What if the Leaf doesn't stop charging?

[saintyohann]

I posted this to another thread, but it's buried on page 17 so I thought if wanted more answers, it needed a new thread:

I had a question for those that know more about the charging system and batteries:

Normally the charger ramps down as it gets full. I've watched the readout on some EVSEs and it will drop from about 3.8KW to 100-200W right at the end. I always thought the was to protect the battery.

My question is, what happens if it doesn't start to taper off? What if it keeps putting in 3.8KW until the battery is full and even then keeps going? Battery damage? Worse?

- jon

 

[DarkStar]

My question is, what happens if it doesn't start to taper off? What if it keeps putting in 3.8KW until the battery is full and even then keeps going? Battery damage? Worse?

Without having the battery management system (BMS) schematic handy, I suspect Nissan designed the charging system similar to how most hobbyists do it and they've placed a relay on the AC input designed to fail-safe if one of the BMS monitored cells reaches a specific voltage or the BMS fails to receive voltage from a cell.

 

[adric22]

If the question was, what if no safeguard existed? Or if the safeguard failed? The answer is simple. The batteries would get very, very hot. Then they would probably rupture.

 

[saintyohann]

If the question was, what if no safeguard existed? Or if the safeguard failed? The answer is simple. The batteries would get very, very hot. Then they would probably rupture.

I guess it is more of a "if I hadn't noticed that it wasn't stopping, and manually unplugged, what would or could have happened?"

 

[EatsShootsandLeafs]

I imagine the same thing that would happen with any lithium battery, which is heat and then poof and then fire. But, considering this doesn't happen with laptops, phones, etc. it's really not worth worrying about. The fail safe is pretty good.

 

[ksnogas2112]

But, considering this doesn't happen with laptops, phones, etc. it's really not worth worrying about.

Dell and Sony have both had recalls of their batteries for starting fires. Don't know if it's because of fail safes failing to safe but feces does occur.

 

[Ingineer]

I posted this to another thread, but it's buried on page 17 so I thought if wanted more answers, it needed a new thread:

I had a question for those that know more about the charging system and batteries:

Normally the charger ramps down as it gets full. I've watched the readout on some EVSEs and it will drop from about 3.8KW to 100-200W right at the end. I always thought the was to protect the battery.

My question is, what happens if it doesn't start to taper off? What if it keeps putting in 3.8KW until the battery is full and even then keeps going? Battery damage? Worse?

- jon

This is hypothetical, as there are multiple and highly unlikely failures that would have to occur before something like this could happen. That being said, the battery would definitely be damaged. It's unlikely there would be any physical catastrophe like the laptop scenarios, as the Leaf's battery is of a different chemistry, and in addition, it has triple containment. (The pouch, the can of pouches, and finally the hermetic battery box.)

If this somehow were to occur, there would be multiple codes set, and the car would not be driveable. There's no way this failure could "sneak" by.

-Phil

 

[saintyohann]

If this somehow were to occur, there would be multiple codes set, and the car would not be driveable. There's no way this failure could "sneak" by.

-Phil

Are you sure about this?

Because at my Lemon Law hearing last week, the Nissan Rep said repeatedly that once the condition of the code went away, the code would be removed automatically.

 

[Ingineer]

Are you sure about this?

Because at my Lemon Law hearing last week, the Nissan Rep said repeatedly that once the condition of the code went away, the code would be removed automatically.

Yes, I'm pretty confident that if there was a fault that caused overcharge, resulting in severe battery damage, it wouldn't just "go away". The Vehicle Control Module (VCM) as well as the On-board charger (OBC) would have to suffer failures of certain rarity that I'm sure it wouldn't just magically repair itself. Even if a fault goes away, the VCM stores history of it.

-Phil