csites
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Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 8:04 am

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-Innova-3721-Battery-and-Charging-System-Monitor/15137663?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227009075049&wl0=&wl1=g&wl2=c&wl3=40839218672&wl4=pla-78652684352&wl5=9009731&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&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.
Last edited by csites on Tue Nov 21, 2017 11:07 am, edited 3 times in total.
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Henryv
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 8:48 am

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

GerryAZ
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 8:59 am

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
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csites
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 11:03 am

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


Not necessary, since the car will already be doing that itself with its built in 12v battery charger/maintainer (the DC-DC converter).
2013 Leaf SV - Built 03/13 - Pearl White - QC Port - LED Headlights - Bosch PowerMax 240LC EVSE - New drive battery for $500 (mostly covered by Nissan) at 75k miles!

csites
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 11:07 am

GerryAZ wrote: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


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.
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Stanton
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 11:13 am

csites wrote: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.


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.
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LeftieBiker
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 11:59 am

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.
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csites
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 12:28 pm

Stanton wrote:
csites wrote: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.


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.


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.
2013 Leaf SV - Built 03/13 - Pearl White - QC Port - LED Headlights - Bosch PowerMax 240LC EVSE - New drive battery for $500 (mostly covered by Nissan) at 75k miles!

smkettner
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Re: Tip: How to Recharge the 12-volt Battery

Sat Jul 16, 2016 12:50 pm

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.
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csites
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Re: Tip: How to Recharge the 12-volt Battery

Mon Jul 18, 2016 8:21 am

smkettner wrote: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.


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. :-)
2013 Leaf SV - Built 03/13 - Pearl White - QC Port - LED Headlights - Bosch PowerMax 240LC EVSE - New drive battery for $500 (mostly covered by Nissan) at 75k miles!

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