Tip: How to Recharge the 12-volt Battery

My 2013 Leaf 12-volt battery dies every 6 to 12 months or so. The dealer has replaced the 12-volt battery several times, but neither they nor the dealer have been able to figure out what's really wrong. Sounds like others have had the same problem. So I'm offering my simple solution to get up and running reliably (for the next 6 months at least).

Updated Nov 21, 2017
1. If the 12-volt battery voltage is very low, but not totally dead (i.e. you can power on the car, but there's error messages on the dash), reboot the car by disconnecting and reconnecting the 12-volt battery. If you don't reboot, the built-in 12v recharger/maintainer will not turn on and the 12-volt battery will die again within a few minutes.
2. Jump start the car.
3. After disconnecting the jumper cables, leave the car on in ready-to-drive mode (not in accessory-only mode) all day or over night. For safety's sake, I make sure the emergency brake is on and my garage is locked.

As long as the car is in ready-to-drive mode, it is recharging/maintaining the 12-volt battery. The owners manual says to leave the car in ready-to-drive mode for 20 minutes after a jump start, but that's not enough, and it will die again very soon, so don't take it out on the road.

I've been through this cycle many times, and to my surprise when the dealer tests my 12-volt battery, they say it's in good condition.

Another option to simply get more 12-volt recharging/maintaining time is to use your old level-1 120v charger to charge your drive battery instead of your 240v level-2 charger for a while.

The key here is to understand that the car's built-in 12v recharger/maintainer is operating only when the drive battery is engaged, i.e. in ready-to-drive mode or with drive-battery charging (actually charging, not just plugged in).

Of course, if anyone is aware of any fix from Nissan for the battery dying in the first place, I'd love to hear about it. After going back to the dealer with this problem so many times (and even leaving the car with them for a whole month once) with no solution, Nissan is suggesting I use their buy-back program. With 55k miles on the car after 3 years, I don't expect a very good offer, but we'll see. Hoping for the best.

Updated Nov 21, 2017
Nissan declined to buy back the car, but did give me an extended warranty instead with an additional 4yrs/48k miles (and that's already saved me around $1,000 on 3 wheel bearing replacements).

I recommend purchasing this cheap and convenient way to keep an eye on the 12v battery during the process above and to learn how it's maintained.
https://www.walmart.com/ip/Equus-In...75035&wl11=online&wl12=15137663&wl13=&veh=sem

When in accessory mode, you'll see around 11-12v - any less and you're having trouble. When in drive mode or when charging the drive battery, you'll see either 13v or 14v - a few minutes at 14v then drops to 13v. Ignore the red, yellow, green lights which seem to be calibrated for a gas car.

Can't you just charge the 12v separately, with a conditioning charger, while you are charging the car?

As you noted, the DC-DC converter will recharge the 12-volt battery after jump-starting either in normal run mode or while actually charging the traction battery. I strongly recommend that you disconnect the jumper cables between the two cars as soon as the Leaf is fully booted into run mode to minimize risk of damage to either car's electrical system. The DC-DC converter will put out over 100 amperes so it will easily recharge the Leaf's battery and could back feed into the other car's battery and electrical system. The DC-DC converter will easily charge the Leaf's battery enough to restart the car in 20 minutes if the battery is not defective. Longer running time or overnight traction battery charging is needed to get the 12-volt battery fully recharged.

Gerry

Henryv said:

Can't you just charge the 12v separately, with a conditioning charger, while you are charging the car?

Click to expand...

Not necessary, since the car will already be doing that itself with its built in 12v battery charger/maintainer (the DC-DC converter).

GerryAZ said:

As you noted, the DC-DC converter will recharge the 12-volt battery after jump-starting either in normal run mode or while actually charging the traction battery. I strongly recommend that you disconnect the jumper cables between the two cars as soon as the Leaf is fully booted into run mode to minimize risk of damage to either car's electrical system. The DC-DC converter will put out over 100 amperes so it will easily recharge the Leaf's battery and could back feed into the other car's battery and electrical system. The DC-DC converter will easily charge the Leaf's battery enough to restart the car in 20 minutes if the battery is not defective. Longer running time or overnight traction battery charging is needed to get the 12-volt battery fully recharged.

Gerry

Click to expand...

