What is causing the voltage drop when the heater is in use? Is it a need for a higher AH, Internal resistance or Inverter too small?

[MartinBe]

I'm puzzled by the reason behind the voltage dip. Here's what's happening: Initially, the battery voltage is stable at 13.0V. However, when you activate a 250W heater, the voltage quickly falls to 10.9V. Interestingly, when you turn off the heater, the battery voltage recovers to a range of 12.9-13.0V.

This test involved an 8Ah 12V LiFePO4 battery, a 500W pure sine wave ETL inverter, a Victron MPPT charge controller, and an Automatic Transfer Switch (ATS). The goal was to determine if the ATS would switch to public power when the battery voltage dropped below a set threshold. The ATS functioned as expected, transitioning to public power during voltage dips, but when the battery rebounded, it reverted to battery power while the heater was still active, causing the voltage to dip again to around 10.9V. This led to a repeating cycle of switching between public and battery power.

Will using a larger 100Ah battery with lower internal resistance and greater capacity or upgrading to a 1000W inverter help alleviate the voltage drop when the heater is activated?

 

[timselectric]

You don't have enough battery capacity to handle the load.

 

[MartinBe]

You don't have enough battery capacity to handle the load.

If I eliminate the ATS from the setup, the battery and inverter are capable of managing the heater without interruption. Although there is a momentary voltage drop from 13V to 10.9V, the heater continues to operate without any issues. Using bigger AH battery would remove the voltage suddenly drop?

 

[timselectric]

Yes