12 Volt Microwave Ovens

[Willallison]

I'm trying to source a 12 volt microwave oven. Samsung used to make (a rather hideous looking) one, but no longer do so.
(I'm trying to avoid going down the 240 v / inverter route for reasons of simplicity, cost and efficiency)
Any suggestions?

[Frosty]

Im not sure about the micro wave but the Tv simply has a small invertor inside so it is infact still a 220 V TV. However thr TV needs only 40 watt or less where as the micro wave needs more like a Kilo watt.

[marshmat]

Interesting problem, Will.

Even a baby 12 V microwave, 700 watts, would need around 60 amps... try a bit under 85 A for a 1000 watt model that would actually be able to cook stuff. That's a lot of fairly hefty (and expensive) heavy gauge battery cable, probably the same kind of stuff you'd run to an electric windlass.

With a 1 kW 12-120 sinusoidal inverter running at 95% plus efficiency and costing less than $300, would the savings from finding a nukebox that runs on 12 VDC really be that significant? A Chinese one with a 4-year lifespan might cost you $80, a good one no more than $200.... even if the 12V oven exists, it'd have to be under $400 to be cost competitive.

Frosty - If you're talking about an old-school tube TV, then yes, it would have to have an internal inverter of some kind- the CRT needs a high-voltage flyback coil and those only work on AC. The more modern LCD ones just have a power filter and voltage regulator on the DC input.

[CDK]

The hideous Samsung had an inverter built in, just like the 24V microwaves that truckers have. The magnetron in the oven needs 1200 V, obtained from a transformer in AC models or an inverter in DC ones.
Just buy the microwave you fancy plus any Chinese 1 kW inverter and install it next to the battery so you won't have large cable losses. The inverter can be remotely switched on and off with a very small switch that carries just a few mA.

[Willallison]

The Samsung unit had an output of 450 watts, I haven't been able to establish its input requirement; whereas the smallest domestic unit I could find was an output of 800w with an input requirement of 1000w. But even so, yes, it requires a significant current, if only for a short period of time. It's not so much the cabling that I would be concerned about, but the size of the battery bank required to run it. At this stage, I would look at running the engine at the same time to overcome that problem.

As far as inverters go, it's true that a modified sine wave inverter can be had for a couple of hundred bucks. But a quality true sine wave inverter is more like $1500. Whilst the cheapie may run the microwave (I guess they must do...?) I'm always hesitant about putting cheap stuff aboard, for obvious reasons.
I also like the simplicity of running a single voltage system. There won't be anything else on board that requires anything other than 12v. This is a pretty simple boat and I'd like to keep it that way wherever possible...

[marshmat]

Will,

I can go to any Canadian Tire store and buy a Xantrex Xpower 1750+, a top quality Canadian built mod-sine inverter, for $300. A pure sine wave unit, 1 kW peak rating, under the Eliminator brand (probably Chinese built, but still fairly decent) is also $300. A Xantrex Prosine 1800i, the absolute cream of the crop, providing better quality power than any power grid on the continent (ambulances often use this line for their medical gear), is less than $1000.

My friend, you need a new electronics dealer!

[Fanie]

I agree with Matt and CDK. A microwave oven is the only thing on a boat you will need an inverter for. Everything else can be worked off DC.

I also did a check since the wife recently got a new micro wave. If you're doing it in a small MW vs a big one the power consumption is almost the same, the big one just does it quicker - the total power consumed to do the same thing with is the same.

Stupid thing, but it keeps the wife happy.

[Willallison]

Matt - $1000 CAN = $1200 AUD - so not that much different! To happily run the 800w unit I was referring to before I would need to put in a 12-1500w (input requirement was 1000w) with a peak load of near double that.
In Oz you're looking at between $1 and $1.20 per watt for a pure sine wave jobbie...

Fanie - it's not the total power consumed that is the primary concern: A microwave running for say a minute might only consume 5 ampere hours. But it will do si at a 'rate' of maybe 80 Amps - enough to very quickly destroy the plates in the sort of single house battery that I'm considering here. This is a planing boat where weight is one of the primary considerations so a big battery bank is out of the question

[Fanie]

Hi Will, I'm aware of those poor batteries suffering under huge micro wave currents while we try and save a few milli amp using LED or CF lighting Kind of rediculous.

I'm putting a small power generator aboard to run the microwave from. I'll let the wife start the thing herself, so maybe she'll use it less

[CDK]

Willallison, for the microwave you best use a starter battery. 80 Amps is just a light load for that.
And nowadays microwaves are advertised as 800 or 1000 watts because it sounds more impressive than the actual 500 watts or less heat they generate.
For this purpose the inverter's waveform is of no concern, even triangles are fine.