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

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Jedlacks said:
BatteryMINDer 1500 along with the ring terminal assembly.

Would plugging my 12v into a BatteryMINDer overnight once a week be sufficient? Or would I need to do it overnight more often than that? I wouldn't ever really be able to do more a longer contiguous stretch than overnight.
 
It depends on several factors. Driving patterns, output of maintainer, and even the year Leaf. Overnight once a week will probably suffice. If you see the battery still isn't full in the morning, you'll know you have a problem.
 
LeftieBiker said:
If you see the battery still isn't full in the morning, you'll know you have a problem.

How do you see that? So far, the only way I can tell is my car doesn't work and I have to call a tow truck.
 
Most battery maintainers have at least one color changing LED. Red means bulk charging, flashing green or yellow means the lower finishing charge, and solid green means the charge is complete. I was talking about what you would see after charging for the night with a maintainer. If it hasn't finished charging the battery back to full by morning, then the drain is too large.
 
Don't mean to resurrect an old thread, but now that I too am dealing with this concern, I'm wondering what came of fooling the current sensor?

Will replacing the battery with standard replacement allow another 5yr? Reason I ask is, I just replaced my TCU and expect that it will have a higher load while sleeping.
 
Does anyone one for sure when the 12V charging algorithm was changed/improved/corrected? Ie: from what years of production is 12V charging a non-issue? 2014? 2015?

(I'm not asking about the telematics battery drain issue - just the 12V charging - thanks!)

Best,
Tal
 
I know this is an old thread but I couldn't find a better generic 12V battery thread. Maybe there should be one.

Anyway.....I tried to start my Leaf today for the first time in about a week and 'click click'. There were a few lights on the dash but it was obvious my 12V battery was low. Measured the voltage and found it was at 7.6V :eek: WTF. It had sat for about a week but I've never had an issue with it before and the battery is only 4 years old. Then I remembered that yesterday we had family over and my wife's aunt (90 years old) was inside the car when we were playing hide and go seek (there were kids involved too ;) ). I have to assume the door was left open and I'm hoping if I charge the battery it will be fine but that it is pretty low and I'm not sure it will come back, even if it's only been at a low voltage for 24 hours.

After charging the battery for a few minutes I could get the car into N but not D or R. Lots of funny behavior when the 12V is low. I'm going to charge it for 24 hours or so and see if it's OK then. If not, I'll have to decide on a replacement battery.
 
I'm hoping if I charge the battery it will be fine but that it is pretty low and I'm not sure it will come back, even if it's only been at a low voltage for 24 hours.

Replace it. Even if it does 'come back', it will have a small fraction of the capacity it had before dying. The only time you can really rescue a 12 volt battery that gets too low to start a Leaf is by acting immediately to charge it, and even then it will only work if the voltage stayed above about 10 volts. And even in the best of those conditions, the odds are still about 50/50.
 
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
 
goldbrick said:
I know this is an old thread but I couldn't find a better generic 12V battery thread. Maybe there should be one.

Anyway.....I tried to start my Leaf today for the first time in about a week and 'click click'. There were a few lights on the dash but it was obvious my 12V battery was low. Measured the voltage and found it was at 7.6V :eek: WTF. It had sat for about a week but I've never had an issue with it before and the battery is only 4 years old. Then I remembered that yesterday we had family over and my wife's aunt (90 years old) was inside the car when we were playing hide and go seek (there were kids involved too ;) ). I have to assume the door was left open and I'm hoping if I charge the battery it will be fine but that it is pretty low and I'm not sure it will come back, even if it's only been at a low voltage for 24 hours.

After charging the battery for a few minutes I could get the car into N but not D or R. Lots of funny behavior when the 12V is low. I'm going to charge it for 24 hours or so and see if it's OK then. If not, I'll have to decide on a replacement battery.

So the LEAF will boost the 12 volt regularly ALL the time. The only variable is how much power is used between those boosts. This is where crazy ideas like "don't leave it plugged in or the 12 volt will die" theories come in.

