Amongst the other documentation I’ve found on the CAN - BMS implementation is this:
By way of example, if the BMS sends a CVL of 58V, the MPPT solar charger will add 0.4V to the CVL for
a operating charging voltage of 58.4V. At the same time, the inverter/charger will try and hold the
voltage down to the CVL value of 58V, feed-in limits and maximum inverter power permitting. As a
result, the MPPT solar charger will keep operating at its MPP point, pushing power onto the DC-bus,
while the inverter/charger works to remove that power from the DC-bus by inverting it and feeding it
to the AC side.
If we are to interpret this as the inverter WILL NOT export any power to grid UNLESS the battery voltage is above the CVL, then this means that to get excess export, the CVL must be dynamic. This may well explain why there is still no export with the grid target set to -150W. Does this still apply in “External Control” mode of the ESS?
Given the bug described above, where the system CVL is not the same as the BMS sent CVL, this is going to make life difficult…
Thinking more on the dynamics of the CVL requirement, my BMS software calculates the CCL, so to derive the CVL from this:
Rules:
- Below 3.35V per cell - CVL fixed at 16x3.35 = 53.6V
- Between 3.35 and 3.55 CVL = Battery voltage plus CCL*R_battery
3)At 3.55V per cell CVL Fixed at 56.8V
(Topic moved to beta testing as deemed more relevant).
Having done the dynamic voltage setting, and reset some fixed limits, the CVL dynamic setting now appears to be working. I can only conclude that the original 52.5V limit must have been a default setting from some part of the original setup - not a bug. However, the Lack of turning off of the Solar charging with High (cell) voltage Alarms should be looked into.