LEAF's 12V battery behaviors - and why they go bad

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FalconFour

Well-known member
Joined
Sep 19, 2012
Messages
326
Location
San Jose, CA
I was a little stuck between posting this in "technical discussion" forum or the heavier-traffic General forums. This seems to be a topic very relevant to troubleshooting, less about benign technical details. Here, I'll explain how the Leaf's 12V system behaves, and why those of us without 12V solar panels on the back are screwed so bad.
https://www.youtube.com/watch?v=9VuTDCjMzRw

The problem here is that the 12V battery is maintained at a 13.0V trickle charge with a very brief 14.4V boost charge. First of all: 14.4V is the typical charging voltage for lead-acid batteries. Lower than that, they either charge very slowly, or they don't charge at all. There's a threshold voltage that has to be exceeded in order to actively charge the battery. It's possible that the 14.4V charge is continued until the battery is only absorbing a low number of amps, before it drops down to 13.0V.

The Leaf's DC-DC system (which acts as an "alternator" for converting high-voltage ~380v DC into low-voltage 12v DC) is entirely controlled by the computers in the Leaf - with very precise control. The computer uses a single PWM signal to tell the DC-DC unit exactly what voltage to provide to the 12V system - I think between 10V and 15V DC. See here: https://www.youtube.com/watch?v=BMhcHkOg-Mk

The problem is that, while 13.0V will make all the systems run off the DC-DC power (instead of discharging the 12V battery constantly), it will not actively charge the 12V battery. It'll just maintain the charge level it was last left at after the 14.4V charging phase ramps down.

This is also contrary to what the Nissan EV techs (at the hotline) have told people in the past, as well as what the manual seems to indicate - that charging the 12V battery is only done while in "Ready" mode, and that regular L2 charging, quick charging, and remote climate control won't engage charging. That's a complete load of nonsense. It appears to execute the same charging behavior any time the HV battery is involved for any reason - charging, climate control, and driving alike. It may also perform a maintenance charge every couple weeks, as I've heard, but I don't feel like waiting around a couple weeks with a camera and multimeter to find out ;)

So, while the Leaf does this quick little burst to 14.4V, it seems like it maintains only 60-70% SOC in the lead 12V battery, which subjects it to sulfation and an early need for replacement. Additionally, little bugs in the Leaf's software tend to make it occasionally, and randomly, not go completely to "sleep" after 2 minutes - as seen in the video here. With such a limited 12V capacity available, that lack of deep-sleep makes the 12V battery completely die, and you're then left with a car that won't start (or you may think you need a new 12V battery at that point), when really all you need is a full, proper 12V battery charge.

Leaving the 12V battery at ~60-70% SOC is great for those Leaf owners with a solar panel in the rear, but it's a recipe for disaster for those without. Nissan should've provided a different algorithm (13.5V at least, 14~14.4V optimally) for models without a solar panel, so that the 12V battery is properly maintained and continuously left at a full charge as lead-acid batteries prefer. At voltages like those seen in my video, sulfation is occurring constantly in the battery.

Thoughts?

(edit: OH MY GOD this forum has GOT to stop chopping-up partial words and turning them into links... now I look like a Volt advert - aargh!)
 
That certainly seems to be what's going on. After my 12 volt battery dropped so low, after about a year, that it wouldn't operate the door locks one day, I installed a battery Tender JR lead on the battery, ran it into the charging port compartment, and now I just plug that in as well whenever I have any reason to believe the car will sit plugged in but not charging. Heck, I often plug in just the maintainer, and it always tells me, via its LED, that the battery needed some charge - usually an amp hour or two. Or three. The car's charging behavior seems to have some other quirks, like sometimes (but not always) charging the battery more if the seat heaters are on, but overall it's a case of too little, too briefly. I'm still on that original 2013 battery, but I carry a lithium jumpstart pack just in case...
 
Would one of these for $12.99 (and less if you have a coupon) then help for those without the solar panel?
image_25306.jpg

http://www.harborfreight.com/15-watt-solar-battery-charger-68692.html
 
Dead-on, FalconFour! Thanks!
FalconFour said:
Here, I'll explain how the Leaf's 12V system behaves, and why those of us without 12V solar panels on the back are screwed so bad.
The 12V solar panel makes very little difference. The HIGHEST voltage I have ever seen on the LEAF's battery when parked in the sun is 13.25V. That is only slightly better than the 13.1V that the car normally operates. The problem is that this voltage occurred in the cool of the morning. Once the sun got higher in the sky, the PV panel heated up and the voltage dropped back down to 12.8V. That thing truly is just an ornament. The BEST it can do is to reduce the amount of charge lost during the daytime.
FalconFour said:
Thoughts?
Note that you get 14.4V whenever the wipers are on, so those in rainy or misty climates may do a bit better with their 12V batteries. Also note that sometimes during charging of the Li-ion battery you will get 14.4V continuously (or at least for a long time). I'm not sure how it decides when to do this.
 
