Help diagnosing dead 12v (as opposed to some other problem) SOLVED

[dhettmer]

We have a 2022 Leaf, bought in Oct 2021, no problems last winter (Detroit area). Temperatures this weekend were just below or just above zero F. We had similar temps last year.

Saturday I ran the heater for at least 15 minutes while shoveling the driveway. 99% sure it was in ready to run mode - braking and pushing the button is pretty automatic for me when I sit in the seat.

Traction battery is at 98%.

Sunday we got the no power to system warning. After trying to get it into ready mode a few times over an hour, it finally went into ready mode and we drove it it for grocery shopping as well as around the neighborhood just in case that would help the battery. Didn't run accessories during that period. Since the car started at the store it seemed we'd done the right thing.

Today (Monday) we got the no power to system warning again, but fussing around like on Sunday didn't help. Tried jumping the battery with our ICE car, but that didn't work.
Battery reads 12.15v. I don't have a load tester.

Were this an ICE vehicle I'd just go buy a new battery and be confident it was the right thing to do. But EVs are new to me. I expected the traction battery would recharged the 12v while running the heater on Saturday, but since the 12v appears dead I think I'm wrong about something.

I would appreciate any recommendations from the more experienced folks. Thanks in advance!

UPDATE: The problem is resolved. I'm recording the solution for future Googlers and am putting it in the original post for people who want the TL;DR version rather than reading the whole thread.

Running the heater pulled the 2-year-old battery way down.
Charging the battery didn't solve the problem.
It required a trip to the Nissan service department. (Also got some overdue work done and minor recall addressed.)

As near as I can tell from a discussion with the service manager (who talked to me like a customer rather than a software architect who's changed timing belts, rebuilt carburetors, etc., and would understand the details), the car couldn't tell if the battery was dead or its 12V charging system wasn't working. So it just stopped trying to start out of fear that if it *did* start it might flake out while driving.

It wouldn't have started even if I had put in a brand new battery.

The tech verified everything was working properly, then had to reset something (using tools I don't have access to) to convince the car all was well.

The battery is fine. They load tested it and ensured it was fully charged.

Also, contrary to what I read (or misread) in the owner's manual, the car changes the battery only when driving, not when in ready to run mode.

 

[cornbinder89]

A fully charged Lead acid battery has as voltage of 2.2 volts/cell and 6 cells, so should have a fully charged voltage of 13.2 volts at rest. Either yours is not charged or is defective. You could try charging with a normal battery charger.
2 years old it shouldn't be bad, I would charge over night before condemning it. a load test would be good to do.

 

[vectormax]

I was having similar issues with my 2020 Leaf Plus. I would get in the car and dash etc. wouldn't lite up. Usually a quick jump would get things going. I would hear a contactor or fuse click. Something like a battery low voltage safety cutoff of sorts.

Anyway I invested in a NOCO Genius 1 (my car is always garaged) and now keep the battery trickle charging at all times.
The Genius 1 is not weather proof, but others do have outdoor ratings.
https://no.co/products/charging
PS: Started having issues after I retired and the car would sit for a week or two without use. Never had problems when I commuted 64 miles round trip 5 days a week.

 

[mrlithium]

To avoid guessing the State of health of the battery, you may want to get a BK - 200 battery checker like this one; LITHIUM CHARGERS | LithiumMoto
( in the orange box at bottom of page )

 

[woeful]

At zero degrees, 12.15V is very low for the open-circuit (with no load and no charging for an hour or more) voltage. The reference voltages for a 12V lead-acid battery increase in the cold, by 38 mV/°C or 21 mV/°F relative to the nominal figures at 20°C or 68°F. That makes the "20% charged" value 1.5 volts higher than the 12.0 volts at reference temperature, i.e. 13.5 V. Conclusion: your 12V battery is not charged; either it's failing (draining charge overnight), being run down by lights left on, or it's not being charged properly by the car.

To check whether the car's 12V battery charge system is working, it's best to monitor the voltage when driving (more precisely, when the car's in READY state - not OFF, ACC (accessories) or ON (without pressing the brake pedal)). Leaf, and most EVs, uses IUoU battery charging - Wikipedia and should run the 12V battery up to at least 15 volts at 0 degrees F/-20 C. If it doesn't, either the battery current and temperature sensor's faulty or something more costly is wrong in the DC-to-DC converter which powers the 12V circuits from the traction battery.

The more likely cause is that the battery's failing. It may be cheaper to replace it than to pay for a proper diagnosis. If it's out of warranty, I'd replace it. If the battery's still in warranty, use that warranty to ask for a replacement.

