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

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Stanton said:
Lithium...and it did just fine in the ridiculous freeze (down to 0 degrees F) we had here in Texas last winter (and everyone knows how hot it gets in Texas).

0F isn't cold, much less ridiculous. -35F, that's cold.

Look at some specification sheets.

https://relionbattery.com/products/lithium/rb52-lt


CHARGE SPECIFICATIONS
Recommended Charge Current 2.5 A - 25 A
Maximum Charge Current 50 A
Charge Current 14 to 32 F (-10 to 0 C) <0.1 C
Charge Current -4 to 14 F (-20 to -10 C) <0.05 C

0.1 C charge rate is 2.5 Amps.

0.05 charge rate is 1.25 Amps.
 
knightmb said:
In the Leaf, it's a small blip of power to turn it on and then the Leaf has to be nice enough to give a good kick of power if the voltage is low enough. That's why I've always said, it seems the Leaf charging algorithm for the 12 volt system seems more adapt to a Lithium battery than Lead for some reason. :?
I have often thought the same thing!
 
Ok, I'm having slow battery discharging trouble and this tread seems to have the right discussion. But I can't find a definitive answer in the 21 pages

Should the 12V battery current sensor be

A) Disconnected
B) Removed from measuring the -ve cable but remain connected to the wiring harness
C) Removed from measuring the -ve cable and also be disconnected from the wiring harness
D) Other (if so, please explain)

Thanks in advance
 
This is just my experience, I just unplugged the current sensor. As you have probably read, all that does is the car isn't sure the state of charge for the 12v battery so it keeps the 12v battery at absorb, in my car about 13.9v all the time. This doesn't fix the phantom suck on load that runs the battery dead, but what it does do is makes sure the 12v is fully charged whenever the high voltage converter to 12v is turned on. I know many have said this isn't good for a lead acid, but 95% of the cars in that use good old alternators do this, just always sit about 14.4v range whenever the car is running. I wish there was a better solution, but I now find a dead battery about once every other month. I do also put the 12v on a trickle charger if we aren't going to use the car for a few days (gone on a trip).
 
xafalcon said:
Ok, I'm having slow battery discharging trouble and this thread seems to have the right discussion. But I can't find a definitive answer in the 21 pages
The best answer was the one right above your post.
I don't recommend disconnecting any electrical sensors. If you are having that much trouble with your lead acid starter battery, replace it with LiFePO4.
 
xafalcon said:
Ok, I'm having slow battery discharging trouble and this tread seems to have the right discussion. But I can't find a definitive answer in the 21 pages

Should the 12V battery current sensor be

A) Disconnected
B) Removed from measuring the -ve cable but remain connected to the wiring harness
C) Removed from measuring the -ve cable and also be disconnected from the wiring harness
D) Other (if so, please explain)

Thanks in advance

You need to use a clamp-on current meter to determine what the current draw is once the Leaf enters its sleep mode.
It should be less than about 50 milli-amps (.050 amps). Here's a meter to consider;

https://www.amazon.com/Current-Auto-Ranging-Digital-Ammeter-V-Alert/dp/B094R8CB4W/ref=sr_1_19?crid=111XEZTTMOVX9&keywords=clamp-on+ammeter&qid=1649347879&sprefix=clamp-on+ammeter%2Caps%2C119&sr=8-19
 
Posting on here as I am blaming the 12v for my onboard charger (OBC) going bad. I bought a 2012 Leaf in 2017. Had weird brake issues one morning in 2019, and replaced the 12v - all good.

Last week, we notice the Leaf didn't charge overnight at home on the wall Nissan charger. No alarm bells yet. Plugin at work, but notice at the end of the day, again no charge.

Replace the 12v, under the 3-year warranty, but still no charge. Join the forum and see if others have had this issue. The likely cause is a failed diode in the OBC.

So my question is if I figure out how to fix this issue, what's to stop it from failing again next the 12v goes?
 
