Hi all,

So I have the following setup and wondering if there is a way for me to add more solar panels.  Every way I see, I will either exceed the amps or voltage that the inverter allows.

Currently have 5 panels in series going in on either side of the inverter.

This almost hits the 250v on each side but I stay under it nicely.  Any way for me to get to 8KW of panels while not exceeding the inverter specs?

 

1 x RCT Axpert MX2 8KVA/8KW Inverter 48V 2x4000W MPPT

Solar Charger Type MPPT

Maximum PV Array Power 8000W (4000W x 2)

MPPT Range @ Operating Voltage 90VDC ~ 450VDC

Maximum PV Array Open Circuit Voltage 500VDC

Maximum Solar Charge Current 120A

Maximum AC Charge Current 120A

Maximum Charge Current 120A

Maximum Input Current 18A x 2

48V DC
Build-in 8000W MPPT Solar Charger With 500V DC Max Open PV Voltage
BMS Port
Include Parallel Kit for Parallel Operations up to 6 Units
Configurable Color With The Built-in RGB LED Bar
Built-in WI-FI For Mobile Monitoring (app is required)
Supports USB On-The-Go Funtion
Built -in Anti-dusk Kit

 

10 x 545 Watt Canadian Solar

Nominal Max. Power (Pmax) 545 W
Opt. Operating Voltage (Vmp) 41.2 V
Opt. Operating Current (Imp) 13.23 A
Open Circuit Voltage (Voc) 49.4 V
Short Circuit Current (Isc)13.95 A
Module Efficiency 21.3%
Operating Temperature -40°C ~ +85°C

 

1 x Greenrich UP5000 Lithium battery

Perhaps I'm not understanding the question or the Axpert specs, but is that not 500V max (incl safety margin) per MPPT string, i.e. you can comfortably have 8-9 panels per string? Over-current will presumably be clipped but you're nowhere near the upper limit of 18A with the panel's Isc of 13.95.  

2 hours ago, Marcel said:

This almost hits the 250v on each side but I stay under it nicely.

you can happily go up to 400V, so 8 panels in series would be ok, so if you can get the same panels, add 6 panels, 3 to each existing string, that would give you just over 4kWp on each MPPT, in terms of Voltage you'd be well within limits (8 x 49.4Voc = under 400V) and in terms of current at 13.95A Isc, you'd also be perfectly within limits...

why you worry about 250V on the MPPT is not clear to me, since...

2 hours ago, Marcel said:

MPPT Range @ Operating Voltage 90VDC ~ 450VDC

Maximum PV Array Open Circuit Voltage 500VDC

and

Maximum Input Current 18A x 2

would even allow you to have 9 panels in series to still be within the MPPT's spec, but 8 is what I'd be comfortable with and ending up with 8 x 41.2Vmp = 329.6V or thereabout during max power production and 8 x 49.4Voc worst case under no power taken from the panels which is just shy of 400V...

So are you guys saying I can go 500v x 2, so 500v on each side?  Is it not 500v in total for the full system, meaning I can only go up to 250v per side.

This is the recommended panels to put on, but that would be so expensive to get 32 panels of 250w

3 hours ago, Marcel said:

So are you guys saying I can go 500v x 2, so 500v on each side?  Is it not 500v in total for the full system, meaning I can only go up to 250v per side.

The Voc is 500V per MPPT VoC in the specs, so use that spec when planning. However, that's the absolute maximum, you need to leave a safety margin, so aim for the operating max voltage spec (450V), which is around 9 panels max, per MPPT, if using larger panels of around 550W each. 

The table you posted suggests as much, e.g. look at their proposed config of say 2 x 12  250W panels, using their illustrative panel spec (Voc 37.7V). 

That indicates just over 450V per MPPT.

Use this 450V per MPPT as a planning maximum. With larger panels, you'd be limited to a smaller number of panels per side given the higher W per panel. Not sure to what extent 8000W is some kind of hard maximum power for the array that the inverter can handle, and maybe that inverter is happier with a larger number of smaller panels to reach its maximum watts while still capping the volts to around 450V per MPPT.

The volts can be reached through various panel configurations but you also need to probably also consider the maximum array size of 8,000W. You could for example achieve close to 8KW power by using two strings (1 per MPPT) of 8x 550W panels = VoC of around 400V per MPPT, total array of 8,800W (maybe too much?), Ioc of 14A per MPPT (make sure panels in series), and less mounting hardware than those 32 panels they mention in the table. 

Edited February 27, 20233 yr by Kalahari Cruiser
clarification

Thanks Everyone,

I think I will just get 4 more of the 545w panels and add them 2 on each string.  That should be my best and cheapest option currently.

That will keep me under 8000w in total and probably the closest I will get to that with my current setup.