Thread: Power inverter

Yes and Yes

Amps = watts divided by volts

So 600W unit would draw at least 50A

Anyone has this setup? How big the inverter and battery do i need? Or it is just not practical

Hi dearot, the smallest 600w micro wave oven actually needs at least 1500w to operate.

The wattage shown on any micro wave is it’s cooking power NOT it’s power consumption.

So to use even a small micro wave, you will need at least a 2,000w inverter and this in turn means a current draw of close to 150 amps and this is a battery killing current draw.

There is no way to be able to use a micro wave powered from batteries unless you are running a VERY LARGE battery bank.

Looks like i have to scrap power inverter idea. How about running a small generator?

itd want to be a good genny. as a rough rule of thumb 3x the cooking power is the required startup power draw for a microwave and it then levels out to about 1.8-2 times the rated cooking power.

In my house I use a microwave on my battery/solar setup. It is running off a 2kVA inverter rated at 6kVA for 30 seconds. Steady current draw while operating is about 60A at 24v, equivalent to 120A at 12v. But it dims the light when switched on - I haven't actually measured the starting current.

Worth noting that the inverter will draw the power it needs from the battery - for example, if a 12v inverter is supplying a draw of 1200w at 90% efficiency (which is pretty good) it will need to draw 1333w from the battery. If the battery was fully charged at 13.8V, this would be 102.5A. But your fully charged battery (unless it is huge) will not be giving 13.8V under this load - a more likely figure is 11V, at which voltage the current draw is 121.2A. Further, at this current, the voltage drop to the inverter is probably about 0.5V, so the inverter is seeing only 10.5V, and the current draw will be 126.9A. (And the inverter will be close to low voltage shutdown!)

If running from a generator, I would suggest you need to be looking at one around 6kVA, which will probably have a motor of about 10hp. (Neither very small nor very portable.)

Worth noting however, that given adequate wiring it is probably possible to have an alternator running off your car engine that will, with a suitable inverter, and using your battery as a peak load sharer, run a microwave. And since the microwave is only used for short periods, this may be feasible. But a suitable inverter will be neither small nor light nor cheap, and you will also need a hand throttle to run the engien fast enough to provide the power when using it.

John

There are 12V microwaves on the market that draw about 65A on full power. They come in at around the $800 mark though, from what I remember.

Originally Posted by mike_ie

There are 12V microwaves on the market that draw about 65A on full power. They come in at around the $800 mark though, from what I remember.

Occasionally seen on ebay for a fraction of that...ideal as it removes one level of power conversion from the process.