LeftieBiker said:
that the battery needed some charge - usually an amp hour or two. Or three.

That means battery is nearly full if 55Ah battery can take FEW Ah after raising charging voltage above 14V.

According to Exide "charging & storage guidelines" they recommend to recharge battery if SOC is at or below 60%, or 12.5V OCV.
 
FalconFour said:
It's possible that the 14.4V charge is continued until the battery is only absorbing a low number of amps, before it drops down to 13.0V.

The problem is that, while 13.0V will make all the systems run off the DC-DC power (instead of discharging the 12V battery constantly), it will not actively charge the 12V battery. It'll just maintain the charge level it was last left at after the 14.4V charging phase ramps down.

This is exactly what it does. Use LEAFSpy to watch the amperage going into the battery. It'll start dumping power into the battery at an alarming rate if you've used the battery a lot, then the battery slowly stops taking the power and eventually the LEAF is happy with how slow the battery is charging and switches back to 13 volts. Except sometimes, it seems when it's cold out there are times when it'll sit at 14.4V "forever". Or if you use your windshield wipers, that brings it up to 14.4 volts as well.

I seem to recall that the 13 volts it normally runs at after charging is enough for around 3/4 of amp to be measured going into the battery so presumably some of the power is actively charging the battery, slowly.

FWIW I'm on 5.5 years with my original battery though a couple years back I did somewhat regularly start putting it on a desulphating charger.
 
So I got tired of you guys thinking that Leaf is not charging battery correctly.
So I did something.

Facts.
My battery is OEM Nissan-Renault 12V 50Ah battery, manufactured in the first half of 2014.
While it was at 13V float charge I disconnected EVSE.
Switched on full-beams , front fogs, rear fog, standing lights. Got a draw of 19.8A (should be 2x60W, 2x35W, 1x21W, 4x6W). Discharged my
50Ah battery SOC by 20% just be keeping that load for 30 minutes.
Average voltage during 30 minute draw was 11.5V. That means around 10Ah discharge, 115Wh.
Stopped the discharge. Car started to fall asleep. Draw was getting down below 1A.
After waiting for only 2 minutes voltage got up to 12.1V. It would most likely get to 12.2V easily.
That means battery was above 50% SOC, more likely 60% after 20% (10Ah out of 50Ah theoretical) discharge.
Old battery is very likely below rated 50Ah and temperature was 7C - so definitely below 50Ah.

And now comes exactly what I expected.
I connected EVSE back.
Voltage spiked to 14.43-14.47V. Ammeter measured charge above 70Amps for few seconds.
Dropping down to 50Amps. Average charge was around 45Amps during the first minute.
Then 40Amps during the second. 37, 35, 32, 29, 26, 24, 23, 21 during 10th minute, 10.4Amps 20th, 4,9Amps 30th, 1,5-2,0Amps 40th.
During the whole charging process voltage was absolutely steady at 14.42-14.45V. I did measure every minute.
While charging rate was between 1-2A it switched to 13V mode.
Using Excel and video I took I got down to this:
During 40 minute charge cycle 9.27Ah of juice went in. At 14.4V it is 133Wh. Process is 85-90% efficient.


Leaf WILL charge the battery if BATTERY takes the charge. I will test something else soon. I will trick the current sensor with halogen
bulb. I want to verify that switching to 13V mode happens as soon as charge rate at 14.4V drops below 1,3-1,8A, something like that.

I did notice that right after switching back to 13V mode and longer charge time there was a draw from the battery even after Leaf fell asleep (-0,4A)
This is expected as voltage after charging is always above resting voltage for a period of time.
Resting voltage should drop below 13V after like 10 minutes maybe.
Also I noticed that electrolyte was bubbling at very slow rate when battery was charging at 14.4V. This is normal but not recommended on daily basis due to loss of water.

Also we can conclude that SOC definitely stays above 70% during Leafs everyday use. Most likely it is at 80%. Which is not FULL state of charge but not low enough for sulfation to happen within few years.
Like I already mentioned, BMW-s keep their AGM battery charged specifically at 80% to have regen available on demand (3,5kW regen only).
Those batteries last for 5-7 years of heavy use. There is nothing wrong with keeping Lead acid batteries slightly discharged. Like I mentioned in another topic APC UPS's keep their battery at constant 13.5V. This kills the battery (99% guarantee) during 1-2 years of use. I've replaced them multiple times, always the same - ran out of electrolyte.

