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RCT Axpert 5.6K Mk4 Inverter Pylontech Issues


Don

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I installed a RCT 5.6K Mk4 inverter, one UP5000 Pylontech battery and 4 x JA 545 watt solar panels at my mom's flat. The system works great. Last weekend I added some plugs to the essential side feeding from the inverter. After I completed the wiring I had to boot up the inverter. Normally I start off with switching on the AC power from Eskom. This time I decided to boot up the Pylontech battery first. The battery went into fault mode immediately with Red Fault light. I tied again, battery goes into fault mode with Red light.

I then switched off the battery and flipped the AC power switch and booted up the inverter first, then started up the battery. No issues, battery started up. Then switched on the solar panels. That is an issue for me. If I switch everything off to work on the system and we do load shedding, I will have to wait for load shedding to end before I can boot up the system.

This morning my mom phones me and informs me the Red fault Light is on the battery. She switched off the battery and switched it back on, but the Red Fault light comes on immediately. Now the battery will not boot up even with Inverter running on AC power. I tell her to pull the battery disconnect fuses between battery and Inverter and switch on the battery. The battery boots up. Close the battery fuse disconnect and the battery connects to inverter and starts charging. All up and running.

The Pylontech battery cannot boot up connected to the Inverter.

Is this a battery problem or is it an Inverter problem?

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8 hours ago, Don said:

The Pylontech battery cannot boot up connected to the Inverter.

Is this a battery problem or is it an Inverter problem?

I assume that this is because you have no pre-charge, so the inverter initially looks like a dead short to the battery. But i thought that Pylontechs and probably other battery brands just limited the current with the internal MOSFETs in the battery. I don't hear of such complaints from 8+ kW Maxs, so I assume it's not because of the 5.6 kW inverter size. Indeed, no-one should have to worry about pre-charge any more as long as they have a battery with a BMS.

The quick fix might be to add pre-charge: a beefy resistor of a few ohms to tens of ohms, preferably one that can take a good surge power (like kilowatts for a fraction of a second), and a dc-rated switch across that resistor. Of course, teaching your mom to use it safely and not burn it up could be tricky...

Maybe there is some hardware glitch in the inverter or the battery.

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20 minutes ago, Coulomb said:

Maybe there is some hardware glitch in the inverter or the battery.

Thanks @Coulomb. I am thinking the inverter has a problem. I have never before had a problem to boot up the inverter with a battery. As you say, when the battery does it checks when booting up, it might see the inverter as a short and go to fault mode. Now I have to disconnect the battery from the inverter and boot up the battery first, then connect it to the inverter. What bothers me is that sometime during the night, the battery went into fault mode while everything was up and running. 

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8 hours ago, Don said:

What bothers me is that sometime during the night, the battery went into fault mode while everything was up and running.

Yes, that seems to be a separate issue. Or I'm just wrong about it being pre-charge related.

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