Does the traction battery charge the 12v? is it safe to leave car on the charger for a month?

[WBYeats]

Well, I guess the title pretty much explains what I'm asking. We plan to be gone for about a month in November, and usually when we're away we leave our 2012 Leaf on the charger. Never a problem, but the recent scare stories about EV lithium batteries on fire brings up the usual anxiety again -- not disabling anxiety, but still. The car sits in our carport -- everything but the floor is wood. This car has been just about flawless since we bought it new more than 12 years ago (24,000 miles -- it's a city car, bless its little heart). But before we leave, I usually have a short-lived vision of the car bursting into flame and burning our wood house down. Is this particular (old) Leaf any more at risk than modern EVs? Is it wise to leave it on the charger for that long? Our 12-year-old habit is to leave it on the charger unless we're driving it. Does the risk increase the longer we leave it charging undriven? Would it be safer to park it in our totally tree-shaded driveway away from the house?

Also, I've always wondered but can't find any info on whether the traction battery keeps the 12v battery charged up, either while on the charger or driving. The 12v is the only thing we've replaced.

Thanks in advance for any insights.

 

[nlspace]

If you are concerned like this, then just charge the HV Pack up to 80% before you go and leave it off the charger while you are gone. It will be fine.

But do get a good quality 12V trickle charger and leave it connected to maintain the 12V battery while you are gone. i use a Yuasa 12V 1A Smart charger in nearly constant rotation between several vehicles that are inactive. It will charge up to 14.4 to desulfate the plates, and then drop the voltage and current down to hold it at Full 12.8V

 

[WBYeats]

Good idea about the trickle charger -- I have them for our two other cars (hybrid and gas), but was wondering if the Leaf traction battery had some role in charging the 12v. The traction battery is down 3 bars (or is it 4), so I'm not sure how long it would last not being charged at all. And I wonder if the car is safer left plugged in or unplugged. Or if it makes no difference.

 

[nlspace]

1. The leaf control system does charge the 12V battery using energy from the HV Pack for about 5 minutes every 24 hours. It turns itself on to energize the DCDC Converter, then shuts off.

2. It also charges the 12V battery while the HV Pack is being charged when the EVSE is plugged in to the charge port. After the HV Pack is fully charged the EVSE will be cut off and the 12V will be "maintained" as described in 1.

This is what it has been doing when you left it plugged in in the past, and it worked just fine, as designed and intended.

Do you shut off your water line at the meter when you leave for a month?

 

[WBYeats]

Thanks! Just what I was trying to find out -- can't believe I haven't learned that in 12 years of owning this car.

No, we don't shut off the water, ever. Why?

 

[lorenfb]

You can't rely on the Leaf's battery system to adequately charge (~5 minutes) the 12V battery.
An external 12V charger is required when not driving the Leaf frequently.

 

[Drew21]

People shut off their water when they're away from home because there is a tiny chance that some water line in your home (or the water heater itself) can burst/leak at any moment. If it happens while you're there it's an inconvenience and a mess. If it happens when you're away for days/weeks you might need a new house.

Similarly, there's a tiny chance of a really bad outcome by leaving a Lithium ion battery plugged in for weeks at a time, whether you're talking about a cell phone, laptop, or EV. What we do know is that leaving Li-ion batteries at 100% charge for long periods of time, especially if you add in high ambient temperatures, is accelerated battery degradation. Again, this applies to common devices like cell phones or laptops, but also to much larger batteries in an EV.

If you're parking your Leaf for a prolonged period charge the HV battery to somewhere in the middle of the range and unplug. I usually go for 50-60%. If you're concerned about your 12v battery hook it up to a trickle charger as suggested above or remove it completely (which the downside of losing all your presets in the infotainment system).

 

[cornbinder89]

People shut off their water when they're away from home because there is a tiny chance that some water line in your home (or the water heater itself) can burst/leak at any moment. If it happens while you're there it's an inconvenience and a mess. If it happens when you're away for days/weeks you might need a new house.