Therefore there is NOTHING wrong with Leaf charging the battery. It is designed not to charge it to 100%. And there is nothing wrong with that. Charging it to so-called 100% is stressing electrolyte and is not efficient (most likely there are additional losses). If there is a failure it is either because of battery internal defect or unplanned parasitic load. Leaf will charge the battery if it has been drained but will NOT set off an error code like 2005+ BMW-s do.
Therefore if there is a problem it will definitely kill the battery and then the user might do something (if vehicle is out of warranty, otherwise "don't care" policy)

Also Leaf keeps 12V battery at 13V voltage for hours and hours every day during vehicle lifetime! This is like keeping it trickle charging for years. Most Leafs are used daily. Older type Leafs that are used rarely might have problems as recharging happens only after 5 days while draw is more than on average ICE vehicle due to telematics.

Now we need to measure draw during sleep with 0.01A precision (clamp will not do it) 5 minutes after falling asleep and 12 hours after that to be sure (without any disconnections or touching any buttons). Please. Anybody besides me :lol:
 
arnis said:
LeftieBiker said:
that the battery needed some charge - usually an amp hour or two. Or three.

That means battery is nearly full if 55Ah battery can take FEW Ah after raising charging voltage above 14V.

According to Exide "charging & storage guidelines" they recommend to recharge battery if SOC is at or below 60%, or 12.5V OCV.

I don't think that the US spec batteries are 55AH. Does anyone have the actual number? The fact that these batteries tend to get drained if never externally charged would argue against your position. Some drivers do manage to accidentally use the car in a way that keeps the battery charged enough to stay out of trouble, but it's largely a crap shoot. BTW, most of these batteries seem to measure about 12.5 volts when checked, so that also argues against the battery being almost full. More like 55-70%.
 
arnis said:

Okay, I think you believe lead-acid batteries have the same characteristics as a capacitor or a lithium battery.

Head to Battery University and do some skimming. In fact, maybe the Nissan techs could use some experience on this site as well.

First of all, it's worth noting, my 12V battery has gone dead at least 8 times in its life so far, because of how sh!t the Leaf maintains it. Usually, they come in bursts - it goes dead once, I jump start it, it's happy for a day or two, then it goes dead again, rinse and repeat. Once I took the battery out and fully charged it overnight, it holds up for months. This highly indicates a problem with the charging system. In fact, when I capacity-tested my 12V battery on an actual metered tester that speaks mAh, not rough calculations, it came out to around 25 Ah and could only deliver about 18 of that before it could no longer sustain a 20A load (so the load decreased until it could only sustain around 4A) -- in other words, it was fuq't.

Lithium batteries don't like staying fully charged all their life. Lead batteries do. Battery University also has a handy table to explain proper habits - and the Leaf breaks several of these rules.



It takes 12 hours to fully absorb a lead battery, so you can't just shove 14.4V into it and wait for it to slow its absorption, then say "aha, it's done" and kill the charge. Also, there's practically no scenario by which running the battery at 13.5V for a charging period (even an L1) would harm the battery (as your APC UPS case). That's why my 12V is being abused as in this video - the battery is not "dead" and it doesn't need to be replaced; it merely has high internal resistance. It has plenty of load capability to operate the car, and it'd be even better-off if the Leaf actually charged the battery properly.
 
I verified by reading studies about lead-acid charging efficiency. Charging lead-acid battery below 80% SOC is something like 90% efficient. Above 90% is less than 50% efficient (due to oxygen production (quiet bubbling) that will recombine, having 0% efficiency). I'm absolutely satisfied with my finding that Leaf does NOT charge 12V battery to 100%. Also I understand WHY float voltage during the rest of charge cycle (either driving or charging the vehicle) is around 13V. This is to make sure battery is not being charged (or almost not being charged) further than was already set by the 14.4V CV charging current threshold which on its own sets SOC pretty accurately without counting Ah (like BMW current sensor does: reads voltage/temperature/current few times per minute and calculates SOC/SOH, something like Leaf Li-ion pack BMS does).

This picture is illustrational but still represents what other studies have mentioned:
h9IfH.png


Also found out that most lead acid battery manufacturers do not require topping charge above 80% SOC.
This means shelf life is not expected to be any longer above that threshold.
This also explains why BMW batteries that are only 80% charged do not degrade any faster.

This all explains Leaf charging behavior in every possible way. The only mistake they made was with the 2011/12 Leaf top-up charge while long-time stationary. They most likely fixed that too now with 24h limit.


IF leaf would hold 14.4V for longer it would result in parasitic drain not only while EVSE charging but also while driving. 12V battery might be 20% discharged when starting a journey. If Leaf tries to charge the battery it will consume some additional power. As 50Ah battery has about 0.6kWh of energy (main pack contains 24kWh) imagine charging 12V battery from 80% to 95% would take additional 0,1-0,15Wh of electricity EVERY SINGLE DAY. Not to charge the 12V but to heat it up. This results in 3kWh loss each month for nothing.
All that has to be done is NOT charge lead acid battery above 75-80%. Leaf is unable NOT TO CHARGE after 14.4V charge because it is unable to disconnect 12V battery. Therefore simplified version of float voltage 13.0V has been utilized which still unfortunately charges 12V battery way above 80% if kept long enough. Also this inefficiency happens during wipers being used but that is necessary for wiper motor voltage most likely. Also would randomly top the recommended 80% limit.
 