I don't think the 12V battery has anything to do with the diode in the onboard charger failing. Diagnostic trouble codes (DTC's) with things related to charger can prevent charging. Clear any trouble codes and try several different charging units before you conclude something is wrong with the onboard charger.
 
i've become fascinated with the 12V topic, as my 2017's OEM battery is presumably nearing the end of its life :)

question about Leafspy... when it says the current for the 12V is whatever it is, that's the amount of amps flowing into (charging) the 12V battery; it's always a positive number.
Why doesn't is every show the discharge from the 12V? e.g. when it's in accesory mode. It shows 0.00A
 
ebeighe said:
i've become fascinated with the 12V topic, as my 2017's OEM battery is presumably nearing the end of its life :)

question about Leafspy... when it says the current for the 12V is whatever it is, that's the amount of amps flowing into (charging) the 12V battery; it's always a positive number.
Why doesn't is every show the discharge from the 12V? e.g. when it's in accesory mode. It shows 0.00A

Yes, when LEAFSpy shows 12 V amps being positive, current is flowing into the 12V battery at the 12V buss voltage shown. (At least for my 2011 LEAF, but I believe that is correct for all model year LEAFs).

But the 12V amps is NOT always a positive number. If the 12V battery is fully charged, LEAFSpy has sometimes shown a negative value.

With regards to auxiliary mode, keep in mind that the LEAF has in some sense two different types of auxiliary mode. The true auxiliary mode is the initial button push of the START button that only energizes the 12 V buss. It does not fully activate the CANBUS. Note that in this mode LEAFSpy does not display 12V amps, as the 12V amp detection may not be available on the CANBUS. In the other quasi-auxiliarry mode that the LEAF goes into with a 2nd START button push without pressing the brake pedal, more of the CANBUS is active, and the 12V amps is displayed by LEAFSpy.

But in neither of these two auxiliary modes is the contactor of the high voltage battery closed. Therefore, the 12 V to 12 V DC converter is not powered with main pack high voltage in either of those LEAF modes. Therefore, for those modes the 12V battery amps will always be negative due to LEAF loads on the 12V buss.

I recommend strongly against leaving the LEAF in either auxiliarry mode for long. Both are a quick way to kill the 12V battery.
 
I had some minor issues. And the search around finally brought me here.
I will post my findings here, but also later I will start a new thread regarding my observations with this.

First a little summary over what happened to my swedish 2017 model, 30 kWh.

It started with FOB not working, needed to hold the key close to the start button in order to start up. And a message:
« When parked apply parking brake ».

Next day on my way to buy new batteries to FOB, I noticed that the rear light was blinking, and a new message in display:
« T/M system malfunction. Visit dealer.

After a little search I found out that last message was about the original Nissan/Renault 12V battery, and this is the error code for defect battery/low voltage.
Also there comes with a bunch of DTC, because of the 12V battery is defect/low voltage.
Battery voltage 11.5V
I am not going in on those DTC, they are all covered better in other threads. But of course they are not realistic, they only are there because of the 12V battery is defect/low voltage.

So I bought a new budget 62Ah 12V silver calcium battery (brand is Biltema), only one I could find the same day, and charged it up for 24H before I installed it in the car.
Everything was OK the next 4 days.
Until the whole round with blinking rear light and warning beeps and DTC when I was on my way out the 4 day in the morning.
Battery voltage 12.1V.

And here is when I am coming to the point. The 12V behavior.

I am working with lithium batteries, mostly LiFePO4, but also the other lithium battery chemistry.
And of course lead acid batteries.
So when I see this behavior in 4 days old battery I understood that something odd is going on here.

I charged it up again for 24H, and installed it. After clearing all the DTC, including taking off the minus pole some times and wait a couple of minutes, It all started over again when I parked after driving. Nor I could charge.

OK, since this happened because of the FOB batteries beeing low, and the old Leaf original 12V battery probably did not handle this blinking and power draw, and went out, it could not be water damage in the electronics because of bad sealing wind shield. I took a quick check and took down the dashboard and checked all connections and boxes, but all looked OK. Also swapped the start relay with the blower relay. Since one of the DTC mention that. They have the same part number.
Still the same.

I know that the 12V battery is the weak link on most EVs, so I decided to check out whats really happened while in use. Using a clamp A meter is not an option, I needed more meat on the bone, so to say...

So I build up a 12.8V 100Ah LiFePO4 battery with a 100A Bluetooth BMS (I reckon it can handle 150A peak)

So this built is living its life on the border here...

And here comes the important;
I can monitor Volt, A, temperature, SOC and other parameters with my cellphone and Bluetooth in real time.

Everyone is talking about voltage here, very few about A. Because that DCDC can really deliver high power.
And can the original (or any?) lead acid battery in this size take that power? No.
You cant blow in 110A charge to a lead acid battery with this Ah size. Or draw 55A out of it, again and again.

