Phoenix and Hot Climate Leafs - Try L1 Charging

http://img259.imageshack.us/img259/3326/ncai.jpg" onclick="window.open(this.href);return false;

this is for NCA, lots of locations, phev10 & phev40 - no special cooling - prius like battery environment

late charging (80% or 100% - it didn't matter if the battery will basically be depleted) is better than early charging
and additional daytime opportunity charge makes things even worse.


why, look at the bottom graph - the longer an elevated SOC is held at a given temperature, the more wear on the battery. so a single late charging to 100% then driven down to 70%, then driven down to 40% and left overnight is far less damaging then twice daily maintaing the battery at 80% (and hypermiling would even make it worse)

drees said:

That doesn't make any sense. Warming up a battery pack doesn't "create" additional charge. Warming up a pack only speeds up chemical reaction in the battery as you say, so it only appears to create additional charge since the internal resistance of the pack goes down as the pack warms up.
It's not like the voltage of the pack changes with temperature to any significant degree, which would indicate a change in SOC.

Click to expand...

It does if you charge your battery in cold conditions and then it warms up, DaveinOlyWA may be worried about that but how cool does it really get overnight at Phoenix?.. Perhaps this is the effect Nissan test engineers did not detect at Casa Grande.

Very interesting ydnas7, is that on the web somewhere?

I have additional information about the car mentioned earlier, on L1 charging but no loss of 12th bar

L1 Car
---------
Purchased: Sept 2011 (White SL-e)
Pack Info at 100% Charge on 7/21: GIDs=225; Volts=392V, Temp=89degrees
Capacity Meter: 12 Bars
Charged on L1, while parked outside on driveway. Rarely charged at L2. L3 charged 1-2 times.
Miles: 10,368

Their GID reading was a surprise to me, as my GID reading on my Leaf this morning was 219, while their car reads 225, but I lost my 12th bar last month (on the list), at the GID reading of 235.

My Car
-------
Purchased: Aug 2011 (White SL-e)
Pack Info at 100% Charge on 7/21: GIDs=219; Volts=393V, Temp=93degrees
Capacity Meter: 11 Bars
Charged on L2, inside garage with End Timer set to 7:00 AM. Almost always charged at L2, L3 charged <8 times.
Miles: 15,196

Conclusions:
- Their GID reading tracks closely to mine, even though I have about 50% more miles.
- It's clear that the capacity bars are not a function of ONLY the GID reading, but must be considering cycle counts or mileage also.
- L1 charging didn't make a difference in their GID reading.

I don't know why they haven't lost a bar, but it's not solely GID readings.

ydnas7 said:

why, look at the bottom graph - the longer an elevated SOC is held at a given temperature, the more wear on the battery. so a single late charging to 100% then driven down to 70%, then driven down to 40% and left overnight is far less damaging then twice daily maintaing the battery at 80% (and hypermiling would even make it worse)

Click to expand...

Great chart - would be very interesting to find the study behind it (even though not the same chemistry as the LEAF's, same general principals apply).

Edit: Found the source of the chart: http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/53817.pdf" onclick="window.open(this.href);return false;

It's very clear that more time spent at high SOC = faster capacity degradation - even down to 20% (and probably lower) is beneficial. It's also clear as to why Nissan recommends 80% charge instead of 100%. This is also why Toyota recommends storing the PiP fully depleted - I'm sure the Volt is similar.

It's also clear that there is some exponential factor to storage at high temps (more visible at 100% SOC) - it would be very interesting to see the temperature chart expanded to 45C (113F) which AZ LEAFs are going to see. The chart tops out at 35C which is close to the minimum temp LEAF batteries in AZ will see in summer. If you want to see 10 years of life, you need to limit SOC to 60%.

One interesting tidbit - at 80% SOC, the battery should last more than 5 years before hitting 20% capacity reduction at 35C (I'd guess around 5 years even at 40C). Dangerous to conclude anything from this chart since the chemistry is not the same as the LEAFs, and my brief search couldn't find any comparison between the two.

Moral of the story - keep SOC as low as possible on average to improve battery life. In theory then L2 should be better than L1 as you can more quickly charge to desired SOC with the result being lower average SOC level.

phxsmiley said:

I don't know why they haven't lost a bar, but it's not solely GID readings.

Click to expand...

Very interesting - I wonder if it's because they typically don't deplete the battery as far as you do which perhaps triggers some internal capacity calculations?

given the issue of separating the heat of charging from the heat of driving,
why is end charging a good idea, if that means you leave the car standing for 5-8 hours, then charge, with the intention of driving off shortly afterwards?

is it all about that you should NOT charge AFTER you have driven?

thankyouOB said:

given the issue of separating the heat of charging from the heat of driving,
why is end charging a good idea, if that means you leave the car standing for 5-8 hours, then charge, with the intention of driving off shortly afterwards?
is it all about that you should NOT charge AFTER you have driven?

Click to expand...

You sort of answered your own question, but to summarize the advantages of 'end only' charging are:
1) Battery pack has time to cool BEFORE you charge (which itself warms the pack)
2) Battery pack doesn't sit at a high SOC for very long (assuming L2 charging and you go to work in AM)
3) it is (typically) cooler early in the AM (before sunrise) which (again) is better for the battery while charging

For the same reason, I no longer 'opportunity charge' during the day if I have >6TB.

I get the let it sit through the nightime part.
I think my questions was really about: is it better to end charge and then drive immediately. isnt that a temperature issue, too?

this is prompted for those of us who can charge at work during the day.
best to let the car sit and charge before leaving? or charge when you arrive?
assume the temps are not above 75 degrees.

thankyouOB said:

given the issue of separating the heat of charging from the heat of driving,
why is end charging a good idea, if that means you leave the car standing for 5-8 hours, then charge, with the intention of driving off shortly afterwards?

is it all about that you should NOT charge AFTER you have driven?