FalconFour said:
First of all, it's worth noting, my 12V battery has gone dead at least 8 times in its life so far, because of how sh!t the Leaf maintains it.


There are 200 000 Leafs sold in the world.
Exception verifies the rule. Most do not have any problems with 12V battery. All cars have the same charger algorithm (difference between 2011/12 and newer) like you do.
You are either doing something that others don't (parasitic load like USB charger, siren, OBD adapter) or you have some part that is defective, usually battery itself. Unacceptable self-discharge of lead-acid is common problem. We also know that Leaf should be used often.

I read ALL battery-university pages years ago. Before I even knew what Leaf was.
Today I read like 50 more pages of stuff specifically with lead-acid and SOC.
I knew a lot before today. I know much more today. This picture you showed is for storage.
Also it has a lot of generalizations, even incorrect data (lithium, must stay cool while charging, do not charge when frozen etc)
Leaf is designed be used daily. Storing and using is not the same.
Also please read all I've already written today in this topic. If something is not understandable then ask. My English can't be perfect.
Like I already wrote it is not ok to charge any higher than what Leaf does. Though sleep discharge is another topic we are not discussing jet.
 
arnis said:
And now comes exactly what I expected.
Just as I predicted:
RegGuheert said:
I won't be too surprised surprised if it restores the lost charge fairly well, since it can meter such high currents.
arnis said:
Therefore there is NOTHING wrong with Leaf charging the battery.
Here is where you are wrong. Your test does not address the KNOWN problem with the LEAF charging system. As I wrote to you recently:
RegGuheert said:
The issue is that the measurement resolution in the LEAF is only 1A, so it cannot tell what goes on when the car is off and the current draw is very low, as TimLee has mentioned:
Again, (everyone but?) you can see that charge that is lost due to light loads is not restored by the LEAF, thus allowing the SOC to gradually drop and thus lead sulfate to build up in the battery and then to harden, resulting in permanent capacity loss:

69800_s_LEAF_Battery_Voltage_7_day.png


The effect is cumulative unless the battery is FULLY charged on occasion. Unfortunately, that rarely, if ever, happens outside of action by LEAF owners with an external 12V charger. Capacity that has been lost is not regained unless a desulfating charger is used.

Note that the battery charging algorithms in BMW cars are so sophisticated that the car needs to be programmed for the EXACT battery which is being installed and only a few specific batteries are acceptable to the car. That is why BMW owners are BILKED to the tune of $750 for what should be a simple battery replacement. If this programming is NOT done, owners report odd vehicle malfunctions and battery life of less than one year.

Speaking of vehicle malfunctions, the particular malfunction that owners have experienced in the Nissan LEAF when the 12V battery fails during operation is quite severe: complete loss of braking ability (pedal to the floor).
arnis said:
It is designed not to charge it to 100%. And there is nothing wrong with that.
Nonsense. That is what leads to premature battery failure in a VERY large number of Nissan LEAFs. It is nothing more than Nissan corporate throwing a bone to Nissan dealers so that they can make some money off of LEAF owners.
arnis said:
Charging it to so-called 100% is stressing electrolyte and is not efficient (most likely there are additional losses).
There is absolutely a trade-off between sulfation versus efficiency combined with reducing loss of water from the electrolyte. Unfortunately, Nissan has gone WAY too far toward the efficiency end of the scale. To wit, the OEM battery in my LEAF has only lost about 10% of the electrolyte level between the full and empty lines in over five years of operation (and most of that is probably due to activity of my external charger).
arnis said:
Also Leaf keeps 12V battery at 13V voltage for hours and hours every day during vehicle lifetime! This is like keeping it trickle charging for years.
No, that is a float voltage, and a VERY low one at that. The battery is not discharged, but it also is not charged. My trickle charger provides 1.5 A to the battery and brings the voltage up to 14.5V rather quickly. After properly charging the LEAF's battery at 14.5V for a few hours, it drops to a PROPER float voltage of 13.5V. Per Battery University:
Battery University said:
The recommended float voltage of most flooded lead acid batteries is 2.25V to 2.27V/cell. Large stationary batteries at 25°C (77°F) typically float at 2.25V/cell. Manufacturers recommend lowering the float charge when the ambient temperature rises above 29°C (85°F).
For anyone without a calculator, the recommended float voltage for a 12V flooded lead-acid battery is 13.5V to 13.62V. In other words, the battery can be kept at this voltage CONTINUOUSLY once full charge has been achieved. The LEAF floats at 13.1V even though the battery is not fully charged. Unfortunately, it does not know this is the case since it cannot meter currents into the battery below 1A.
arnis said:
Now we need to measure draw during sleep with 0.01A precision (clamp will not do it) 5 minutes after falling asleep and 12 hours after that to be sure (without any disconnections or touching any buttons). Please. Anybody besides me :lol:
A couple of us did that years ago.
 