If you shut off the water you should shut off the water heater as well. At least turn it to "pilot" if gas. If it bursts and drains and then still tries to heat, bad things can happen.
That said, if your 12 year old habit has worked for you, it is hard to justify changing now.
I wouldn't leave fully charged and on the charger, I would follow the above recommendation of somewhere more than 20% and less than 90%, with a maintainer on the 12 volt.

 

[DaveinOlyWA]

Well, I guess the title pretty much explains what I'm asking. We plan to be gone for about a month in November, and usually when we're away we leave our 2012 Leaf on the charger. Never a problem, but the recent scare stories about EV lithium batteries on fire brings up the usual anxiety again -- not disabling anxiety, but still. The car sits in our carport -- everything but the floor is wood. This car has been just about flawless since we bought it new more than 12 years ago (24,000 miles -- it's a city car, bless its little heart). But before we leave, I usually have a short-lived vision of the car bursting into flame and burning our wood house down. Is this particular (old) Leaf any more at risk than modern EVs? Is it wise to leave it on the charger for that long? Our 12-year-old habit is to leave it on the charger unless we're driving it. Does the risk increase the longer we leave it charging undriven? Would it be safer to park it in our totally tree-shaded driveway away from the house?

Also, I've always wondered but can't find any info on whether the traction battery keeps the 12v battery charged up, either while on the charger or driving. The 12v is the only thing we've replaced.

Thanks in advance for any insights.

Leaving the car plugged in assumedly at 100% SOC is the worst possible thing you can do.

Best to leave the car unplugged at 50% SOC for any period over a few days. The car will boost the 12 volt on a regular basis.

Leaving the car plugged in means a greater load on the 12 volt because its monitoring the charge level, etc. Small overhead but over time, it can be enough to exceed the small 12 volt boost the car receives which leads to premature death of the 12 volt.

FYI; I have left my car sitting in outside airport parking for as much as 23 days w/o issue.

As far as the car maintaining the 12 volt, no the car never fully charges the 12 volt...EVER. But there are things you can do to circumvent this a bit. Something to consider the next time you are headed to a place where the car will sit for extended periods of time.

https://daveinolywa.blogspot.com/2021/04/charge-your-leaf-every-day.html

 

[khbkhb]

Ditto for a 12v charger (I like the “battery tender” brand, I’ve had one since the 80’s still going strong). As for leaving the traction pack plugged in, if you have one of the more advanced EVSE’s (e.g. WallBox Pulsar) I feel reasonably comfortable leaving the LEAF plugged in … with the WallBox *off* or on a schedule to turn on for a while every few days. Leaving the LEAF at 100% is bad, but if you can read the SoC remotely, and can turn on the charger remotely … why not?

 

[WBYeats]

Well, I guess we've been charging the car wrong for a decade+ now -- when we got it the jury was still out on whether to leave it plugged in all the time, couldn't find anything in the manual about that (doesn't mean it wasn't there). Hard to know what to do. At this point I don't see much reason to change. The car stops the charging once the battery is full up. First 5 years we had a 220v socket and no garage, car sat fully exposed 24/7; last 7 years it's been 120v in a carport. We never used the timer function, always plugged it in immediately after returning home -- both unwise things to do, I now read (we plead ignorance). Now the maximum range is 60 miles; usually down to 35-40 when we get back from running around town, including climbing the long hill to our house, and that's enough. This battery must be very safe, high quality, and not likely to catch fire if it hasn't after 12 years. So I guess I'll leave it plugged in while we're gone and put a Battery Tender on the 12v. Thanks to you all for sharing your knowledge.

