Inverter's alarm activated

[Kunaifi]

Hi. A solar pumping system has been installed in my facility for demo purpose. The system consist of the following main components:
- 10 solar modules, @ 50 Wp, Vmp 17.5 V, Imp 2.9 A, all connected in series,
- Charger controller + MPPT 45 Amps,
- Four 12V batteries (not deep cycle batts.) connected in series, system voltage 48 Volts,
- a 48 V/1200 Watt pure sinewave inverter,
- A submersible water pump, 260 Watts.

The inverter's alarm is activated for about 30 seconds each time the pump started. From the inverter specification, it activates the alarm when the battery voltage goes down to 43.6 Volts.

Question: why is the alarm activated and what would be the risks and solution.

Thank you.

Kunaifi

[sensij]

The pump will pull a lot more current at startup than it does while running. The high discharge from the battery causes the voltage to drop (peukert's law), apparently below the inverter's alarm limit, and once it drops to running amps the battery can recover. This will especially be true if the battery is not at full capacity or has been degraded by incomplete charging.

You could look into a soft-starter for the pump, so that it doesn't pull so hard.

175 Vmp of solar is an unusual value to be accepted by an MPPT controller... what model are you using?

[Mike90250]

You could upgrade the wires connecting the batteries and inverter. Voltage loss in the wires can trigger a alarm. If you are not using deep cycle batteries, then you have starting batteries, which are supposed to be able to deliver a large surge. So I would again look at the wires being too small or a bad connection somewhere.

Having said that, we have no idea what the charge of the batteries is, depending on how long/often the pump runs, there may not be enough solar panels to recharge the battery fully and it is not starting with a full charge,

[Logan005]

Is this a deep well pump? How deep is the well. is this a 220 volt pump or 110 volt? Is all wiring brand new and properly terminated? gauge of wire from CC to battery bank? gauge of wire running to the inverter? gauge of wire running AC to pump? Have you inspected all the wiring for damage loose set screws? If this is a deep well pump rated at 260 watt. upon start up with significant head pressure, could actually draw 6 to 10X that, just to get the dead weight moving. Lot's of variables.

[Kunaifi]

sensij : Thanks. We will try a soft-starter for the pump. The PV modules athe the BP 350U.

@mike90250: We have looked into the wiring and all seem okay. The battery bank uses four 120Ah batteries. The charger controller indicated 80%-100% charged when the alarm rang. We do not run the pump continuously. I agree that the solar panels are not enough to recharge the battery fully.

@Logan005: We use a Lorentz submersible 220 V pump. The depth of the well is 18 m. All wiring are brand new and properly terminated.