Inverter Powered Microwave in your Caravan / Camper

Good Morning All

Has anyone successfully set up a 240v microwave in a caravan / camper for use with batteries and inverter. (Not running solely on 240v mains)

We are wanting to set up an inverter powered 240 v microwave for use in our camper so that we can use it for quick meal reheats on the side of the road. We don't intend to use it for "cooking meals" and we don't intend to use it all the time.

We have a camper with 315Ah of deep cycle batteries and a 1500 watt inverter. Good solar input to keep batteries up to charge with charge circuit of the tow vehicle.

If you have managed to achieve the above;

How many batteries, total Amp hours?
How many watts is your inverter?
What wattage is your microwave?

Cheers

Anthony
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Reply By: Notso - Friday, May 29, 2015 at 14:05

Friday, May 29, 2015 at 14:05
I haven't done it but it could be possible. You just need to bear in mind that your Microwave may say 750 or 900 watt but that is only the output wattage. The input could be as high as 1500 watts which would probably be too high for the 1500 watt inverter. (check the back of the microwave to see what it draws)

To run it at say 1500 watts at 240 volts would require around 115 amps from the battery to supply the 1500 watts at 12 volts. That doesn't take into account any losses in the system which can be considerable depending on the efficiency of the inverter.

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Follow Up By: Member - ACD 1 - Friday, May 29, 2015 at 22:51

Friday, May 29, 2015 at 22:51
Thanks for that Notso

I had considered input vs output and was thinking a small M/oven. It is only for reheating not cooking. And only on the quick in transit overnighters.

Batts should be OK as they are 315 amps total.

Cheers

Anthony

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Reply By: Member - mike g2 - Friday, May 29, 2015 at 14:57

Friday, May 29, 2015 at 14:57
Hi acd, fairly sure I have seen this topic covered onsite before: try looking up some of the good blogs such as: ( search terms..) electricity for camping , battery power, inverters etc.. MG.
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Follow Up By: Member - ACD 1 - Friday, May 29, 2015 at 22:53

Friday, May 29, 2015 at 22:53
Thanks Mike

Have done a search and come up with some rsults but nothing difinitive.

Will try with a broader search.

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Anthony
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Reply By: deserter - Friday, May 29, 2015 at 15:05

Friday, May 29, 2015 at 15:05
Try asking the question here

http://www.caravanersforum.com/
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Follow Up By: Member - ACD 1 - Friday, May 29, 2015 at 23:02

Friday, May 29, 2015 at 23:02
Hi Deserter

As for my reply to Mike above, have had a look but again nothing difinitive.

As I am not registered / or a member I can't ask questions. Perhaps I need to register.

Cheers

Anthony
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Follow Up By: deserter - Saturday, May 30, 2015 at 09:31

Saturday, May 30, 2015 at 09:31
Yep. They just continually blow me away with the electronics knowledge of some of the people. Quite a few are on here also though.
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Reply By: Member - bungarra (WA) - Friday, May 29, 2015 at 19:26

Friday, May 29, 2015 at 19:26
We have a 240v microwave in our caravan...........from memory it is a 1000w but might be 1200

I have a 1500w inverter and it runs it easily.........having said that I don't believe the heat is as efficient when compared to it running on 240v...but we never use it for cooking......only reheat a quick meal or snack ...so probably maximum run time has been perhaps 10 mins at a time

our power system is 3x105ah deep cycles..........the power consumed is minimal and shouldn't affect a well balanced system a s the time frame in our case is still minimal use...and only used for convenience at times

if that's any help
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Follow Up By: Member - ACD 1 - Friday, May 29, 2015 at 23:09

Friday, May 29, 2015 at 23:09
Thanks for the working knowledge Bungarra

It looks like you have the same battery setup as I have. System charges well on solar and from the Landcruiser, so recovery shouldn't be a problem.

Like I said its not for making food - just reheating. Also a smaller m/oven would probably be more suited for our needs.

Possibly a bigger inverter up to 2000 from the 1500

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Anthony
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Follow Up By: Member - bungarra (WA) - Saturday, May 30, 2015 at 09:54

Saturday, May 30, 2015 at 09:54
Our charging system for the last 3 years has been 100% solar on the roof........3 x 120w and the times we have used the inverter it has never compromised the battery's

Only last week I have added a charge circuit from the 'cruiser simply because two recent trips into the goldfields gave us cloud and rain for a couple of days and our battery reserve approached 50% and I don't like going below that......

