Hi,
for more than 2 years I have a simple system: grid-tied, one phase, MultiPlus II 48/3000/35-32, SmartSolar MPPT 150/35, 4x150Ah AGM batteries (w/ balancer), ESS enabled, Keep Batteries charged mode, no feed-in of excess power, AC grid setpoint 75W
Most of the time it works nicely, however time to time it becomes unstable. And this bugs me a lot.
For example: perfect sunny day outside, AC load cca 1kW, battery full, but suddenly MPPT is not producing. Strange behaviour is that MPPT is switching from bulk to absorption mode (1/3Hz frequency). MPPT production cycles and tries to ramp up, eg.. 0W, 5W, 16W, 60W, 80W... and than back to 0W.
Battery power jumps from e.g. -200W... to 200W... and back.
This takes for cca 20minutes and then it is back to normal. I have not found out what causes this. It looks like something trips the whole system into unstable mode.
Any ideas?
Thanks,
Matej