MANY people have parked for several days, weeks even w/o issue. The car spent all its time in minimal power mode. I had my car at the airport 22, 15, and 11 days w/o issue. IOW; under the BEST of circumstances, the charging algorithm is sufficient.

But that is the issue. The algorithm never fully charges the 12 volt so its basically barely hanging on to a questionably acceptable state of charge. This means any "extracurricular" activity can (and frequently does) lowers the SOC to a point where the traction battery is unable to connect to start the boosting process.

On the "don't leave it plugged in" issue. Leaving the car plugged in means the car is constantly checking for power, checking SOC of pack, etc. All this is an additional load the charging algorithm apparently does not account for.

Other times when the car is simply sitting in the garage on a long weekend probably has to do with the random proximity of the fob.
 
knightmb said:
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
While I agree a Lithium 12v battery is probably the way to go in warmer climates, if the cost is OK with you, in colder climates, the OP lives in CO, I think an AGM battery is probably the best comprimise. Lithium batteries don't like extreme cold, by extreme, I mean low single digits or below zero F. A lithium works OK in EVs for the traction battery in cold climates because it has enough capacity to actually use the battery to heat itself for shorter periods of time but a 12v battery just doesn't have the capacity and I don't believe any 12v batteries would have a built-in heater and even if they did, it would kill the battery after not too long of running the heater.
Personally, I think a decent 51R AGM battery is the best for climates where the temps get below zero.
 
I have to disagree, Lithium is the better choice for colder climates if your budget allows for it and you plan on keeping the Leaf for a long time, like you bought nearly brand new for example. As others here will will probably post, AGM is far superior to Lead Acid for battery life because it can handle not being fully charged all the time and thus doesn't lose capacity as quickly as the Lead Acid. When it comes to colder climate, Lithium holds capacity much better than AGM or Lead Acid, which is what you need to start the Leaf, but has a lower limit. If you live in a location where the temperature can get below -40F/C frequently, AGM is the best option as that is the limit of Lithium. Single digit temperatures for weeks though, from my own experience, has no effect on the Lithium, works just fine and always starts the Leaf right away. The Leaf charging algorithm does not provide much power to the 12V battery if the voltage is high all the time, thus for Lithium, keeps it from being overloaded with current in cold weather since it can still hold +13V in even the coldest of times. Before I changed out the 12V battery in my wife's Leaf (2018), I took her 12 V battery to Nissan and a local auto store to test the battery. Both of them said it was just fine via their own testing machines, but those are testing for a gas vehicle, not an EV. Doing a simple drain test, you can see from the video that the voltage drops a lot, even when putting a +160 watt load on it (which is still less than the power it takes to just turn on the Leaf), so this Lead Acid battery, while it "looks" like it is fine, is actually way below it's 36 AH rating in capacity and thus would probably leave my wife stranded in cold weather trying to start her Leaf. We don't live in a location of extreme cold, actually can get quite hot here and the Lead Acid still has given a slow death.

Budget aside, if you live in a place where temperatures frequently get below -40F/C then, I agree, Lead is the only thing that can safety work in those temperatures. If you live anywhere else, even if in a colder climate, but not that cold, Lithium can still work just fine. Budget though will reign though, just so people understand that if you go the cheap route (Lead Acid), be prepared to replace it every few years like my wife did. AGM will buy you a lot more time, just a better battery technology. I don't know what the time limit is on AGM, some other's here will have a better idea. Lithium will work for at least 7 years in climates that are above 0F (-17C) in my experience, would have to wait for someone from a colder climate to post their Lithium results to get a better idea.

https://www.youtube.com/watch?v=mRk4TvITjdQ

jjeff said:
knightmb said:
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
While I agree a Lithium 12v battery is probably the way to go in warmer climates, if the cost is OK with you, in colder climates, the OP lives in CO, I think an AGM battery is probably the best comprimise. Lithium batteries don't like extreme cold, by extreme, I mean low single digits or below zero F. A lithium works OK in EVs for the traction battery in cold climates because it has enough capacity to actually use the battery to heat itself for shorter periods of time but a 12v battery just doesn't have the capacity and I don't believe any 12v batteries would have a built-in heater and even if they did, it would kill the battery after not too long of running the heater.
Personally, I think a decent 51R AGM battery is the best for climates where the temps get below zero.
 
