question

It's difficult to tell exactly without more details of your system.
What arrangement are your batteries connected in? 12V, all in parallel?
Also how are you PV panels connected I might assume 2S 2P. Do they all get good sun exposure?

400W on a 12V battery should give you around 30A in absolutely ideal full sunshine conditions.
Any shading will significantly reduce PV output.

Hi. The 7 batteries are all in parralell. The panels are connected two and two together. We're in the Caribbean, so the sun is good.

is the 7 amps on the input or on the output of the MPPT?
(7x50V = 350W)

It's on the output, and the voltage is never higher than 12,7.

Hi Havard. This reeks to me of a polarity mismatch somewhere within your panel wiring. It's not uncommon to see this, and perhaps a little carelessness with MC4? connectors is the reason.

If that's not it, a warranty should be easy to claim with the necessary proof-of-purchase, etc.

But I must say it - I don't much like your 7x (+2 more?) parallel batts. Presuming Pb's, the danger of imbalance destroying them is real. At the very least, when they're later into a charge period, give each a touch-test to determine if one (or more) is hotter than the others. It will need culling. And it's not really a matter of 'if' this will occur, it's a 'when' scenario.

Good luck though..

Please check your panels that they are connected correctly as per this sample diagram.

Make sure ALL joins are of good quality and none are loose

check to make sure that each string has the same voltage. and that the connection polarities are correct, if you have 50 volts then the short circuit amps should be around 4 amps per string

remove the solar connections from the Regulator and in good sun put a amp meter across the neg and pos of each string and the amps should be about the same.

All panels in the same string must each have the same current output

the current output should be close to the panels rated output.

Maybe the battries a charged and only need that much current

Try turning more things on and see does the charge current go up

There is a setting to limit the charge current on the controller. Can you confirm what it ?