LEAF's 12V battery behaviors - and why they go bad

[FalconFour]

Okay, so it happened again today. Went out to the car to head to work, and the door request button did bupkis. Key? Nope, held key in hand and tried pushing again. Dead, dry, done. Went around, opened the car with the emergency key, no dome lights, no dash.

To explain clearly, I'll use a timeline.

• Friday night (Saturday) 12:30am - drove home, parked car. I don't charge at home - battery was at 61%.
• Saturday 3:30pm - went out to car to look for something. Decided to move it back to "defragment" street parking spaces. Started it, moved it about 20 feet, turned it off.
• Sunday 10:45am - went out to car, found it totally dead. Went to glove box, grabbed the jumper attachment for the little jump battery I keep in my laptop bag for cell phone charging :mrgreen: , popped the hood.
• 10:47am - rudely blasted awake by alarm horn going off when connecting the jump battery. Yeah, car was completely dead. After reflexively removing the jumper cable when blasted with the horn, I held the key in my hand over the "unlock" button and connected it again - and shut the alarm off by hitting the unlock button right when it started. With jumper connected, I turned the car on, everything was happy.
• 10:50am - after resetting clock and a couple prefs, I hit the road and fire up Leaf Spy. Noticed that the 12v system was maintaining 14.4V this time...
• 11:19am - Watching the 12V voltage the whole time, the system decided to stop charging the 12V battery just as I'm pulling into work - and it went back to 13V - so, charging for about a grand total of almost exactly 30 minutes.
• 11:25am - used a quick charger at work (video in the gallery here), found that it also charges the battery with just the same pattern as always, while quick charging. It seems to stop charging around 12 amps, and then it seemed to actively find the point at which the 12V battery neither charges nor discharges -- for a moment, it was providing power out to the car, then it settled on ~1A charge.

No matter how you cut it, the Leaf seems to do a crap job of recovering a dead 12V - just giving it a charge until it drops below 12A, then stopping? That's absolutely no good way to maintain a 12V battery. And, given that I usually have 12V problems after leaving it unused for just a single night, that also seems to be an interesting pattern. My Leaf has had pretty much daily use (except maybe 2 weekends a month when I don't go anywhere) ever since I got it, throughout its now-60,000 mile life.

Now that I know how it behaves, and that I can use Leaf Spy to watch the 12V level, I plan on watching it much more closely in the following commutes... maybe that'll help tell me how dead the 12V battery got each night.

 

[arnis]

LIGHTBULB! I just recalled that I've left Leaf switched on in ACC mode (nav on) few times. Accidentally. Double-press without brake pedal.

Could you just check one thing. Can you lock the doors with remote if vehicle is in ACC? gauges are dead, center LCD awake.
Was the car definitely locked when it was dead? Did you check with the handle?

Definitely my and your Leaf stop 14.4V at different battery states. Now I'm starting to suspect current measuring device feedback.
Checked documentation and it explains that current sensor should get 5V input and around 2.5V output.
It could be either some PWM based signal (if so then wiring is not a problem) or voltage based feedback signal that travels to VCM.
If it is voltage based then any extra resistance will fool VCM to stop 14.4V sooner than factory prescribed.
Like I mentioned, my Leaf stops 14.4V at much lower current and my Leaf doesn't do funky stuff. Yours stops at 10+Amps and does tricks.

 

[FalconFour]

- Yep, you can lock the doors (with handle switch, though it won't "beep-beep" to confirm, it'll lock) while it's in ACC or Run. However, closing the door with the ignition on also gives the "beep, beep, beep!" when you close all doors with the key located outside the car (it has directional antennas that pick up if you're in or out of the car).
- If you leave the ACC mode on, it'll turn it off for you after 30 minutes - even if you're still inside the car listening to it. (experience :lol: )
- Yeah, it was definitely locked - I remember walking away from the car and double-checking my memory (I did lock it, right? Yeah, 10 seconds ago it "beep-beep"d at me). And I also pulled the handle this morning, for sure

 

[arnis]

Ok, so we can cross this out. I'll read about how current measuring devices work and can they
be screwed easily (vibration, corrosion, over-torquing, water ingress etc) soon.
Maybe it will explain 5V input ~2.5V output (and can it be verified with simple multimeter, not gonna
invest into DSO for that :lol: ) I'm super-dead now. Gonna charge my battery until it boils.

