Need help! 48 volt caught fire

Gazoo

Dumb Dumb
I am amazed the converter wiring could but pan up the cell cable connection.
Same here. I am confused by that as well. I think something else was not wired correctly in addition to the converter. + and - tied together will give a very bad result.
 

7TZ

New Member
Both the black wires where connected to ground, the input one is the one that is melted was connected to the negative bus bar that had the bms going to it. I used the below diagram for the BMS
 

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7TZ

New Member
Here are my BMS settings
 

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Gazoo

Dumb Dumb
Both the black wires where connected to ground, the input one is the one that is melted was connected to the negative bus bar that had the bms going to it.
I see that now. The only wire connected to that terminal is the yellow one. I can't tell where the burnt wire was connected. Also on the other side of the terminal there is a red/white wire connected to it. Where does the black wire go that's connected to that terminal?

I think you need to post a wiring diagram of your system.
 
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7TZ

New Member
Sorry I’m not a artist but this is how I had it connected.
 

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jwelter99

Solar Addict
Also the way the cells are mounted into the L channel frame - you need to be careful as the case of the cells is hot and that blue wrap is not the most durable stuff. You can easily get a short to ground if that frame is metal (it appears to be).
 

AussieSim

Solar Addict
48V is a life threatening voltage if wired incorrectly. You might be wiser to start at 24V, with safety glasses and gloves. Make sure there is no bare metal, cover busbars and terminals in Kapton tape. Use insulated tools. Use appripriate fuses and safety switches.

I would also suggest you run in the system in a detached shed so that you don't burn down your house.
 

jwelter99

Solar Addict
48V is a life threatening voltage if wired incorrectly. You might be wiser to start at 24V, with safety glasses and gloves. Make sure there is no bare metal, cover busbars and terminals in Kapton tape. Use insulated tools. Use appripriate fuses and safety switches.

I would also suggest you run in the system in a detached shed so that you don't burn down your house.

IEC 62368-1:2014 defines "safe" as 60VDC or 2mA DC, whichever is less. For AC the limits are 30VAC and 0.5mA. These are considered safe for an ordinary person but you still cannot leave exposed connectors/wires lying around as there's the whole chapter of "electrical fires" to consider.

It only takes about 30mA of 60Hz AC current through the heart to cause fibrillation, compared to 300-500mA of DC current. So the limits above are well below this.

The impedance of the human body at 50V is around 45kΩ. You will need to pass through the skin twice unless you really do something creative.

50V/90kΩ = 550uA.

So while 48V might make your fingers tingle a bit it is not dangerous in handling.

It certainly will make bigger sparks and the smoke genie is bigger then with 12 or 24V systems.
 

Sanwizard

Photon Sorcerer
Same here. I am confused by that as well. I think something else was not wired correctly in addition to the converter. + and - tied together will give a very bad result.
You need to keep the lines on the converter Seperate! Looks like your negatives both go to the same place.
 

7TZ

New Member
You need to keep the lines on the converter Seperate! Looks like your negatives both go to the same place.
I had the battery black going to the negative on the battery and the 12 volt negative going to the frame. Should I not ground the 12 volt negative on the frame?
 

Hedges

I See Electromagnetic Fields!
The cells and battery cable are supposed to carry much higher current. For one cable/terminal to burn off suggests to me it was heating up more than other things. Might have poor contact. I would have expected the smaller wire producing a short to burn out before the fat cable overheated, (but maybe not), so I expect resistive contact getting hot.

After you reassemble, try a test load (e.g. space heater powered by inverter), check for hot connections (which takes time to warm up) and check voltage drops.
 

Gazoo

Dumb Dumb
You need to keep the lines on the converter Seperate! Looks like your negatives both go to the same place.
Could this alone cause the battery cable to get so hot the battery burned? The battery cable looks like a much larger AWG than the converters cable., and the negative input cable of the converter is badly burned. That's what is confusing me.

As Hedges suggested it could be the connection to the battery positive was poor. So there could be two separate problems. A poor connection on the battery and the fact the grounds of the converter were not isolated.
 
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