When does MP2 need pre-charging?

DIY
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1

I’ve recently setup my first Multiplus2 system.
My setup is: MP2 3kva, CerboGX, Lynx Distributor, BlueSea 9001E, MPPT 100/50
DIY Battery with 24V 314AH, JK Inverter BMS

Using a decent clamp-meter (KAIWEETS HT206D) set to Maximum amp mode, I have not been able to detect any inrush. I monitored the main battery positive during initial connection, and power-on. I’ve seen at most 1 amp draw, which was likely going to the Cerbo & MPPT.

Does the MP2 actually have an inrush current? Does it pre-charge itself?

I would guess it would charge capacitors:

  1. At initial power-on
  2. At soft-switch turn to “anything but off”

I would guess it would not charge capacitors:

  1. When Battery leads are connected, but physical switch is Off.

But I do not seem to be seeing any kind of inrush current. Perhaps my clamp-meter isn’t capable?

2

My best guess is the MPPT is charging the inverter. Does anyone know how many watts are needed to charge it?

3

Yes, it has a very large in-rush current. And yes, if your MPPT is enabled it will pre-charge the capacitors in the inverter. An MPPT is one way to accomplish pre-charge because it is inherently current-limiting device. However, that’s only useful during the day time :slight_smile:

Here’s an example of an easy way to add a pre-charge circuit to your inverter: Inverter Pre-Charge Assembly | Off-Grid Power Systems

Get a resistor of suitable size and a momentary switch. Mount the switch to the inverter or panel it’s installed on. Press button for 5 seconds and you’re done. The caps will discharge in short order so the pre-charge circuit is nice so you aren’t switching under load (inrush) and you will extend the life of the main switch contacts as well as the caps.

4

I have the resistor. This thread is more about why it wasn’t necessary. MPPT makes sense.