Definitely my and your Leaf stop 14.4V at different battery states. Now I'm starting to suspect current measuring device feedback.
Checked documentation and it explains that current sensor should get 5V input and around 2.5V output.
It could be either some PWM based signal (if so then wiring is not a problem) or Voltage based feedback signal that travels to VCM.
If it is Voltage based then any extra resistance will fool VCM to stop 14.4V sooner than factory prescribed.
Like I mentioned, my Leaf stops 14.4V at much lower current and my Leaf doesn't do funky stuff. Yours stops at 10+Amps and does tricks.

 

[Rauv]

Have you ever ran out of 12V battery charge:
YES

No (just write No, more comments not necessary)
Yes (if yes mention did you
had OBD adapter plugged in,
YES
left for long time,
A FEW DAYS AT A TIME; NOT CONTINUOUSLY

car is rarely driven (less than 3x per week)
CAR IS DRIVEN AND PLUGGED IN EVERY DAY. HAS SOLAR PANEL. PARKED OUTSIDE BUSINESS HOURS

was the battery replaced,
YES. REPLACED AT 22 MONTHS UNDER A 24 MONTH REPLACEMENT WARRANTY
happened many times,
JUST ONCE.
how many years after purchase
22 MONTHS. THIS NEWER 12V BATTERY IS STILL IN SERVICE AFTER AN ADDITIONAL 20 MONTHS.

 

[GerryAZ]

FalconFour and Arnis,

FalconFour's observation of the 2011 dropping back to float voltage at 10 amperes or higher matches my experience with my 2011. Arnis' measurements showing that charging current tapers to much lower level before dropping to float mode matches my observations on my 2015. Nissan changed the charging algorithm between 2011/2012 and 2015 models.

Gerry

 

[lorenfb]

Read here for additional insight:
http://www.mynissanleaf.com/viewtopic.php?f=9&t=19471

 

[RegGuheert]

FalconFour's observation of the 2011 dropping back to float voltage at 10 amperes or higher matches my experience with my 2011. Arnis' measurements showing that charging current tapers to much lower level before dropping to float mode matches my observations on my 2015. Nissan changed the charging algorithm between 2011/2012 and 2015 models.

Thanks, Gerry! That's a HUGE change which explains a lot!

 

[arnis]

Thanks Gerry.
I read that most other vehicles default to always 14V mode if current sensing sensor is not working (or is disconnected).
If this trick works on 2011/2012 cars it will solve that problem. Though 14 something volts for hours every day is definitely
a lot. I wouldn't recommend that for those who charge longer than 6 hours per day and temperatures above 20C 68F..

Anybody want to try disconnecting current sensor and checking 2011/2012 Leaf reaction?
I can't do that any more due to 0*C/32*F temperature. Leaf keeps 14.5V always active.
Also as we now verified that problem is with early Leafs that drop 14.4V mode at 10+Amps, not 1-2Amps.

 

[FalconFour]

Whoops - I think things are getting a little confused here. Mine, and my testing, is done on a 2013 LEAF - a late build, too (I think, September or August... forgot which). Still stands to reason that something changed between the old ones and the new ones...

(I used to have a 2011, long story. Not sure if I should update my profile info though... it gives me greybeard credits :ugeek: )

 

[GerryAZ]

Whoops - I think things are getting a little confused here. Mine, and my testing, is done on a 2013 LEAF - a late build, too (I think, September or August... forgot which). Still stands to reason that something changed between the old ones and the new ones...