Click to expand...

This thread is about L1 that adds virtually no heat. And you will very likely be immediately charging due to the slow rate.

Otherwise the end time issue I believe is to minimize time at 100% charge. Of course Nissan recommends 80% for long life so the thought is to minimize time at 1oo%. I would have to speculate in a hot (100F+) climate, sitting at 100% has a multiplier effect on reducing life.

due to battery pack thermal mass, its reasonable to model an EV as being at seasonal ambient temperature.

http://img98.imageshack.us/img98/238/phoenix.gif" onclick="window.open(this.href);return false;

but if the car sits in the sun during the day and and sits in a single story garage at night, its ambient is higher than average
conversely
if the car sits in the shade during the day and sits in the moon shine at night, its ambient is lower than day and night average

and if its sits in sun during day and moon during night, or is covered both day and night, then its ambient is about average



both exposed nighttime parking or garage in the lower story of a 2 story house will be cooler than single story garage.


there are about 400 LEAFs in AZ, and about 30 of those have lost a bar.

perhaps the AZ owners should consider if the night time garaging allows the LEAF to cool to down sufficiently

ydnas7 said:

there are about 400 LEAFs in AZ, and about 30 of those have lost a bar.

perhaps the AZ owners should consider if the night time garaging allows the LEAF to cool to down sufficiently

Click to expand...

Misleading. 400 LEAFs in Arizona, some perhaps in cooler, higher elevation northern Arizona. Many of those aren't even close to a year old. Also, of 30 reports are here, on this website, I doubt even a majority of Arizona LEAF owners frequent here.

There are about 1000 LEAFs in San Diego, but there is nowhere close to that number here on the website.

All the hot area cars will be affected with capacity loss; what is different is how much loss, and when it appears.

ydnas7 said:

there are about 400 LEAFs in AZ, and about 30 of those have lost a bar.

Click to expand...

Not true! There are 40 cases REPORTED now on this forum. But not all LEAF owners from AZ are in the forum to report their losses, so who knows what the actual number of how many in AZ who have lost a bar. I would bet that the real number is MUCH bigger than 40.

Of course many of the 400 LEAFs in AZ are still only a few months old and may not have seen a loss YET. The 40 cases reported have had between 9 to 15 months ownership. But you can rest assured that after they've been on the road long enough like those reported, they WILL see their first and second bar losses shortly (unless they're up in Flagstaff or the cooler countries in AZ).

I haven't seen ANYBODY on this forum coming forward and say that they've had their LEAF in AZ for 12 months or so but haven't lost a bar yet.

what is showing?

the average ambient temperature is as related to min temp as it is to max temp.

Use the seasonal average.

red circles scenario VS blue circles scenario (for Az)

this is NCA so not directly comparable but the ratios between the 2 scenarios probably are.

2 neighbours in AZ, same commutes

neighbour 1. charges to 80% twice a day, uses a single story insulated garage at night, parks in the open at work, and carefully hypermiles

neighbour 2. end charges to 100% once only per day, just before leaving to work, at night the car is in an open carport, at day at work its in shaded multilevel concrete car park. Drives with a heavy foot.

Both LEAFs have batteries whose average ambient temperature is quite different to the other.

2nd LEAF has about 3-4 times slower fade than the 1st LEAF

Volusiano said:

Not true! There are 40 cases REPORTED now on this forum. But not all LEAF owners from AZ are in the forum to report their losses, so who knows what the actual number of how many in AZ who have lost a bar. I would bet that the real number is MUCH bigger than 40.

Click to expand...

I think it was Oppossum that did an informal survey of his Phoenix acquaintances, 80% had lost a bar in the first year. That is a scary number and if correct it tells you that the owners are not at fault.

The hot area cars will be affected with premature capacity loss,
this is primarily an ambient temperature effect/SOC

Ambient temperature is averaged from night time lows and day time highs.
which comes from conditions at Parking for both night and day.

phxsmiley said:

Their GID reading was a surprise to me, as my GID reading on my Leaf this morning was 219, while their car reads 225, but I lost my 12th bar last month (on the list), at the GID reading of 235.

Click to expand...

Wow! Somehow I completely missed this post! Thanks for collecting and reporting this data! That's very interesting!

phxsmiley said:

Conclusions:
- Their GID reading tracks closely to mine, even though I have about 50% more miles.
- It's clear that the capacity bars are not a function of ONLY the GID reading, but must be considering cycle counts or mileage also.
- L1 charging didn't make a difference in their GID reading.

I don't know why they haven't lost a bar, but it's not solely GID readings.

Click to expand...

I'm surprised there hasn't been any discussion on this issue.

It almost seems as if the L1 charging is not reducing the GID loss, but it is somehow keeping the BMS from reporting the loss of capacity. This data indicates that there is more to this story than we have yet uncovered.

slower charging rates, lower expected pack temperatures at target SOC means less TTID (temporary temperature induced degradation) adjustment

When switching from L2 to L1 charging, did you change EVSE? If so, what are the EVSE models you're using?

I'm running on a theory that what's destroying the batteries is a combination of factors, and one is the EVSE...

jfreire said:

When switching from L2 to L1 charging, did you change EVSE? If so, what are the EVSE models you're using?

I'm running on a theory that what's destroying the batteries is a combination of factors, and one is the EVSE...

Click to expand...

The EVSE does nothing but switch the power on and off. It has no effect on that actual battery charging which is done by the car's internal battery charger.