In my experience, if you disconnect the jumper cables between the two cars immediately after booting into ready-to-drive mode, it will die again in just a few minutes (You can watch the voltage dropping fast) - hence my recommendation in #1 to leave them connected for 10-15 minutes before removing the jumper cable.

csites said:

In my experience, if you disconnect the jumper cables between the two cars immediately after booting into ready-to-drive mode, it will die again in just a few minutes (You can watch the voltage dropping fast) - hence my recommendation in #1 to leave them connected for 10-15 minutes before removing the jumper cable.

Click to expand...

There's no way to diagnose via posts in a forum, but the bolded statement above (by me) tells me something else is going on with your Leaf. I have been through a couple of dead batteries (and now have a 12v Lithium) and agree with the statement that the DC-DC converter is able to top off a "dead" 12v battery very quickly.

I'm sorry, but this is a bad idea. Instead of leaving the car on in Ready mode for ridiculous lengths of time, ready to steal and wasting power, the best approach is to use a battery maintainer. It will charge the car even while the charging system is active. I use a hardwired lead that I connected to the 12 volt battery positive terminal and a ground on the large housing on top of the 'PDM Stack' in the motor compartment. I ran the cable into the charge port compartment, and can connect the battery maintainer whenever I'm charging the car, or whenever else I like. The original poster here has a charging system problem that needs to be diagnosed, and his (or her) "solution" is inadvisable at best.

Stanton said:

csites said:

In my experience, if you disconnect the jumper cables between the two cars immediately after booting into ready-to-drive mode, it will die again in just a few minutes (You can watch the voltage dropping fast) - hence my recommendation in #1 to leave them connected for 10-15 minutes before removing the jumper cable.

Click to expand...

There's no way to diagnose via posts in a forum, but the bolded statement above (by me) tells me something else is going on with your Leaf. I have been through a couple of dead batteries (and now have a 12v Lithium) and agree with the statement that the DC-DC converter is able to top off a "dead" 12v battery very quickly.

Click to expand...

Thanks GerryAZ and Stanton. Based on your comments, I'm wondering if I should just ask for a new DC-DC converter (and/or related components). I know parts swapping may not be the best way to diagnose, but multiple dealers have run their diagnostics multiple times and found nothing.

If the volts are dropping fast you need a clamp-on meter to determine if there is a draw or self discharge.
When fully charged get and post some hydrometer readings.

smkettner said:

If the volts are dropping fast you need a clamp-on meter to determine if there is a draw or self discharge.
When fully charged get and post some hydrometer readings.

Click to expand...

Thanks. I won't be able to check that for probably another 6 months or so when it happens again.

Along with the clamp-on current meter, I need a permanently installed low-voltage alarm loud enough from under the hood in the garage to wake me in the middle of the night, so I can see the draw killing it in the first place and make a video of it happening to prove it to Nissan, and maybe start pulling fuses to see if I can get it to stop. Of course, all that assumes there's an intermittent phantom draw, which might not be the case. Could also be that the DC-DC converter stops working every 6 months - maybe until the 12v battery dies causing the car to be rebooted.

Come to think of it, maybe I should just put a quick disconnect on the battery terminals and reboot the car every 5 months.

LeafSpyPro will log your 12 voltages.
Here is my Leaf over about 3 days



thanks,
Dan

Danl said:

LeafSpyPro will log your 12 voltages.
Here is my Leaf over about 3 days
[snip]
thanks,
Dan

Click to expand...

Thanks Dan! Sounds like it's time I bought LeafSpyPro for my iPhone. A few further questions if you don't mind...

1) Will most any OBDII device work, or should I choose a specific one (especially one that draws the least power possible)?
2) I see references online to both Bluetooth and WiFi devices for LeafSpyPro. Which is best for my iPhone?
3) I see your logs are for 3 days. Did you have to leave the car on overnight to get those, or will the OBDII device work even while the car is off?
4) Are the logs stored in the car or on the OBDII device, and for how many days before I must download the data to my phone?
5) I need to log the 12v battery voltage for 6 to 9 months at a time to try to find out what's discharging it overnight every 6-9 months (or whether the DC-DC converter is intermittently not charging it properly while driving or L2 charging). Will I be able to get 6-9 months of uninterrupted logs some way?

Three different Leaf techs have found nothing wrong, and Nissan deflects by saying I must be double-tapping the power switch, so I'm on my own to diagnose and then prove what's happening.

csites said:

Danl said:

LeafSpyPro will log your 12 voltages.
Here is my Leaf over about 3 days
[snip]
thanks,
Dan

Click to expand...

