Another Battery Degradation Thread

Sure, but I believe the first graph, "Impact of temperature on battery in a parked car", is based on yearly average as well as peak temperatures (Phoenix 27C or 80.6F average).

This is why Nissan LEAF batteries have been degrading rapidly in Arizona and other hot climates. Even in moderate areas like the greater San Francisco Bay Area have seen 15% loss of range in 3 year old LEAF cars with 30,000+ miles. PiP will do better because of a more tolerant chemistry and cooling fans (of which the LEAF has none).

I'm not saying the PiP battery is going to shrivel up in the sun and turn into a Lithium electrolyte-filled raisin. I'm just saying that cabin temperatures that feel hot to humans are likely contributing to somewhat faster battery aging in the PiP battery and should be minimized or avoided when it's not too much effort. Just basic common sense.

 

What about the parking at home?

Here in the north, many of us have insulated garages... mainly to protect from brutal winters.... but now an added benefit for summers.

That's quite a difference from an open carport common in the south... which likely wasn't taken into account with the study.

 

I have a 2014 PIP Advance with Tech Pckg - purchased in April. The car is parked outside and I charge it every night. My goal is to have zero left in the battery when I arrive from home after my 40 mile commute. The charge always kicks off at 2:30 AM. When the car was new, the range would show 13.3 and sometimes 13.4 when the charge would complete. Recently, I have noticed that every couple of days or so, it drops a bit. This morning, for example, the car showed 11.4 mile range after the overnight charge (Two days ago, it was 11.6, yesterday 11.5). I leave for work at 6:30 AM so if the charge ends about 5:00 AM, the battery has about an hour and a half to 'rest' before I take off for work.

Is this kind of EV Range reduction within the norm?

Thanks,

Phil

 

That's just an estimate based on recent driving.

This thread addresses the actual range itself (what you get, rather than what the computer anticipates), if any of us have noticed a change so far.

After 2.3 years, I have not.

 

there is a blurb about this in the faq, but, the ev range guesstometer is not designed to give you the actual range. it's an aid to help give you an idea. to determine your actual ev miles, you would have to start with a full charge, and drive until the ice comes on. for any type of future comparison, you would have to do that same route again, in the same weather and driving style.

 

I believe all Nissan Leafs allow charging to 100%, but you have to manually set it to do so

 

My impression is that the 2014 LEAF now only understands how to charge to 100% -- they took away the 80% charging choice that was on earlier models. The apparent reason for doing this was to game the EPA window sticker rules so the car would have a higher EV range estimate. Also, the battery degradation may be bad enough at "80%" charge levels that charging to "100%" wasn't likely to generate that many more complaints.

I don't recall offhand with any certainty the actual SOC range from doing a "100%" charge but my vague memory is that it allows about 87% of the nominal 24 kWh to be used.

 

I'm more interested in the inconsistencies between the "battery life" of #117 and

I've got the same model purchased in March, and I'm taking a WAG that when the car was new you might not have used the A/C and/or fan, and perhaps in the recent past with warmer temps, you might by default always have the Climate control system on. This is consistent with the hit on estimated EV range you relate.

 

Not really. If you read the threads at the LEAF forum the consensus is that charge levels and quick DC charging have only a modest effect. Most of the degradation is associated with average climate temperatures, calendar aging, and miles driven. They have developed a battery aging model in a spreadsheet. You can apparently enter those parameters and it will predict your LEAF battery energy capacity reduction. I haven't tried playing with it yet.

I see posts there from people in moderate climates with primarily 80% charging, 2-3 years of use, and 20,000+ miles who have 10-15% battery loss.

The "lifetime" shown typically assume 20% degradation of either power or energy capacity loss. That's an arbitrary battery industry convention.

Actual battery warranties are often vague about capacity loss or fail to warrant it at all. I'm not aware that CARB requires any capacity loss warranty coverage. It does presumably require that the batteries can still operate the car.

