My red led does no longer come on, on my 5 Kw MUST inverter

BertKu · January 2023

For 2 months the 5kw Must inverter, performed a fantastic job, until I needed to shut the system down to make menu changes, and when I removed the terminal of the 48 Volt batteries, it gave an enormous bang when i placed it later back. I have not been able to figure out why. With my old 2 Kva inverter, it was because the electrolytic capacitors were charged up in a very short time, but it never damage the 2 Kva inverter. Anybody who can help me out what the reason is the the 230 Volt site is no longer working.

BB. · January 2023

No chance that the + and - battery bus terminal polarity was reversed when connected to the inverter?

Double check the inverter's input fuses... Some inverters are "polarity protected" by blowing the input fuse(s) if +/- connections are reversed.

Good luck,
-Bill

BertKu · January 2023

BB. said:

No chance that the + and - battery bus terminal polarity was reversed when connected to the inverter?

Double check the inverter's input fuses... Some inverters are "polarity protected" by blowing the input fuse(s) if +/- connections are reversed.

Good luck,
-Bill

I am so sorry Bill, My error, it was not the red light not coming on , but the green flashing light does not want to come on anymore, It only flashes, indicating that the 230 Volt AC is not connected to the system. It worked flawlessly for 2 months until I removed the plus 48 Volt cable terminal from the plus of the 48 volt side of the 4 batteries and put back , when the big bang occurred. Thanks for replying, we have a 12 hour time difference as I live in South Africa, Bert

BB. · January 2023

Good day Bert,

I really do not have anything more I can add... There is the old erase the settings and reprogram. And before attaching the final DC lead, can use a low value resistor to "pre-charge" the input capacitors (high surge current is not good for capacitors--But not many mfg. seem to do anything about it).

Keep battery cables short... And +/- cables together (even twisted). This lowers the inductance and can help reduce over voltage on the DC bus. High current surge (spark) can + inductance could damage the DC Front End of the inverter (at least in theory). But this will not "fix" your current box.

-Bill

BertKu · January 2023

BB. said:

Good day Bert,

I really do not have anything more I can add... There is the old erase the settings and reprogram. And before attaching the final DC lead, can use a low value resistor to "pre-charge" the input capacitors (high surge current is not good for capacitors--But not many mfg. seem to do anything about it).

Keep battery cables short... And +/- cables together (even twisted). This lowers the inductance and can help reduce over voltage on the DC bus. High current surge (spark) can + inductance could damage the DC Front End of the inverter (at least in theory). But this will not "fix" your current box.

-Bill

Thank you very much Bill, I should have used my 20 Watt ,047 Ohm power resistor . Tough luck, You are right, I may have been able to have it prevented, I probably have to open the inverter and see whether I can repair it. There is no reset switch in the MUST 5kva inverter., To return it to the supplier means, long distances 1200 km, and that with 3 times per day load shedding of up to an accumulated period of 8 hours, I may as well give it a try. Thank you so much for your reply. Bert

My red led does no longer come on, on my 5 Kw MUST inverter

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