OK, I'll trust your expertise on battery technology so far. It does seem like sleep issues are a major problem in the Leaf. As you've probably seen, there's nothing that a user could do - aside from leaving it in "Run/not ready" overnight by accident - that could kill the battery. It turns off ACC mode after 30 minutes or so, and turns off the interior lights after 15-20 minutes (can't recall the exact time). So, there's basically nothing you can really, accidentally, do to kill the battery. It definitely seems like the Leaf's firmware is bugged in a way, so that sometimes, it'll stay "awake" overnight and kill the 12V battery. Might be worth wiring up a meter to constantly measure the voltage... who knows how many close-calls I've had in the mornings that just weren't low enough to set off all the alarms :lol:

I also find it curious that you've ever actually had the Leaf sustain 14.4V charging while the 12V battery was low. I wonder if they've corrected the programming issue in later models/firmware versions, and mine just has bum firmware that doesn't properly "charge" the 12V battery. I do know that my battery now has relatively high internal resistance due to sulfation, so it'll easily trigger a false "done charging" signal if it relies on "amps < 10 then stop charging" as a solid fact... as mentioned before, lead chemistry takes somewhere in the ballpark of 12 hours to mechanically absorb a full charge. Bursting it in a matter of minutes will only ever partially charge the battery...

So, when a battery is anything but brand-new, the Leaf's "if amps < X then stop charging" algorithm will result in ever-more-increasingly degraded 12V batteries, which... basically... just sells more 12V batteries, when a 12V battery in an EV should - in theory - last for decades or forever, with the light loads they're subjected to.
 
RegGuheert said:
arnis said:
Now we need to measure draw during sleep with 0.01A precision (clamp will not do it) 5 minutes after falling asleep and 12 hours after that to be sure (without any disconnections or touching any buttons). Please. Anybody besides me :lol:
A couple of us did that years ago.

Please share findings.
Also you can either disconnect current sensor or use discharged battery on the Leaf. I'm sure it will charge it.
It appears Leaf is not counting anything. It just applies 14.4V until amps fall to really low.

I repeat. Leaf acid battery doesn't have to be charged 100% to stop sulfation.
If you have proofs that battery sulfates at SOC 80% please share.
I also repeat that there is massive inefficiency above 80% SOC. That alone is enough to avoid going over.
And 13V is still charging. The lower the SOC the faster it charges at 13V. 13V continues for hours and hours every day.
No more saying that 13V does not charge. Please measure. +0.3A is charging! Multiply with 8 hours you get minimum 5% of capacity.

FalconFour.
Please do this small test. You have the equipment.
Discharge your 12V battery the way I did. Switch on all lights while Leaf is off.
Discharge at least 10% so readings would be more noticeable.

There is definitely a sleep issue with anything plugged into OBD. Even I had that few times. On the other hand
200 000 Leafs had more than a 100 million sleep cycles and less than 0,0001% resulted in something bad.

You are right that lead acid battery that is heavily sulfated will drop charge rate faster than new.
But 1-2A at 14.4V limit would be considered really low. So if battery is that sulfated it is already too late.

12 hour charge requirement is a myth. Different lead acid batteries have different internal design. Starter batteries have plates
that are MUCH thinner than deep cycle batteries (like PV storage). Also short charging cycle is mostly a problem with cold climates
(below freezing) as charging/discharging happens on the surface and penetrates deeper much more slowly.

In addition to that I'll bring ICE vehicle back again. Those have 13,6-14,2V charging voltage and usually for less than an hour per day.
Those vehicles are also not able to charge to 100%. Never. And mostly batteries do not fail early if nothing is wrong with the vehicle.
100% charge requirement is a myth like recommendation to fully discharge li-ion before fully charging.

So today is a new day and I did a little bit more research. I will point out only one graph.
Talks about positive plate corrosion according to voltage it is at (doesn't matter is it charging, discharging, just waiting) per unit of time (like minutes).
lander_corrosion_speed_curve.jpg

This is a reading that is used to calculate how long will battery survive according to SOC, temp, etc etc...
Even a 10yo would say it skyrockets after 2. I extracted that it goes above "1" after 2,125V (per cell, so 2.125x6=12,75V).
This means corrosion on positive plate happens even at 13V, pretty fast. If Leaf falls asleep we measure usually something around 12.5-12.6V. This is exactly what I've been noticing with ALL vehicles I have ever had. This voltage is exactly at the border of corrosion.

