Update - decided to stay with Renogy and spend money (saved on Victron) on one more panel. Also, got a Bluetooth BT-1. Not from Renogy - they wanted $CAD 49, so I figured that BT is just a BT and got it from Aliexpress for $CAD 25:
Bluetooth dongle. There were other slightly cheaper, but this one was said to work with Renogy - don't remember where, probably on Reddit. Strangely, BT arrived from China in 10 days. To modify the MPPT settings you need Admin password for BT, it was provided in the tiny BT manual that I was about to throw away.
Downloaded Renogy app, some Chinglish - not much, app works fine, set User profile for my LFP. The app has Temperature Compensation -
everything I read about LFP says that Temp Comp should be zero, please correct me if I'm wrong.
Boost Duration can't be set shorter than 10 minutes - don't know whether this is the Renogy app or the Renogy controller. Will have to live with that.
Don't know whether the "demand effect" is still there, but it probably is. The battery is full so I can't tell.
Now, why you people think that 5A load is "excessive" for MPPT controller Load terminals that support 20A, I don't know. The above-mentioned "demand effect" was observed with controller current both below the 2-5A load requirement and well above, at 9A controller output. Same effect was also observed when I connected the load directly to battery posts.