 

[TronJockey]

Well, I guess the title pretty much explains what I'm asking. We plan to be gone for about a month in November, and usually when we're away we leave our 2012 Leaf on the charger. Never a problem, but the recent scare stories about EV lithium batteries on fire brings up the usual anxiety again -- not disabling anxiety, but still. The car sits in our carport -- everything but the floor is wood. This car has been just about flawless since we bought it new more than 12 years ago (24,000 miles -- it's a city car, bless its little heart). But before we leave, I usually have a short-lived vision of the car bursting into flame and burning our wood house down. Is this particular (old) Leaf any more at risk than modern EVs? Is it wise to leave it on the charger for that long? Our 12-year-old habit is to leave it on the charger unless we're driving it. Does the risk increase the longer we leave it charging undriven? Would it be safer to park it in our totally tree-shaded driveway away from the house?

Also, I've always wondered but can't find any info on whether the traction battery keeps the 12v battery charged up, either while on the charger or driving. The 12v is the only thing we've replaced.

Thanks in advance for any insights.

The 12V battery is charged from the traction battery which applies essentially a 13.0V float charge but only when the Leaf is being driven. It also receives a 14.3V burst initially for about 60 seconds after the Leaf is started but returns to 13.0V afterwards (operating the windshield wipers will also place 14.3V across the 12V battery as long as the wipers are engaged). I've heard some people mention that the Leaf can somehow detect the car has been sitting and will automatically charge the 12V battery but I've never been able to confirm this so I think this is nonsense. It will go dead unless it's put on a battery tender or the Leaf is driven often enough.
Now, having said all this, as far as I'm aware there's been only two Nissan Leafs that have ever caught fire and neither was ever proven to be battery related. Also, (in case I've mis-read your comment and you're actually talking about leaving the traction battery plugged into a charger) you should never leave your traction battery at 100% SOC for more than a few hours (or perhaps a day or two at most), as it accelerates capacity degradation. I used to charge my 2015 Leaf to 100% and leave sit from Friday evening until Monday morning when I left for work. This did cause more degradation than the vehicle should have experienced. Even leaving it sit at 100% from 9pm until leaving for work at 7am the next morning caused some degradation. Only a tiny bit each time but it's cumulative. Doing this when ambient temperatures are extremely cold or hot only makes this worse. This may be especially true for some very early Leafs which had a BMS that would allow charging to a true 100% which is known to accelerate capacity degradation. Finally, our Leaf traction batteries have a very low self-discharge rate and unless they're being left sitting for several months there's little reason to worry. If leaving it for more than a few days just charge it to between 40-60% and leave it. Good Luck..........

 

[WBYeats]

Thanks. I wish I'd known all this about 100% charging from Day One of ownership. We were always concerned that we'd have enough charge in the morning to have no delays in going to work, and we needed plenty because it was L.A. -- stop, go, slow and go, lots of stopping and waiting with the AC and stereo going, freeways, city streets, hills, a pretty challenging place to drive an EV that had at most 70-80 predicted miles, so when we got home it could be at 20. It usually finished charging some time after we went to bed. And we were clueless about the timer thing. That manual is thick, a good match for the owners! With 3-4 bars down (I forget), I wonder if it makes any sense now to not charge it to 100% and to leave it unplugged after 80%, because 80% of 55 predicted miles would induce my wife's range anxiety (it's her baby) even in our smallish town, esp. in the winter. And we live hundreds of feet above the town so although we pick up a few miles on the way down, we lose much more on the way back up.

Just ordered another Battery Tender for it.

 

[ACDCPhilip]

" And we live hundreds of feet above the town so although we pick up a few miles on the way down, we lose much more on the way back up. "

Another reason not to leave it 100% charged.
While the battery is at 100% it can't absorb much regen on the way down the hill, so most of that potential regen energy will be lost & turned to heat in the brakes.

Try charging to 90% & see how much regen gets put back into the battery by the time you get down to level road again.

 

[MikeFerro1]

Good idea about the trickle charger -- I have them for our two other cars (hybrid and gas), but was wondering if the Leaf traction battery had some role in charging the 12v. The traction battery is down 3 bars (or is it 4), so I'm not sure how long it would last not being charged at all. And I wonder if the car is safer left plugged in or unplugged. Or if it makes no difference.

