power invertor

[Julie798]

Hi ,

If I bought a 800 watt power invertor that plugs into the cigg lighter, will it run a700 watt microwave? sorry I really do not understand it all, but i am trying to get a grip of it LOL.

Thanks

 

[Deleted member 2636]

The short answer is "No"
You will need as a minimum a 1200w Inverter and that would be working at its peak capacity. Better still, go for a 1500w or 2Kw model and the inverter will not have to work so hard.
You didn't say what size of battery storage that you had. A chap who used to post on here, had 2 x 110A of leisure batteries and his inverter would start its low power warning after 3 to 6 minutes running.

 

[Deleted member 3011]

An 800 watt inverter MAY actually run that size microwave for a second before it trips out PROVIDED it was hooked to a supply that could deliver something like 130Amps.

So "no" is really the practical answer because clearly the average lighter socket can't deliver that sort of current anyway.

Even if that inverter just supplied 800watts, that needs about 75 amps and no lighter socket will deliver that either.

A 150 watt inverter would be about the maximum from a lighter socket and even then you should make sure your insurance policy covers fire.

Why someone would even sell that size inverter with a normal lighter plug on it is beyond me.

 

[shortcircuit]

Baloo is spot on. Whilst the microwave indicates 800 watts it looses a lot of power to create the microwave energy. I would guess about 50% lost.

To get high power out of an inverter it needs to be connected to the battery with very short, heavy duty cable. Even if not being used an inverter will draw current from the battery.

I have a 180w invertor that I run the tv etc from. I wired it to be within a short distance of the leisure batteries. Its actual switched off and on by a relay I have wired with remote switch. I have a 2000w invertor that is used for the microwave, hairdrier etc. It again is very close to close to the leisure batteries and has heavy cable. I have not fitted a relay as when working it will draw a considerable current. The 2000w unit draws 1 amp on standby and is only switched on when needed.

I originally had a single 110 A/h battery and have doubled this by adding a second 110 A/h battery.

The logic behind the 2000w inverter is than when you are on a small output hookup, say 6Amp you could possible trip the supply mcb. By using the invertor the load is taken by the batteries which are subsequently recharged from the hookup.

Hope you find this usefull

 

[walkers]

Hi Julie, You would need a generator as your best option!

got to agree with graham on that, the power you want to take off the batteries would create a considerable amount of heat (potential fire risk) and wouldconsiderably reduce the life of your leisure battery.
with a genny the heat from that would be outside of the van and no draw whatsoever on your batteries.

 

[Julie798]

invertor

Thanks everyone, one that note I have finally decided to stick to what is in the van or buy a gennie, I really dont need a microwave, but hubby wants to shell out on a gennie and I was looking for a cheaper option LOL,
Thanks Julie

 

[shortcircuit]

Whether you go for a geni or inverter will depend on the use.

The statement "considerable amount of heat (potential fire risk) and would considerably reduce the life of your leisure battery." is unsubstantiated garbage. A properly installed inverter present no dangers.

If you are going to use a generator ensure you allow it to warm up and settle down before taking a load. In addition fit a spike protector at the generator

 

[Nosha]

***** - SNAP!
Our new motorhome didn't have an oven, so I fitted a cheap microwave - used it once when we were on hook up!!! And just like you we carry a George Formby! Again this has been used 2 or 3 times.

The gas BBQ on the other hand has had loads of use! So I would say if you can't BBQ or grill it, can't heat it in a saucepan or frying pan... DON'T BUY IT!!! There's always a chippy nearby!

 

[walkers]

Whether you go for a geni or inverter will depend on the use.

The statement "considerable amount of heat (potential fire risk) and would considerably reduce the life of your leisure battery." is unsubstantiated garbage. A properly installed inverter present no dangers.

If you are going to use a generator ensure you allow it to warm up and settle down before taking a load. In addition fit a spike protector at the generator

properly installed maybe not but the inverter in question was to be connected to a cigarrette lighter

 

[shortcircuit]

"properly installed maybe not but the inverter in question was to be connected to a cigarrette lighter"

Which would be protected by the correctly rated fuse.

No way will a cigarrette lighter output provide sufficient current to run a microwave. The fuse would blow, and prevent "considerable amount of heat (potential fire risk)"

You need to consider ,and understand,the actual situation.

 

[GeorgeTelford]

Mains Microwave through invertor

Modern 240v Microwaves are getting more efficient (most are anyway) so for 700w cooking power they require about 50% more input ampage so a 700w microwave would need 1050w of power in.

1050w thru an invertor would cost about 10% extra to allow for invertor efficiency so thats 1155w so the ampage required would be in the order of 96 amps. Microwaves tend not to run at 100% efficiency on quasi invertors so allowing for this we get 630 cooking watts costing 96 A

So an Invertor fed mains microwave gives roughly 6.56 watts per Amp

Direct 12v microwave

12v microwaves have not advanced as much efficiency wise, a 450 watt Samsung uses 750w, 750w at 12v = 62.5 Amps

So a 12v Microwave gives 7.2 watts per Amp

Overall a 12v microwave is only slightly more efficient.

Other Factors

Price a 240v Microwave can be had for as little as £25, with a brand and good guarantee £40. A 12v version costs up to 10 times more than the average entry level mains version

Size Mains microwaves tend to be 25% bigger capacity

Speed mains will cook quicker (having 630w, against the 450w of the 12v version)

Battery bank size , to maximise the life of your battery bank no current draw should exceed 10% of the amp hour rating of the battery bank, so for a 12v the battery bank "officially" should be greater than 650 ah, for the mains version 1,000 ah is the "reccomended" size.

Another effect of this is that taking say 5 amps per 100 ah battery bank is the 20 Hour rate which allows 5 amps to be withdrawn for 20 hours before flattening battery completely at 10A draw the battery will not last 10 hours as expected. This is just to show that the amp hour draw will cost you more amp hours than the consumption suggests, this would apply to either microwave.


In practice most take the performance "hit" in terms of longivety and actual ah usage.

In the end its all down to what is important to you, cost £, performance (cooking), efficiency (watts per amp used), actual amps used, size of cooking area and ease of replacement out in the cuds (will always be easier to replace a mains microwave)

Ah Comparison figures for a 5 minute warm (not allowing for battery bank size)

12v 5 mins @ 62.5 amps = 5.21 Ah

240v 3.57 mins @ 96.25 amps = 5.73 Ah (the mains will cook quicker 630w against 450w)

Other points have already been covered, it will never work from a ciggy lighter socket.

PS I have done the above and used it, also sorted this out for other self build campers..

Regards George