I have made that charging system removable with Andersons as I don't need another wire to catch in the bush when off road so will only connect as needed...........now I have installed it probably will not need it for another 3 years!

As for going up to a 2000 inverter I wouldn't bother if your microwave doesn't need it..........more expense and more unnecessary power usage
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Follow Up By: Member - ACD 1 - Saturday, May 30, 2015 at 12:16

Saturday, May 30, 2015 at 12:16
Thanks for the added info and advice

Cheers

Anthony
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Reply By: wholehog- Friday, May 29, 2015 at 20:08

Friday, May 29, 2015 at 20:08
We have a 240 volt microwave..1800 watt inverter..6 solar panels and 4 deep cycle batteries. I hardly ever use the microwave..the evening from meat/dinner gets defrosted on the engine tappet cover over a beer or 2 when we pull up and I had forgotten to take the food from the freezer at lunchtime.
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Follow Up By: wholehog- Friday, May 29, 2015 at 20:10

Friday, May 29, 2015 at 20:10
..and for food reheats..just use gas. You can be sure its ALL reheated and mixed.
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Follow Up By: Member - ACD 1 - Friday, May 29, 2015 at 23:57

Friday, May 29, 2015 at 23:57
Thanks for the reply whole hog

We only want it for the quick roadside stop when we are in the middle of nowhere.

Do you know how big (watts) your microwave is?

Also how many watts total are the solar panels - I am assuming the batteries will total about the 420 aH

Cheers

Anthony
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Reply By: Member - Alastair D (NSW) - Sunday, May 31, 2015 at 08:12

Sunday, May 31, 2015 at 08:12
Anthony,
We are currently building up a 4wd truck based expedition vehicle and I am not having gas. Everything will either be diesel fuelled or electric. The inside cooking will be done on an induction hotplate, with toaster and microwave. As a part of the planning I did lots of testing of various appliances to size my system needs.

In regards to the microwave I am going to use a small unit that we have from when we sold our weekend cottage. It is labelled as being 1200w and when I run it my power monitor tells me it is pulling just on 1000w. It pulls quite a bit more when starting but any good inverter will normally have a surge capability twice its rated output. Only use a quality true sine wave as too many appliances will not work well on modified or square wave.

I measured the current draw for the 1000w Projecta inverter that I used for the test and got about 85amp. My test mimicked the morning heating of my wife's hot chocolate which takes just on 5 mins to boil the big mug of milk. So this equates to about 7AH used. You can scale from this as to the battery capacity you need. Just remember to never take a wet cell, AGM or any lead/acid style battery below 50% SOC if you want good life.

I have Lithium batteries which is a totally different story but not relevant here.

Hope this helps.
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Follow Up By: Member - ACD 1 - Sunday, May 31, 2015 at 10:54

Sunday, May 31, 2015 at 10:54
Alistair

Thanks for the very detailed response.

It looks like the system I have in the trailer is more than capable of doing the job I am after.

I only use pure sine wave inverters so that if something sensitive gets plugged in it doesn't end up damaging it.

Can you tell me the gauge of wiring you are using from the batteries to the inverter. I know most people will say as heavy as possible but the term overkill comes to mind.

Cheers
Anthony
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Reply By: Frank P (NSW) - Sunday, May 31, 2015 at 09:54

Sunday, May 31, 2015 at 09:54
'Morning Anthony,

My van came with an 1800W Xantrex pure sine wave inverter and an 800W (output) Sharp Carousel MW oven. The specs say that the MW needs 1200W input.

We don't "cook a meal" with the MW, but frequently use it to reheat left-overs and defrost when we forget to organise that in advance (although, like Wholehog, we often defrost on a hot engine after a day's driving :-)).

At full output the MW pulls 130 amps according to both the inverter control panel and the battery monitor.

I used to have 315Ah of AGM, now have 360Ah of lithium batteries. 200W of solar on the roof and 240W of portable panels. I charge from the vehicle with a 25 amp dc-dc charger. The system worked/works on both battery types, but is far better on lithium. But as Alastair D said, that's another topic.

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Follow Up By: Member - ACD 1 - Sunday, May 31, 2015 at 11:10

Sunday, May 31, 2015 at 11:10
Hi Frank

Again, it looks like this is extremely "do-able" task.

