Eeek help! Eve280amp Batterys melted! Is my bms faulty or what happened here ?

[YOTA]

Maybe you have an idea what went wrong ? Bms failure … ?
It’s in a bus ?

I have x2 24v packs connected togther.

So x2 bms. One on each bank.

System seemed to work okay for about 2 weeks.. and suddenly on an afternoon parked under a tree for about 5days not moving..

I smells nothing strange.. not sure what it was .. few days later opened the battery box melted casings on all the batterys.
Battery bank shut down. X2 cells reading 0.2 or something dead flat.

what seems to be happening is one bms. Is charging its battery bank from the other. (As I have no power input from solar or anything at this moment in time)

Is the bms meant to do that ? Or is the bms faulty

See photos for bms settings and damage.

I have since removed the positive cable connecting this bank to the other.. my other bank seems to work as it should.

But now I don’t know what to do with this one where to start.

There are no shorted cable points or weld marks on connectors wires don’t appear burnt out or anything it just got Uber got it the box and yeah I mean I thought the bms would shut down over temperature ?
?

I tried charging one of the dead cells with a desktop charger.. it seems to be okay the other one not.

The strange thing is the two dead cells are not melted all the other okay cells are melted

View attachment 171626

 

[HighTechLab]

Do your cells have separators in between them? It’s possible the aluminum cases rubbed together. Also it looks like they are in an aluminum box - how well are the bottoms of the cells insulated?

Overall I would say your build quality looks pretty poor…if you rebuild this, you should take some pride in it and make it look less like the spaghetti monster.

 

[SeaGal]

Total Cycle Capacity is set wrong on the BMS, but that is not a cause of the failure. Other settings look OK.

As @HighTechLab said - what insulation / separators are between the cells? The thin blue plastic sheathing of the cells is not enough for a static application let alone a mobile environment. My best guess is movement caused failure of insulation between cells.

 

[Supervstech]

Also, you NEVER want to use copper bussbars on aluminum terminals... Likely rather is your first issue.

 

[Quattrohead]

Your BMS settings are quite conservative and look fine but as others have suggested, the build quality leaves a lot to be desired. Mixing copper and aluminum is a no no, letting the cell sit right next to each other is a no no, crimp only BMS balance cables are huge no no.
I am not sure why but it looks like they all got rather hot. You got away with a significantly bigger problem here.

 

[HRTKD]

It looks like there is corrosion on the bus bars/terminal. What does the bare cell terminal look like?

In picture 3025 (2nd of the three battery pictures) it looks like something dripped on the black wires at the back of the picture.

Note: moved the thread to the "Up In Smoke" subforum.

 

[Supervstech]

Your BMS settings are quite conservative and look fine but as others have suggested, the build quality leaves a lot to be desired. Mixing copper and aluminum is a no no, letting the cell sit right next to each other is a no no, crimp only BMS balance cables are huge no no.
I am not sure why but it looks like they all got rather hot. You got away with a significantly bigger problem here.

On your balance cables note.
Why is that a huge nono?
How would you connect the balance cables?

 

[Quattrohead]

On your balance cables note.
Why is that a huge nono?
How would you connect the balance cables?

Soldered connections.

 

[Supervstech]

Soldered connections.

Any particular reason?
Soldered would likely be less susceptible to a vibration load, but balance conductors are minimal amperage, so properly crimped should be fine.

Teach me. I like to know why.

 

[Brett V]

Are there lead acid batteries in the same compartment? Routine exposure to saltwater mist? That level or corrosion is NOT normal! Looking at the whole mess, I can imagine the condition of the BMS.

 

[Quattrohead]

Any particular reason?
Soldered would likely be less susceptible to a vibration load, but balance conductors are minimal amperage, so properly crimped should be fine.

Teach me. I like to know why.

The only way you can make a proper crimp is with hundreds of dollars worth of tools and expensive crimps, your harbor freight 5.99 kit ain't going to do it.
However most people that have a soldering iron can probably use it ok and make a good solid connection for about 20 bucks worth of tool.

 

[Alkaline]

Maybe you have an idea what went wrong ? Bms failure … ?
It’s in a bus ?

I have x2 24v packs connected togther.

So x2 bms. One on each bank.

System seemed to work okay for about 2 weeks.. and suddenly on an afternoon parked under a tree for about 5days not moving..

I smells nothing strange.. not sure what it was .. few days later opened the battery box melted casings on all the batterys.
Battery bank shut down. X2 cells reading 0.2 or something dead flat.

what seems to be happening is one bms. Is charging its battery bank from the other. (As I have no power input from solar or anything at this moment in time)

Is the bms meant to do that ? Or is the bms faulty

See photos for bms settings and damage.

I have since removed the positive cable connecting this bank to the other.. my other bank seems to work as it should.

But now I don’t know what to do with this one where to start.

There are no shorted cable points or weld marks on connectors wires don’t appear burnt out or anything it just got Uber got it the box and yeah I mean I thought the bms would shut down over temperature ?
?

I tried charging one of the dead cells with a desktop charger.. it seems to be okay the other one not.

The strange thing is the two dead cells are not melted all the other okay cells are melted

View attachment 171626
View attachment 171632

Sorry YOTA but I think you bit off more than you can chew with this project... so many issues, no insulation, also how did you secure your cells or were the bouncing around? If so maybe the sides rubbed against the aluminum wall and shorted out.


Yes need to redo the entire pack and line the sides of the case you have with fiberglass sheets.