So the LEAF will boost the 12 volt regularly ALL the time. The only variable is how much power is used between those boosts. This is where crazy ideas like "don't leave it plugged in or the 12 volt will die" theories come in.

Dave, please don't post nonsense as advice. You then followed this up with an explanation of exactly why you shouldn't leave a Leaf plugged in for long periods after charging. (See below.) There is nothing "crazy" about telling people to avoid a dead 12 volt battery.

The algorithm never fully charges the 12 volt so its basically barely hanging on to a questionably acceptable state of charge. This means any "extracurricular" activity can (and frequently does) lowers the SOC to a point where the traction battery is unable to connect to start the boosting process.

On the "don't leave it plugged in" issue. Leaving the car plugged in means the car is constantly checking for power, checking SOC of pack, etc. All this is an additional load the charging algorithm apparently does not account for.

I'm also going to disagree on the SOC theory above. When my 2013 Leaf's 12 volt battery had a near-death experience, it wasn't low on charge. We've had others post here that the 12 volt battery died when the SOC was fine because they had charged the car before leaving it plugged in.
 
knightmb said:
I have to disagree, Lithium is the better choice for colder climates if your budget allows for it and you plan on keeping the Leaf for a long time, like you bought nearly brand new for example. As others here will will probably post, AGM is far superior to Lead Acid for battery life because it can handle not being fully charged all the time and thus doesn't lose capacity as quickly as the Lead Acid. When it comes to colder climate, Lithium holds capacity much better than AGM or Lead Acid, which is what you need to start the Leaf, but has a lower limit. If you live in a location where the temperature can get below -40F/C frequently, AGM is the best option as that is the limit of Lithium. Single digit temperatures for weeks though, from my own experience, has no effect on the Lithium, works just fine and always starts the Leaf right away. The Leaf charging algorithm does not provide much power to the 12V battery if the voltage is high all the time, thus for Lithium, keeps it from being overloaded with current in cold weather since it can still hold +13V in even the coldest of times. Before I changed out the 12V battery in my wife's Leaf (2018), I took her 12 V battery to Nissan and a local auto store to test the battery. Both of them said it was just fine via their own testing machines, but those are testing for a gas vehicle, not an EV. Doing a simple drain test, you can see from the video that the voltage drops a lot, even when putting a +160 watt load on it (which is still less than the power it takes to just turn on the Leaf), so this Lead Acid battery, while it "looks" like it is fine, is actually way below it's 36 AH rating in capacity and thus would probably leave my wife stranded in cold weather trying to start her Leaf. We don't live in a location of extreme cold, actually can get quite hot here and the Lead Acid still has given a slow death.

Budget aside, if you live in a place where temperatures frequently get below -40F/C then, I agree, Lead is the only thing that can safety work in those temperatures. If you live anywhere else, even if in a colder climate, but not that cold, Lithium can still work just fine. Budget though will reign though, just so people understand that if you go the cheap route (Lead Acid), be prepared to replace it every few years like my wife did. AGM will buy you a lot more time, just a better battery technology. I don't know what the time limit is on AGM, some other's here will have a better idea. Lithium will work for at least 7 years in climates that are above 0F (-17C) in my experience, would have to wait for someone from a colder climate to post their Lithium results to get a better idea.

