 10 minute granularity (=120 minutes or 2 hours in my example)
4) Leave 80% charge on in case you make a calculation error, or leave the car plugged in for 48 hours (the latter has happened to me)

Works perfectly, pretty accurate, cycling is a little shallower, less time at higher SOC.

 

[DaveinOlyWA]

i am averaging 1000 miles a month (see my Signature) and i only charge 3-5 days a week. i will not charge today since i have about 55-60 miles of range (i did plug in at Blink for an hour tonight while eating dinner, might as well get as much of the freebie stuff while i can)

i have no timers set, never have, we dont have TOU here so it does not matter much. on days when i plan to do more than the regular amount of driving i may do a full charge but that is rare, maybe 4-5 times a month.

my normal charge is come home with say 40%. plug in for 3 hours and unplug with anywhere (it varies depending on the starting charge) from 65-90%.

 

[dgpcolorado]

I also do a variation on a partial charge: when I come home almost empty I want to charge a bit to put the battery pack back into the middle range, so I just charge via override for an hour or hour and a half by setting a kitchen timer. Then I unplug/replug and allow the car to go back to the 80% timer set for midday, so that I can use my solar power directly on sunny days (or middle of the night if it is cloudy). If I am already in the middle of the battery pack and don't need the range I will skip charging entirely.

I'm going to have to remember Stoaty's 25 minutes-per-bar rule-of-thumb. That's helpful.

 

[baumgrenze]

Thank you, everybody, for your insights.

Somewhere (here on the forum at large, I believe) I found the suggestion to set start and end times the same and charge to 80% to get 80% charge. I will try it again, but I believe I need to override to charge, and I believe I get 80% charge when it times out. I'm still trying to understand where to look to get that information. Isn't it the bars on the right hand side of the display?

I'd be ready to consider PV to charge my car, but the photo I took (ImageShack link below) shows that years ago, the neighbor behind me elected to plant a row of cedrus deodara right along the fence line. This time of year, well past the solstice, these trees cast a mid-afternoon shadow that extends a good car length beyond the sidewalk in the foreground. At the summer solstice, we get a few days of sun on the entire roof. It's just not a justifiable investment.



Uploaded with ImageShack.us

I'm relieved to learn that each plug-in does not count as a 'charge cycle.' I will be more careful when it is hot (+/- September) to time charging to avoid a full charge for a whole day when I can.

FWIW, I read another thread here:

http://www.mynissanleaf.com/viewtopic.php?f=31&t=4295" onclick="window.open(this.href);return false;

and learned that the 'power bar' across the top of the display is a very useful tool in learning how to drive to get the most out of each kWhr. I try to use hypermiling when I drive the Prius. It is clear that getting up to speed 'quickly' and then feathering the throttle does not gain you anything with the Leaf, it costs a bit more. It was also interesting to read the opinions about ECO.

Thanks again to all for your input.

baumgrenze

 

[91040]

Thank you, everybody, for your insights.

Somewhere (here on the forum at large, I believe) I found the suggestion to set start and end times the same and charge to 80% to get 80% charge. I will try it again, but I believe I need to override to charge, and I believe I get 80% charge when it times out. I'm still trying to understand where to look to get that information. Isn't it the bars on the right hand side of the display?
baumgrenze

With your timer set and on, with the setting you describe, the car will start to charge as soon as it is plugged in. It will stop at 80%. If you push the override button, the car will charge to 100%.

Not sure what information you are looking for. If it is the timer settings, on the Nav unit, push the Zero Emission button then touch Charging Timer on the screen. That will bring you to the window that controls the settings of the timers. CH-17 in the owners manual and after.

If it is the indication of charge you want, there will be 10 SOC bars on the right side of the dash for 80% charge, all 12 for 100% charge. (They are the long bars second in from the far right.) P-29 in the manual.

 

[GaslessInSeattle]

charge to 80% whenever you want. Don't bother using the EVSE charging timer (if you have one) to adjust the time, use the one on in the car, set the timer from say 12AM to 12AM so it will charge to 80% 24hrs a day 7 days a week, whenever you plug in. use the over ride or smart phone app to charge to 100% when/if you ever need more than 80%. the temptation when first getting the car is to try and ultra baby the battery, you don't need to stress about it, go with simple and convenient, let the battery management system do the rest.