Thanks Dan! Sounds like it's time I bought LeafSpyPro for my iPhone. A few further questions if you don't mind...

1) Will most any OBDII device work, or should I choose a specific one (especially one that draws the least power possible)?
2) I see references online to both Bluetooth and WiFi devices for LeafSpyPro. Which is best for my iPhone?
3) I see your logs are for 3 days. Did you have to leave the car on overnight to get those, or will the OBDII device work even while the car is off?
4) Are the logs stored in the car or on the OBDII device, and for how many days before I must download the data to my phone?
5) I need to log the 12v battery voltage for 6 to 9 months at a time to try to find out what's discharging it overnight every 6-9 months (or whether the DC-DC converter is intermittently not charging it properly while driving or L2 charging). Will I be able to get 6-9 months of uninterrupted logs some way?

Three different Leaf techs have found nothing wrong, and Nissan deflects by saying I must be double-tapping the power switch, so I'm on my own to diagnose and then prove what's happening.

Click to expand...

First, you need to research the LeafSpy thread in Accessories/mods....CanBus. It has information much above my knowledge level.

You do not need the car on all the time. but data collection may be hit and miss when the car is off. That's OK. it will still give you good data when it is on, or when it is charging. so you will get good data at least once a day. I had removed the times with questionable data on my chart, but you still can see what the 12v is doing.

Turn on logging and drop box. The phone is storring the data and putting it into dropbox on the internet.Tthere it will say day after day no mater what you do with the car or phone. I then pull the file from dropbox into my lap top and chart it with excel. Get me one of your log files and I can chart it for you.


Thanks,
Dan

Danl said:

First, you need to research the LeafSpy thread in Accessories/mods....CanBus. It has information much above my knowledge level.

Click to expand...

Thanks. I just purchased an LELink bluetooth OBDII adapter on eBay for $20, per Turbo3's iOS-related May 16th post near the end of the thread you mentioned.

Added another 5 days or so.

When the car is on or when charging the dc-dc drives to 14v for a short time. Then drops back to maintain at 13v. So those readings are of the dc-dc rather than the12v battery. You also see times at 12v. This fluctuates between 11.7v and 12.5v depending on the 12v SOC.

Finally there are times that I have the accessories on(hit the power button 2 times without stepping on the break) in those you see the 12v start at 12v and ramp down over time. One time is as low as 10.5v.

This is all normal.

Thanks,
Dan

csites said:

Thanks. I just purchased an LELink bluetooth OBDII adapter on eBay for $20, per Turbo3's iOS-related May 16th post near the end of the thread you mentioned.

Click to expand...

Has the adapter worked as expected? Can you leave it in place without draining the 12 volt battery? Does it restart seamlessly each time you start your Leaf? Still holding out for consistent good results with iOS bluetooth LE.

OK, Today I went out and the 12v would not boot up the car. Here is what data I caught.



The car had completed an 80% charge two days ago and was not driven on Aug2nd. The OBDII was pluged in all the time and Leaf spy had been left on on my phone all day and night on Aug 2nd. But it only caught data for 2 minutes in the morning I added the blank area in the chart to show that I have a day with no data.

The car would not respond to any attempt to charge or turn it on. I had to put a 12v charger on it to get any response. It started at 8v and dropped to 6v with 7 amps going from the 12v charger into the battery. It would not recognize the key fob at one point and would not connect to Leafspy with the car off. Kept trying to turn the car on with a little wait for the 12v charger to bring up the 12v a little.

More later.....

hmm.... the 12v battery normally does not go from 12v to <8v instantly. you were able to run accessories and saw the voltage to drop to 10+v gradually..... did you check the ODB-II dongle for any sign of short circuit happened?

A lead acid battery that drops below 10 volts or so - usually under an extremely heavy load (doubt you have that) is likely a dead battery - I'd guess you know that!

soldcake said:

hmm.... the 12v battery normally does not go from 12v to <8v instantly. you were able to run accessories and saw the voltage to drop to 10+v gradually..... did you check the ODB-II dongle for any sign of short circuit happened?

Click to expand...

Hello soldcake,
I did not say it went from 12v to <8v instantly. I said I did not get data in that timeframe. I assume it went down sometime during the Aug 2nd time that LeafSpy did not get data.

Thanks,
Dan