kombiman

https://diyshop.co.za/products/battery-disconnect-fuse-box-onesto?variant=44194423865594&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjw9fqnBhDSARIsAHlcQYQNBTCtFEBJaFDnYYYSlpFBzDBgOVmW47o69ZHAyhEbbtDpluUeIvUaAugCEALw_wcB
 

I use the blade type fuses which are rated up to 1000V DC.
 

You would need to have a small Solar charge controller, which you would then connect the panel to, and the battery you're using on the UPS to. The panel would then help to recharge that battery much quicker than the UPS does.

you didn't tag @Coulomb correctly so he may not see your question (now he would...) you would leave everything as it is and add the separate MPPT controller with its own solar panels also connected to the battery, in parallel with the inverter...

Firstly, congratulations, may your plant serve you and your family according to your expections.  Cometh the Hour, Cometh the Man. 
Like Nirvana , the inverter says to the MPPT : Come As You Are! So, unlike the battery, the pv does not need to match the inverter power. The inverter just takes what is on offer.
I think the 600W limitation is probably to do with product cost and size. 
 
 
 

You would need to have a small Solar charge controller, which you would then connect the panel to, and the battery you're using on the UPS to. The panel would then help to recharge that battery much quicker than the UPS does.

Thanks for the response @Energy-Jason, Please do keep me\us updated. I have a wok collegue who needs two urgently.
thanks so much
Alan