Source:
https://www.google.ee/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjkqqKNmeTPAhXkYJoKHcIvAZ8QFggZMAA&url=http%3A%2F%2Forbit.dtu.dk%2Ffedora%2Fobjects%2Forbit%3A88309%2Fdatastreams%2Ffile_7710966%2Fcontent&usg=AFQjCNGUDLLmUh1JIdkpT-QR5LHNaSoKUA&sig2=2rTqsepWS5E3FrPcNLZgbw&bvm=bv.135974163,d.bGs
 
arnis said:
RegGuheert said:
arnis said:
Now we need to measure draw during sleep with 0.01A precision (clamp will not do it) 5 minutes after falling asleep and 12 hours after that to be sure (without any disconnections or touching any buttons). Please. Anybody besides me :lol:
A couple of us did that years ago.

Please share findings.
Here is the first measurement I made in 2012:
RegGuheert said:
Previously, I had estimated the tare current draw on the LEAF battery to be C/600, but that was based on battery Voltage measurements rather than direct current measurements. This morning, I measured the tare current for the LEAF 12V battery with the EVSE unplugged. Here is what I found:

- For the first ten minutes or so the car drew 330mA.
- After about 10 minutes, the tare current dropped to a lower value. It normally sat at 15mA, but pulsed up to 24mA every two seconds or so.
- Occasionally it would rise up to 115mA for a few seconds. I do not know how often this occurs.

According to this post, the pubished capacity of the factory 55B24L(S) battery is 45Ah at a 20-hr rate. Let's suppose it has about 50Ah at very low rates. If we suppose the tare current is a constant 15mA, then that equates to a discharge rate of C/4000. But since it pulses above that level, sometimes significantly so, the average current must be higher than that.
Unfortunately, even though this was an accurate measurement, it was made during the daytime on an SL with a PV module on the roof. Even though the vehicle was in the garage, the PV panel may have helped to reduce the tare load. I have no idea how much difference that made.

In April 2015, lorenfb made the following measurement which seemed to agree with my battery discharge curves fairly well:
lorenfb said:
Note: The 'sleep'/standby current draw (hood closed, doors locked) is 60-70 ma without any sun (morning overcast).
I don't know how accurate his measurement is.
arnis said:
I repeat. Leaf acid battery doesn't have to be charged 100% to stop sulfation.
If you have proofs that battery sulfates at SOC 80% please share.
As FalconFour said, the proof is that 12V batteries which do very in an EV that should last for over a decade with proper charging are failing after about two years from sulfation. You have been quoting battery manufacturer's data that "80% charge is good enough" convinces you that it's O.K. to abuse your battery like that. These same battery manufacturers have lowered their warranty to a single year in most cases in the U.S. In other words, they have convinced automobile manufacturers to just keep the batteries above 80% so that we can sell a battery for each car every couple of years rather than every seven or eight years. It's a great business plan for battery manufacturers wanting to increase revenues, but it is a horrible idea for the environment.

But even if you believe the 80% bullcrap, you haven't addressed the fact that the LEAF maintains the battery BELOW 80%. I learned this in 2012 when the 12V battery in my LEAF was just one year old. Within three weeks, of being fully charged, the resting voltage dropped down to less than 12.4V:

file.php


It is clear from that plot that the charge after sitting for five days (day 19) did little or nothing to restore lost charge. So doing one after each day would have a similarly-useless effect. After another year of life in my LEAF, this same battery would typically have a resting voltage (in the car) of around 12.25V. That is when I decided to purchase a desulfating charger to try to recover the capacity of my battery which had been lost to sulfation. Today this battery will stand (in the car) above 12.7V 24 hours after a proper charge. There is no reason for me to be concerned about "corrosion of the positive plate" since this is how 12V batteries have been properly charged for decades.

Please feel free to provide proof that newer LEAFs do not abandon their 12V batteries to sulfation. You have given no evidence of the normal behavior of the LEAF.
arnis said:
I also repeat that there is massive inefficiency above 80% SOC. That alone is enough to avoid going over.
As I said, that is easily resolved by simply charging for the first hour of each Li-ion charging session. That would give a very long battery life while preventing sulfation.
 
What's wrong with voltage dropping below 12.4V for few days? It is around 70% SOC.

Do you understand that sulfation only starts at that voltage and is completely reversible if not kept for weeks.

No you don't. Why did I even ask.

Thanks for discharge data. Whatever is less than 0.1Amps is fine for majority, especially 2013 and newer Leafs.
On the other hand 0,1*24h*5days=12Ah. Safe if top-up charge starts it's counter as soon as it drops to 13V mode,
not fine if it starts 600 second counter after 14.4V charge starts.


