sbms40 stopped working

[john groen]

Hi there, I have an sbms40 that was working great for months until it suddenly stopped working and went completely blank. Lucky it did turn off the inverter so no damage or issue to anything else. Looking at the board, I can not find any signs of damage but checking voltages showed battery voltage at the top green fuse on the right hand side but no voltage on the left side. thermal image immediately heats the fuse on power up. Any ideas? Pictures attached. Thanks

[Dacian Todea (electrodacus)]

John,

I do not think I have seen anything similar before. It looks like the resealable fuse is at +105C meaning is tripped.

So there is either some short circuit like one of the ceramic capacitors around there or it is the DC-DC converter the 6 pin device that somehow failed (it is rated 60V on the input so not sure how that could have happened).

Did you try to power it over USB ?

If you have a multimeter try and test the green reset-able fuse resistance when it cools down. Also test what is the resistance between ground and the output side of the fuse.

You can send it to me for a free repair and then I can get a bit of a better idea of what failed. 

[john groen]

Yes, I have tried usb but no life. The resistance across the fuse in situ is 0.9 ohms and the output side to earth is 63 ohms.

[Dacian Todea (electrodacus)]

The fuse seems fine but that 63ohm seems to not be useful as it is not looking like a short so unlikely to be  cracked ceramic capacitor and at 5V / 63ohms = 0.08A the fuse will not open so not a useful measurement.

Unfortunately it looks more like damage after the DC-DC converter so micro controller most likely.

Did you had anything connected to the black 2x8 pin connector (maybe some computer over serial or some additional EXT IOx)?

Did  you had an external current shunt ? and if so is it directly connected to the battery+ connector ?

Seems like you will need to ship it to me for repair unless you want to attempt to do that yourself.