I have a MPPT RS 450/100 chargecontroller where my eastroof and westroof string is connected to. They both are 3800Wp and have a OCV of around 400V
I have a streetlight which shines on the solar panels all the night and generates about 80V. not enough current for the MPPT to do something, but constant 80V
The chargecontroller works fine together with my DIY LFP battery, besides of one little problem.
I have set a fixed absorption time of around 1,5h. The problem is, that the chargecontroller often dosn´t go into absorption mode, it simply skips the absorption and goes direkt into float mode.
I have searched around this Forum and found :
There I have found that this could have something to do with the off state of the MPPT... it never goes into absorption because it thinks the absorption time is already over.
And this is exactly my problem, I have tried to shut down the east roof string over night to confirm if the MPPT goes into OFF state, and if it enters absorption mode at the next day, and this is exactly what it does.
If I shut down the East roof string which has constant 80V because of the streetlight it goes into OFF state after about 3 seconds. After turning the string back on at the next morning it jumps into Bulk mode and enters Absorption correctly
If I left the East Roof running over night, the MPPT doesn´t turn off at all (it stays in Float or Bulk, wherever it was in the evenig) and if it should switch to absorption mode it skips it and jumps direkt into float mode.
Now my question:
It is very unpractical to switch of the east string every night, so is there an other way to tell the MPPT to go into off state?
(i think normaly it turns off if the voltage at the MPPT tracker falls below Battery voltage, but this is impossible for that string near the streetlight)
Maybe some other Ideas ?