Crap ~ Both my 225 amp Class T Fuses Blew

[MrM1]

I get 0.000 OHMs across +/- inverter terminals

 

[MrM1]

This

 

[HRTKD]

Maybe it's just my lack of electronic knowledge, but of course there's continuity there. The pos/neg come together within the components of the inverter. If you had no continuity I would be worried.

 

[MrM1]

Actually, when I put the meter across the inverter positive and negative it starts at 0.2 then drops to 0.1 and then to 000 across inverter +/-

Across the busbar with inverter DISCONNECTED and scc connected I get no reading.2.Just DL on the meter

 

[MrM1]

Maybe it's just my lack of electronic knowledge, but of course there's continuity there. The pos/neg come together within the components of the inverter. If you had no continuity I would be worried.

Yes.... my lack of electrical knowledge too. But when I have just the charge controller external connected there is no continuity between positive and negative

This is like the battery positive and negative we're touching each other which I'm guessing is why the fuse blew. But I have no idea on that unless I go home and check my own inverter

 

[MrM1]

Actually, when I put the meter across the inverter positive and negative it starts at 0.2 then drops to 0.1 and then to 000 across inverter +/-

Across the busbar with inverter DISCONNECTED and scc connected I get no reading ... Just DL on the meter

View attachment 136683

 

[chrisski]

Looks like your portable build is in your signature block. Very nice.

I’m sure you’ve tested for something as simple as cables loosening during the trip?

In my limited experience, the parallel batteries will not provide a perfectly equal load no matter how much care you give in making the wires. A few percentage points away as measured from each BMS is reasonable and highly unlikely 1% will be reached. Any loose cable under load would give a bit of resistance, more under load, and drop the voltage at the inverter and increase the amperage needed to run the load at the same wattage.

That could cause a thing where the total draw is 400 amps but 250 amps is pulled from one side and 150 amps from the other, although a BMS should trip if the fuse doesn’t. A class T fuse can take a bit of time to trip if just barely over the limits.



A loose cable would not show on a continuity test; its close enough to 0 ohms that minute current won’t change enough to make the beep go off or to show on any ohmmeter I’ve ever tried.
The other thing I’ve seen cause problems like this is a cable fraying internally and corroding in a place not visible until parts are pulled away so the whole run can be seen.

 

[MrM1]

Interesting. Especially the current idea.

My question still is, should the DVM beEp when touched across +/- at the inverter with inverter disconnected?

 

[MrM1]

Is it supposed to to do this?

 

[MrM1]

I just don't want to hook it back up and blow another fuse for no reason

But I'm also not excited about reaching out the signature solar for warranty or tech support. The wait times are horrible

 

[TacomaJoe]

I just poked my Samlex 600W inverter and it started with low (near zero) then drifted up (as the cap charged?). Your low ohms is suspicious to me.

 

[chrisski]

Interesting. Especially the current idea.

My question still is, should the DVM beEp when touched across +/- at the inverter with inverter disconnected?

I’m not sure about the DVM EP.

If you’re at a dead end and everything else checks out, that’s when I’d start looking for loose/frayed/corroded cables. I don’t think powering it up and blowing two $25+ fuse until something is found is a good idea.

I have a 9 panel portable panel array and I constantly deal with loose connections. Sometimes an Anderson Plug connector has worked itself out, other times wires have worked themselves out of circuit breakers, other times a wire has come loose from a combiner. Once had a poor connection at a plug and it melted.

 

[TacomaJoe]

Save your fuse. Put a 12V load in series with your inverter connection (basically in place of the fuse). If the inverter is shorted the 12V load will have full power and operate just like it was tied to the battery. While this is pulling some current you can measure the voltage drop across the inverter and across your 12V load. If the inverter is shorted it's voltage drop will be near zero.

 

[MrM1]

I’m not sure about the DVM EP.

If you’re at a dead end and everything else checks out, that’s when I’d start looking for loose/frayed/corroded cables. I don’t think powering it up and blowing two $25+ fuse until something is found is a good idea.

I have a 9 panel portable panel array and I constantly deal with loose connections. Sometimes an Anderson Plug connector has worked itself out, other times wires have worked themselves out of circuit breakers, other times a wire has come loose from a combiner. Once had a poor connection at a plug and it melted.

Everything else is powering up and working correctly , ( my powering up I mean the solar charge controller is coming on when battery voltage is applied) voltage is as expected all the way to the bus bar before the inverter. I have the solar charge controller connected to that bus bar, I just have the inverter disconnected and am afraid to connect it.

I've checked and am checking and cannot find any dead shorts in the wiring. Everything is new and clean, heat shrinked and tight

 

[MrM1]

Save your fuse. Put a 12V load in series with your inverter connection (basically in place of the fuse). If the inverter is shorted the 12V load will have full power and operate just like it was tied to the battery. While this is pulling some current you can measure the voltage drop across the inverter and across your 12V load. If the inverter is shorted it's voltage drop will be near zero.

A 12 volt load, like a 12 volt light or something? I really do not understand this. What would cause it to operate and have voltage? The capacitors of the inverter?

 

[TacomaJoe]

Think of the inverter as a short. It will complete the path to one side of your power, the other side will run to the load. If the inverter was open, your 12V load wouldn't work. Good news here is that you can't blow anything up. An old car lamp will work (just not LED).

LET ME TAKE THAT BACK, I SEE THAT YOU ARE A 48V SYSTEM, YOU NEED A 48V LOAD.

 

[MrM1]

Think of the inverter as a short. It will complete the path to one side of your power, the other side will run to the load. If the inverter was open, your 12V load wouldn't work. Good news here is that you can't blow anything up. An old car lamp will work (just not LED).

LET ME TAKE THAT BACK, I SEE THAT YOU ARE A 48V SYSTEM, YOU NEED A 48V LOAD.

But does there need to be a battery in that? What powers the light or load?

 

[DougfromdaUP]

But does there need to be a battery in that? What powers the light or load?

This load is placed in series with the battery leads, for testing only. It will allow you to energize your inverter without risking your expensive fuses yet still limit current to a low value. Your battery powers the inverter once its caps are charged, but you won't be able to apply much of a real load.

 

[TacomaJoe]

Yes, you need a battery. Think of it this way. It's like a pre-charge resistor. In this case if your inverter is shorted, it won't charge up but at the same time instead of blowing a fuse the pre-charge just gets warm.

 

[MrM1]

Yes, you need a battery. Think of it this way. It's like a pre-charge resistor. In this case if your inverter is shorted, it won't charge up but at the same time instead of blowing a fuse the pre-charge just gets warm.

Got it.

Now to find a 48v load.

Would a standard water heater element work?