How to Quickly & Simply Charge a Leaf’s Weak 12 Volt Battery

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lorenfb

Well-known member
Joined
Dec 17, 2013
Messages
2,683
Location
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Some Leaf owners have experienced the condition where the 12V battery was weak preventing
the Leaf from “starting”, requiring a jumper 12V battery. This problematic 12V battery condition
may occur if the Leaf has not been driven or connected to an EVSE for a number of days/weeks,
or when the 12V battery nears its end of life.

Obviously one can always connect an external 12V charger, but occasions may occur where an external
charging source is not available. Typically Leaf1 & Leaf2 charge the 12V battery while in the “run” mode
to 12.9/13.1 volts, which is not very effective when the 12V battery is weak or has prevented the Leaf
from “starting”. Although when the Leaf is initially started, the 12V battery is typically charged to about
14.2 volts for about a minute.

Under a unique condition, i.e. the windshield wipers being on, the Leaf’s 12V battery charges to about 14.2V
as long as the wipers are on. By using the wipers in the intermittent mode with delay being the longest,
the 12V charging voltage will be continuously at about 14.2V. With just one momentary activation
of the wipers, the 12V battery will be charged at about 14.2V for about one minute. So, leaving the
wipers on with longest delay will continuously charge the 12V battery to about 14.2V without
having the wipers fully on. It is unknown whether this Leaf function is documented in any Nissan info,
so some might consider it a software “easter-egg”.

After having posted this on MNL shortly after leasing my 2013 Leaf, I never really thought of a use
until today when 2013 Leaf had not been driven in over a week and the door button unlocking function
appeared to not function. After a few tries, the door unlocked and I was able to "start" the Leaf.
After remembering the feature I had discovered, I decided to leave the wipers in the delayed mode
as I drove for about 30 minutes to assure that the 12V battery received an adequate charge.
 
If the 12V battery is low so that it will absorb charging current, then the DC-DC converter will charge at between 14 and 14.5 volts until the current flowing into the battery drops below a threshold (indicating that the battery is fairly well charged) so there is no advantage to running the wipers. The DC-DC converter will charge the 12V battery when the car is in run mode and also when the car is actively charging the traction battery. The 12V is not charged when the car is plugged in but not actually charging.
 
GerryAZ said:
If the 12V battery is low so that it will absorb charging current, then the DC-DC converter will charge at between 14 and 14.5 volts until the current flowing into the battery drops below a threshold (indicating that the battery is fairly well charged) so there is no advantage to running the wipers.
That's definitely not been my experience with a 2012. Either the current threshold is too high, or it just assumes that a few minutes of over-14V charging should fill the auxiliary battery.

My understanding is that later models behave better, but are still not ideal.
 
I have one of those Antigravity Battery Tracker devices on my 12v...and it shows that the charge level "spikes" to 14v every 15 minutes (or so). You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain. Those of you who follow my 12v Lithium thread know that I'm way past 5 years on mine with no issues (and no special treatment).
 
Stanton said:
I have one of those Antigravity Battery Tracker devices on my 12v...and it shows that the charge level "spikes" to 14v every 15 minutes (or so). You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain. Those of you who follow my 12v Lithium thread know that I'm way past 5 years on mine with no issues (and no special treatment).

Interesting. I am guessing this only happens when car is running? How long do these spikes last?
 
DaveinOlyWA said:
Stanton said:
I have one of those Antigravity Battery Tracker devices on my 12v...and it shows that the charge level "spikes" to 14v every 15 minutes (or so). You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain. Those of you who follow my 12v Lithium thread know that I'm way past 5 years on mine with no issues (and no special treatment).

Interesting. I am guessing this only happens when car is running? How long do these spikes last?

That's what's key!
 
GerryAZ said:
If the 12V battery is low so that it will absorb charging current, then the DC-DC converter will charge at between 14 and 14.5 volts until the current flowing into the battery drops below a threshold (indicating that the battery is fairly well charged) so there is no advantage to running the wipers.

Do you know what this actual value is?

GerryAZ said:
The DC-DC converter will charge the 12V battery when the car is in run mode and also when the car is actively charging the traction battery. The 12V is not charged when the car is plugged in but not actually charging.

Most are aware of this, and it isn't the issue.
 
The threshold level depends upon the model year, but is less than 10 amperes on 2011 and lower on later models. I have never connected an external charger to any of my LEAFs. I saw sustained charging current of about 80 amperes while driving home from my office after the battery in the 2011 was completely discharged because I left the Bluetooth adapter plugged into the OBDII port and the Android device running Leaf Spy on the passenger seat while parked for 6 days. I used some test leads to "jump start" the Leaf from my office vehicle and drove home without issue.
 
You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain.

Lead acid batteries will last just fine, as long as they don't get and stay discharged too low. They are designed for constant use, albeit in a fairly narrow charge range.
 
LeftieBiker said:
You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain.

Lead acid batteries will last just fine, as long as they don't get and stay discharged too low. They are designed for constant use, albeit in a fairly narrow charge range.

Well, I thought my Plus had a significantly better charging algorithm but now it appears I simply had bad timing. Checking every morning for almost 2 weeks before charging, I am seeing it dip to ~ 12.15 volts give or take before seeing a boost that lasts 2-3 days. Saw the same this morning 12.12 volts but didn't charge at home since I had errands to run near a charger so took off and was at 14.48 volts for 12 mins before dropping down. I think my garage's ambient rarely dropping below 50ºF is my only advantage.
 
