I have a small homemade portable generator setup comprising a 12V 36Ah deep-cycle lead acid battery (VMF DC36-12) and a 500W pure sine wave inverter bought from AliExpress (the brand says Carutu). I use it for backup power during power cuts.
I have a hall-effect coulometer for measuring voltage across the battery terminals and current flow, and several kill-a-watt style inline power meters for measuring AC power and voltage at the output.
Today I was powering a 3D printer with it, and when the battery was getting low, around 10.5V, the inverter was no longer able to hold 230V output, it sagged as low as 192V. The current on the DC side at that point was 33 Amps (almost 400W). When the bed heater cuts out (several times a minute, to maintain a constant temperature with bang-bang control), power falls to 120W, DC current falls to 12A, battery voltage rises to 11.5V and inverter output rises to 230V.
Is this normal behaviour for an inverter? Originally I thought it would maintain the output voltage constant over the whole range of permissible input voltages (10.5-15V). But it seems on mine there's some degree of dependence on input voltage.
I have a hall-effect coulometer for measuring voltage across the battery terminals and current flow, and several kill-a-watt style inline power meters for measuring AC power and voltage at the output.
Today I was powering a 3D printer with it, and when the battery was getting low, around 10.5V, the inverter was no longer able to hold 230V output, it sagged as low as 192V. The current on the DC side at that point was 33 Amps (almost 400W). When the bed heater cuts out (several times a minute, to maintain a constant temperature with bang-bang control), power falls to 120W, DC current falls to 12A, battery voltage rises to 11.5V and inverter output rises to 230V.
Is this normal behaviour for an inverter? Originally I thought it would maintain the output voltage constant over the whole range of permissible input voltages (10.5-15V). But it seems on mine there's some degree of dependence on input voltage.