i got the following setup:
- bluesolar MPPT 150/35
- pylontec us3000c (full at around 53 V)
- deye SUN 300
First i want to report that the pylontec is correctly recognized by the venus os: voltage, current, temperature and SOC are reported. Also the MPPT is connected via ve.direct and recognized.
DVCC is enabled. SVS and STS is forced to be enabled by the system. I enabled SCS. But it reports SCS Status "Disabled, external control". Manual current or voltage limits are disabled. The systemconfig "has DC System" is enabled.
I got the following problem:
Imagine the battery is full and the pylontec BMS sends a charge current limit of 0 A and a volatge limit of 53 V. Then the MPTT would set its output voltage to that 53 V and control its current output in such a way that it reads 0 A. Everything would be fine.
But in my setup i have a dey SUN 300 connected that is pulling 8 Amps from the DC bus. This results in a net current of -8 A at the battery. But the MPTT does not increase its current to counter the DC load. I assume because the BMS send charge current limit of 0 A.
The MPTT first starts to counter the DC load when the pylontec BMS starts sending a charge current limit greater than zero. This happens when the SOC is below 100%. (100% --> charge current limit 0 A, 99% --> charge current limit 15 A).
I would expect that the MPPT uses the current measurement provided by the BMS. And in fact would delived 8 Amps in my described situation. This would result in a net charge current to the battery of 0A but would give 8 Amps to the deye SUN. The battery would still float at 53V as requested by the BMS.
My current workaround:
I am setting a DVCC voltage limit of 51 V. This forces the MPTT to provide a maximum Voltage of 51V to the Battery. Since the battery won't charge beyont 95% SOC this means the charge current limit is always greater than 0 A. This results in the wished behaviour. The MPPT provides the current to the deye SUN and the battery floats at 51 V with net current 0 A.
Is there a better solution? Might this even be a bug?