Replaced 12v Lead with 12v Lithium

I know I'm a single data point, but my first summer with my 2015 LeafS, I naively left it garaged, plugged in, for 6 weeks. With no ill effects.
What SHOULD have happened to my car?

gncndad said:

I know I'm a single data point, but my first summer with my 2015 LeafS, I naively left it garaged, plugged in, for 6 weeks. With no ill effects.
What SHOULD have happened to my car?

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Are you talking about the 12v battery? If your "first summer" means it was "brand new", then it was too "fresh" to see any ill affects. If you would do that now (5 years later), it would be dead in a week.

Car had 10k on the odo, still at 12 bars.

I don't know when the change was made, but my 2011 would not turn on the DC-DC converter to charge the 12-volt battery if there was anything (such as Bluetooth OBDII adapter) that kept the car's computers from going completely to sleep. I suspect leaving it plugged in would also keep the computers from sleeping. If everything went to sleep, it would turn on the DC-DC converter for a few minutes every 5 days. That was adequate to keep the 12-volt battery charged whenever I parked it long term at my office or the airport.

The 2015 seemed to monitor the 12-volt battery and charge it when necessary even if I inadvertently left the OBDII adapter plugged in while parked. The 2019 has significantly higher power off draw from the 12-volt battery than the two previous cars (I suspect the radio/navigation system remains somewhat active), but it turns on the DC-DC converter as needed to keep the 12-volt battery charged. All three cars are (were) frequently parked for extended time without being plugged in at either my office or the airport.

I am probably in the minority, but I have NEVER connected an external 12-volt battery charger to any of my LEAFs. The original batteries in the 2011 and 2015 both lasted longer than typical for OEM car batteries in my climate. When each failed, I replaced it with a yellow-top Optima deep cycle battery. In each case, I just plugged the car in to charge the traction battery and new 12-volt battery overnight. I will buy the same Optima battery and follow the same initial charging procedure when the OEM battery fails in the 2019.

gncndad said:

I know I'm a single data point, but my first summer with my 2015 LeafS, I naively left it garaged, plugged in, for 6 weeks. With no ill effects.
What SHOULD have happened to my car?

Click to expand...

Your 12 volt battery was run down. When plugged in, the car is using more power than normal. Unplugged, the car goes into low power mode in several hours. Also when unplugged, an algorithm will kick on to boost the 12 volt battery on a regular interval.

You probably just got lucky with a still new battery. I keep thinking that Nissan would improve the process but in my S Plus, the connected voltage is still in the low 12's. Way too low for lead acid.

They did improve it, in that the 12 volt battery doesn't seem to get low enough to die, since about 2015. It is just kept chronically undercharged.

LeftieBiker said:

They did improve it, in that the 12 volt battery doesn't seem to get low enough to die, since about 2015. It is just kept chronically undercharged.

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But the issue still exists. It maybe better but imm, only because it couldn't be worse. No 2019's have died (that I have heard) but a few 2018's have and yeah, some will be user error but it happens too much to blame all the incidents on that.

I can say with our 13 S it is a bummer, we have had it happen three times in the last three month and it is totally random. These most recent onn was while out running errands, third stop at a store, came out and it was dead, once at work and once when we woke up it was dead and hadn't charged the traction battery becasue the 12v had died. I do at least once a week, usually twice, charge the 12 battery and even replaced it last summer again with the same larger 51R that has 1.5 times more capacity than the 35N. It is the randomness of it that totally drives me nuts.

BrockWI said:

I can say with our 13 S it is a bummer, we have had it happen three times in the last three month and it is totally random. These most recent onn was while out running errands, third stop at a store, came out and it was dead, once at work and once when we woke up it was dead and hadn't charged the traction battery becasue the 12v had died. I do at least once a week, usually twice, charge the 12 battery and even replaced it last summer again with the same larger 51R that has 1.5 times more capacity than the 35N. It is the randomness of it that totally drives me nuts.

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You should measure the stand-by current draw on the battery, 3+ minutes after locking the vehicle. It should be about 50-60ma (.050 - .060 amps).
Your TCM ECU (telecommunications) may be randomly powering-on

I have tried that and only one time a few years ago I saw about a 2 amp or 2100mA draw. I thought that was odd, turn the car on and off and after it settled it was back to the normal 60mA. In retrospect, I should have tried to trace what it was at the time. The part that bugs me is with even a 50 Ah 12v battery a 2 amp load shouldn't be a problem for a few hours.

My guess is that the big new battery isn't being charged fully often enough to make up for that high intermittent drain. If you can fully charge the 12 volt battery once a week, and top it off whenever plugged in, that may help, but yeah - you need to find and eliminate the drain. The TCU is usually the #1 suspect.