GerryAZ said:
The threshold level depends upon the model year, but is less than 10 amperes on 2011 and lower on later models. I have never connected an external charger to any of my LEAFs. I saw sustained charging current of about 80 amperes while driving home from my office after the battery in the 2011 was completely discharged because I left the Bluetooth adapter plugged into the OBDII port and the Android device running Leaf Spy on the passenger seat while parked for 6 days. I used some test leads to "jump start" the Leaf from my office vehicle and drove home without issue.

How did you "see" a charging current of 80 amps? That seems excessive for the small 12V battery used by the Leap.
 
lorenfb said:
GerryAZ said:
The threshold level depends upon the model year, but is less than 10 amperes on 2011 and lower on later models. I have never connected an external charger to any of my LEAFs. I saw sustained charging current of about 80 amperes while driving home from my office after the battery in the 2011 was completely discharged because I left the Bluetooth adapter plugged into the OBDII port and the Android device running Leaf Spy on the passenger seat while parked for 6 days. I used some test leads to "jump start" the Leaf from my office vehicle and drove home without issue.

How did you "see" a charging current of 80 amps? That seems excessive for the small 12V battery used by the Leap.

I measured it with a DC clamp-on ammeter when I first jump-started the car. It tapered as the battery charged on the drive home. Charging current into the battery is a function of the source available, state of charge, and internal resistance so when the battery is deeply discharged it can accept high current.
 
lorenfb said:
GerryAZ said:
The threshold level depends upon the model year, but is less than 10 amperes on 2011 and lower on later models. I have never connected an external charger to any of my LEAFs. I saw sustained charging current of about 80 amperes while driving home from my office after the battery in the 2011 was completely discharged because I left the Bluetooth adapter plugged into the OBDII port and the Android device running Leaf Spy on the passenger seat while parked for 6 days. I used some test leads to "jump start" the Leaf from my office vehicle and drove home without issue.

How did you "see" a charging current of 80 amps? That seems excessive for the small 12V battery used by the Leap.

Just over a 1000 watts? Not really...
 
Thinking back, I might have had the clamp-on in a position to measure the output of the DC-DC converter instead of only input to the battery--I just remember being surprised at the initial current level. If so, then the actual current into the battery might have started at around 40 amperes before tapering since there could have been 40 amperes of other load with A/C fans, computers, lights, etc.
 
GerryAZ said:
Thinking back, I might have had the clamp-on in a position to measure the output of the DC-DC converter instead of only input to the battery--I just remember being surprised at the initial current level. If so, then the actual current into the battery might have started at around 40 amperes before tapering since there could have been 40 amperes of other load with A/C fans, computers, lights, etc.

Even at 40 amps charging current, that's still excessive. Are you sure you used the correct meter scale?
Maybe you were actually measuring the jumper battery current into the Leaf's battery.

Furthermore, based on your initial statement;
I saw sustained charging current of about 80 amperes while driving home
How were you able to read a clamp-on amp-meter while driving, if it was properly connected directly to one of the battery cables?
 
I connected the clamp on and read it for a few minutes before I started driving because I wanted to make sure the battery was taking a charge so I would not get stranded on the way home. I saw it tapering while the car was still parked and then put the meter away. I used the clamp on again when I got home to verify that the current was down to a level indicating the battery was recharged enough to reliably start the car again. I did end up replacing the battery a month or so later because it was damaged by being deeply discharged, but it still lasted longer than typical OEM batteries in my hot, dry climate (probably because temperatures under the hood of the Leaf are much lower than ICE vehicles).

I guess I should not have used the word sustained in my original comment because it did taper. I will not go back to edit that post because it would make the replies confusing.
 
DaveinOlyWA said:
Stanton said:
I have one of those Antigravity Battery Tracker devices on my 12v...and it shows that the charge level "spikes" to 14v every 15 minutes (or so). You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain. Those of you who follow my 12v Lithium thread know that I'm way past 5 years on mine with no issues (and no special treatment).

Interesting. I am guessing this only happens when car is running? How long do these spikes last?
It happens both when the car is on and when it is charging. While these 14v spikes only last a minute or so, the cycle repeats while in either of these modes (so some benefit occurs).
 
Stanton said:
DaveinOlyWA said:
Stanton said:
I have one of those Antigravity Battery Tracker devices on my 12v...and it shows that the charge level "spikes" to 14v every 15 minutes (or so). You can't expect a (standard) lead acid battery to last in any car, let alone an EV with parasitic drain. Those of you who follow my 12v Lithium thread know that I'm way past 5 years on mine with no issues (and no special treatment).

Interesting. I am guessing this only happens when car is running? How long do these spikes last?
It happens both when the car is on and when it is charging. While these 14v spikes only last a minute or so, the cycle repeats while in either of these modes (so some benefit occurs).

Stanton how is that LiFEPO4 battery doing? I am considering getting one from Ohmmu for my 2013 Leaf SL.
Thank you.
 
R1200RT said:
Stanton how is that LiFEPO4 battery doing? I am considering getting one from Ohmmu for my 2013 Leaf SL.
Thank you.
Been running strong for almost 9 years now...so I'd say it's doing pretty well. Here's a link to my thread about it: https://www.mynissanleaf.com/viewtopic.php?t=11999
Remember: you get what you pay for, so if you buy a "cheap" Chinese-sourced battery...you probably won't have as good of luck as I have. ;)
 
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