https://www.youtube.com/watch?v=mRk4TvITjdQ

jjeff said:
knightmb said:
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
While I agree a Lithium 12v battery is probably the way to go in warmer climates, if the cost is OK with you, in colder climates, the OP lives in CO, I think an AGM battery is probably the best comprimise. Lithium batteries don't like extreme cold, by extreme, I mean low single digits or below zero F. A lithium works OK in EVs for the traction battery in cold climates because it has enough capacity to actually use the battery to heat itself for shorter periods of time but a 12v battery just doesn't have the capacity and I don't believe any 12v batteries would have a built-in heater and even if they did, it would kill the battery after not too long of running the heater.
Personally, I think a decent 51R AGM battery is the best for climates where the temps get below zero.
I don't know the exact temp that Lithiums don't like but I thought it was around 0F, which would make sense as thats the temp that our Leafs start heating the battery but as in the winter we frequently get below zero I was told a 12v lithium might not be the best choice. Now if it's -40c I could live with that as it's been years since it's gotten that cold in my area but does happen regularly in the iron range of MN.
 
Lithium batteries do function ok down to somewhere near -40. It's charging them in frigid temps that is dangerous. The general recommendation for small lithium batteries is that charging not be done when the temperature (or temp of the battery) is below freezing. That's +32F. I'd want to see documentation on the safety of those 12 volt lithium batteries when charged at double negative temps. Until them I'm recommending AGM batteries. I'd likely even do that anyway, as they function well for much less money than a lithium car battery.
 
knightmb said:
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
I agree...and I can't believe how much "air time" the 12v battery discussion gets.
I have had the same LiFePO4 battery in my Leaf for over 7 years now (see sig), so I "put my money where my mouth is" when I tell folks to go 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).
 
Stanton said:
knightmb said:
15 minutes of lights shouldn't kill the battery, just means it is failing, replace it to your budget allocation. Lead acid for cheap, AGM for long term use, Lithium forever use. :)
I agree...and I can't believe how much "air time" the 12v battery discussion gets.
I have had the same LiFePO4 battery in my Leaf for over 7 years now (see sig), so I "put my money where my mouth is" when I tell folks to go 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).

Thanks, I knew someone else here also had a lithium 12V besides me :D I replaced mine in 2015 for my 2013 SV Leaf, when I traded it in for 2020 Leaf this year, I moved the battery from the old Leaf to the New One and put my Lead Acid battery in storage with a maintainer (hey, never know when I might need it). I did take the time to do a full capacity test on a 6 year old 12V Lithium by charging it all the way up and doing a very slow drain test over hours and measured the energy output. My 6 year old 12V Lithium which is rated at 20AH (or 12.8x20 = 256 watt hours) still came in within 95% of rated capacity after a full discharge (19.0 AH). So both my 2013 and current 2020 Leaf have not managed to kill it yet. The long life of my lithium I suspect is because the battery is only ever charged to +86% capacity by the Leaf due to the difference in full charge voltage levels of the Lead vs Lithium. Lead is fully charged when it reaches 14 volts, Lithium is fully charged at 14.6 volts but never reaches that if you measure the voltage yourself and watch it.
 
LeftieBiker said:
Lithium batteries do function ok down to somewhere near -40. It's charging them in frigid temps that is dangerous. The general recommendation for small lithium batteries is that charging not be done when the temperature (or temp of the battery) is below freezing. That's +32F. I'd want to see documentation on the safety of those 12 volt lithium batteries when charged at double negative temps. Until them I'm recommending AGM batteries. I'd likely even do that anyway, as they function well for much less money than a lithium car battery.

I can agree with your statement fully, I don't know how well the battery I use or others here have used will work when temperatures get below 0F because I have no experience with it. I would also recommend the Lead path for those areas, better safe than sorry. I do know from my own measurements when watching the charging behavior of the Leaf on the 12 volt system that the lower the voltage, the more power it plows into the battery. Since the Lithium sits at a high voltage all the time, I suspect that is why it only seems to trickle charge power into the battery. 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. Just like an alternator in a gas vehicle would do after you start it, the Lead battery is more at home to give out a large amount of power to start the car and take in a large amount of power to recharge back and be ready for the next time. 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. :?
 
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