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

[BluetoothMonster]

I agree, pumping that many amps into a smallish 12v lead acid battery can't be good.
Truth!


Not sure how ICE vehicles with a higher output alternator handle this as they to could have the same potential......
Car manufactors never take out much higher A then the batteries can handle, using thinner cables from alternator in order to make the A low. You never se more then what the batteries can handle. In my case on my RV with 150A alternator, around 30A since I have two 100Ah lead acid start batteries. Infact, one of the things I am doing most on work, is to sell and install DCDC in order to juice up the RV batteribanks for custumers. And of course sell the LiFePO4 batteries. I have a 90A DCDC in my RV, feeding 600Ah LiFePO4.

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.
This is interesting. I think they are into something good here.

Lead acid hates that when it comes so rapidly, violently and high numbers, lithium loves it.

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".
I think you have been clever!

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

And on the other 21 pages here there are not any errouneous conclusions? :roll:

All I can say is that this works now. Did not before. I would love if someone with the same year model could measure the A draw when charged like I have described.
Of course we need more input on this before its valid, but I find it very strange if the software for some reason suddenly should go into this behave, doing like it does now. We know for sure that Leaf have a 12V batterproblem now, very many of the earlier statements about this in the start is clearly wrong.

It seems for me that the voltage has been the big issue here in this discussion, and not A that blows internally this small lead acid batteries.

This thread need a new angle on things, and you are not coming with any useful information right now.

 

[Nubo]

...
This thread need a new angle on things, and you are not coming with any useful information right now.

I gave you some simple facts. Whether or not you find them useful is up to you.

 

[BluetoothMonster]

When my wife still had her Lead Acid battery, I would watch it easily plow +100 amps of power into that thing when the voltage got down below the 11 volt range.
I did not notice this one before now, this confirms my findings. Can you please tell us a little more if you can? Year model and if you have more info about this? I guess the poor lead acid battery had enough A at this voltage, and simply could not handle the higher voltage at the same time with this insane charge rate.

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 can not understand anything else. I work with lithium batteries. A 12V lithium battery is the best match for the DCDC in a Leaf.
But be aware of one thing, It really should handle voltage up to 16V without closing down the BMS. Most ready to go 12.8V LiFePO4 batteries has a upper limit around max 15V before shutdown.
On the other hand it shuts down only the charge, so very unsure if this will affect anything at all really...
I have cranked up the cell parameters in the BMS to 4V each, making 16V total before BMS shuts down on my test LiFePO4 pack. Also it have protection cold and warm and max/min A.
But before its start to be cold here in the North, I will have installed the permanent lithiumpack that withstand almost whatever, without a BMS.

I have noticed another thing, I can not confirm this for sure yet, that this is connected.
No more stiff/sluggish/bad/strange brakes after the battery swap.
At this point this is observation is not worth anything. But if it continues...

 

[knightmb]

Sorry, the quote blocks got confusing, had to re-arrange them...

When my wife still had her Lead Acid battery, I would watch it easily plow +100 amps of power into that thing when the voltage got down below the 11 volt range.

I did not notice this one before now, this confirms my findings. Can you please tell us a little more if you can? Year model and if you have more info about this? I guess the poor lead acid battery had enough A at this voltage, and simply could not handle the higher voltage at the same time with this insane charge rate.

She has a 2018 Leaf, when at the time, the factory FLA battery was still installed. I actually still have the battery in storage just in case as it's not useless, just low capacity now or for future testing. I changed out her battery with Lithium before it became a problem, but the first issue I noticed was during the fall/winter time the "lights" in the cabin would be dim before she turned on the Leaf. In all the +8 years of using my Lithium 12V in my Leaf, the cabin lights were always bright no matter the temperature outside.

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 can not understand anything else. I work with lithium batteries. A 12V lithium battery is the best match for the DCDC in a Leaf.
But be aware of one thing, It really should handle voltage up to 16V without closing down the BMS. Most ready to go 12.8V LiFePO4 batteries has a upper limit around max 15V before shutdown.
On the other hand it shuts down only the charge, so very unsure if this will affect anything at all really...
I have cranked up the cell parameters in the BMS to 4V each, making 16V total before BMS shuts down on my test LiFePO4 pack. Also it have protection cold and warm and max/min A.
But before its start to be cold here in the North, I will have installed the permanent lithiumpack that withstand almost whatever, without a BMS.

I have noticed another thing, I can not confirm this for sure yet, that this is connected.
No more stiff/sluggish/bad/strange brakes after the battery swap.
At this point this is observation is not worth anything. But if it continues...