 

[YOTA]

Okay so… what it sounds like is the plastic casing of the batterys maybe rubbed off and other the batterys connected to eachother via casing or maybe even made the whole box live ?

All the connectors are properly crimped, bms wires are crimped and soldered and all the cabling has heavy duty heat shrink.

There are no signs of melted cables. (Bms wires, or main lines) obviously the pack got really hot.. as all the tops are melted and you can see the terminals have changed color due to heat.

All the weird sutt is from melting battery casing. I assume.

This bank is brand new only a month not even.

No signs of weld marks from bms touching or anything.

So now I’m starting to think it’s what was mentioned about making padding between. All the cells, box. Insulating it.

- from reading above comments the plastic casing is usless. Got it.

- still don’t understand why my bms is letting 3000watts go through it (taking from my other battery bank) to charge this one.. that’s not meant to happen is it ?

 

[YOTA]

Are there lead acid batteries in the same compartment? Routine exposure to saltwater mist? That level or corrosion is NOT normal! Looking at the whole mess, I can imagine the condition of the BMS.

Yeah not normal at all.. it’s a brand new pack. All that messy smoke / sutt is from the batterys melting. Plastic. Glue. Ect.

 

[YOTA]

Total Cycle Capacity is set wrong on the BMS, but that is not a cause of the failure. Other settings look OK.

As @HighTechLab said - what insulation / separators are between the cells? The thin blue plastic sheathing of the cells is not enough for a static application let alone a mobile environment. My best guess is movement caused failure of insulation between cells.

Thankyou this is somthing I wasn’t thinking about this could may actually been the problem.

 

[YOTA]

Thankyou this is somthing I wasn’t thinking about this could may actually been the problem.

What’s the total cycle capacity should be ?

 

[SeaGal]

What’s the total cycle capacity should be ?

As I said above this value will not be a cause of the overheating issue.

My understanding of the two capacity values used in the JBD / Overkill BMS is:-

Total Battery Capacity / Designed Capacity

This is set to the stated battery pack’s capacity. It is not used by the BMS to calculate the SOC. It is only there for users of the BMS to see the intended capacity of the cells. So basically it does nothing active.

Total Cycle Capacity

This should be set to the actual capacity of the pack and is used by the BMS to calculate state of charge as the cells are charged and discharged (*).

This value may be higher than the stated capacity if the cells exceed their stated capacity or lower if the cells are a lower grade and didn't meet their stated capacity.

If you have measured the actual capacity of your cells then enter the actual capacity here to allow the BMS to more accurately report the SOC.

NOTE
(*) when the BMS is reset or any changes are made to the BMS's settings, the BMS will base its starting point SOC using an interpolated calculation based on the voltage / percentage settings you have defined. Hence, if you were to start with the cells at (say) 3250mV, the BMS will estimate the SOC is 50% - this is based on your definitions of 3200mV = 40% and 3300mV = 60%. Then, from that starting value of the SOC, the BMS will increment the SOC during charging and decrement the SOC during discharge based on the measured charge/discharge current and the specified total cycle capacity setting.

 

[ericfx1984]

If one battery is charging off the other battery... It means that you've either not properly balanced them or that You have more resistance on one of your battery banks or wiring causing a mismatch

Alternatively you could have one pack that has a smaller capacity

I have a 460 amp hour, 2P4S battery and a roughly 1300 amp hour 4P4S battery and these two are in parallel with each other

As you can imagine the 460 amp hour battery reaches full charge sooner than the 1300 amp hour battery

If my charge cycle ends before they are both at full charge... The battery that is that a higher state of charge, and therefore higher voltage will transfer current to the other battery until they equalize

Additionally we see similar situations during both charge and discharge cycles

Assuming that I'm starting from a full state of charge on both batteries, well discharging, initially virtually identical current will be pulled from both batteries despite the difference in capacity

However, as the voltage starts to fall you

will have less current being pulled from the smaller battery and more current being pulled from the larger battery

Eventually the batteries will hit a battery voltage that is the same... Of course this is just the flat part of the charge and discharge curve

We also see something similar happen to this during the charging cycle... Just in reverse

 

[YOTA]

Thankyou for the reply makes total sense now ! Thankyou!

 

[YOTA]

As I said above this value will not be a cause of the overheating issue.

My understanding of the two capacity values used in the JBD / Overkill BMS is:-

Total Battery Capacity / Designed Capacity

This is set to the stated battery pack’s capacity. It is not used by the BMS to calculate the SOC. It is only there for users of the BMS to see the intended capacity of the cells. So basically it does nothing active.

Total Cycle Capacity

This should be set to the actual capacity of the pack and is used by the BMS to calculate state of charge as the cells are charged and discharged (*).

This value may be higher than the stated capacity if the cells exceed their stated capacity or lower if the cells are a lower grade and didn't meet their stated capacity.

If you have measured the actual capacity of your cells then enter the actual capacity here to allow the BMS to more accurately report the SOC.

NOTE
(*) when the BMS is reset or any changes are made to the BMS's settings, the BMS will base its starting point SOC using an interpolated calculation based on the voltage / percentage settings you have defined. Hence, if you were to start with the cells at (say) 3250mV, the BMS will estimate the SOC is 50% - this is based on your definitions of 3200mV = 40% and 3300mV = 60%. Then, from that starting value of the SOC, the BMS will increment the SOC during charging and decrement the SOC during discharge based on the measured charge/discharge current and the specified total cycle capacity setting.

Thankyiu thanks ??