Parallel cells with a dud?

[Hummina Shadeeba]

can you please explain how it will play out if one of a couple parallel cells dies. a dead cell would hit it's low voltage and high voltage max quicker but it's held safe from the voltage limits by the other cells ..and the only downside is a decrease in capacity as the good cells are limited in their ability to take on charge by the one dud? Or can someone please link me to how this will play out
How do u even know u have a dud in there when they're all in parallel and u can't put ur meter on a single cell
Just put together my pack and shorted a cell to 4 others and it cooked it hot and it even puffed the steel can a bit and it dropped .2 volts!!! So bummed. Don't have an extra and I threw it in and will see.

 

[Punx0r]

If the cell fails open-circuit then you simply loose capacity. If it's still in circuit (most likely) then you risk fire/death as charging current is pumped into the damaged cell.

You can't test/measure it without physically separating it from the other cells in the parallel group.

 

[amberwolf]

Just put together my pack and shorted a cell to 4 others and it cooked it hot and it even puffed the steel can a bit and it dropped .2 volts!!! So bummed. Don't have an extra and I threw it in and will see.

Please notify the people that live near you so they can be ready to evacuate quickly when your home burns from the fire that cell could cause.

Why on earth would you put something you KNOW is a fire risk into anything you will be using?

I highly recommend you remove that cell immediately and discharge it and recycle it, before you or someone else else is killed by it.

 

[dogman dan]

We'll see you in the news. Hope nobody actually dies in the fire.

As said above, it might fail without a fire, but the cell you ruined, and kept, IS likely to cause one. Mo bettah to run your pack with 1s less than put that known to be dangerous cell in there.

Generally a dud that just wears out will drag the others down with it, so finding the one dud is a non issue. They all get ruined, when they all get discharged below 100%. This can happen slow enough to not cause a fire, despite a bms shutting down discharge. Or,, a bms malfunction can discharge the whole string to 0v. But either way, the dud is usually found because it dragged the whole string of paralleled cells with it.