inverters

Feb 27, 2015
1,165
1,083
UP North
Funster No
35,253
MH
Hobby 725
Exp
since 2012
Can anyone recommend an inverter to run a microwave?
I am looking towards a 3kw pure sign wave inverter.
We have 4 12v batteries onboard.
any recommendations as to a make and model would be appreciated
We would mount the inverter in the garage so a remote would be needed

Many thanks in advance for those who take the time to read and answer
Kev
 
Jan 19, 2014
6,561
16,070
Derbyshire
Funster No
29,757
MH
Elddis Accordo 105
Exp
since 2014
Can anyone recommend an inverter to run a microwave?
I am looking towards a 3kw pure sign wave inverter.
We have 4 12v batteries onboard.
any recommendations as to a make and model would be appreciated
We would mount the inverter in the garage so a remote would be needed

Many thanks in advance for those who take the time to read and answer
Kev
What's your budget?
The Studer AJ series are good but expensive, victron are middle of the road, and some of the Chinese ebay ones maybe OK.

I fitted a cheap Chinese PSW one that's been good but it's only 1000w. Made by Meind.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
31,833
57,378
On the coast in West Sussex
Funster No
658
MH
Hymer B678 Dynamic Line
Exp
Since 2008 & many years tugging
Victron are pretty good but if only for the microwave a cheaper one may do. The inverter needs to be mounted as close as possible to the batteries if you mount it in the garage you will need huge cables.

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OP
Duck Truck
Feb 27, 2015
1,165
1,083
UP North
Funster No
35,253
MH
Hobby 725
Exp
since 2012
Hi its a 750w microwave minimum inverter would be 2kw
but would prefer 3kw as we often have Tv on whilst I am cooking
we have 4 Gel batteries all located in the garage within 2 feet of where our existing inverter is.
The existing inverter wont power up the microwave (actually lights come on dish spins but it wont fire up the magnatron)
hope that helps

I didn't fit the existing inverter
 

funflair

LIFE MEMBER
Dec 11, 2013
15,179
20,008
Guisborough
Funster No
29,351
MH
MORELO palace
Exp
since 2012
All sounds good to me but need big cables whatever, I used 80mm2 for a similar set up.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
31,833
57,378
On the coast in West Sussex
Funster No
658
MH
Hymer B678 Dynamic Line
Exp
Since 2008 & many years tugging
A 1500 watt inverter should be more than enough, the TV will only take about 50 watts.
Microwaves can take up to twice their rated power on startup but it's usually not as bad as that, a decent inverter should handle it, the cheap ones often fall over with the high startup power required, they often don't live up to their peak rating.

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OP
Duck Truck
Feb 27, 2015
1,165
1,083
UP North
Funster No
35,253
MH
Hobby 725
Exp
since 2012
sorry for the delay in replying our current inverter is 1500w
and doesnt drive the microwave
 
Dec 2, 2019
1,446
3,104
Amersham
Funster No
67,145
MH
van conversion
Your inverter may be 1500w but, your batteries can’t keep up with it. In order to deliver 1000w resistive load, like a heating element, inverter will draw 1100w out of batteries. That’s 91-92 amps out of batteries. Too much for your batteries. That’s what the inverter tells you. Now, the microwave is a resistive load 1:1 power factor at full load. If you try to run your microwave at half load, becomes very inefficient in power factor as low as 0,5. That means for 750w absorbed by microwave, the inverter needs to supply 1500va apparent power. To do that the batteries needs to feed the inverter with 125a. It may be less once started and stabilise in between. You are killing your batteries. A lead 100a battery can give you sustained 10a or 20a for short bursts. That’s it. You try to take more, the voltage will drop quick, until inverter disconnects on low voltage protection. To run your microwave, you need more battery power, the inverter is just a middle converter, but the source of that power remains with the batteries.
 

two

Aug 4, 2011
4,372
3,401
West Midlands
Funster No
17,624
MH
A-Class Fiat
I hope you ave plenty of payload?
Microwaves tend to be pretty heavy and you'll need a large battery bank.

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Apr 22, 2013
851
599
Cotswolds
Funster No
25,654
MH
Bailey Approach 625
Exp
Since 2011
Our 800Watt microwave requires 1250Watts of power according to the manufacturer.
We have a 1500Watt inverter its displays says that it is producing 1280watts when the microwave is on.
The inverter/microwave combination has worked well for the past 6 years.
 
Dec 2, 2019
1,446
3,104
Amersham
Funster No
67,145
MH
van conversion
We used to have one, left it at home in the kitchen. Swooped it with a Dualit mini grill & oven. It has proper resistive elements 2x 700w, no transformers, and the choice of turning on either one, or both, use it as a grill with top one on or both as a oven. Very light. Power factor 1, same as the water heater, no energy wasted. And incredibly efficient on a multiplus 2kva.
 
Oct 26, 2014
1,128
1,574
Dumfries and Galloway
Funster No
33,996
MH
Pilote G720FC Euro6
Exp
since 2014
Our 800Watt microwave requires 1250Watts of power according to the manufacturer.
We have a 1500Watt inverter its displays says that it is producing 1280watts when the microwave is on.
The inverter/microwave combination has worked well for the past 6 years.
how do your batteries fair when using the microwave

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Dec 2, 2019
1,446
3,104
Amersham
Funster No
67,145
MH
van conversion
Very nice, with that capacity and a 1,5kw inverter is a smart choice. The batteries will never need to be 100% full, and a low discharge rate will last you ages, maybe outlive the van.
 