 

[dhettmer]

Thanks for all the feedback!
This morning the car says to have the 12v charging system checked. I don't know if the car can distinguish between a battery that won't take a charge and a problem with the charging system.
I'm going to buy a charger today and see if I can revive the battery.
The battery is only 2.25 years old (from date of our ownership), so that should still be under warranty. If it doesn't hold a charge I'll contact the dealer about replacement.

 

[nlspace]

Your 12V battery is depleted; if left in a low charge state the plates will sulfate over and permanently lose capacity. A lead acid battery must be kept fully charged all the time or it will suffer capacity loss and shorten the useful lifetime.

 

[dhettmer]

I charged the battery (to 99%), but that doesn't seem to have fixed it. The car continues to say there's no power. It sounds like there's something else going on and I need to call the dealer for service.

 

[Drew21]

Your 12v that worked fine last winter is now a year older. If it's weak, undercharged, or failing you LEAF will have all sorts of issues. Cold temperatures will exacerbate all of these conditions, and an old, cold battery is a recipe for problems.

Since it sounds like you have another car, pull the 12v out of the Leaf and take it to an auto parts store where they can run various tests on it. If it's dead they'll sell you a new one. If it's good then you have confirmed that you have some other issue with your Leaf.

 

[fotajoye]

Here is an associated discussion on replacement 12 volt battery recommendations;
https://mynissanleaf.com/threads/12v-battery-replacement-recommendations.33422/page-2#post-629492

 

[hradek]

At zero degrees, 12.15V is very low for the open-circuit (with no load and no charging for an hour or more) voltage. The reference voltages for a 12V lead-acid battery increase in the cold, by 38 mV/°C or 21 mV/°F relative to the nominal figures at 20°C or 68°F. That makes the "20% charged" value 1.5 volts higher than the 12.0 volts at reference temperature, i.e. 13.5 V. Conclusion: your 12V battery is not charged; either it's failing (draining charge overnight), being run down by lights left on, or it's not being charged properly by the car.

To check whether the car's 12V battery charge system is working, it's best to monitor the voltage when driving (more precisely, when the car's in READY state - not OFF, ACC (accessories) or ON (without pressing the brake pedal)). Leaf, and most EVs, uses IUoU battery charging - Wikipedia and should run the 12V battery up to at least 15 volts at 0 degrees F/-20 C. If it doesn't, either the battery current and temperature sensor's faulty or something more costly is wrong in the DC-to-DC converter which powers the 12V circuits from the traction battery.

The more likely cause is that the battery's failing. It may be cheaper to replace it than to pay for a proper diagnosis. If it's out of warranty, I'd replace it. If the battery's still in warranty, use that warranty to ask for a replacement.

I am on my third 12 volt battery on my 2022 leaf. It seems pretty clear that the cause is overcharging. The charging start up every time you turn the car on and every time you charge the car and on a small EV high voltage battery you tend to have more charging cycles. All three batteries started out at 12 volt resting state but starts dropping below 12 volts within several months. The third battery is now below 12 volts with clear evidence of liquid leaking around the battery caps. My thoughts are that an AGM battery may have a longer live span.

 

[mrlithium]

flooded batteries are designed to fail. I dont know why they keep being sold, yes i do.. It keeps people constantly coming back to the stores to buy another and another, they're cheap and thats what the majority of people want. AGM will last a little longer, Lithium longer still, but, they cost more than flooded, so, never mind...

 

[dhettmer]

Updated the original post with the resolution.

 

[Yodrak]

I am on my third 12 volt battery on my 2022 leaf. ...

There are a lot of threads and posts on the 12 volt battery, most starting off with a bad experience. You seem to be at the worst end of the experience scale. To add a data point, I'm still on my second 12 volt lead-acid battery in my 2013 Leaf. Seems like Your-Mileage-May-Vary is the golden rule with regard to 12 volt batteries in a Leaf.

 

[knightmb]

We have a 2022 Leaf, bought in Oct 2021, no problems last winter (Detroit area). Temperatures this weekend were just below or just above zero F. We had similar temps last year.

Saturday I ran the heater for at least 15 minutes while shoveling the driveway. 99% sure it was in ready to run mode - braking and pushing the button is pretty automatic for me when I sit in the seat.

Traction battery is at 98%.

Sunday we got the no power to system warning. After trying to get it into ready mode a few times over an hour, it finally went into ready mode and we drove it it for grocery shopping as well as around the neighborhood just in case that would help the battery. Didn't run accessories during that period. Since the car started at the store it seemed we'd done the right thing.

Today (Monday) we got the no power to system warning again, but fussing around like on Sunday didn't help. Tried jumping the battery with our ICE car, but that didn't work.
Battery reads 12.15v. I don't have a load tester.

Were this an ICE vehicle I'd just go buy a new battery and be confident it was the right thing to do. But EVs are new to me. I expected the traction battery would recharged the 12v while running the heater on Saturday, but since the 12v appears dead I think I'm wrong about something.