Please feel free to provide proof that newer LEAFs do not abandon their 12V batteries to sulfation.
Failing battery? My battery is older than 2 years and 1) is not failing 2) is not sulfated 3) has a lot of capacity left.
It does not ramp up current slowly while 14.4V is being applied. It sucked more than 70Amps during few seconds.
That is normal and safe for short period. Also it means battery is not sulfated.
So what's wrong with my Leaf? Why doesn't it ruin my battery. I'm so disappointed.
 
arnis said:
On the other hand 200 000 Leafs had more than a 100 million sleep cycles and less than 0,0001% resulted in something bad.
Well, that's a load of hooey. A very small number of them actually raise their hand to complain and be counted, but it's a very common issue with the Leaf. Here in the Bay, a tow truck driver (frequently contracted by roadside services for Tesla, Nissan, Fiat, etc) tells me that EVs make up "1 in 3" tows for various issues, and half of those are because the MAIN battery is dead. The other half, it's something gone screwy with the car -- that is, a 12V battery problem, most likely, because of how it manifests itself (even when 12V is restored, car doesn't start due to the "Christmas Tree effect", setting every code in the book and refusing to start).

arnis said:
You are right that lead acid battery that is heavily sulfated will drop charge rate faster than new.
But 1-2A at 14.4V limit would be considered really low. So if battery is that sulfated it is already too late.
Hmm? No, in my video, it dropped to 1-2A charge at 13V, which means that battery was really trying to suck in power when the car cut it off. It cuts off the charging at 7 amps or so, which for my battery is still actively charging.

arnis said:
12 hour charge requirement is a myth. Different lead acid batteries have different internal design. Starter batteries have plates
that are MUCH thinner than deep cycle batteries (like PV storage). Also short charging cycle is mostly a problem with cold climates
(below freezing) as charging/discharging happens on the surface and penetrates deeper much more slowly.
Yes! Those starter batteries are not deep-cycle construction, and thus they are ill-suited for EVs (that don't need high starting current), and are more sensitive to abuse/sulfation.

arnis said:
In addition to that I'll bring ICE vehicle back again. Those have 13,6-14,2V charging voltage and usually for less than an hour per day.
Those vehicles are also not able to charge to 100%. Never. And mostly batteries do not fail early if nothing is wrong with the vehicle.
100% charge requirement is a myth like recommendation to fully discharge li-ion before fully charging.
Right? The entire 12V system in those cars operates at 13.6~14.2v voltage, without some stupid limiter throttling it down to 13.0V when it decides "eh, I guess it's charged".

arnis said:
So today is a new day and I did a little bit more research. I will point out only one graph.
Talks about positive plate corrosion according to voltage it is at (doesn't matter is it charging, discharging, just waiting) per unit of time (like minutes).
lander_corrosion_speed_curve.jpg

This is a reading that is used to calculate how long will battery survive according to SOC, temp, etc etc...
Even a 10yo would say it skyrockets after 2. I extracted that it goes above "1" after 2,125V (per cell, so 2.125x6=12,75V).
This means corrosion on positive plate happens even at 13V, pretty fast. If Leaf falls asleep we measure usually something around 12.5-12.6V. This is exactly what I've been noticing with ALL vehicles I have ever had. This voltage is exactly at the border of corrosion.

Source:
https://www.google.ee/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjkqqKNmeTPAhXkYJoKHcIvAZ8QFggZMAA&url=http%3A%2F%2Forbit.dtu.dk%2Ffedora%2Fobjects%2Forbit%3A88309%2Fdatastreams%2Ffile_7710966%2Fcontent&usg=AFQjCNGUDLLmUh1JIdkpT-QR5LHNaSoKUA&sig2=2rTqsepWS5E3FrPcNLZgbw&bvm=bv.135974163,d.bGs
Well, that's a really, very long document. What's the chart really explaining? It's pretty, but it doesn't have much context tying it into the discussion. It also defies every known principle of lead batteries over the past 100 years - basically it says that lead batteries never like being charged. Could you explain more context behind the image -- other than the "even a 10yo" obvious part about a rocketship at the end of the chart?
 
arnis said:
What's wrong with voltage dropping below 12.4V for few days?
A few days? In my LEAF, unless I intervene, it doesn't stay there a few days, but almost continuously. And, as I noted, after the second year. It was spending its time around 12.2V. That gradual drop in operating voltage is the clear result of sulfation.
arnis said:
Do you understand that sulfation only starts at that voltage...
Of course I don't, since that is utter nonsense. Lead sulfate is THE chemical product of the discharge reaction in a lead-acid battery. If you discharge your battery AT ALL, lead sulfate is formed. It starts out in solution with the electrolyte, but eventually it will come out of solution and form crystals on the plates. That is sulfation.

From Battery University:
Battery University said:
Sulfation occurs when a lead acid battery is deprived of a full charge.
Note that it does not say "deprived of an 80% charge".