I wouldn't recommend this as I did it by accident one time, but the "open" voltage of the DC to DC for the Leaf is 15 V. I was doing some 12V battery test on my wife's Leaf and I had meters and all kinds of clips connected up to do some testing when the battery lead clip fell off the connectors and I saw the voltage jump up to 15V instantly (didn't kill the Leaf though, interesting) but I was able to reconnect it quickly so I don't know if you can drive a Leaf without any 12V battery or not after it's started. Having the positive and negative connectors hanging around in the battery compartment would be a fire hazard if the positive somehow touched the ground anywhere.

 

[BluetoothMonster]

She has a 2018 Leaf.
Thanks!
This is confirming what I say about to high A and damaging the lead acid battery.



I wouldn't recommend this as I did it by accident one time, but the "open" voltage of the DC to DC for the Leaf is 15 V.

Modern cars will without any problem take 15.5V, even that budget 12V battery I bought and blow now recently would take max 16V it said.
Thats becuase of the insane smart alternators, going from anywhere between 10.5V and nearly 16V. :twisted:
I think the Leaf also will be the same regarding to the max voltage.

We have no measurements on the older Leaf that I have found. I think that, besides the low charge voltage problematic, they to cranks up the charge power to insane levels, anything else would be strange.

I have read something more about the software upgrade I have mentioned, and it seems like that is regarding the first years, and adds/changes? 12V charge when charging the traction battery. This is only what I have read, no documention.
Also found a Youtube commenter who owns a 2018 Leaf that confirms the same high charge power as knightmb mentions.

For me this is clear:
This high A draw and charge behavior is normal in a Leaf, and kills the 12V batteries rapidly.
The different years can have different A numbers on this.
The better battery you have, the longer it takes, but your new 12V lead acid battery is doomed before you install it. :idea:

 

[LeftieBiker]

My first one, in my 2013, was still there when I turned the car in after 5 years.

 

[Nubo]

I think that, besides the low charge voltage problematic, they to cranks up the charge power to insane levels, anything else would be strange.

Electricity simply does not work this way. "Charge power" (i.e. current) is determined by the voltage. The only way to apply more charge current to a given battery is to increase the applied voltage. The DC/DC converter (or alternator for that matter) cannot "push" more current into the battery by any other method. You cannot have "low charge voltage" AND "insane charge power levels" at the same time.

Also, can you please stop abusing bold text?

 

[BluetoothMonster]

My first one, in my 2013, was still there when I turned the car in after 5 years.

Sadly that does not mean anything in this discussion.
Most of the EVs have problems with the 12V battery, just do a search.
On the Leaf low charge voltage and to high A seems to be the problem.
And I cant really understand this thread.
You have used several years and 22 pages arguing on a volt discussion, there only the few have been into what the real issue is. And it seems like some wants to argue more. I am not into that.

To you all: Show me a spec sheet that says that an normal automotive lead acid battery on this size can be charged with these high numbers.

The expensive 100Ah AGM batteries I swap out on work have an absolute max on 0.3C. Thats 30A.
And thats max, recommended is 0.1C, 10A charge for a normal life expectancy.
And this is the top of the line AGM. The best.
And as we all know, the original Leaf 12V batteri is 50Ah, and I do not think max there is 0.3C. This is a much cheaper battery compared to an AGM.
I have not found any data sheet on it.

Also, can you please stop abusing bold text?
I write the way I want. If you dont like that, go elsewhere in order to get annoyed.

 

[LeftieBiker]

And it seems like some wants to argue more. I am not into that.

It may not seem that way to you, but you are in fact going beyond youthful enthusiasm and into Righteous Fervor. Your point about high amperages is taken, but you dismiss all previous discussion of the subject because it doesn't fit with your current (heh) passion about amperage. Voltage is discussed so much because diagnosing charging issues would be difficult to do without talking about it. In your skimming of the subject you seem to have missed the discussions about phantom drains - which are tracked down by measuring amperage, not voltage. You also dismiss, with a wave of the hand, the success experienced by people who switch to AGM batteries and to lithium batteries. If all that mattered was ability to handle higher amperage, then neither AGM batteries nor smaller capacity lithium batteries would work. The fact that they usually DO work should suggest to you that perhaps looking at the problem solely from the perspective of managing high amperage loads isn't going to yield a full solution.

Please, be a bit more civil.