I would appreciate any recommendations from the more experienced folks. Thanks in advance!

UPDATE: The problem is resolved. I'm recording the solution for future Googlers and am putting it in the original post for people who want the TL;DR version rather than reading the whole thread.

Running the heater pulled the 2-year-old battery way down.
Charging the battery didn't solve the problem.
It required a trip to the Nissan service department. (Also got some overdue work done and minor recall addressed.)

As near as I can tell from a discussion with the service manager (who talked to me like a customer rather than a software architect who's changed timing belts, rebuilt carburetors, etc., and would understand the details), the car couldn't tell if the battery was dead or its 12V charging system wasn't working. So it just stopped trying to start out of fear that if it *did* start it might flake out while driving.

It wouldn't have started even if I had put in a brand new battery.

The tech verified everything was working properly, then had to reset something (using tools I don't have access to) to convince the car all was well.

The battery is fine. They load tested it and ensured it was fully charged.

Also, contrary to what I read (or misread) in the owner's manual, the car changes the battery only when driving, not when in ready to run mode.

Well, as others have already posted here, provided it's not an issue with the Leaf 12V system itself, it sounds like the 12V battery is failing. When they did a "load" test on the battery, that was the wrong test. A load test is for a ICE vehicle, meaning can the battery provide enough power for a few seconds to crank over the engine. An EV needs a "capacity" test on the 12V battery. EVs don't need large burst of power to start, only a small, consistent amount for a few seconds. A failing 12V battery can't do that because the voltage drops too low under this small load. I would have the 12V battery check again because cold weather makes a failing battery very easy to detect.

All the tech did was reset the DTC for the 12V battery failing, usually "restart inhibit" I think it's called for the "14v Power Supply EVC"

 

[dhettmer]

We'll see how it goes. This has all the appearances of a Stupid EV Owner trick. As I mentioned in the original post, I drained the bleep out of the battery running the heater while shoveling snow. I really didn't think about how the 12V battery is recharged in an EV. There was a brief period where it started, but we didn't drive the car long enough to recharge the battery back to an appropriate level.

The tech ran the battery through a multicycle load/charge process that demonstrated it was OK as far as their equipment can tell. It's apparently a $7K charging system. The service manager is really chuffed about it and says it's more thorough than others he's had.

They also ran a diagnostic of the charging system before resetting things.

 

[knightmb]

We'll see how it goes. This has all the appearances of a Stupid EV Owner trick. As I mentioned in the original post, I drained the bleep out of the battery running the heater while shoveling snow. I really didn't think about how the 12V battery is recharged in an EV. There was a brief period where it started, but we didn't drive the car long enough to recharge the battery back to an appropriate level.

The tech ran the battery through a multicycle load/charge process that demonstrated it was OK as far as their equipment can tell. It's apparently a $7K charging system. The service manager is really chuffed about it and says it's more thorough than others he's had.

They also ran a diagnostic of the charging system before resetting things.

If the Leaf was in ready mode, running the heater would have no effect on the 12V battery as the traction battery was providing all the power. Now, if you had it in "standby" mode, which is pressing the start button twice with no foot on the pedal and then proceeded to run the seat and steering wheel heaters, rear defroster, lights, etc., then yeah, that would drain the 12v battery pretty fast.

Load test can be done in a few seconds, capacity test can take over an hour or more. Less if the battery fails early while measuring power history. They might have a fancy battery test system that can do that, but if they finished within a few minutes, they were not using the capacity test mode.

Sounds like the 12V system in the Leaf is fine, that kind of puts the blame back on the 12V battery then. I wouldn't blame yourself just yet.

 

[hradek]

There are a lot of threads and posts on the 12 volt battery, most starting off with a bad experience. You seem to be at the worst end of the experience scale. To add a data point, I'm still on my second 12 volt lead-acid battery in my 2013 Leaf. Seems like Your-Mileage-May-Vary is the golden rule with regard to 12 volt batteries in a Leaf.

It is clear that the battery is just getting overcharged. I am going to ask the techs to fix this by only starting a house battery charge cycle when the car is turned on and not every time the car is being charged. On a different issue, do you think it is OK to charge my Leaf at this Tesla charging site. I can see at least two different interpretations of the sign.

 

[LeftieBiker]

I'm sorry, but overcharging is just about the last thing a Leaf accessory battery experiences as a cause of death. I think that you're close, though. I believe that it's all the times the 12 volt battery gets very low and is then charged up, but it isn't the charging that kills it - it's the being run nearly dead. Lead-acid batteries HATE that...

 

[Chad E. Mo]

It is clear that the battery is just getting overcharged.

I'd put a logger on it for validation. Some mentioned here: How to get moving if your 12v battery is dead (ZE1)