Crap ~ Both my 225 amp Class T Fuses Blew

[MrM1]

I have 2 48v 280ah DIY batteries. System has been up and running for several months no problem. The entire system (except Solar panels) is mounted in a cargo trailer and today, out at the farm, them moved the trailer. After powering everything down, moving the trailer, then powering everything up, the system seemed to work. Then 10 min later it did not.

In testing, both of my 225 amp Class T fuses (one on each battery bank) were blown. Because I was not on site, I do not know what they did other than move the trailer. As far as I know 400 amp main fuse (see diagram) is not blown.

What could have caused the 2 Class T Fuses to blow after the system has been up and running for several months?

Could it be that I used a fuse that was too small at 225a?

What should I be testing / looking for before installing new fuses?

Set up:
- 48v system
- 16 EVE 280 ah cells in 2 banks parallel (32 cells total)
- 225 amp fuse on each battery bank (x2)
- 200amp JK Heltec BMS on each battery bank (x2)
- 400 amp main fuse before inverter (x1)
- Cable from batteries to parallel busbar = 00
- Cable from busbar to inverter = 0000
- Growatt 12k AIO inverter with pre-charge resistor switch
- Victron Smart Shunt before the 400 amp fuse

As installed x2



Diagram

 

[Supervstech]

It could be they connected the inverter without charging it up first, and the inrush blew them.

 

[MrM1]

The batteries according to the BMS app still has voltage

We have voltage (53.25v dc) on the battery side of the fuse block, but not on the fuse protected side

So I know the fuses did their job ... I just do not know why they did their job

 

[MrM1]

It could be they connected the inverter without charging it up first, and the inrush blew them.

Good thought. I was "TOLD" ... the used the pre charge switch .... but maybe not

But I was also told, the system powered up for about 10 minutes, and then the inverter shut down.

 

[MrM1]

It could be they connected the inverter without charging it up first, and the inrush blew them.

I am asking now how long OR even if the system powered back up after the trailer was moved.

 

[MrM1]

OK, so they tell me they turned off the array breakers and unplugged the array, but never turned off the inverter. Just turned off the AC out put breaker.
- moved the trailer
- moved it back a bit later
- Plugged in the panels
- and a few minutes later (or maybe instantly, still trying to determine) the inverter turned off

 

[MrM1]

Seems like the battery fuses may have blown when the array was switched back on and qualified to the inverter.

Any idea if the Growatt SC48120 solar charge controller has capacitors in it? They did switch it off and back on. Those caps (if it has caps) might have discharged

 

[Quattrohead]

My money is on the switch melted down.

 

[timselectric]

Any idea if the Growatt SC48120 solar charge controller has capacitors in it?

It does.

 

[MrM1]

My money is on the switch melted down.

Would that blow the fuses before the switch?

He's telling me they never turned off the main switch or the inverter. The trailer was put back in place And every thing reconnected and was running, and system was connected to the building and the building was running (current draw is not more than 4000 AC watts plus tool surge).

Would an AC short blow DC battery fuses? Seems it would blow 15 Amp ac breakers 1st?

 

[MrM1]

I've Got A Fistful of fuses ordered. And we'll have them next week. But I want to have some kind of idea what I'm testing for before I just throw new fuses in and blow them again

 

[timselectric]

I can't think of a normal operation that would blow a 225a fuse. Especially after 10 minutes.

 

[timselectric]

Unless they're running on only one battery. And heavily loaded.

 

[MrM1]

Unless they're running on only one battery. And heavily loaded.

That could b

 

[MrM1]

I can't think of a normal operation that would blow a 225a fuse. Especially after 10 minutes.

Well I've go 4 225a and 2 400a fuses as replacements and spares ordered. Guess I'll go down next week and continuity test everything for(+) to (-) dead shorts, and then put it together and test one section at a time as I power it up.

 

[time2roll]

I assume one battery was supplying most of the power under heavy load due to a poor connection or a BMS tripped off. Then the load shifted and the other fuse opened.

 

[Shimmy]

It does sound like one fuse blew at some point in time, and then the other fuse blew on heavy load or inrush. Do you have data from each BMS to suggest otherwise? I would inspect carefully before replacing the fuse as it could very well be an issue that is going to repeat itself.

Do you have audio amps on site for the first time?

 

[MrM1]

I assume one battery was supplying most of the power under heavy load due to a poor connection or a BMS tripped off. Then the load shifted and the other fuse opened.

It does sound like one fuse blew at some point in time, and then the other fuse blew on heavy load or inrush. Do you have data from each BMS to suggest otherwise? I would inspect carefully before replacing the fuse as it could very well be an issue that is going to repeat itself.

Do you have audio amps on site for the first time?

Not ruling those out. Thx

I'll be able to get at least some data early next week.

 

[Jennifer]

Unrelated but wouldn't this drawing be a bit safer, I moved the 400amp fuse as close as possible to the combined power feed/battery source?

 

[TorC]

Might be better. It's also possible this drawing would have resulted in blowing the 400A fuse instead, if there's any issue in that switch. I'd definitely be inspecting the switch with a jaundiced eye, as it appears to have been between the fuses that blew and the one that didn't.