SmartSolar MPPT 75/15 supplied by panel but without battery

DIY
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1

Hi,

my new SmartSolar MPPT 75/15 is not yet wired up in the final system, so far I just did a few measurements: The module draws around 20mA quiescent current from the 12V battery when connected only to the battery and a PV module without any solar power. To avoid draining the battery in this situation, I’d like to have a battery disconnect switch in the system. For simplicity, I would like to leave the PV module connected to the MPPT.

However, the MPPT manual carefully avoids this situation - PV module connected but battery disconnected - in the startup and shutdown procedures.

Is the SmartSolar MPPT 75/15 allowed to receive power from a PV module while not being connected to a battery? I am not trying to supply a load using the load output in this situation. I also do not expect a reliable bluetooth connection. I just would like to have the confirmation that the MPPT will not be damaged in this situation.

Thank you,
Klaus

2

The battery should NOT be disconnected while the PV is connected.
20mA x 12h of darkness (approx!) is only 0.24Ah, so unless you have a really small battery, this is negligible.
It would be possible to use a PV powered relay to disconnect the battery - as long as the relay also disconnects the PV. However, this is not recommended.