Freebee
Well-known member
Are they any good?
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12 volt microwave cookers
- Thread starter Freebee
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kghowe
New member
Don't do it! Get a good inverter and a 240V unit, there cheaper, WORK and cook quicker, IMHO.
KGH
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KGH
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ccscott49
Active member
Mains one with an inverter are fine! Dont know about 12volt ones.
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Freebee
Well-known member
Ok then next question is how do I size the inverter to drive the microwave?
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Kevin
New member
Hi
if you have a 800w microwave this isnt the power it obv. pulls in, normally its about 40% higher so that would mean its drawing in about 1100 watts. inverters are about 90% efficient ( so we are up to 1200w needed) plus say 20% for safety reasons meaning you would need about 1500w inverter just for a microwave, this means your drawing about 5 amps which will drain a car battery quickly if its not being charged at the same time.
this doesnt take into consideration resistance which might be a small factor and mean it draws more current, should the inverter be placed a long way from the microwave.
all the above IMVHO
Kevin
if you have a 800w microwave this isnt the power it obv. pulls in, normally its about 40% higher so that would mean its drawing in about 1100 watts. inverters are about 90% efficient ( so we are up to 1200w needed) plus say 20% for safety reasons meaning you would need about 1500w inverter just for a microwave, this means your drawing about 5 amps which will drain a car battery quickly if its not being charged at the same time.
this doesnt take into consideration resistance which might be a small factor and mean it draws more current, should the inverter be placed a long way from the microwave.
all the above IMVHO
Kevin
boatone
Well-known member
Wish a 1500watt invertor did draw only 5 amps /forums/images/icons/laugh.gif
More like 125amps I think you will find.......
That means a battery drain of roughly 2.1 amp/hours per minute of operation which is actually not that bad if youve got decent batteries. You do need really beefy cables though.
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More like 125amps I think you will find.......
That means a battery drain of roughly 2.1 amp/hours per minute of operation which is actually not that bad if youve got decent batteries. You do need really beefy cables though.
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brianrunyard
New member
1500w = 6.25amps at 240v.
1500w = 125amps at 12v
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http://homepage.ntlworld.com/brunyard
1500w = 125amps at 12v
<hr width=100% size=1>Brian
http://homepage.ntlworld.com/brunyard
Kevin
New member
Hi
I=P/V where V is the source voltage (12) not the final voltage (240) that makes sense. I based mine on 1200w at 240 volts instead of the 12, to get the 5 amp-oops
result is the same you need a good 1500w inverter to power a microwave (allowing 20% for safety) though! -smiley face-
Kevin
I=P/V where V is the source voltage (12) not the final voltage (240) that makes sense. I based mine on 1200w at 240 volts instead of the 12, to get the 5 amp-oops
result is the same you need a good 1500w inverter to power a microwave (allowing 20% for safety) though! -smiley face-
Kevin
ccscott49
Active member
Remember Kevin, if its a 12 volt microwave and its drawing 1500 watt, @ 12 volt, its still drawing a bunch of amps, (125) so whats the point you are making, please.
Remembering that the 12 volt micros are expensive and mains ones cheap, (and good choice of models) plus you can use the inverter for other things. IMHO, inverter is the only way to go.
One other point, you need big cables from your batteries to the microwave, if it draws 125 amps and galleys are normally a far way from the batteries, so they have to be both big and long. (expensive) If you use an inverter however, the battery to inverter cables can be short (cheap) and the ac cable long, (cheap)which doesn't really matter, as the current is comparatively low. I hope this makes sense, I know what I mean, but not sure if you know!
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Remembering that the 12 volt micros are expensive and mains ones cheap, (and good choice of models) plus you can use the inverter for other things. IMHO, inverter is the only way to go.
One other point, you need big cables from your batteries to the microwave, if it draws 125 amps and galleys are normally a far way from the batteries, so they have to be both big and long. (expensive) If you use an inverter however, the battery to inverter cables can be short (cheap) and the ac cable long, (cheap)which doesn't really matter, as the current is comparatively low. I hope this makes sense, I know what I mean, but not sure if you know!
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Kevin
New member
Hi
I was really answering the original post that asked what size inverter was needed for a 240 volt microwave (at say 800W). i made the point that if its 800w micro it draws 40% more than that plus any margin of safety hence 1500w inverter for 800w microwave
I then wandered off and got side tracked into thinking how many amps that would be drawing adn wondered if a microwave on for say 2/3 mins regularly would drain the battery quickly- the last part was a thinking out loud.
