jim0266
Posts: 68
Joined: Fri Mar 17, 2017 10:14 am
Delivery Date: 17 Mar 2017
Leaf Number: 330446
Location: Akron, Oh

Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 8:32 am

By accident I may have discovered a weird Leaf battery quirk that could benefit a small group of Leaf drivers who drive short distances. This turned into a long post but I hope someone finds it useful.

Some background first. I’m about 15 months into ownership of my 2014 Leaf SV, purchased as a CPO with only 8,750 on the odometer for $9,800. The car was still showing 100% SOH at purchase with 67.36 AHr and 104.28% Hx as reported by LeafSpy.

Viewing this purchase as an experiment, I started keeping detailed records of my battery health and amount of charging.

My work commute is a massive 9 miles RT, where I also have free L2 charging in our parking deck. This short trip and small trips of about the same range around town constitute the majority of my Leaf trips. Other journeys are less frequent, but are to nearby towns that average around 90 miles for the RT. I charge at the destination before returning home.

About two months after purchase my battery health plunged to 91% SOH, 60.01 AHr and 91.83% Hx. I assumed the age of the car was the main culprit for the battery stats. After all, I was babying the car and grandpa driving. I was only at 10,300 miles.

That’s when I bumped into someone who clued me in to pulse driving. My Leaf Yoda explained all the grandpa driving was killing my battery. He recommended L3 charging the car and pulse driving. My Leaf cannot QC, which seems helpful to others with good battery stats over time. The theory is pulse driving mirrors the effects of quick charging.

I started finding excuses to take the car on longer trips and pulse drive. My battery SOH soon climbed back to 100%. Keeping my SOC in the mid-to-high 90’s did take effort. As soon as I reclaimed the numbers they would immediately start falling the next day. Once a week I needed to work the battery to keep the numbers high.

My current technique for pulse driving is while in ECO > D mode I keep repeating gentle accelerations to 4-5 power bubbles and lift off the accelerator for a few seconds and keep repeating this process. I start with 100% SOC. The technique starts working around 95% SOC when you regain the double regen bubbles. It works down to 32% on the dash, which is 40% SOC in LeafSpy. Secondary roads with sparse traffic where I can keep speeds around 55mph are perfect for this.

I started in Eco > B mode for pulse driving and generated as many power bubbles as possible. I have found no advantages in this mode or going above 4-5 power bubbles. It heats the battery faster and makes my wife nauseated due to the stronger regen. In ECO mode it's also easier to keep to 4-5 power bubbles due to the less responsive accelerator pedal.

Pulse driving was also finicky as to when the battery was ready to accept these shocks and bring up the stats. Some sessions saw my battery pack hungry to add Hx while other times it rose grudgingly. When pulse driving you can watch the Hx numbers rise in real time in LeafSpy. The AHr number resets pretty quickly but the SOH numbers take longer to reset, usually at least a few hours.

Once winter arrived and the battery temp of the pack dropped into the 40’s, my battery stats also froze at 100% SOH where I happend to be. I didn’t pulse drive all winter. I was now closing in on 19k miles.

Winter seemed to show the benefits of a thermally managed pack.

The arrival of spring brought battery pack temps back into the 50’s and the battery stats once again started to plunge. Now, however, I could not keep the SOH above 94%.

Whenever I ended a pulse driving session I would leave the car at a low SOC overnight, above 30% SOC but below 40% (as reported by LeafSpy) to minimize degradation overnight while the pack cooled off. The pack temp would often end in the high 80’s sometime in the low 90’s after pulse driving. That golden zone, according to a chart I found online, claims to show the zone for the least amount of battery degradation according to SOC and and battery temp. At 90F battery temp that is between 30 and 40% SOC.

Since I have a short commute and working L2 charging (as well as L2 at home), once summer arrived I kept my SOC in the golden zone for the leaset amount of battery degradation when ambient temps alone drove the battery pack temp into the 80’s.

That’s when I noticed something odd. I was stopping my charging sessions no higher than 39.6 SOC because 40% (as reported by LeafSpy) is when pulse driving stops working. My battery stats also froze. For two weeks not going above 40% SOC my SOH has remained locked at 93.53%, 91.93% Hx and 61.17 AHr. Thanks to my short daily commute and L2 charging at home and work, it's easy to live in this narrow band of charge. 40% SOC is the tipping point. I charged to 40% at work one day and went down a steep hill a half mile away and regened over 40% and the stats dropped a tiny amount.

