Why did our 2019 leaf die (completely) overnight?

[handee]

This morning our 2019 leaf was nearly completely dead. We managed to open the driver side door with the electronic key and then everything went dark: power button does nothing at all.

We've summoned recovery however we are in a fairly remote area and expect the mechanic to take ages, and when they get here they won't know anything about electric cars. Our nearest Nissan dealership involves a day trip. So I am interested in trying to work out what the problem is.

Yesterday I drove the car for about 70 minutes in total, using about 15% of the main battery (up a big hill in the morning, then down a big hill again in the afternoon, if it matters that the battery was mostly used in the morning and in the afternoon it was mostly regen).

When I parked I didn't bother plugging it in, as the battery meter was still reading over 60%.

Does anyone have any theories as to what might have happened? Looking at other posts on this forum it seems it could be something to do with the 12v battery. However, I thought the 12v charged from what I think of as "the big battery" when the car is driving - and i did quite a bit of that just yesterday. I can't have left the car switched on, as it was locked and it won't lock if it's on.

Update, in case anyone is interested:
Nissan replaced the battery, at the end of August.
Now visiting parents and it's gone again so we're waiting for recovery again. Since the last event in Aug I have been very careful about leaving it plugged in but not charging, and we're careful about doing long drives every now and then so it's not sat on the driveway.
Had it's 2 year service mid November, full check, everything reported to be fine.
Colour me unimpressed.

 

[alozzy]

Earlier in this post you mentioned you were "going to go out tomorrow" to buy a 12V battery charger or maintainer (wasn't clear which one)...

If you bought a maintainer, have you been using that?

It sounds like you have a parasitic load on the 12V battery somewhere. It's tedious, but you could troubleshoot that by pulling a different fuse each night (from the under dash fuse panel) to try to isolate which circuit that parasitic loss is on. At least that might narrow down the scope of the problem.

Did you have any after market accessories, requiring a 12V supply, installed anywhere in the vehicle?

 

[user 24513]

Update, in case anyone is interested:

We are definitely interested, and thanks for posting. Please let us know what the problem turns out to be....

 

[handee]

Thanks for the response, alozzy!

We bought a charger but not a maintainer last time. The original 12v battery had lasted 18 months and I thought there might be a possible cause of drain originally* i had hoped it was a one off problem.

Since then we've been charging the big battery for 1h+ on a 7kw at least once a week. Am I wrong in my understanding that also charges the 12v?

We have nothing plugged in (no leaf spy, yet), and don''t usually charge phones in the car.

Cheers
H.

*we have a zappi charger at home that will charge the big battery when the solar is generating, so on cloudy days we would often leave the main charge port open with a charger plugged in; lots of people mentioned that plugged in but not charging could be an issue. we've stopped doing that.

 

[handee]

Update: nice RAC guy just left, very knowledgeable chap, taught me things I didn't know.

12v battery was flat - totally depleted (reading <5v). However all the battery health measures said it was fine. He shut the car down to work out what the residual drain was when the car is not on and there was nothing he could detect draining the 12v. However, it remains the case that we did ~300 miles on the 26th, then some short trips on the 28th (10 minutes to a rapid charger, back again, then two 35 minute trips including a bit of motorway), and when we try to move the car on the 30th it's totally dead.

I think something must have been draining the battery when it was sat on the driveway.

 

[SageBrush]

Leaving the car plugged in but not charging was a common 12v killing method for earlier Gen LEAFs; I don't know if it still applies to to OP's LEAF.

My suggestion, during periods of light use, is to NOT leave the EVSE plugged in but to put the 12v on a trickle charger *. Depending on what 12V was bought 18 months ago, a deep discharge could have killed it and OP now has to get a new one, or it might be recoverable. The testing that the mechanic did is not likely to be reliable since a discharge test under load is needed and that takes time.

* People in the forum have mentioned running a pigtail from the 12v to the charge port cubby to make it convenient to connect the trickle charger.

 

[handee]

Update update: we left the 12v battery charger connected to the car for a few hours yesterday. It's a "smart" charger with progress bars and it tells what voltage the battery is taking as it's charging. Got to 2-3 "bars" on the smart charge meter.

This morning, we plug it in again to top it up again (car has been on the driveway locked, not plugged in, switched off all night) and the 12v is reading 0-1 bars. I don't have a multimeter here so can't do any more tests, but it seems to me there could be an unexplained overnight drain.

 

[LeftieBiker]

Unless the battery itself has a high self-discharge rate for some reason, that would appear to be the case.

 

[handee]

actuallly - i guess the "smart" battery charger has to estimate the capacity of the battery it's charging. not sure how they do that. it has gone from 0-1 to 2-3 bars quickly, so maybe things aren't as bad as i thought?
we will monitor and we will also go for a short drive today and see what happens

 

[nlspace]

If the 12V battery was down to ~5V, then it will take one or two days of constant charging with a smart charger to do the bulk charging. It needs to get up to 14.4 and held there long enough to desulfate the plates if possible (it may be too far gone for that).

In my experience and from what i have seen on this forum, the laef charging system doesn't properly maintain a lead acid battery and requires external countermeasures if you desire to get a good service life.

 

[GerryAZ]

Handee,

I suspect you will find that the 12V battery installed by the dealer is weak even though the rescue service test indicated discharged, but OK. Car dealers often stock lower quality 12V batteries and they can sit on the shelf for a long time. Try connecting your smart charger whenever the car is parked and see if the battery ever reaches full charge (according to the smart charger). It should reach full charge after 12 hours or less of charging with the smart charger (assuming the charger is capable of at least 4 amperes).

 

[LeftieBiker]

The other reason that the new battery may be weak is that auto parts dealers (and sometimes even Nissan dealers) assume that a new battery will be fully charged in a short time by the car's alternator. This is usually the case - in cars that have alternators. The DC-DC converter in the Leaf is capable of charging the 12 volt battery fast enough, but it often doesn't, and even when it does it often takes it much longer.

Gerry has had no trouble with any of his 12 volt batteries, though. I think it may be something about the climate in AZ...

 

[GerryAZ]

The other reason that the new battery may be weak is that auto parts dealers (and sometimes even Nissan dealers) assume that a new battery will be fully charged in a short time by the car's alternator. This is usually the case - in cars that have alternators. The DC-DC converter in the Leaf is capable of charging the 12 volt battery fast enough, but it often doesn't, and even when it does it often takes it much longer.

Gerry has had no trouble with any of his 12 volt batteries, though. I think it may be something about the climate in AZ...

Conventional 12V batteries have short lives in gas cars here because under hood temperatures cook them. The OEM batteries in all three of my LEAF's lasted longer than typical for gas engine cars because temperatures under the hood are much lower. AGM batteries do much better in my climate as long as they are not overcharged. I use AGM batteries in all of my vehicles. Deep cycle AGM batteries are ideal for the LEAF because they have enough reserve to supply residual load while the car is off and they have low internal resistance so they recharge quickly when the DC-DC converter is active. The DC-DC converter can provide as much current as a heavy-duty alternator, but a battery that has been sitting on a shelf for a long time may not absorb current unless the charging voltage is high so even a smart external charger may not charge it adequately.

 

[LeftieBiker]

The DC-DC converter can provide as much current as a heavy-duty alternator, but a battery that has been sitting on a shelf for a long time may not absorb current unless the charging voltage is high so even a smart external charger may not charge it adequately.

I understand. It's just that the DC-DC converter is controlled by a charging system that can seem downright...lazy. That's why new batteries of any type should be fully charged before or right after installation in a Leaf.