The traction battery charges the 12 volt battery in my 2013 Leaf only when the car is switched on and ready to drive, not otherwise. If left unattended the battery will go flat after three to four weeks. When the car is out of use for a period I charge it using a trickle charger once a month and if left somewhere where I can't charge it this way then I disconnect the 12 volt battery.
My car is one of the Japanese ones with a solar panel in the roof but I don't the panel is working

 

[Daklein]

I've observed my 2020 SV+ salvage car charging the 12v from the HV pack. 12v connected as normal, but car not turned on, just sitting in the garage. The contactors will clunk on, third light blinks for a while 5-10 minutes?, then contactors clunk back off.
The car has been sitting for months, HV batt at 30-50%, I've L2 charged it once or twice, but really shouldn't since there's a coolant leak might be risky for the PDM.

 

[Drew21]

I've observed my 2020 SV+ salvage car charging the 12v from the HV pack. 12v connected as normal, but car not turned on, just sitting in the garage. The contactors will clunk on, third light blinks for a while 5-10 minutes?, then contactors clunk back off.

I have observed the same thing over the past two days. I've had the Leaf on jack stands reminding myself why skilled mechanics are worth all the dollars/hour that I can't afford to pay. Both days I heard the "clunk, clunk" and then the third light (right side looking from the front) flashed for five-ish minutes, then "clunk, clunk" and then light went out.

I took it as a sign that I should plug in the battery trickle charger for the night so that the Leaf is ready for a test drive tomorrow to see if the new suspension will allow the car to pass MA annual (re-)inspection. The ball joints on what I think were the original control arms were completely gone, which was causing the noise that led to the failed inspection. Interestingly, the crusty and rusty sway bar links, which are a common point of failure (and noise), and which also appeared to be original (2014, 79K miles) feel identical to the replacements I purchased. But, I figured that since I lost roughly 7-8 years of lifespan from the pain and frustration of struggling to remove the originals that I should replace them anyway. I've said it here before, but the engineer who decided that the bottom nut on the sway bar links should face in towards the motor instead of out towards the DIY idiot trying to remove it should burn in hell.

 

[gmcjetpilot]

Not sure why the thread drifted ha ha.

Charge LEAF drive battery to 60-70% and leave it unplugged. The drive battey will be fine.

The 12v you can put on trickle charger but I would just charge it manually to 100% and also leave it off charger. If the 12v battery is healthy 5 weeks it should be fine.

As far as shutting water off, turning gas water heat to pilot. No. I don't do it, but its not a bad idea. If your heater is old it can spring a leak. Mine is in attic. It is also gas. It leaked once and it drained out pan to outside slowly. I was home and noticed water on sidewalk where drain comes out house. If the side walk was not there ( I had installed after I bought house) and it was grass never woukd know.* Even still it leaked for a week before I noticed. Water heater was only 6 yrs old. I got extended 9 yr warranty. I am now changing the anode rod every 2 or 3 years.
* I use to have water alarm in pan. It stopped working when I tested it, never replaced. Need to get another. Water heater should be in garage so if it leaks it runs our garage and under garage door down drive.

 

[Bombastinator2]

1. To make is more like a regular car
2. Yes, though any time you leave a car for a long time it is recommended to disconnect the 12v. Here too. If you do it a lot they sell disconnect switches to make a wrench unnecessary. Basically you store it like an ICE car. (All this was likely covered by others earlier)

 

[aqn]

From the owner's manual of my 2011 SV (YMMV), red emphasis is mine:

Page EV-4
CHARGING THE 12-VOLT BATTERY
While vehicle is driven
The Li-ion battery charges the 12-volt battery as necessary when the power switch is in the READY to drive position.

While the vehicle is not in use
When the EV (Electric Vehicle) system is off, the 12-volt battery charges automatically for 5 minutes every 5 days.

The charge timing resets to 5 days without charging the 12-volt battery if:
* The vehicle is placed in the READY to drive position for more than 5 minutes.
* The Li-ion battery is charged for more than 5 minutes.