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planet4ever
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 12:25 am

mkjayakumar wrote:I am planning to only charge through L1 at my home for the foreseeable future. Would that make any difference ? I am planning to not plug in until it comes down less than 50%, and then charge fully to 100%. That might mean charging every day or skipping a day or two depending on how much I end up driving that day.
That seems like an odd strategy. Even using L1, charging from 50% to 100% will take longer than charging from 30% to 80%, because charging slows significantly as you approach 100%. And especially when using L1, that extra time is going to be painful, since you would have to be talking about charge times well over 10 hours. (Remember, Nissan's 21 hour estimate is from Low Battery Warning to 100%, not from Turtle to 100%. That means it is really for only about an 83% charge.)

So why not go 30% to 80% instead, which would give you better regen, faster charging, and possibly longer battery life? I don't see what the downside would be, unless you were afraid you might need 80% or more on some days. And if you are worried about that, you are going to be in real trouble trying to restore your charge using L1.

Ray
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mkjayakumar
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 4:51 am

Ray,

Charging time, for the most part is not an issue. I plug in at 8 pm and stays plugged in till next day till 9 am when I leave. On most days it is fully charged to 100% and some days may be around 95% depending on how low I was the earlier night.

All I am saying is, I am not going to make a conscious decision to stop at 80%, because:

- I don't see a clear consensus here that charging 100% or closer to it using an L1 on a regular basis is bad for the battery (am I right ?)

- that extra 20% gives me an extra range of 18 miles on the city streets or 12 miles on the highway. There might a day or two in a month when I would need that extra range, and I don't want to be caught off guard.

- if I restrict myself to 80% every time then essentially this is a 80 miles city/60 miles highway car.

Jay

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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 5:19 am

mkjayakumar wrote:if I restrict myself to 80% every time then essentially this is a 80 miles city/60 miles highway car.
Yeah, so what? If you only need 50 miles, who cares if it's a 60 mile, 120 mile or 1000 mile car?
mkjayakumar wrote:that extra 20% gives me an extra range of 18 miles on the city streets or 12 miles on the highway. There might a day or two in a month when I would need that extra range, and I don't want to be caught off guard.
Is this extra need ever a surprise? Sure, you might need a little more extra planning if you are using only L1, but we manage this just fine by planning out our next day and switching between 80% and 100% timers as appropriate. You said yourself that you were planning on waiting until the car was below 50% to charge up anyway, so what would happen if you were sitting at 7 bars and had an unexpected (if that's a possibility) long day the next day and you didn't charge?

I think you really need to consider Ray's points about added regen and avoiding the longer charging times between 90-100%. Those are very valid points. I know he suggested going from 30-80%, but I don't see why you'd necessarily have to wait til 30% (unless you were confident that your next day's driving would fit within a 30% charge) and just go for a 50-80% target most of the time, and 100% when you knew you were going to use it.

I think the biggest issue with charging to 100% is if it sits around at 100% charge for "long". I don't really have a good sense for how "long" is, but if I'm going to charge to 100% I like to try to be in the car and driving within 4-6 hours. Maybe I'm being conservative, but I usually have no problem with this.
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edatoakrun
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 5:26 am

mkjayakumar wrote:Reading through the posts in this topic, do I conclude there is no clear consensus that charging full to 100% all the time does some harm or no harm from the perspective of long term health and capacity of the battery ?...
Jay
I think the best statement of the "consensus", is that leaving the battery at higher rates of charge, above 80%, for a large proportion the time will have some effect of accelerating loss of battery capacity.

How much effect, is really unknown.

In addition, charging to 100% will reduce charging efficiency a bit, and driving efficiency will be reduced, and friction brake wear will be increased, depending on how much braking you have to do, before your charge is reduced, to to the point that allows the use of Regen to slow your LEAF.

So, optimal charging is really dependent on your own situation, IMO.

I drive on an irregular schedule, often leaving my LEAF parked for several days, between trips. I start almost every drive from home with a 1,500 ft descent over 7 miles. My minimum trip length is about 50 miles and have almost no public charging availability.

I find I get almost the full benefits of increased range from a 90% charge, as I do from 100%, and almost the same efficiency gains by charging to 90%, rather than 80% (calculated by watching the Regen gauge, referring to the Carwings regeneration kWh, and checking the disc brake temperature, at the bottom of the 7 mile grade).

But I don't have a 90% timer option.

So, I charge to 80% by timer every night. I try remember to start the charger about a half an hour before leaving home, in winter, and at least an hour before I drive, on the occasional day I expect to need maximum range.
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 5:59 am

I find the charge timer thing to be irritating. When I plug the car in, I want it to start charging in case I need to go somewhere later.

Having said that.. After reading some of the threads on here about this topic, I decided a few months ago that I would not plug the car in unless it had 80% charge or less. Often I arrive home from work with 90% battery capacity. So I'll just skip charging that night. I'm pretty sure 90% would be enough to take me somewhere in an emergency. (besides we have another car anyway)
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 7:21 am

Thanks guys. I am getting a couple good take a ways here :

- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

- Regen doesn't kick in at 100%, and that means I am getting lesser miles on the top 10% of power (from 100 to 90%) than I would at lower capacity.

- more wear & tear on brakes at the top 10% of capacity, due to poor regen.

- Having the car sit overnight or a day with 100% capacity is not advisable.

I never knew any of these until I read through this topic.

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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 7:32 am

I just set my charger for 80% finishing at 6am and charge everyday - even though most days i only drive 20 miles. I don't think about it and if there ever was a power outage during one night (early morning, really) I'd still be OK for that day. i suppose if I ever planned to drive more than 50 miles in a day I might consider charging to 100%

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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 7:44 am

essaunders wrote:I just set my charger for 80% finishing at 6am and charge everyday - even though most days i only drive 20 miles. I don't think about it and if there ever was a power outage during one night (early morning, really) I'd still be OK for that day. i suppose if I ever planned to drive more than 50 miles in a day I might consider charging to 100%
This is exactly what I do, save for the one day a week I charge to 100% since I know I'll need it for lunch. I have NO timers set for the weekend: I (bypass) charge to 100% only when I know I'll need it (like this weekend).
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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 8:12 am

mkjayakumar wrote:Thanks guys. I am getting a couple good take a ways here :

- the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%

- Regen doesn't kick in at 100%, and that means I am getting lesser miles on the top 10% of power (from 100 to 90%) than I would at lower capacity.

- more wear & tear on brakes at the top 10% of capacity, due to poor regen.

- Having the car sit overnight or a day with 100% capacity is not advisable.

I never knew any of these until I read through this topic.

To clarify, sitting at 100% and then not diving the next morning and letting it sit another day or two is less preferable. Charging to 100% (94%) and driving the next day every time is not an issue.

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Re: Charging from 80% to 100% -- What's the issue?

Thu Mar 22, 2012 8:50 am

mkjayakumar wrote: - the higher end of charging is inefficient, in the sense that more electricity is spent to charge the last 20%
I don't know about inefficient (although it may be, I really don't know). But it's definitely slower. For the last 10% or so the charger tapers off the current drawn so while you normally get around 1 bar every 90 minutes hours on L1, the last bar may take 3 hours or so (I don't charge enough at L1 to know whether those are accurate, but that's the basic idea). So if you have the time anyway, that's fine, but on average you'll get more charge per hour if you start and end lower than you would if you start higher and end closer to 100%.
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