Why we need a BMS...

K

KaminoReal

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Some days ago I forgot over night a battery on charger connected without BMS(defective) it was on CV stage (set to max 4.2V/cell) and in the middle of night a big explosion woke me instant, lucky I was home and could eliminate the fire otherwise today I would be homeless...
 
I had the same issue last week. But I was there to stop the probleme. It was not du to overcharge but to a direct short.
The cell has propelled to the ceilling and make a big hole.
 
I have to question why people are doing this inside their homes? The focus on safe practices must be our main focus. Glad to see you got to it in time but sad to see it even happen in the first place. Time for everyone to step up their game and learn from the mistakes of others. Kudus to KaminoReal for taking the time to share and educate others!
 
Never fun to see. I can say that in RC i have seen many and i say MANY fires over last years where people have charged unattended or in a wrong way. Always balance charge or use proper BMS.

Glad you were there to sort it!
 
Funny, I was just watching a video from Jehu and another dude saying you don't need BMS! This topic can be confusing for us newbies.

I've assumed BMS is good for larger installations but not for smaller ones.

I wonder what type of charger you're using. I don't watch my batteries charge either but I only charge/discharge at 500mA and I use an OPUS so it will turn off if it gets too hot.
 
Oderus420 said:
Funny, I was just watching a video from Jehu and another dude saying you don't need BMS! This topic can be confusing for us newbies.
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Jehu said in his live feed yesterday (Dec 10, 2017) that a bms doesn't need to be used on new cells. Which, I will mostly agree with. New cells you know pretty much exactly what the condition of all the cells are, as they most likely came outta the same chemical batch; so they are basically clones of each other. On reclaimed cells, a bms is highly recommended due to the uncertainty of the condition of the cells, especially when mixing different types, manufacturers, capacities, brands, etc, etc together into an amalgam of power.

Also, it's not that he was using a defective charger, or a cheap one, or custom, or what ever. The problem came in is that he charged several cells in series without the bms to control the charging. So a cell within the series string went severely over-voltage. That is why you need a bms. Over-voltage is far more troublesome and need of protection far more than under-voltage.
 
Korishan said:
Oderus420 said:
Funny, I was just watching a video from Jehu and another dude saying you don't need BMS! This topic can be confusing for us newbies.
Click to expand...

Jehu said in his live feed yesterday (Dec 10, 2017) that a bms doesn't need to be used on new cells. Which, I will mostly agree with. New cells you know pretty much exactly what the condition of all the cells are, as they most likely came outta the same chemical batch; so they are basically clones of each other. On reclaimed cells, a bms is highly recommended due to the uncertainty of the condition of the cells, especially when mixing different types, manufacturers, capacities, brands, etc, etc together into an amalgam of power.
Click to expand...

So he's suggesting those new cells remain new even 2, 12, 24, 50 months later? When do the cells no longer classify as "new" and need a BMS? Sorry, but that's a dumb remark for him to make.
 
that's how I understood. Maybe I misunderstood him. It's possible. wouldn't be the first time I misunderstood someone :s
 
Korishan: That's how I understood it as well.

The other guy I watched said to ditch BMS and use a balance charger instead which seems to be the better thing to do as you're not as reliant on some unknown BMS.

Larger project use Batrium which makes sense from a cost perspective but not for smaller batteries like ebike.
 
Personally I'm gonna use a BMS at all levels. I like the control over the cells performance. Plus, I want a smart BMS so that I can see the numbers coming and going so I can see what's going on with the cell and be able to judge it's life expectancy. So it wouldn't matter to me whether I'm using new/old cells, small/large packs; a BMS will be used. But, then again, I'm a control nut :p
 
Korishan said:
Personally I'm gonna use a BMS at all levels. I like the control over the cells performance. Plus, I want a smart BMS so that I can see the numbers coming and going so I can see what's going on with the cell and be able to judge it's life expectancy. So it wouldn't matter to me whether I'm using new/old cells, small/large packs; a BMS will be used. But, then again, I'm a control nut :p
Click to expand...

So you'd buy a Batrium for a 52V ebike battery vs. wire it up for a balance charger?
 
Oderus420 said:
Korishan said:
Personally I'm gonna use a BMS at all levels. I like the control over the cells performance. Plus, I want a smart BMS so that I can see the numbers coming and going so I can see what's going on with the cell and be able to judge it's life expectancy. So it wouldn't matter to me whether I'm using new/old cells, small/large packs; a BMS will be used. But, then again, I'm a control nut :p
Click to expand...

So you'd buy a Batrium for a 52V ebike battery vs. wire it up for a balance charger?
Click to expand...

He said a BMS, not a Batrium.
 
yes, a BMS, not Batrium. Batrium is one of many types of BMS setups. Kinda like a Ford Mustang is one of many types of cars.
 
mike said:
Oderus420 said:
Korishan said:
Personally I'm gonna use a BMS at all levels. I like the control over the cells performance. Plus, I want a smart BMS so that I can see the numbers coming and going so I can see what's going on with the cell and be able to judge it's life expectancy. So it wouldn't matter to me whether I'm using new/old cells, small/large packs; a BMS will be used. But, then again, I'm a control nut :p
Click to expand...

So you'd buy a Batrium for a 52V ebike battery vs. wire it up for a balance charger?
Click to expand...

He said a BMS, not a Batrium.
Click to expand...

Fair point but the only BMS I'm hearing about that's worth purchasing is Batrium. Cheap BMS from Aliexpress/Ebay etc. seem to be not what little money they're worth.
 
daromer has posted reviews on several other type of bms units that are <$100
 
Korishan said:
daromer has posted reviews on several other type of bms units that are <$100
Click to expand...

Cool, I'll go through his videos again but this time looking for BMS stuff. :)

Thanks.
 
 
What's funny is YouTube says I've watched that video. Must have been a long time ago as I don't recall the details.
 
That's scary KaminoReal! Glad you are ok! Hope you give us more description of what happened so we can learn from it!
 
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