 

[Nubo]

Also, can you please stop abusing bold text?
I write the way I want. If you dont like that, go elsewhere in order to get annoyed.
And, you keep inserting your bolded statements into what are supposed to be quotes of what others have posted. Can you see the problem?

 

[BluetoothMonster]

And it seems like some wants to argue more. I am not into that.

It may not seem that way to you, but you are in fact going beyond youthful enthusiasm and into Righteous Fervor. Your point about high amperages is taken, but you dismiss all previous discussion of the subject because it doesn't fit with your current (heh) passion about amperage. Voltage is discussed so much because diagnosing charging issues would be difficult to do without talking about it. In your skimming of the subject you seem to have missed the discussions about phantom drains - which are tracked down by measuring amperage, not voltage. You also dismiss, with a wave of the hand, the success experienced by people who switch to AGM batteries and to lithium batteries. If all that mattered was ability to handle higher amperage, then neither AGM batteries nor smaller capacity lithium batteries would work. The fact that they usually DO work should suggest to you that perhaps looking at the problem solely from the perspective of managing high amperage loads isn't going to yield a full solution.

Please, be a bit more civil.

All I can say is that the numbers are what they are.
And look back at your first answer, clearly totally wrong, based on what have been discussed in this vacuum chamber I guess. But will you ever admit it?

Next update from me will be a video and the new lithium battery. (if not someone who clearly hates to be wrong ban me from this group, then it will be some other place.)

 

[LeftieBiker]

And look back at your first answer, clearly totally wrong, based on what have been discussed in this vacuum chamber I guess. But will you ever admit it?

I suggested that you have an abnormal, high drain on your battery. Unless I missed it, you never addressed that, instead building a high capacity lithium battery to at least mask the problem. If all Leafs needed a 100AH lithium 12 volt battery to function properly, then I'd be pretty busy with the volume of posts about it. Anyway, there are several people here who are quite capable of addressing your concerns, so I'm going to enjoy the lovely weather here. If I receive complaints about hostile posts, I can always return to this topic. Enjoy the site, and please try to be civil.

 

[coulomb]

You cannot have "low charge voltage" AND "insane charge power levels" at the same time.

True, but the issue could be that the target voltage is too low (13.xV) for too much of the time (needs to be 14.xV for longer), but when it does decide to go to the higher voltage, it ramps up too fast, and with the powerful DC-DC, this could push quite high current into the battery.

I only have experience with a 2012 Leaf, and it seems to ramp up the voltage fairly slowly, over about 10-15 seconds. I haven't measured the resulting charge current, but at a wild guess, that seems slow enough to me to keep the charge current reasonable. But maybe later models ramp up faster.

Edit: Ideally, and perhaps in fact, the voltage should be ramped at a speed that is adjusted to keep the charge current at a fixed, reasonable value. So a weak battery with higher internal resistance would be voltage ramped faster than a strong battery. They do measure the battery current, so I hope that's actually how it works.

 

[LeftieBiker]

I have a little voltmeter in the 12 volt accessory socket of my '21. The voltage ramps up slowly, increasing every few seconds. No fire hose of electrons being dumped into the 12 volt battery.

 

[Nubo]

You cannot have "low charge voltage" AND "insane charge power levels" at the same time.

True, but the issue could be that the target voltage is too low (13.xV) for too much of the time (needs to be 14.xV for longer), but when it does decide to go to the higher voltage, it ramps up too fast, and with the powerful DC-DC, this could push quite high current into the battery. ...

I'm unfamiliar with this. Can you point me to a source that explains how voltage ramp rate affects charging current of lead-acid batteries?

 

[coulomb]

Can you point me to a source that explains how voltage ramp rate affects charging current of lead-acid batteries?

Sorry, no. I keep getting PV ramp rate hits for large solar farms when I search.

A battery is a little bit like a giant capacitor, as long as you don't vary the voltage too much. Over the range of 12-14 V, the capacitor model isn't too bad.

Think of a 50 Ah 12 V battery discharging from 13.0 to 12.0 V at 50 A for 1h (3600s). So that's dV/dt = 1/3600 V/s.

I = C. dV/dt

C = I / dV/ft = 50 / (1/3600) = 180 kF. That's 180,000 farads; I did say giant.

Now suppose that you take that capacitor from 12 V to 14 V in 2 seconds. That's 1 V/s.

