Hence my question:
"Does anybody know how efficient pure sinewave invertors tend to be in comparison to modified sine wave units? What capacity (Ah) battery are you using Scottish?"
D.c. connector terminations, fusing, flexibility of cables, heat-resistance/thickness of insulation, etc, etc, need to be considered carefully I reckon. As does whether earth-bonding's necessary. The inverters I've looked at are mains O/P and dc input-ground referenced.
Efficiency is quite an important issue when you're trying to give some margin for continuous operation near its limit. 1.25V O/P at 240V for a 300VA rated inverter meaning an input current of 25A off a 12V battery (assuming 100% efficiency).
Efficiency (Pout/Pin x 100%) is more likely to be nearer 80% or 90% at best I think. Hence a 12V d.c. load of ~31A at 80% with a mains load of 300VA (assuming a purely resistive load and a 240V rms sinusoidal O/P).
Last edited by Mr R J Ling; 20/06/07 3:13 PM.