It looks like I might need to up the ante on the solar, I am running 2 roof tops at 180 watt and a portable 120 watt. Although they are Powerfilm which are supposed to be "more efficient" than the traditional solar panel. So far we have had no issues with charging with the SOC never getting below 80% (except when we left the pressure fan and diesel heater fan on all night).

Again, like I asked Alistair, what gauge wiring are you using between batteries?

Cheers

Anthony
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Follow Up By: Frank P (NSW) - Sunday, May 31, 2015 at 13:00

Sunday, May 31, 2015 at 13:00
Anthony,

My AGM system consisted of 9 small 12V batteries connected in parallel with flat metal bus bars. The lithium system is an arrangement of cells interconnected with metal straps. So in both cases I cannot give you a gauge equivalent for the interconnections between batteries or cells.

However, the van manufacturer has used about 3 gauge cabling from the battery to the inverter, about a 1.5 metre run, and that seems to be adequate for what we do with the microwave.

I agree with Alistair's comments below.

Cheers





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Follow Up By: The Original JohnR (Vic) - Sunday, May 31, 2015 at 22:11

Sunday, May 31, 2015 at 22:11
Anthony, I had a system similar to Frank that when the microwave finally went I converted the space to a cupboard. Much more useful. My experience with the microwave was that having it means someone will be tempted to use it for long enough to deplete the batteries. Then of course with deep cycle batteries they take effort to get them charged if that has happened. Cooking rice was the big killer from memory
Cheers,
Who?
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Reply By: Member - Alastair D (NSW) - Sunday, May 31, 2015 at 11:59

Sunday, May 31, 2015 at 11:59
Anthony,
In my install I have a big inverter which is fed by 0BS cable. For your system I would go no smaller than 4BS to make sure that the voltage losses are minimised. One big difference between Lithium and Lead/acid is that the voltage for Lithium stays quite constant during discharge until just before reaching full discharge. As you would know for lead the voltage drops progressively and you need to save every millivolt to get the best value from your batteries. The size depends a lot on the cable length too so the rule is - as short as possible and as big as you can afford.

As a guide if you pull 100A through a 5m length of 4BS cable you will lose just over 0.4v and dissipate approx. 50w in the cable. This energy is better used in your inverter and by going to 2BS you would halve these numbers. If you can keep the cable short then 4BS will be ok.

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Reply By: Wayne's 60 - Sunday, Jun 14, 2015 at 21:55

Sunday, Jun 14, 2015 at 21:55
Hi Anthony,

Long time no hear from, though we hope all is well with you.

We gave some thought to your post and on our last trip bought a small microwave to run off an inverter.

SOOOOOOO glad we were not relying on it.

We have a 700w microwave and a 1000w (2000w peak) inverter.

The microwave would start, though would not continue to run.

Maybe we need a larger inverter to ride over the initial start up where the oven needs (an indicated) 1100w.

Maybe someone can let us know why our set up doesn't work.

All good for learning :-)

Cheers,
Wayne & Sally.


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Follow Up By: Peter_n_Margaret - Sunday, Jun 14, 2015 at 22:29

Sunday, Jun 14, 2015 at 22:29
Either the inverter is incapable of delivering the constant draw of the microwave (it may exceed the 1000W), or the battery voltage drops with the load and the inverter shuts down.

Cheers,
Peter
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Follow Up By: Member - ACD 1 - Sunday, Jun 14, 2015 at 23:52

Sunday, Jun 14, 2015 at 23:52
Hi Wayne and Sally

Yeah! Long time since I last caught up with you guys. All is well had lots of new adventures in the last 2 years.

What I have discovered with the set up is:

1) Yes it is possible.
2) You need good batteries (315 ah in my setup and will be going to LiPo)
3) A good inverter (1500 watt pure sine wave)
4) Good cabling that decreases voltage drop (I've gone with 0BS due to the run length)
5) Good recovery system (240 watt amorphic panels with 120 watt portable backup)
6) Appropriate sized microwave (1100 watt input - 800 watt output)
7) Limit use to roadside reheats.
8) As a precaution, boost batteries with 240v charging (before trip and when possible whilst away)

As I mentioned in the Opening post, we only want it for the occasional meal reheat when we are on a long push between stops. Most of the time we have stopped at 4pm and are setting up for the night, but sometimes distance and the weather can be against you.

Cheers

Anthony
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