I = C. dV/dt = 180,000 x 1 = 180 kA. Obviously, the battery's internal resistance will be way too high to allow anything like that sort of current, and of course the DC-DC is limited to something like 125 A, but you get the idea. A slower ramp will allow the voltage of the battery (the battery's back EMF, if you like) to catch up and rise with the DC-DC's applied voltage, so that there will be less voltage difference across the internal resistance of the battery, and hence less charge current.

But now that I type this, I realise that the state of charge of the battery, and hence its voltage, won't change significantly in the ~10 seconds ramp of the voltage. I guess that the voltage ramp must be to allow a bit of time for the chemical reactions to translate into a voltage change. When you apply a significant charge current to a lead-acid battery, it does seem to take a few seconds for the voltage to rise, after the initial instant rise due to the internal resistance. So if that voltage ramp is too fast, the terminal voltage of the battery hasn't had time to rise much, so there could be of the order of a volt across the internal resistance of the battery: battery at 13.0 V, ramping to 14.0 V, that's one volt dropped across the internal resistance, A decent ~50 Ah lead acid battery should have an internal resistance of the order of 10 milliohms (0.01 ohm), so that one volt could translate to of the order of 100 A. Eventually the battery voltage will rise to say 13.9 V, so that the charge current becomes a much more modest 0.1/0.01 = 10 A.

Edit: So I'll admit that my "too fast voltage ramp" theory is looking a bit shaky.

 

[LeftieBiker]

I've been watching this "feature" of Nissan for quite a few years now, and I don't recall seeing ANY batteries getting cooked by the charging system. Plenty of evidence for the opposite, but I'm pretty skeptical that our Leafs are compensating for too little charging voltage with too much charging amperage. I have no doubt that it's possible in isolated cases, but it just doesn't fit with the vast majority of the complaints I've seen here.

 

[GerryAZ]

The LEAF's DC-DC converter is just a temperature-compensated, dual mode, constant voltage charger. The output voltage is about 14 volts until the absorption current of the 12V battery drops below the threshold current (temperature and current are measured by the sensor at the negative battery terminal). The float voltage is about 13 volts after the absorption current drops below the threshold. Based upon measurements on my cars, threshold current was 6-8 amperes for the 2011; 4-6 amperes for 2015; and 2-4 amperes for 2019. The output voltage can vary by +/- 0.5 volts depending upon temperature.

The Nissan OEM flooded cell batteries have relatively high internal resistance while AGM batteries have relatively low internal resistance. Therefore, discharged AGM batteries will absorb higher charging currents when the car is turned on or plugged in than discharged OEM flooded cell batteries. Charging currents will drop off for either battery type as internal voltage increases (state of charge increases).

FWIW, the OEM batteries in each of my LEAF's lasted longer than typical for OEM car batteries in Phoenix. Also, I have never connected an external charger--the DC-DC converter keeps the 12V battery adequately charged with my typical driving/charging pattern.

 

[coulomb]

Based upon measurements on my cars, threshold current was 6-8 amperes for the 2011; 4-6 amperes for 2015; and 2-4 amperes for 2019.

Thanks, GerryAZ; great post. It sounds like doubling the 2011's shunt resistance might improve battery charging (so the 6-8 A threshold becomes in reality a 3-4 A threshold), but of course there could be serious side effects from this. In particular, when the DC-DC thinks it's charging at 50 A, it's really charging at 25 A, so it might cut back the charge current needlessly. I hope and assume that it limits the maximum charging current to a value that is comfortable for the provided flooded lead-acid battery.

I don't suppose you've noticed the criteria for returning to absorb stage, apart from when the windscreen wipers come on?

 

[GerryAZ]

Based upon measurements on my cars, threshold current was 6-8 amperes for the 2011; 4-6 amperes for 2015; and 2-4 amperes for 2019.

Thanks, GerryAZ; great post. It sounds like doubling the 2011's shunt resistance might improve battery charging (so the 6-8 A threshold becomes in reality a 3-4 A threshold), but of course there could be serious side effects from this. In particular, when the DC-DC thinks it's charging at 50 A, it's really charging at 25 A, so it might cut back the charge current needlessly. I hope and assume that it limits the maximum charging current to a value that is comfortable for the provided flooded lead-acid battery.

I don't suppose you've noticed the criteria for returning to absorb stage, apart from when the windscreen wipers come on?

I am not sure what you mean about shunt resistance. The Hall-Effect sensor measures actual current into the 12V battery and the DC-DC converter drops to float voltage when the current drops below the threshold. I have never seen the charging voltage increase back up to absorption level without turning the car off and back on or turning on the windshield wipers.