(I used to have a 2011, long story. Not sure if I should update my profile info though... it gives me greybeard credits :ugeek: )

I'm sorry for misleading everyone over the model year of your current Leaf. Since you see the charging drop to float voltage at 10 or 12 amperes on your 2013 (which is what I saw on my 2011) and Arnis see the switch to float at low current, the change in the charging algorithm must have happened in 2014. You could note your current Leaf in your signature area and keep your original delivery date in your profile for graybeard credits.

Gerry

 

[arnis]

Drop might also be temperature dependant. Hot lead-acid battery will have parasitic "charge" impression
at 14.4V with much higher current. This current is still flowing when SOC is at ~107%, faster with hot electrolyte
and slower with cold electrolyte. It would be reasonable to stop at 5 Amps with warm battery - my quess.
I'm not going to reanalyze research again to find the correct current rate to stop :lol:

At the same time I also suspect that there has been a new algorithm since some random production week :lol:


Anybody tried disconnecting current sensor?

 

[lorenfb]

At the same time I also suspect that there has been a new algorithm since some random production week

Right, so having an inadequate 12V battery charging is a needless concern for most Leaf owners.
Of more concern for some should be to avoid a parasitic draw, e.g. an OBDII BT device continuity
plugged in or any system anomaly causing a draw exceeding 100ma.

 

[BrockWI]

Or the random thing out of your control that the cars keeps on randomly :shock:

 

[lorenfb]

Or the random thing out of your control that the cars keeps on randomly :shock:

Yes, which also commonly occurs with ICEVs, i.e. given the extensiveness of present day automotive CAN bus systems
with numerous controllers, e.g. 20+, any one of which can keep a CAN bus active resulting all controllers failing to enter their "sleep mode" resulting in an excessive battery current draw.

 

[arnis]

Leaf is not that complicated. I would say pretty basic BMW 3-series is at least a third more complex.
5-series is at least twice as complex.
It does have pretty basic algorithms for sleeping and it appears random stuff is happening rarely.

Doesn't really matter. 50Ah flooded battery from quality manufacturer costs about 70€ here :lol:
Don't need stealer to change it. Can't say that for BMW :lol:

 

[mrggg]

I would just like to throw in here that I have an RV with a deep cycle battery ( golf cart battery from Costco ). The "converter" ( 120V AC battery charger ) in the RV floats that battery at 13.6V. I have it plugged in all the time in my driveway when not in use, and hardly have to add any water over a one year period in Portland, OR. The total of 220Ah ( two 6V batteries ) draws a charge of about 400mA. The batteries are like new after three years. It seems to me therefore that 13.6V is an almost ideal float voltage. I take the point about charging efficiency, but it seems insignificant by your calculations : 3kWh per month? Thats only ~ 10 miles of range if you NEVER plugged in for a whole month? Who cares ! So, I agree with whomever said Nissan skewed the charging algorithm way too far to the efficiency side.

 

[arnis]

At what temperature is battery kept at 13.6V.

 

[mamarley]

Drop might also be temperature dependant. Hot lead-acid battery will have parasitic "charge" impression
at 14.4V with much higher current. This current is still flowing when SOC is at ~107%, faster with hot electrolyte
and slower with cold electrolyte. It would be reasonable to stop at 5 Amps with warm battery - my quess.
I'm not going to reanalyze research again to find the correct current rate to stop :lol:

At the same time I also suspect that there has been a new algorithm since some random production week :lol:


Anybody tried disconnecting current sensor?

I tried unplugging the current sensor on my 2014 SL today. It does indeed make the 12v system operate at 14v (14.24v exactly, in my case) continuously. It doesn't seem to make any warning lights come on, but it does set the "P1551 000B EV/HEV Battery Current Sensor EVC-165" and "P1557 000B EV/HEV Battery Temp Sensor EVC-173" codes.

 

[LeftieBiker]

The above might suggest yet another bandaid "solution" for those who can't use an external battery maintainer. If the current sensor were connected to the battery through an On/Off switch, it would be possible to enable - preferably from the cabin - a "continuous charge mode" to top off the accessory battery from the car's charging system, while on a short trip, or for an hour or so on a longer one. It might be wise to only switch "modes" when the car is off.