DC only Solar Monitoring

I have 3 different solar systems.
1 is my main 3500w AC FiT system
2 is a 750w DIY install AC system
3 is a small 340w DC battery stoage system I’ve just started playing about with.
My question is with regard to my system 3, do any members know of an inexpensive way to monitor & upload DC only solar data to the PVOutput website that does not require the use of any manufacture specific charge controller addons.
Ideally something like the Current Cost equipment I’m using for systems 1 & 2 that can
Are there DC current clamp monitoring systems available like those that are in abundance for AC monitoring