After several weeks of normal charging above 40% and making short trips around town, from past experience my battery stats would have plunged. My SOH had gone as low as 88.63% this spring.

The real test of living below 40% SOC came on my golf league night. The course is 11 miles away. I left work with 39.5% SOC and arrived with 33.2% SOC charge remaining. I eco-drove the hell out of that run, which is all back roads. Home was the same distance away so I had plenty of charge remaining. It's amazing how far you can go when eco driving.

The next test was to charge to 100% and take a long drive using the pulse driving technique once our summer temp dropped to something reasonable and my pack temp was at least in the 70's. The destination was about 40 miles away and offers two good, free L2 charging stations a few miles apart. Both use renewable resources for their power as well, a nice bonus.

I feared my stats would plummet and the battery would be stubborn after several weeks of living below 40% SOC. My Hx initially dropped from 91.93% to 91.84% (LeafSpy will show you these changes in real time) for the first 20 miles or so before slowly starting to climb. Near the end of our destination the Hx value started to rise faster. We arrived at our destination with the Hx value now at 93.16%, up from 91.93% at the start.

We returned from dinner to just shy of 80% SOC. Close to home we hit 40% in LeafSpy (32% on the dash), where pulse driving stops working. The Hx value had risen to 95.59%. I left the car around 35% SOC overnight with the battery pack at 93.8F. That's still 6 temperature bars.

Next morning the AHr value had reset to 63.79 and the SOH to 97.54%. Over the next two days I drove around town staying below 39.5% SOC and my battery stats have stayed the same.

Going forward my plan is to keep the SOC at 39.5% at the highest and charge to 100% and pulse drive when taking longer trips.

There are currently 20,800 miles on my Leaf.

View my battery stats at
https://docs.google.com/spreadsheets/d/1GW3yY2nQ18X7M_GhTqpYP5BtN4gR25AMBLCy4rDQil8/edit#gid=206197239
Last edited by jim0266 on Mon Aug 27, 2018 6:53 pm, edited 5 times in total.

WetEV
Posts: 2256
Joined: Fri May 04, 2012 8:25 am
Delivery Date: 16 Feb 2014
Location: Near Seattle, WA

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 12:41 pm

jim0266 wrote:About two months after purchase my battery health plunged to 91% SOH, 60.01 AHr and 91.83% Hx. I assumed the age of the car was the main culprit for the battery stats.


No, your original statistics were probably due to a BMS reset or similar "pulse driving".

Leafspy just reports on what the BMS estimates the battery capacity is. The BMS can be fooled. Fooling the BMS doesn't improve the battery. Resetting the BMS doesn't improve capacity. Recharge and range tests confirm this.

DCQC and high discharge and regeneration probably wear the battery faster.
WetEV
#49
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red (Totaled)
2014 Leaf SL Red

be236
Posts: 79
Joined: Sun Jul 15, 2018 9:13 pm
Delivery Date: 07 Jul 2018
Leaf Number: 309258
Location: Seattle, WA

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 1:21 pm

Wow,, that's a long post. Hard to follow along..

So, let me see if I get this correct:

1. If I drive short trips (eg, less than 10 miles a day), I should pulse drive (which means to repeatedly accel and let off of the pedal, instead of holding the pedal steady?)...

2. And to keep the the SOC (as shown in the cluster display) to around 40% (which is about 4-5 bars)? And charge up to what SOC? 80%?
Nissan LEAF 2017 S.

Reddy
Posts: 1534
Joined: Fri Feb 11, 2011 3:09 pm
Delivery Date: 18 Aug 2011
Leaf Number: 006828
Location: Pasco, WA

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 6:53 pm

Ok, I think that I will try something like this for a few weeks. I've got nothing to lose because my commute is 8 mi RT and I'm down to 9 bars on my 2011. If I can regain something I'll let you know. FYI, I've kept my average SOC fairly low for the the past 7 years, but still have seen significant calendar degradation with less than 50,000 mi so far.
Reddy
2011 SL; 9 bar, 45.80 AHr; 45,000 mi; rcv'd Aug 18, 2011
Long: http://www.mynissanleaf.com/viewtopic.p ... al#p226115"
Cold: http://www.mynissanleaf.com/viewtopic.p ... 60#p243033"

jim0266
Posts: 68
Joined: Fri Mar 17, 2017 10:14 am
Delivery Date: 17 Mar 2017
Leaf Number: 330446
Location: Akron, Oh

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 7:05 pm

be236 wrote:Wow,, that's a long post. Hard to follow along..

