Club 80-90 Forums

I`m going to run a microwave oven from my invertor in my camper. The oven is 850 watts, 240V, running from 12volts on the invertor. I work it out as drawing 71 amps. Does this sound right, or is there another calculation to work out the amps draw, as it`s being "inverted" from 12V to 240V ?? The invertor is a 1500Watt example, so is well capable of running the oven.

Inverters are NOT 100% efficient so you are looking nearer 100A
you will need a very big battery and some very heavy cable.


T

tonytech wrote:Inverters are NOT 100% efficient so you are looking nearer 100A
you will need a very big battery and some very heavy cable.


T

I second that - they are about 85 - 90% efficient according to my inverter spec..

However, a 1500w inverter should have sufficient cables on it.

if its only on for 5 minutes then you shouldnt have a problem.

If you have a 110ah leisure battery it should manage an hour at least - providing you don't run anything else of it!

Be careful and watch the cables dont overheat (from the battery to the inverter) - i seem to remember a bay going up in flames at van fest because an inverter wasn't correctly connected....

Thanks chaps, that`s what I was thinking, just wanted confirmation that it would actually be pulling those big amps. The cables are very heavy, and very short so should be OK. Will be connected directly to the battery, and I will have to run a short extension lead from the 3 pin plug on it to the microwave. It will only be used for a few minutes at a time anyway (nuke some curry)

I have dual leisure batts, 70 amps each.

if you can run a microwave on a inverter, you definately deserve a blue peter badge!!! the battery must be very very LARGE too. 1kw drain for a few minutes is no mean feat.

concur with WEAZLECHIN. Most inverters have a low voltage cut off point. The 110 AHr is to flat - about 12 volts. Way below the cutoff point. Plus you are unlikely to have 110AHr stored in there anyway so you may get 15 minutes out of it, maybe more, maybe less.

I feel there is only one way to find out.....

Westy, please let us know if you manage to warm up your curry

Full culinary report forthcoming

I wasn't talking from personal experience but for a man who knows a man who tried, have a look at post #22 in this thread:http://sbmcc.co.uk/forum/index.php?showtopic=15949

look forward to your report.

I would say the battery, cable and space requirements make the project unpractical for a T25 situation.

2 Points here

1 = an 850 Watt Microwave is NOT 850 Watts
850 Watts is what it puts into the food and nothing is 100% efficient.
You need to look on the back of the microwave for a sticker that will give the actual current draw, it will be well over 850 Watts.

2 = I find that take out curries etc warm up just fine in a pan on the cooker.
to heat the rice, just slowly pour boiling water through it.
We often buy a take out and heat it up like this later on.

Disclaimer = the nanny state dictates that I point out that you are not supposed to re-heat curries, and if you choose to do so, make sure it is thoroughly heated through to melting point !!

Another point worth mentioning is that the rating of a leisure battery e.g. 110Ah is the capacity when supplying a continous 1A i.e. it would supply 1A for 110hours. However the battery starts to behave differently when you draw larger currents from it so you wouldn't get 11hours @ 10A and no way would you get 1hour @ 100A probably a mere few minutes. Also the plates in a leisure battery are designed differently to an engine cranking battery and drawing huge currents from them can cause the plates to warp, then it's time for a new battery.

Gas or mains hookup are the sensible options.

Tobzman -

The battery amp hour rating is not to be interpreted literally for high current draw. You might roughly halve the expected figure, provided the voltage holds up to run the invertor.

Practical or not - useful or not - who cares ?

Will it work ? Will it work without the engine running ? I want to know!

I have never put my microwave on for longer than 10 minutes at home - so i can't imagine you would want to in a van either. Not to mention a 850W microwave is fairly hefty - it doesnt need to be on for long does it.

If it wasn't practical to draw 100A or more from a battery - then it would be impossible to claim an inverter was 1500W.

I suggest a garlic chilli lamb with pilau rice. Maybe a chicken tikka starter too.

Hmmmm

ringo wrote:
If it wasn't practical to draw 100A or more from a battery - then it would be impossible to claim an inverter was 1500W.

I suggest a garlic chilli lamb with pilau rice. Maybe a chicken tikka starter too.

Hmmmm

Those sized inverters are sold for use in things like narrow boats, with banks of huge traction batteries.

I approve of your menu though