Injection problem Nissan Leaf, what to do ?

LEAF’s 12V battery behaviors — and why they go bad

I was a little stuck between posting this in «technical discussion» forum or the heavier-traffic General forums. This seems to be a topic very relevant to troubleshooting, less about benign technical details. Here, I’ll explain how the Leaf’s 12V system behaves, and why those of us without 12V solar panels on the back are screwed so bad.
https://www.youtube.com/watch?v=9VuTDCjMzRw

The problem here is that the 12V battery is maintained at a 13.0V trickle charge with a very brief 14.4V boost charge. First of all: 14.4V is the typical charging voltage for lead-acid batteries. Lower than that, they either charge very slowly, or they don’t charge at all. There’s a threshold voltage that has to be exceeded in order to actively charge the battery. It’s possible that the 14.4V charge is continued until the battery is only absorbing a low number of amps, before it drops down to 13.0V.

The Leaf’s DC-DC system (which acts as an «alternator» for converting high-voltage

380v DC into low-voltage 12v DC) is entirely controlled by the computers in the Leaf — with very precise control. The computer uses a single PWM signal to tell the DC-DC unit exactly what voltage to provide to the 12V system — I think between 10V and 15V DC. See here: https://www.youtube.com/watch?v=BMhcHkOg-Mk

The problem is that, while 13.0V will make all the systems run off the DC-DC power (instead of discharging the 12V battery constantly), it will not actively charge the 12V battery. It’ll just maintain the charge level it was last left at after the 14.4V charging phase ramps down.

This is also contrary to what the Nissan EV techs (at the hotline) have told people in the past, as well as what the manual seems to indicate — that charging the 12V battery is only done while in «Ready» mode, and that regular L2 charging, quick charging, and remote climate control won’t engage charging. That’s a complete load of nonsense. It appears to execute the same charging behavior any time the HV battery is involved for any reason — charging, climate control, and driving alike. It may also perform a maintenance charge every couple weeks, as I’ve heard, but I don’t feel like waiting around a couple weeks with a camera and multimeter to find out

So, while the Leaf does this quick little burst to 14.4V, it seems like it maintains only 60-70% SOC in the lead 12V battery, which subjects it to sulfation and an early need for replacement. Additionally, little bugs in the Leaf’s software tend to make it occasionally, and randomly, not go completely to «sleep» after 2 minutes — as seen in the video here. With such a limited 12V capacity available, that lack of deep-sleep makes the 12V battery completely die, and you’re then left with a car that won’t start (or you may think you need a new 12V battery at that point), when really all you need is a full, proper 12V battery charge.

Leaving the 12V battery at

60-70% SOC is great for those Leaf owners with a solar panel in the rear, but it’s a recipe for disaster for those without. Nissan should’ve provided a different algorithm (13.5V at least, 14

14.4V optimally) for models without a solar panel, so that the 12V battery is properly maintained and continuously left at a full charge as lead-acid batteries prefer. At voltages like those seen in my video, sulfation is occurring constantly in the battery.

(edit: OH MY GOD this forum has GOT to stop chopping-up partial words and turning them into links. now I look like a Volt advert — aargh!)

Sep 2014 — 35,737 miles
2013 LEAF S+Charge — Jan 2014-Feb 2017 — 68,065 miles
2014 LEAF SV+Premium+QC — Feb 2017-present

Re: LEAF’s 12V battery behaviors — and why they go bad

Re: LEAF’s 12V battery behaviors — and why they go bad

Re: LEAF’s 12V battery behaviors — and why they go bad

Re: LEAF’s 12V battery behaviors — and why they go bad

That means battery is nearly full if 55Ah battery can take FEW Ah after raising charging voltage above 14V.

According to Exide «charging & storage guidelines» they recommend to recharge battery if SOC is at or below 60%, or 12.5V OCV.

Re: LEAF’s 12V battery behaviors — and why they go bad

FalconFour wrote: It’s possible that the 14.4V charge is continued until the battery is only absorbing a low number of amps, before it drops down to 13.0V.

The problem is that, while 13.0V will make all the systems run off the DC-DC power (instead of discharging the 12V battery constantly), it will not actively charge the 12V battery. It’ll just maintain the charge level it was last left at after the 14.4V charging phase ramps down.

This is exactly what it does. Use LEAFSpy to watch the amperage going into the battery. It’ll start dumping power into the battery at an alarming rate if you’ve used the battery a lot, then the battery slowly stops taking the power and eventually the LEAF is happy with how slow the battery is charging and switches back to 13 volts. Except sometimes, it seems when it’s cold out there are times when it’ll sit at 14.4V «forever». Or if you use your windshield wipers, that brings it up to 14.4 volts as well.

