Split PV Input Across Both DC Input Jacks?

Product Discussion BLUETTI Apex & AC Series
1

In the event that grid power is down during sunlight hours, I would like to connect several of the PV panels from our grid-tied system to the Apex 300.

  1. The user manual says 20A for a PV panel. There are 2 DC input ports on the Apex 300. Is this 20A limit per port? That is, can I have one set of PV panels that supply 16A to the top port simultaneously with another set of PV panels that supply 16A to the bottom port?

  2. If I want to use 3 PV panels, each which are 48V (open circuit) and 5.6A max, would it be better to wire them all in parallel to a single DC input port, or would it be better to put 2 in parallel to 1 port, and the other to the other DC input port?

Note: Our grid-tied system uses SunPower SPR-230E-WHT-D panels, each of which connects to an Enphase micro-inverter. They are installed on a trellis (not the roof), which makes access fairly easy. To switch from the grid-tied system to the Apex 300, I would prepare a cable, unplug one or more panels from its micro-inverter, and plug it into the cable.

2

I recommend connecting two solar panels in parallel to one DC input port, while connecting the third solar panel directly to the other DC input port. This will help balance the current and ensure system stability. If you have any other questions, feel free to ask!

3

You will physically damage the MPPT cables over time if you unplug them and replug them with a current flowing. They are not designed to handle unplug under load so the DC plasma arcing as you do so will damage them and can over time produce hot spots and other problems.

Properly you want a disconnect of some kind rated for the DC current of the panels you can use to isolate them before you change the cables over. In particular once you are dealing with two panels in series you are waving 90v+ at 5.6A around which is enough to damage connectors and is enough to kill you.

4

Thanks for that reminder about the plasma arcing. It appears it is not possible to turn the the charging off using the app, so it looks like I have several choices to prevent an arc from damaging the connector:

  1. Wait until the SOC reaches 100% (with AC output turned off) and the display indicates 0W PV input.
  2. Wait until the sun sets and the display indicates 0W PV input.
  3. Cover the PV panels with cardboard first.
  4. Wire a (replaceable) disconnect in the cable.

I am not worried about electrical shock because the user manual clearly says the maximum voltage for the solar panel input is 60V, and therefore I will not be wiring these panels in series.