And that is what happening here. I have measured 110A charge on the most, and over 55A draw on the most. And I am very sure that there are higher numbers than that. Because I cant log these numbers in this specific BMS.

When Leaf is on charge on the small TYPE 2 charger at home, the 12V battery goes in a 4minute cycle. Its a power draw between 2.5-3A for around 4 minutes, before it pulses 3-5 times up to over 100A charge for maybe 15-20 seconds.
Counts down the charge 3-5 times, and it starts over again. I dont know for how long, but every time I check in, it continous.
I can not log this BMS.

When driving with AC on, it can draw around 25A, before it rapidly pulses up to 110A charge for max 10 seconds, before it goes back to anything between 0A or 55A draw, for then rapidly goes up in charge again.

That poor new 12V battery I bought never had an chance. (Not the original ones either...)
Shocked to an early death...


Spec sheet says max charge 15A on this new battery I bought. And that is very common on lead acid batteries of this size.
This was a budget battery, more expensive ones will hold much longer as we know.

But finally they have to give in they as well.

This battery build is just something I mixed rapidly together, looks ****, but its safe.
I have ordered some other lithium cells, because LiFePO4 can not be charged under 0 degree C without taking damage. :)





 
Welcome. You have an unusually high drain happening in the 12 volt system, and it may be going on when the car is Off as well. First, a few obvious questions - please forgive them.

* Are you using any sort of device plugged into the OBDII diagnostic port?

* Are you using Accessory mode with the car on or off?

* Are you leaving the car plugged in for long periods after charging has ended, or before charging begins?

AGM type lead acid batteries generally work well with the Leaf, as do lithium batteries, but a consistent high drain will kill those as well. You need to find that drain...
 
LeftieBiker said:
Welcome. You have an unusually high drain happening in the 12 volt system, and it may be going on when the car is Off as well.

Thanks for answering. :)
Well. Is this a drain?
This looks normale for me. Nothing happens when the car is off. Stone dead. I have full control with the SOC on the 12V battery on the Bluetooth BMS, and of course the SOC in the car.
I will order a log instrument, so I can catch up when the DCDC kicks in for the maintenance charge. And IF some strange things happens.
For me everything works as it should. I rather think this is normal, but if someone with exact same year model have other numbers regarding the power draw, and charge, please chime in here.
In fact, have anyone any numbers on this at all? On any years? I have only seen voltage numbers, and that is not so interesting any more.

This fits very well in the 12V problem. Big A numbers in and out takes out the battery.


First, a few obvious questions - please forgive them.

* Are you using any sort of device plugged into the OBDII diagnostic port?

* Are you using Accessory mode with the car on or off?

* Are you leaving the car plugged in for long periods after charging has ended, or before charging begins?

No on all answers. :)
 
BluetoothMonster said:
I had some minor issues. ...

Welcome. Thank you for the very informative post.

I also think you may have a bad high load on the 12V buss.

I agree with you that 100A charging of the 12V can be very bad.

But I do not think the LEAF has any means to control the current flow into the 12V.

When the windshield wipers are operating, the DC TO DC converter raises the 12V buss voltage to ~14.28V (There may be an adjustment with temperature. But that is what my 2011 did in recent summer temperatures.)

If the 12V is only somewhat depleted, current flow in will be like mine the other day at 20 amps.

But if the 12V is horribly depleted, such as if the car would not Start due to 12V buss voltage too low (my recollection is buss voltage must be above 10V for LEAF to even attempt to start) and you have jumped the LEAF off with another battery or charger with really high current capability; when that jump source is disconnected and the DC to DC converter raises the buss voltage to 14.28 V, a badly depleted 12V will draw 100 amps the maximum current output of the DC to DC converter on the LEAF. On two or three different occasions I watched it on LEAFSpy and would show 100A for five to eight minutes. Current would than gradually decline over another twenty or thirty minutes.

I agree that is not good.

But that is what it does.
 
Numerically, most Leafs seem to manage their 12 volt batteries at least tolerably well, although they tend to be too low on charge on average for it to be described as "well." Some Leafs have parasitic loads that cause problems, and others have drivers whose behaviors have a negative effect on the SOC of the 12 volt battery. Both together are also quite possible. If this were a serious design issue as the OP describes, then Nissan would have been forced, by enormous failure rates, to address it. Instead, the problem is just uncommon enough for Nissan to largely ignore it.
 