I seem to recall that the 13 volts it normally runs at after charging is enough for around 3/4 of amp to be measured going into the battery so presumably some of the power is actively charging the battery, slowly.

FWIW I’m on 5.5 years with my original battery though a couple years back I did somewhat regularly start putting it on a desulphating charger.

Re: LEAF’s 12V battery behaviors — and why they go bad

So I got tired of you guys thinking that Leaf is not charging battery correctly.
So I did something.

Facts.
My battery is OEM Nissan-Renault 12V 50Ah battery, manufactured in the first half of 2014.
While it was at 13V float charge I disconnected EVSE.
Switched on full-beams , front fogs, rear fog, standing lights. Got a draw of 19.8A (should be 2x60W, 2x35W, 1x21W, 4x6W). Discharged my
50Ah battery SOC by 20% just be keeping that load for 30 minutes.
Average voltage during 30 minute draw was 11.5V. That means around 10Ah discharge, 115Wh .
Stopped the discharge. Car started to fall asleep. Draw was getting down below 1A.
After waiting for only 2 minutes voltage got up to 12.1V. It would most likely get to 12.2V easily.
That means battery was above 50% SOC, more likely 60% after 20% (10Ah out of 50Ah theoretical) discharge.
Old battery is very likely below rated 50Ah and temperature was 7C — so definitely below 50Ah.

And now comes exactly what I expected.
I connected EVSE back.
Voltage spiked to 14.43-14.47V. Ammeter measured charge above 70Amps for few seconds.
Dropping down to 50Amps. Average charge was around 45Amps during the first minute.
Then 40Amps during the second. 37, 35, 32, 29, 26, 24, 23, 21 during 10th minute, 10.4Amps 20th, 4,9Amps 30th, 1,5-2,0Amps 40th.
During the whole charging process voltage was absolutely steady at 14.42-14.45V. I did measure every minute.
While charging rate was between 1-2A it switched to 13V mode.
Using Excel and video I took I got down to this:
During 40 minute charge cycle 9.27Ah of juice went in. At 14.4V it is 133Wh . Process is 85-90% efficient.

Leaf WILL charge the battery if BATTERY takes the charge. I will test something else soon. I will trick the current sensor with halogen
bulb. I want to verify that switching to 13V mode happens as soon as charge rate at 14.4V drops below 1,3-1,8A, something like that.

I did notice that right after switching back to 13V mode and longer charge time there was a draw from the battery even after Leaf fell asleep (-0,4A)
This is expected as voltage after charging is always above resting voltage for a period of time.
Resting voltage should drop below 13V after like 10 minutes maybe.
Also I noticed that electrolyte was bubbling at very slow rate when battery was charging at 14.4V. This is normal but not recommended on daily basis due to loss of water.

Also we can conclude that SOC definitely stays above 70% during Leafs everyday use. Most likely it is at 80%. Which is not FULL state of charge but not low enough for sulfation to happen within few years.
Like I already mentioned, BMW-s keep their AGM battery charged specifically at 80% to have regen available on demand (3,5kW regen only).
Those batteries last for 5-7 years of heavy use. There is nothing wrong with keeping Lead acid batteries slightly discharged. Like I mentioned in another topic APC UPS’s keep their battery at constant 13.5V. This kills the battery (99% guarantee) during 1-2 years of use. I’ve replaced them multiple times, always the same — ran out of electrolyte.

Therefore there is NOTHING wrong with Leaf charging the battery. It is designed not to charge it to 100%. And there is nothing wrong with that. Charging it to so-called 100% is stressing electrolyte and is not efficient (most likely there are additional losses). If there is a failure it is either because of battery internal defect or unplanned parasitic load. Leaf will charge the battery if it has been drained but will NOT set off an error code like 2005+ BMW-s do.
Therefore if there is a problem it will definitely kill the battery and then the user might do something (if vehicle is out of warranty, otherwise «don’t care» policy)

Also Leaf keeps 12V battery at 13V voltage for hours and hours every day during vehicle lifetime! This is like keeping it trickle charging for years. Most Leafs are used daily. Older type Leafs that are used rarely might have problems as recharging happens only after 5 days while draw is more than on average ICE vehicle due to telematics.

Now we need to measure draw during sleep with 0.01A precision (clamp will not do it) 5 minutes after falling asleep and 12 hours after that to be sure (without any disconnections or touching any buttons). Please. Anybody besides me

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