Hi all. My spare inverter is giving error code 55 when the battery is not fully charged. It is switching itself off every 5 minutes. I saw elsewhere on this forum that it is due to loads with too much DC in them. 

I switched off everything in our house and later switched off the main breaker. Still,the inverter switched off and displayed error 55. 

What can I do to fix this, as my primary inverter is in for repairs. Could it be fixed by updating the firmware?

[ Edit: Apologies for the duplicate post. I didn't realise that the OP had duplicated his post, and I thought my reply somehow didn't go through. This thread could be deleted. ]

Is the spare inverter a 64 V model (i.e. can the bulk charge voltage be set to as high as 64 V)? If so, it may be a mismatch between your inverter and your battery. The 64 V types have trouble making a 230 V sine wave with a battery voltage below about 49 V. But I usually would not expect fault code 55.

Fault code 55 sounds like a hardware fault to me. Is this spare inverter rather old now? Over 5 years? If so, the original, mediocre quality electrolytic capacitors might have dried out and started to cause problems. Doubly likely if it's a clone.

Unfortunately, the repairs and modifications thread doesn't mention fault code 55 in the index, and a quick search doesn't reveal anything useful. Sorry.

Edited January 12, 20242 yr by Coulomb

Thank you very much. I was suspecting that it could have to do with 49V, because it drops out below 49 V and starts up by itself as soon as the battery (Pylontech UB3000) is almost full. It is quite old, bought in 2018. Bulk charge voltage can be set to 64V. It did work fine for the first few days though.

Thanks, now I know what to expect. I also know that I should get my inverter back from the repair shop

Edited January 12, 20242 yr by Reinhard