So, let me see if I get this correct:

1. If I drive short trips (eg, less than 10 miles a day), I should pulse drive (which means to repeatedly accel and let off of the pedal, instead of holding the pedal steady?)...


Sorry, this is not what I was saying.

Like you on many days I only drive 9 miles RT to and from work. I leave in the morning with 36-39% SOC as shown in LeafSpy. I arrive at work with 33-34% SOC. I top off to 39.5% SOC at work and drive home. I do not pulse drive around town at a low SOC. My goal is to keep the battery pack at a low SOC for the battery temp. My battery pack temp was 78.3°F tonight when I got home from work. All did was drive it gently to and from work today. A battery SOC of 38% is smack in the middle of the golden zone for the least amount of battery degradation so that's were it sits tonight.

be236 wrote:2. And to keep the the SOC (as shown in the cluster display) to around 40% (which is about 4-5 bars)? And charge up to what SOC? 80%?


4-5 bars is too many. You need LeafSpy to see the exact SOC.

When I'm only running around town I have not been charging past 39.5% SOC. I could probably drive 30-35 miles on 39.5% SOC if needed in good weather. If I come home with 20% SOC I charge back to 39.5%.

My new strategy if I make longer trips, say 40 to 60 miles (80-120 miles RT), is to charge to 100% right before departure and pulse drive on that trip. I recharge at my destination and pulse drive back. Then the car will stay around 35-38% SOC once I'm back home.

be236
Posts: 79
Joined: Sun Jul 15, 2018 9:13 pm
Delivery Date: 07 Jul 2018
Leaf Number: 309258
Location: Seattle, WA

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Jul 23, 2018 8:29 pm

jim0266 wrote:
be236 wrote:Wow,, that's a long post. Hard to follow along..

So, let me see if I get this correct:

1. If I drive short trips (eg, less than 10 miles a day), I should pulse drive (which means to repeatedly accel and let off of the pedal, instead of holding the pedal steady?)...


Sorry, this is not what I was saying.

Like you on many days I only drive 9 miles RT to and from work. I leave in the morning with 36-39% SOC as shown in LeafSpy. I arrive at work with 33-34% SOC. I top off to 39.5% SOC at work and drive home. I do not pulse drive around town at a low SOC. My goal is to keep the battery pack at a low SOC for the battery temp. My battery pack temp was 78.3°F tonight when I got home from work. All did was drive it gently to and from work today. A battery SOC of 38% is smack in the middle of the golden zone for the least amount of battery degradation so that's were it sits tonight.

be236 wrote:2. And to keep the the SOC (as shown in the cluster display) to around 40% (which is about 4-5 bars)? And charge up to what SOC? 80%?


4-5 bars is too many. You need LeafSpy to see the exact SOC.

When I'm only running around town I have not been charging past 39.5% SOC. I could probably drive 30-35 miles on 39.5% SOC if needed in good weather. If I come home with 20% SOC I charge back to 39.5%.

My new strategy if I make longer trips, say 40 to 60 miles (80-120 miles RT), is to charge to 100% right before departure and pulse drive on that trip. I recharge at my destination and pulse drive back. Then the car will stay around 35-38% SOC once I'm back home.


Ok, this is opposite to what I read earlier.. that it's better to do ONE long charge, say from 20% to 80%, instead of multiple short charges of 20% to 30% (this seems so inconvenient?)... Yeah, I really need to get LEAF Spy.. but I ordered an ODB2 unit, it was supposed to be v1.5, but turned out to be v2.1, which dont work with LEAF Spy.
Nissan LEAF 2017 S.

TheLostPetrol
Posts: 46
Joined: Thu Jul 13, 2017 8:19 am
Delivery Date: 21 Feb 2018
Leaf Number: 307105
Location: Greater Chicagoland

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Tue Jul 24, 2018 1:22 pm

jim0266 wrote:By accident...
The AHr and SOC numbers take longer to reset. The SOC numbers reset in a few hours while the AHr number usually takes until the next day to reset.
...