OP
Duck Truck
Feb 27, 2015
1,165
1,083
UP North
Funster No
35,253
MH
Hobby 725
Exp
since 2012
We are on the verge of replacing our existing1,500w modified sign wave inverter.
We want the new inverter to be able to run our microwave.
THE EXISTING SET UP
The EXISTING set up is 4 x 12v gel leisure batteries each linked to each other by 7mm cables all located in the garage under the bed.
The inverter is 1.5metres away from the end of the battery and the cable to the inverter are 12mm all located in the garage under the bed.
The batteries are connected to the inverter via a relay which is operated via a switch from inside the habitation area,
this means we can cut the 12v supply to the inverter ensuring it is TOTALLY OFF and isn't constantly running in the background.
The Relay also switches to shore power if we plug in

THE NEW SET UP
This what we want to replace it with.
Keep the existing 4 Gel leisure batteries
Replace the inverter with an EDECOA 3,500w pure sign wave Inverter currently £319
it comes with a remote control which we can wire into the habitation Area.
My questions are?
1) The 7mm cables linking the batteries together can they be kept or should they be replaced and if so with what gauge?
2) The cables that come with the new inverter are 16mm thick but only 600mm long NOT LONG ENOUGH to reach where the inverter has to be.
3) What size cables DO I NEED for a 1.5 metre run?
4) Can I still use the existing relay and switch to totally isolate the inverter

I think that about covers it all
Thanks to everyone who takes time to read this
Kev
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
31,833
57,378
On the coast in West Sussex
Funster No
658
MH
Hymer B678 Dynamic Line
Exp
Since 2008 & many years tugging
We are on the verge of replacing our existing1,500w modified sign wave inverter.
We want the new inverter to be able to run our microwave.
THE EXISTING SET UP
The EXISTING set up is 4 x 12v gel leisure batteries each linked to each other by 7mm cables all located in the garage under the bed.
The inverter is 1.5metres away from the end of the battery and the cable to the inverter are 12mm all located in the garage under the bed.
The batteries are connected to the inverter via a relay which is operated via a switch from inside the habitation area,
this means we can cut the 12v supply to the inverter ensuring it is TOTALLY OFF and isn't constantly running in the background.
The Relay also switches to shore power if we plug in

THE NEW SET UP
This what we want to replace it with.
Keep the existing 4 Gel leisure batteries
Replace the inverter with an EDECOA 3,500w pure sign wave Inverter currently £319
it comes with a remote control which we can wire into the habitation Area.
My questions are?
1) The 7mm cables linking the batteries together can they be kept or should they be replaced and if so with what gauge?
2) The cables that come with the new inverter are 16mm thick but only 600mm long NOT LONG ENOUGH to reach where the inverter has to be.
3) What size cables DO I NEED for a 1.5 metre run?
4) Can I still use the existing relay and switch to totally isolate the inverter

I think that about covers it all
Thanks to everyone who takes time to read this
Kev
A 3,500W pure sine inverter for £319, you areally not going to get much for that. A 3000w inverter if you want something decent is going to cost around £1000.

If the Gels are 80 ah, a 1500 w inverter is the max if you value your batteries, or fit another 6 batteries, or fit Lithium.
The 7mm sq cables linking your batteries is far too small for normal use without an inverter, I would upgrade them to at least 35mm sq, preferably 50 mm sq and the same to the inverter.

I take it you have 2 relays one switching the mains sockets and one for the inverter. For the inverter you will need a 350 amp contactor.

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Apr 22, 2013
851
599
Cotswolds
Funster No
25,654
MH
Bailey Approach 625
Exp
Since 2011
How much did they cost?

Cheers James
I’m not at home right now so I don’t have the invoice to hand, but £1700 comes to mind in 2019.
Get on to rj-lithium.com for the latest price. I didn’t pay any import duty or VAT but it was pre brexit.
 
OP
Duck Truck
Feb 27, 2015
1,165
1,083
UP North
Funster No
35,253
MH
Hobby 725
Exp
since 2012
HOW MUCH
went up the Yorkshire war cry
Just priced it
a low power 320w microwave is £114
but its the size of a standard microwave
sadly it wont fit in the space we have
Our exisitng one is cube shaped
not oblong
sods law
 
Aug 6, 2013
10,910
13,750
Kendal, Cumbria
Funster No
27,352
MH
A Class
Exp
since 1999
If you try to run your microwave at half load, becomes very inefficient in power factor as low as 0,5
That bit I don't understand. Microwave ovens (apart from expensive internal inverter types) achieve power variation by switching the magnetron on and off (the on to off ratio determines the power output and the intervals are quite large).

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Dec 2, 2019
1,446
3,104
Amersham
Funster No
67,145
MH
van conversion
The microwave is not a resistive load, where the power is all absorbed. It absorbs less than the source delivers, and returns back to source as reactive power. The less it cycles on a small power setting the least efficient. A microwave will be at its best efficiency at full load setting.
I haven’t measured it, just exaggerated for explanation purposes, but I will very surprised to see a microwave to exceed 0,8 power factor.
 
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