The Prius is well-suited for having the engine seamlessly step in to offset any reduced power or EV range reduction so the PiP battery pack will presumably last the life of the car without actually needing replacement.

I've got a bunch of battery papers from various research groups stored on my phone that I skimmed through the other day to find those graphs.

The same basic graphs and data show up in many of these papers and slide decks. I failed to take notes on which slides came from which documents but 2 of the 3 came from recent reports published by NREL which is one of the US national laboratories.

Here is their publications page:

NREL: Energy Storage - Publications and Presentations

Here is a paper with very relevant things to say about NCA cells, the Prius, and a PHEV 10 model that represents a simplified PiP. Also, a slide deck about battery degradation.

http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/53817.pdf

http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/45048.pdf

 

Thanks for the replies. A couple of items. These readings are taken with the A/C off so that shouldn't impact the mileage reading. Also, these are taken just before I start the car in the am. I now realize that these are estimates based on the way I am driving the car. I do worry that they are dropping so much since my driving hasn't changed. Will keep an eye on it.

Thanks to all for making this forum such a great place!

 

correct. but it's some kine of running average. for instance, if the factory setting is 13.7, and you drive 10 miles in ev before the ice comes on, it's not going to say 10 the next time, it's going to say 13.6 and it will drop a bit every time you drive until it finally reaches somewhere around 10. it takes a good long time.

 

It works like ERA in baseball

SM-G900T ?

 

100% on the dash in a leaf is 94% of the rated battery capacity, they hide the top few percent from the user (they also hide a couple of percent at the bottom as well).

So yes the user can ask for 100% charge but the car will never truly charge the battery 100%.

Kind of stupid in a way that when someone asks about a battery charge percentage you have to ask them which hundred percent do they mean.

Is that battery voltage 100%?
Is that BMS 100%
Is that canbus 100%
Is that MFD 100%
Is that dash 100%
Is that android/iphone app 100%

No car will be in synch with all the possible charge monitoring methods and some cars are happy to show you charge levels with differing levels of modification (hiding raw data from the driver).

oh and to markabele's question it doesn't matter how you charge the Leaf* the degradation is primarily

1. Heat
2. Time
3. Milage Driven (as a proxy for charge cycles)

Battery Aging Model assumptions:

• Both calendar capacity loss and cycling capacity loss are temperature dependent
• Calendar capacity loss is proportional to the square root of time (e.g., 2 years would give 1.41 times the degradation seen at one year, meaning the second year would have 41% of the calendar loss of the first year)
• Solar loading loss (i.e., parking the car in the sun) was estimated based on a study of the Prius battery (Media:HEV Battery Life.pdf) and scaled using average annual solar radiation from the NREL

see Battery Capacity Loss - Electric Vehicle Wiki
and Real World Battery Capacity Loss - Electric Vehicle Wiki

* There are documented cases of people charging to 100% with little degradation after several years of use and cases of people charging to 50-80% and seeing larger degradation due to other factors.

 

In order to drive down to the last couple of percent at the bottom you have to drive past the Low Battery Warning and the Very Low Battery Warning and it stops predicting how many miles you have remaining and then it enters "turtle mode".

I suspect few drivers routinely drive beyond VLBW which seems to be roughly around 16% so the practical routine maximum Depth of Discharge is from 94% at the top to around 16% at the bottom or a DOD of about 78-80%. If you drive it until it stops the DOD is around 90-93% .

The PiP seems to be around 85% to 23% or 62% DOD and the Volt is around 87% to 22% or 65% in model years 2011-2013 and may have been changed to 87% to 18% or 69% DOD in 2014.

 

Of course, now bucking the trend. Yesterday morning. after consistently showing a 'decline' in the available range after charge, it showed an increase going to 11.9 from 11.4.

Thanks again to everyone for their insights and information.

 

is this the leaf or prius?

 

Most of that discussion was about the LEAF.

 

thank you.