I assume when you write "SOC" here you mean "SOH". The other occurances of SOC and SOH look correct.

How can you distinguish whether your acceleration-and-regeneration actually gives you more battery capacity, as opposed to giving you better BMS/LeafSpy numbers for the same underlying battery capacity?

I haven't read anyone here on MNL speculating on how the BMS comes up with its AHr and SOH numbers. I would guess it's a function of measured voltage times measured amperage, integrated over time, then extrapolated to the 0..100% range.
2017-12-16 New Prius Prime
2018-02-21 Used pearl white 2015 LEAF SV Mfd 2014-07 In-service 2015-02-27
2018-02-21 26,938 mi AHr=60.22 SOH=96.98% Hx=90.73% 1 QC 988 L1/L2
2018-07-01 31,601 mi AHr=58.05 SOH=93.48% Hx=87.03% 11 QC 1223 L1/L2

jim0266
Posts: 68
Joined: Fri Mar 17, 2017 10:14 am
Delivery Date: 17 Mar 2017
Leaf Number: 330446
Location: Akron, Oh

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Tue Jul 24, 2018 8:29 pm

Thanks, I did mean SOH.

I'm not sure how I would test that practically. I'm stuck believing the numbers LeafSpy gives me. Below are three sets of numbers from Leafspy when I charged to 100%. The oldest is when the numbers bottomed out a few months after purchase. The second sent is after two months of pulse driving. The 3rd set is the last time I have numbers from a 100% charge last month.

As of 7/23/18 my SOH is back to 97.54%

If I had kept driving the same way I was back in March of 2017 I cannot believe I would have the numbers I have today.

4/16/17
SOC 96.9%
SOH 91%
Gids 260
Ahr 60.11
395.95V
Miles 9,305

6/18/17
SOC 97.0%
SOH 100%
Gids 284
Ahr 66.65
395.45V
Miles 11,065

6/13/18
SOC 97.1%
SOH 92.09%
Gids 261
Ahr 60.23
395.96V
Miles 20,100

Silverfish
Posts: 27
Joined: Thu Jun 21, 2018 10:32 am
Delivery Date: 21 Jun 2018

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Fri Jul 27, 2018 11:25 am

WetEV wrote:
jim0266 wrote:About two months after purchase my battery health plunged to 91% SOH, 60.01 AHr and 91.83% Hx. I assumed the age of the car was the main culprit for the battery stats.


No, your original statistics were probably due to a BMS reset or similar "pulse driving".

Leafspy just reports on what the BMS estimates the battery capacity is. The BMS can be fooled. Fooling the BMS doesn't improve the battery. Resetting the BMS doesn't improve capacity. Recharge and range tests confirm this.

DCQC and high discharge and regeneration probably wear the battery faster.


@WetEV, how can you tell the difference between fooling the BMS and doing things that are actually good for your battery? I've read that the LeafSpy battery stats are kind of meaningless over the short term, like a few months, but I'd think that over 15 months, they would at least mean something.

In the 2+ months I've had my car, I have noticed that babying the battery makes the LeafSpy stats go down, and getting the car to really stretch its legs -- longer distances, freeway driving, deeper discharges and recharges -- makes them go up a bit. I get that those numbers may not be accurate, but in that case, how can I measure and determine what's good for my car?

I've been tracking battery percent discharged as a function of miles driven, but that ratio is all over the place due to varied driving conditions.

Thanks.

specialgreen
Posts: 111
Joined: Sun Mar 26, 2017 1:21 pm
Delivery Date: 26 Mar 2017
Location: Minnesota

Re: Living the Leaf Life Below 40% SOC and pulse driving - battery protection strategy

Mon Aug 06, 2018 1:40 pm

Silverfish wrote:how can I measure and determine what's good for my car?.


If I wanted to measure actual capacity, I'd discharge/recharge a few times with L2, then park in a climate-controlled garage at 70F, L2 charge to 100%, then put the car ON, and attach a 1kw resistive load to the 12v system. and count the hours abd minutes until turtle. Could be 24 hours or so. This could be repeated , as a better "annual battery check".

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