Parasitic draw story

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The OBDLink LX shuts itself off (sleep mode) after a given time, and wakes up when opening the car door and works without needing to unplug. i don't know what the draw is when "sleeping". It uses the STN chipset which i think is superior to the ELM chips.

Kinda hard to believe the dongle draw is what was pulling down the OPs battery. Maybe it was old and sulfated?

 

[Learjet]

I think I have the same dongle, it stays in the glovebox unless I need to diagnose something or want to log a trip.

That is what I do. I wouldn't recommend leaving one plugged in all the time. Really no reason to.

 

[Jarichus]

I don't know if you care, but:
When a Lead acid cell "sulfates" it builds up a layer on the plate reducing the surface area to "make current". The available current slowly decreases but the battery will show normal voltage, just not be able to provide much current.
When a battery is discharged and recharged a small amount of plate material is "sluffed off" and falls to the bottom of the cell. In a healthy but well used cell, the surface area stays mostly as built, and there for the current providing ability, until enough sluffed off stuff accumulates at the bottom and it shorts the cell, killing it.
It is rare to see an automotive battery die in this method. One day it will crank an engine fine, the next day it shows little to no life. I had a 12 year old battery fail in that method.
Most suffer some sort sulphation choking off the output and the engine cranks slower and slower until it can't supply enough current to crank, but will still "light the lights".
EV's are a odd problem. Not really a cranking use, but not really a deep cycle use either. The battery needs to pull in the main contactors and charge the capacitors via the pre-charge resistors. The need to do this without dropping the voltage enough to cause Communication errors on the CAN BUS.
So it works until it doesn't, but offers no indication that it is sulfating, as there is no high current draw to show that a large part of the plates is either covered with hard sulfate or discharged. In short, it isn't a battery failure but a charging failure.
When dark draw is added in, it compounds the problem, you never see it coming and have no idea there is a problem until one day when the car will not work.
In theory, An EV should be able to optimize charging, as there is no engine that needs to be running to charge. The car doesn't even have to be "on" for the battery to charge. Nissan chose to optimize for minimum HV battery draw, over optimal 12 volt life.
It is why I always say, fully recharge and test. No point in replacing a battery that is merely discharged, and will function just fine if fully charged.
You could forestall any problems by replacing every few years, but the same could be said about replacing the whole car. Better to get to the bottom and address the problem.

I learned a lot about lead acid batteries since the two years I drove the Elcar. I completely agree with your take on battery sulfating. Batteries with longer replacement warranties have more space below the plates. I have also worked on lawn mowers for over 20 years and see some batteries go years and some don't make two seasons. I know it is because of how they are kept charged in the off season. Youtube is full of videos showing you how to shock a battery into working again. My experience with shocking a battery will only last for a short time. I am thinking of adding a trickle 12 volt charger when I charge the traction battery.

 

[cornbinder89]

I learned a lot about lead acid batteries since the two years I drove the Elcar. I completely agree with your take on battery sulfating. Batteries with longer replacement warranties have more space below the plates. I have also worked on lawn mowers for over 20 years and see some batteries go years and some don't make two seasons. I know it is because of how they are kept charged in the off season. Youtube is full of videos showing you how to shock a battery into working again. My experience with shocking a battery will only last for a short time. I am thinking of adding a trickle 12 volt charger when I charge the traction battery.

I have taken to charging my 12 volt occasionally. Depending on how the trickle charger is made, you may want to charge the 12 volt and the HV battery at different times.
Some 12 volt chargers may show as GF on the EVSE and prevent charging.
Not exactly sure what is going on, but did have it trip off once when charging both at the same time. Never looked into it further.
I know that deep cycles worked hard and fast charge last longer than batteries stored on "maintainer" for long periods.
I would love to get to the bottom of the issue once and for all. The OEM charge profile is less than ideal, that is a big part of it, but not all of it. It doesn't explain that wide variation in battery life reported.
Charging at a constant voltage may help but is not going to solve all the problem and give full life either. May be "good enough" for some.

 

[Jarichus]

I have taken to charging my 12 volt occasionally. Depending on how the trickle charger is made, you may want to charge the 12 volt and the HV battery at different times.
Some 12 volt chargers may show as GF on the EVSE and prevent charging.
Not exactly sure what is going on, but did have it trip off once when charging both at the same time. Never looked into it further.
I know that deep cycles worked hard and fast charge last longer than batteries stored on "maintainer" for long periods.
I would love to get to the bottom of the issue once and for all. The OEM charge profile is less than ideal, that is a big part of it, but not all of it. It doesn't explain that wide variation in battery life reported.
Charging at a constant voltage may help but is not going to solve all the problem and give full life either. May be "good enough" for some.

I have learned on this forum that the 12 volt battery gets charged when you charge the traction battery, just not long enough for a lead acid battery. LiFePO4 seems to like being charged and kept to a lower level much like the traction battery and would seem to be a better battery for the Leaf if it were not for the cold weather. I see LiFePO4 batteries will work below -5 degrees F but want to be charged above freezing. Some expense batteries do have heaters built in. The Highlander is supposed to keep the 12 volt battery charged to but if it sets over a week the 12 volt battery is dead. Guess I will just have to get into the routine of trickle charging the batteries!