Totally ironic, but today we ran out to my in-laws to drop off groceries. It is about a 25 minute drive, mostly highway. We brought their groceries in, talked to them from the porch for maybe 10 minutes and went to leave and guess what, the Leaf was dead. I thought "You have got to be kidding me", honestly it was less than 15 minutes. So I flipped the back seat down, crawled in the back (hatch wouldn't even pop open), grabbed the battery (12v 9Ah SLA) and 10mm wrench. Plugged the battery in parallel had my wife try to start it, it lit up like a x-mas tree. I had her shut it off, disconnected the neg from the 12v battery and had only the sla battery on and she tried again and it fired right up. Reconnected the main 12v with a tiny spark, disconnected the SLA and put it all back in the trunk and drove away.

So what the heck, I did charge the 12v Saturday morning (2 days ago) full, only took about 4 hours at 2 amps to get to float. But how was it not charging the 12v while we drove out there? It is currently charging the traction pack since we got home with 30% and of course the 12v is showing 13.98v. I will bulk charge it again once the car is done charging.

I am really tempted to add a battery up front with knife switch to parallel it to the other battery. I thought about a solenoid with a momentary switch in the cabin to parallel them, but that would be work, although my wife would like that if it is cold or raining, she has "jumped" it a couple of times herself. But what if one of our kids has the car, which luckily hasn't happened, yet, they would have to call and I walk them through the process.

It sounds like the new battery is bad. It may have been seriously damaged the first time it got too low. Some batteries withstand extreme low voltage better than others, I'm afraid. It could also have been bad off the shelf, but given the vampire drain issue, I think the second possibility is more likely.

Well that's the thing. The 51R that is in there is now 3.5 years old, but last fall (when it was 3 years old) I did load test the battery by charging it full, then putting a 10a load on and ran it for 3 hours and it was still at 11.6v while under load. So last fall it was at least a 30 Ah battery, probably closer to 40Ah if I ran it all the way down. For the heck of it (and since I am working from home) I am going to run the same test once it is full to see how long it can run a 10 amp load.

FYI my totally unscientific method is to use an old xantrex 700w inverter with a 100w incandescent light bulb and an old fashion analog clock. I set the clock to noon and turn it on, then plug the light bulb in and walk away. The nice thing is the inverter will shut off at about 11v under load so the battery will be pretty low, but not dead dead and then I just look at the clock to see how long it ran to get a rough guess of useable Ah in the battery. I know when I start it is usually pulling about 9.5 amps and after an hour about 10 amps and after 2 hours over 10 amps. Basically as the battery voltage drops the amperage increases to maintain the 115v output side of the inverter. Then for fun I charge it back full using a watthour meter and see how much I have to put back in, usually about 15% more than I took out.

3-1/2 years in a Laef is a worn out battery. It has sulfated to the point that it can no longer hold a charge.

Put a voltmeter on it and watch how low it gets pulled down during START.

It only takes 2 hours for charging the bulk stage because it has no room for any charge, and it's only a surface charge that holds the voltage up--but it has no guts and under load it will drop like a brick.

Don't mess with a parallel aux, just buy a new one and be done with it. Also if you want to get longer life then use a smart charger such as a Yuasa every week to keep it fully charged--lead batteries can permanently sulfate in as little as 3 days. Good Luck to you and keep safe.

I believe you are correct, running the battery dead to many times may have killed it. It ran for 40 minutes, which would put it about 6Ah, that's not going to cut it. I will charge it back full again and try one more time but it looks like a new battery is in order. You may not have read, but I do regularly charge it. As far as bulk charging in two hours, that SHOULD be the case if the battery was kept at a decent capacity as it should just be topping off the battery, but alas it is not.

If only just getting a 12v battery would fix this, but I have had the problem of the Leaf running the 12v dead at least once a month since the car was new. This is actually the third battery now, this one has lasted the longest at 3.5 years, but I have been more diligent about charging it regularly. Whatever is running it dead once in a while is basically killing them when that happens.

i went thru a similar issue. i used a clamp-on current probe, then started pulling fuses under the hood to see which circuit was pulling the current. Can't remember what it was but eventually found it. Is there a light in the trunk on a manual switch? It was something stupid like that.

Have you tried removing the fuse for the TCU and leaving it out for a few days? I'm not sure if that fuse powers anything else important, though. Anyone? Bueller?

The clamp-on ammeter can be used to see if the drain is gone as each accessory fuse is pulled.

I don't believe the 13 S model has a TCU, I thought I looked in to that initially and was told the S's didn't have them.

I had the little relay for the other TCU (transmission control unit) intermittently stick closed on the 2011. That kept the transmission control unit energized which caused excessive residual current. It was so intermittent that it took me a while to find it. I replaced the little relay and all was well until the car met its demise.

Edited to add: In my case, I received an ominous message on the dash something like "T/M System Malfunction" the next time I started the car each time after the relay failed to drop out. I was lucky that it never failed while parked long term, but I was worried about that until I found the problem.