Key fob sometimes worked, sometimes didn't.

Hi everyone,

I'd like everyone's opinion on this. I won a 2015 Nissan Leaf S. The car doesn't always fully turn on with I have my key fob on me. As in, the car turns on, but it won't let me drive. I replaced the batteries on my key fobs and the problem persists. However, after multiple tries, the car does fully turn on and I can drive it.

The terminals in the 12V car battery are a little dirty, so I intend to clean them but I wanted to check with you guys and ask if anyone has a similar experience. Would I need to replace the 12V car battery?

Sounds like the 12 volt.

Can you measure the voltage of the 12 volt when the car's off in the bad state and/or after it has sat overnight?

The key fob only makes it possible to turn the car on. The actual bootup has nothing to do with the fob. I agree that it's likely the 12 volt battery.

If you believe there's a problem w/the fob battery, you could try touching the fob to the power button then pressing the brake pedal + pushing power after hearing the chime. You can even try doing this w/the fob battery removed (yes, I've done this before).

Measured voltage of battery. 12.55VDC, 0.17mA.

Your description of the car successfully booting after several tries is consistent with a weak 12V battery because the DC-DC converter will charge the battery a little bit each time the main contactor closes so the voltage eventually becomes high enough for the car to boot correctly. Did you measure the 12.55 volts at the battery terminals after the car had been turned off for some time (say at least 30 minutes)? How did you measure the current? 0.17 mA is way lower than typical power off residual current. If you still have the Nissan OEM 12V battery, I strongly suggest that you replace it with a high-quality AGM deep cycle battery if you plan to keep the car for several years. The OEM 12V batteries failed after less than 3 years in my 2011 and 2015. There are several threads on the forum which explain why a deep cycle AGM battery is a good choice for reliability.

The battery size/configuration is 51R.

Dirty or corroded terminals and clamps can definitely cause problems. Get everything clean and tight; you'll want clean connections anyway even if you end up replacing the battery.

A voltage test under little or no load will not always catch a bad battery. Health should be determined by a load test. Some auto parts stores will do this for free -- I have heard Auto Zone does. On the other hand, 5 years is pretty good service from the OEM flooded battery so you wouldn't be leaving much money on the table by just replacing it. An AGM battery will be better than the original and less maintenance.

Nubo said:

Dirty or corroded terminals and clamps can definitely cause problems. Get everything clean and tight; you'll want clean connections anyway even if you end up replacing the battery.

A voltage test under little or no load will not always catch a bad battery. Health should be determined by a load test. Some auto parts stores will do this for free -- I have heard Auto Zone does. On the other hand, 5 years is pretty good service from the OEM flooded battery so you wouldn't be leaving much money on the table by just replacing it. An AGM battery will be better than the original and less maintenance.

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Good points--I should have mentioned connections. One thing to watch out for is the body ground connection on the left front fender (looks like a cable clamp in the negative battery cable. I had to remove the bolt (screws directly into body) and clean that connection on my 2015. You can check it with a voltmeter by having the car in ready mode (in Park with brake set for safety). Turn on all electrical accessories you can--HVAC with blower fan on high and high beam headlights should be enough load. Measure the voltage between the negative battery terminal and the body (find another screw or bolt within reach for voltmeter lead)--should not be higher than about 0.1 or 0.2 volts (preferably just a few millivolts).

Thanks everyone for the advice! I work at home, so I can stay at home for the most part anyways while I work on doing these tests. Load test at Autozone, measuring voltage after the car is off for 30 mins, etc. I'll keep you all posted, hopefully by Wednesday night.

Everyone,

I went to AutoZone and the worker asked me to disconnect the 12V battery, so the main car battery doesn't mess with the readings. So I did so. When he connected the 12V battery terminals, the tester measured 10.5V before the test even started. So I got a new battery.

Ask them to charge the new battery before installing it

alozzy said:

Ask them to charge the new battery before installing it

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Yup. And if it's too late, either charge it yourself with an external charger/maintainer, or take it for a long drive with the climate control on, but on low. The car won't quickly charge up the battery like an ICE vehicle would.

Just drive the car (or keep it in "Ready" mode while parked) for at least 30 minutes. The 12V battery is charged fairly quickly while driving or while charging the traction battery. It is OK to use an external charger if you have one, but should not be needed because the DC-DC converter will charge at about 14 volts until the current absorbed by the 12V battery drops indicating nearly full charge. It then runs at float voltage of about 13 volts to avoid overcharging the battery while driving or while charging the traction battery. I have never used an external charger--I just let the car charge the replacement battery in the 2011 and again in the 2015 by installing the new battery in the evening and charging the traction battery overnight in each case.

While I did have to "jump" my 12V (and replace once) on my 13 Leaf, so far so good on the 19s.

Thanks for the charging advice everyone! It's too late to charge at AutoZone, but I was able to start the car multiple times today no problem, so maybe it was already fully charged?

But either way, I'm in good shape it seems.

The current required to start a Leaf is low, so unlike a slowly turning over ICE engine to warn you, you have little or no warning when the Leaf's accessory battery starts to get low. The new battery should have come with at least 80% charge. The point being made is that, Gerry's experiences notwithstanding, some Leafs do not do a great job of charging their accessory batteries.

LeftieBiker said:

The current required to start a Leaf is low, so unlike a slowly turning over ICE engine to warn you, you have little or no warning when the Leaf's accessory battery starts to get low. The new battery should have come with at least 80% charge. The point being made is that, Gerry's experiences notwithstanding, some Leafs do not do a great job of charging their accessory batteries.

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Especially the early years (2011 and 2012).

I've got the original 12V battery in my 2014. Been on external charge exactly once.

WetEV said:

LeftieBiker said:

The current required to start a Leaf is low, so unlike a slowly turning over ICE engine to warn you, you have little or no warning when the Leaf's accessory battery starts to get low. The new battery should have come with at least 80% charge. The point being made is that, Gerry's experiences notwithstanding, some Leafs do not do a great job of charging their accessory batteries.

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Especially the early years (2011 and 2012).

I've got the original 12V battery in my 2014. Been on external charge exactly once.

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10.5V is extremely low. That battery is toast if you've been driving the car and it's not charging higher than that.

I have a 2011 and put it on an external maintainer every 2 months just to top it off. There's someone here who posted a graph showing that the early model years slowly let the 12V battery rest to around 50-75% of a full charge, which results in premature wear on the battery. I also have a deep cycle battery to make it more resilient to being stored at partial charge.

I actually installed a 12V hookup where the QC port would be (I don't have QC) so I could easily connect the 12V maintainer to the car. Came in handy during COVID lockdown when I was only driving once a week or less.

Sadly, I'm going to be adding a similar hardwired connection to my 2018. It does a better job of charging the battery than many early Leafs, but I've seen it at about 12.25-12.35 volts a few times.