DC - AC Power inverter

What size battery ?

12v hooked up directly to the terminals..

As in ampere hours, can you measure the battery voltage when the load is connected ?

Bearing in mind that at those levels, the battery will need to supply several hundred amps for the motor to run.

Tested 12.4v before the load, 12.3 with the load,.

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** Wot load ?

You said the vac did not run.

..... Phil

Yeah, like Phil said ??

Mpffff.

One Horsepower = 746 watts. For now, let's ignore the starting surge.

746/110 = 6.78 Amps. That is the *AC* load for the motor when running. 746/12 = 62.2 amps from the battery to make that load.

Now, consider the starting surge (typically six (6) times the running current). That battery would need to put out +/-373 amps for the start.

This also ignores inverter losses (typically between 5 & 15% - 5% for a grid-tie type, 15% for most others).

The inverter may be rated at 4,000 watts. There are very, very few conventional automotive-type lead-acid batteries that could sustain it.

Peter Wieck Melrose Park, PA

I have often wondered why there are inverters out that convert 12 volts to much over 1000 watts. Even that is high, but it may take that to start the small motors or the input rush of other electronics.

As you pointed out it takes a very large battery to provide that much power for very long. If you are going to run an engine to keep thebattery charged, you might as well use a 120/240 volt generator in the first place.

So Hilda there you have it, from multiple sources !!

Ralph Mowery wrote: =================

** These supplies use " modified sine wave" aka variable pulse width rectangular waves.

The peak voltages are the same as the usual AC supply. A lot of overload current could be avoided by having a "soft start" system.

The unit would need a "start" button that brings up the duty cycle of the output wave from zero over a few seconds.

..... Phil