 

[Stoaty]

The temptation when first getting the car is to try and ultra baby the battery, you don't need to stress about it, go with simple and convenient, let the battery management system do the rest.

We won't know if that is true for 4-5 years when we see how well battery capacity is holding up for different battery care strategies. I am sticking with ultra-babying, it isn't much trouble for me anyway.

 

[planet4ever]

3) Watch the dash and plug in the car when the predicted charge time exceeds 2.5 hours.

Now, that's a rule I hadn't thought of, mostly because I always have the trip computer on Energy Economy rather than Charging Time. 2½ hours sounds low to me, but I'll have to watch it a while to be sure.

After playing with this a bit, I think 4 hours (at 240v) would be a better trigger level than 2.5 hours. That will keep your battery level more in the center, while always giving you at least 30 miles you can travel the next day. But, as other people have said, it's probably no biggie.

Ray

 

[Herm]

Charge it to 80% as often as you like, without fear.

80% charge does baby the battery, its actually about a 65% true charge since Nissan never really lets you charge up to 100% either. Nissan only lets you charge up to 4.1V per cell and that is about 85-87% charge.

 

[Stoaty]

80% charge does baby the battery, its actually about a 65% true charge since Nissan never really lets you charge up to 100% either. Nissan only lets you charge up to 4.1V per cell and that is about 85-87% charge.

The numbers I have seen on the forum suggest that an 80% charge is more like a 75% charge, with little room left at the top after a 100% charge.

Edit: see for example post by surfingslovak in this thread http://www.mynissanleaf.com/viewtopic.php?f=6&t=7265&start=10" onclick="window.open(this.href);return false;

Where are you getting the 65% number?

 

[DaveinOlyWA]

if you still have concerns and want to go best route

1) never charge above 90 %, never discharge into the 2 red bars. 90% charging is something that must be done manually. so its an estimate at best. i do it by simply checking it thru my phone or estimating what time to plug in.

to explain. i get home, i have say 4 white bars. that would be enough for me the next day if its a work day since i would drive less than 20 miles. but in case i want to do something afterward, i would want to charge it a bit. so i would guess say 2 hours. well i go to bed at 10 PM. so i would plug in around 8 and unplug before going to bed. you can mess with timers or 80% settting if you want. i dont. less to think about

2) if you must violate either of #1, do so as little as possible. if you need 100% time it so you leave immediately or as close to it when charging is complete. (Nissan does not allow you to charge to the full capacity of your battery so 100% is really the "accessible charge") so charging to 100% is not really much of a risk at all

3) unless you need to, dont charge if you already have at least 7 bars on GOM

4) dont Quick Charge if you have 7 or more bars on the temperature gauge (gauge on left)

 

[abasile]

if you still have concerns and want to go best route

1) never charge above 90 %, never discharge into the 2 red bars.

That's reasonable advice, though I doubt that charging to 90% is any better for the pack than discharging down to one bar.

Remember that on the first LEAFS to be shipped, the "red bars" truly were very close to the bottom of the charge range. My understanding is that the "low battery" warning occurred not too far into the second bar (that upper of the two red bars).

However, since Nissan changed the firmware to remap the charge bars, there is a significant amount of usable, "reserve" capacity even after the last bar has disappeared. This is to reduce the likelihood of people running out of charge.

A few days ago, at the end of a longish drive that I started at 100% (actually only 264 gids), I had no bars left when I pulled into our driveway. Yet the SOC/gid meter indicated 16% charge (just a couple percent below the "low battery" warning). In terms of "true" SOC, my guess is that this was more like 25% or maybe a tad less.

While it might be a little more ideal to avoid using the bottom two charge bars, this isn't something I worry about. My goal on longer, charge-limited drives is to finish just a little above the "low battery" warning, meaning using part of the very bottom bar. Going lower involves more wear on the pack. If I finish with more charge, that means I spent more time away from home charging when I could have been driving. I think this is a reasonable compromise.