I agree with you no question 240v is best way to go.
Kevin
I was really answering the original post that asked what size inverter was needed for a 240 volt microwave (at say 800W). i made the point that if its 800w micro it draws 40% more than that plus any margin of safety hence 1500w inverter for 800w microwave
I then wandered off and got side tracked into thinking how many amps that would be drawing adn wondered if a microwave on for say 2/3 mins regularly would drain the battery quickly- the last part was a thinking out loud.
I agree with you no question 240v is best way to go.
Kevin
TrueBlue
Well-known member
Methinks the 12V microwaves merely have an inverter hidden inside their casings and are really 240Volt units in Wolf's clothing. (Until somebody else corrects me)
On a sensible note, be aware that it is said that microwave cookers are less efficient (that is cook slower) on a "normal" (square-ish wave) invertor than on a full sine wave type. These latter are much more expensive than the former - so nobody bothers. Easiest is to by a slightly more powerful oven in the first place.
All very much IM(H)O as SWMBO will only use an elephant dung fire to cook, and eschews all mechanical assistance...
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Stop what you're doing and wait my signal
On a sensible note, be aware that it is said that microwave cookers are less efficient (that is cook slower) on a "normal" (square-ish wave) invertor than on a full sine wave type. These latter are much more expensive than the former - so nobody bothers. Easiest is to by a slightly more powerful oven in the first place.
All very much IM(H)O as SWMBO will only use an elephant dung fire to cook, and eschews all mechanical assistance...
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ccscott49
Active member
Meant the first bit for you Kevin, then got carried away, as usual!! I didnt know that a micro worked less efficiently on a modified sine wave inverter, now thats interesting, as I always thought mine was a bit slow on inverter compared to genny! Now I know why! Great iinit this forum lark!
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sailorman
Well-known member
i have just fitted one fo these the vendor is fantastic to deal with he has i think one s/hand one left @ £100
I Have three 1500W modified sine wave inverters for sale, one is brand new for which I want £190 and the others are used but in good condition for £100 each.
These inverters new from Machine Mart cost over £300.
For more info call Mark on 07734 232855.
£100 +
£ 60 micro from qed ( quality electricial dierct )
much cheaper than a 12v one + more versitile
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I Have three 1500W modified sine wave inverters for sale, one is brand new for which I want £190 and the others are used but in good condition for £100 each.
These inverters new from Machine Mart cost over £300.
For more info call Mark on 07734 232855.
£100 +
£ 60 micro from qed ( quality electricial dierct )
much cheaper than a 12v one + more versitile
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Salty John
Active member
A microwave powered by a modified sine wave inverter is much more sensitive to battery voltage. "Cooking efficiency" falls to 60% when the battery voltage is at about 11.5 volts, and even at 13.0 volts will only give 80% efficiency. This is why you see a difference between inverter power and genny power.
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duncan
Active member
well the power/12v or 240 seem to have been covered but how robust are these things in small (25ft plannning) boats?
at this time of year heating pasties or pies in a microwave sounds great but bashing through the seas to the fishing grouds is also SOP !
<hr width=100% size=1>madesco madidum ..../forums/images/icons/smile.gif
at this time of year heating pasties or pies in a microwave sounds great but bashing through the seas to the fishing grouds is also SOP !
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Freebee
Well-known member
Ah but this is going in boat number two a beneteau flyer 8, oh crumbs its still a 25 foot planing hull, but it has an extra 100 hp over the Bertram!!
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boatmad2
New member
Inverters are ok but for a good inverter price you can buy a 2600 watt genny.
I carry mine on the fore deck, not good for sea use I know but great on the waterways. It also has enough power for the wifes megga hairdryer.
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I carry mine on the fore deck, not good for sea use I know but great on the waterways. It also has enough power for the wifes megga hairdryer.
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sailorman
Well-known member
new 2000watt inverter just sold on ebay for £125 + del
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duncan
Active member
um....I wasn't asked a rhetorical question or making a comment on your 8m boat Mike - I was asking the panel for my 8m boat!
maybe someone will confirm that these things are fine being dropped on the floor from 3 feet a few times a week /forums/images/icons/smile.gif
<hr width=100% size=1>madesco madidum ..../forums/images/icons/smile.gif
maybe someone will confirm that these things are fine being dropped on the floor from 3 feet a few times a week /forums/images/icons/smile.gif
<hr width=100% size=1>madesco madidum ..../forums/images/icons/smile.gif
