I am preparing a LFP battery install. I want the BMS to be able to shut down the MPPT (2x 75/15 and 2x 100/50). These small MPPT controllers have an unacceptable charge-enable mode (if the plug is loose or falls out, charge is enabled and external control is lost), so I want to put a Battery Protect as a solar disconnect (the BP has a positive charge-enable design – if the control wire is compromised, charge is disabled). My choice of BMS will requires that it control the MPPT at 100% SOC (the SOC reset is the same as the charge limit), so this will turn on and off frequently. I know Victron shows this in reference diagrams, but two questions I want to know for sure:
- Is there any negative impact (physical harm) to the MPPT if I use the BP to disconnect the battery while charging at 100% of the MPPT capacity? I understand some MPPT brands do not like this. This could potentially happen many times a day.
- Is there any operational impact to the MPPT by being disconnected from the battery? Victron seems to want the battery connected to the MPPT before the PV, so it can be configured. But the MPPT doesn’t actually “disconnect” it – it seems the battery can still feed milliamps backwards and keep the MPPT live, so this may not be an issue.