From Rolls Battery:
Rolls Battery said:
Causes of battery sulfation:
- Undercharging of a battery to only 90% of capacity will allow sulfation of the battery using the 10% of battery chemistry not reactivated by not completing the charging cycle.
In other words, whenever the battery is not at full charge, it is possible for lead sulfate to come out of solution and crystallize.
arnis said:
...and is completely reversible if not kept for weeks.
That's only true in cold weather. Like ALL chemical reactions, the formation of lead sulfate crystals from the lead sulfate in solution is a function of temperature. In hot weather, lead sulfate can crystallize in as little as 24 hours. That is why lead-acid starting batteries only tend to last no more than two years in places like Phoenix, AZ, and Las Vegas, NV. As such, your experience in Estonia is not representative of many owners here in the United States. Where I live, lead-acid batteries tend to last about seven years if properly charged. Unfortunately, the LEAF is the exception to the rule.

From Rolls Battery:
Rolls Battery said:
Causes of battery sulfation:
- Batteries sit too long between charges. As little as 24 hours in hot weather and several days in cooler weather.
 
FalconFour:

Well one tow truck driver is too little to make any statistics. Especially if he doesn't really know what's wrong.

What was the outside temperature while you made the video?
Also notice that amps fell very fast. Charger might also conciser that.
They fell fast because your battery wasn't significantly discharged.

Starter batteries are still ok for EV-s. Cheaper and will charge faster at 14.4V and 13.0V. They are more sensitive, correct.

ICE vehicle charger (alternator) operates for very short period. And no 13V charge is applied. We can argue about SOC Leaf vs SOC ICE if SOC was at 50% and vehicle was driven for 20 minutes.

This graph explains that if you keep battery at above 12.6V (resting or charging) it will corrode.

RegGuheert

This rapid drop either means you have unplanned draw or your battery is slightly shorted. Easy to test. Just remove the terminal from the Leaf and charger, measure voltage every day for like 5 days. Remember that permanent sulfation doesn't discharge battery.

Sulfate is formed. It starts out in solution. So tell me, what is SOC when electrolyte has been saturated with sulfate?
Also I need source of the source, not just BatteryUniversity or Rolls Battery.

Sulfate crystallization within 24h requires also some kind of source.

Also what's wrong with some sulfation? It won't continue if SOC doesn't drop further. That means crystals will never get bigger.


It is more common for lead acid batteries to fail in hot weather than in cold weather. No surprise it also applies to Leaf.
Like I said, here in Estonia vehicle lead acid battery tends to work for very long time.

I'm reading even longer thesis about "VRLA battery float charge" (google finds). There was a graph that surprised me.
(I'm reading because I want new information, not complaints that lead-acid s*cks and Leaf is stupid etc).
As these kinds of papers are more worth than random google pictures I would rather take these as more correct.
thesis_page141.jpg


Single cell was being kept at float charge, different voltages. X-axis in hours.

This data is supporting previously mentioned data about heavy inefficiency at high SOC. Any charge pushed above 2.15V per cell
is lost very rapidly and will never return on regular VRLA flooded battery. This is why trickle charger will ALWAYS continue to
suck energy from the grid (if it goes over 2.15V per cell). It doesn't mean irreversible damage to battery is being done, just that
energy is being converted into heat at almost 100% efficiency.
 
arnis said:
This rapid drop either means you have unplanned draw or your battery is slightly shorted.
The drop in my battery voltage over three weeks is due to neither of those things. It is simply due to the state of charge of the battery being lowered due to the parasitic load of the vehicle. If the LEAF's charging system had replaced the lost charge, the battery voltage would not have continued down unabated, but it did. Clearly the LEAF did not charge the battery in any meaninful way during that entire period.
arnis said:
Remember that permanent sulfation doesn't discharge battery.
What permanent sulfation means is that you can no longer achieve a 100% SOC. The result is that your resting voltage will be lower, even after a normal charge cycle. Once that happens, the voltage DOES drop more rapidly following a charge since it is headed for a lower voltage when when it was not sulfated. In the LEAF, this means that the voltage of the battery gradually drops over the course of a couple of years until the vehicle no longer operates.
arnis said:
Also what's wrong with some sulfation? It won't continue if SOC doesn't drop further. That means crystals will never get bigger.
Another nugget of "information" you made up out of thin air? Here's the answer to your question:
Problems from sulfation occur when the sulfate forms a hard crystalline shell that isn't dissolved during charging. Over time, the sulfate crystals grow to cover most of the surface area of the lead plates, reducing capacity. Eventually, the sulfate crystals expand and crack the plates, destroying the battery.

Before complete sulfation occurs, the battery becomes less efficient and is able to hold less charge. The capacity of the battery is reduced to a non-useful level, and the battery is discarded before it is mechanically destroyed.
This has happened to the 12V batteries in MANY (most?) LEAFs within the course of a couple or a few years. This is true in spite of the Japanese LEAFs being equipped with a high-quality lead-acid battery.
 
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