I have read (I think :lol: ) all the comments on this all over Internet last 14 days.

Only a few mentions what the DCDC is capable to do, namely go up to 135A, 1700W if I recall right what I have read. I am not sure in this number either, but that is all we have.
I have no problem beleving that the DCDC will give that to the poor lead acid battery. I have seen 110A charge in the BMS.

But everyone is concerned of the charge voltage. Yes of course, if the charge voltage is not high enough, on Leaf its not, it will be bad charging.
Lead acid battery like to have much higher charge voltage then what it get normally from Leaf, around 13.1V.
Thats not enough, that higher volt pulses that happens sometimes is to short to do anything.
You can have so much A you want, without the higher voltage it does not help.

So I am thinking that Leaf have at least two serious charge problems when it comes to the 12V battery;
1. To low voltage.
2. To high charge power.
Also combined with to high A draw when in use. And it seems like most of this comes in very rapidly pulses. Charge more then draw.
All this is a problem for a lead acid battery.
But not for a lithium pack. Infact, lithium loves this.


Could the Leaf be constructed for a 12V lithium battery in the first place?

There are lithium 12V battery solutions out there, Mercedes ICE have had it on some models for years.

I will build a bulletproof 10Ah lithihum pack that will need no BMS and can be charged down to -40°C without any problem.
Also it will handle the big pulses and higher voltage that can occure, I have seen 15.5V in the Leafspy Pro. But to be honest, I am very unsure on that reading due to the way it was read. Hastly during a drive in traffic.
But modern ICE cars do the 15.5V mark all the time. Some up to nearly 16V.

I am thinking that a premium or standard quality lead acid battery will handle this for a time, but not a long time.
And therfore we have this problems after a few years.

I am aware of the fact that the charge algorithme is different during the Leaf lifetime, also I have noticed that some with these battery problems have written something about a new firmware, when the dealer has changed the 12V battery. Sadly I have no information on what or if.
Does anyone know something about this?


I am open for a software glitch here, that can occure for some reason.

I will put out a video of this when I have time. Its quite interesting. It all make sense for me when I know that the 12V battery is up for it.
The DCDC follows the A draw, and pushes extra in when needed.
Lead acid hates that when it comes so rapidly, violently and high numbers, lithium loves it. :D

MERCEDES GT GTS C190 GTR A0009826205 LiOn 70AH
 
I agree, pumping that many amps into a smallish 12v lead acid battery can't be good. Keeping the float voltage that high is probably OK(although can tend to boil off the water in a flooded acid battery) but what you don't want is that high of a voltage when the battery is low, resulting in a very high current as noted. I suppose the DCDC circuit isn't smart enough to know it's pumping 100a into a load(such as accessories that might be on) vs overcharging the battery. Not sure how ICE vehicles with a higher output alternator handle this as they to could have the same potential......
One thing that would help is frequently topping off the 12v battery to keep it's nominal voltage as high as possible and therefore limit the amperage when the DCDC is trying to keep it's voltage high during driving.
I guess the Koreans(not sure if anyone other than Kia and Hyundai) could be onto something by dedicating a portion of the main Li traction battery to 12v and not having a separate 12v battery......in one way I'm not sure I'd like that as you can't really replace it but maybe it would never need replacing, well as long as the main traction battery stays good......not positive sharing of the main battery for 12v is still done but I now it has been done in the past.
 
BluetoothMonster said:
Lead acid hates that when it comes so rapidly, violently and high numbers, lithium loves it. :D
So are you trying to say that (EV) owners should replace their 12v lead-acid batteries with 12v Lithium? I completely agree (see sig)! Most folks just don't want to spend the $$...but after almost 9 years I think I've "got my money back".
 
BluetoothMonster said:
...
I have no problem beleving that the DCDC will give that to the poor lead acid battery. I have seen 110A charge in the BMS.

Yes, your 100A Lithium pack can accept a 1C charge easily enough because it has extremely low internal resistance.
...
So I am thinking that Leaf have at least two serious charge problems when it comes to the 12V battery;
1. To low voltage.
2. To high charge power. ...
Those two statements are contradictory. The only way for the DC/DC to control the current into the 12V battery is by regulating voltage.

I think you are drawing erroneous conclusions based upon your tests with a Lithium battery.
 
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