I have a 5Kw inverter connected to 4 150ah Tubular deep cycle batteries. Battries are not even a month old and shows 100% health. It is used in case of main power supply faliure. The batteries without any load show 56 volts. But when the load is above 1.5 kw the inverter says voltage drop and it shows a level below 48 volts and at around 2.0 kw load the inverter shuts down. I am unable to use the full capacity of my inverter. Is there something i could do about it?