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Old 23-02-2014, 05:21   #1
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Amps, Watts and Volts Required For Slow Cookers

We have a 120w slow cooker at home which is small, neat and cheap enough that if it breaks there won't be tears, which could find its way onto the yacht for the summer. The UK mains voltage is 230 volts btw.

So if the maximum watts are 120 at 230 volts mains that should be a draw of 0.52 AH, perhaps a bit less if the thermostat switches on and off.

On the boat I have a 350w sterling inverter connected to the house bank. Ignoring the losses for the moment would 120w at 12v require 10AH? and if the inverter is 85% efficient then would the draw would be approximately 12 AH?

In practice running off 180w of solar the voltage is more likely to be 13 - 14v during a summers day so perhaps a draw 10 AH which we could afford for 5 or 6 hours cooking time, house bank is 220 AH btw.

Does this look reasonable for a summer of curries, goulashes and chilli con carne?

Pete
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Old 23-02-2014, 05:24   #2
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re: Amps, Watts and Volts Required For Slow Cookers

I would say yes....
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Old 23-02-2014, 05:36   #3
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re: Amps, Watts and Volts Required For Slow Cookers

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Originally Posted by Pete7 View Post

Does this look reasonable for a summer of curries, goulashes and chilli con carne?

Pete


And botulism

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Old 23-02-2014, 05:51   #4
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re: Amps, Watts and Volts Required For Slow Cookers

It will work as you describe. Your solar panels won't put out 180 W all day, but you probably already know that! You will need some way of recharging your house batteries which will make up the difference.

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Old 23-02-2014, 06:14   #5
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re: Amps, Watts and Volts Required For Slow Cookers

It's perhaps a nit, but may help enhance your understanding (which is pretty good already), and avoid confusion.....

Your cooker draws 0.52 amps (A), not amp-hours (AH). Amp are the current draw any any given time. Amp-hours are the cumulative energy consumption, or in the case of a battery, the amount of energy stored.

Your cooker drawing 0.52A will consume 0.52AH if run for an hour, and 1.04 AH if run for two hours, and so on. The longer you let it run, the more AH is consumes even though the draw remains constant at .052A

You also touched on the reality that your cooker likely cycles on and off. That's referred to as the Duty Cycle. When it's the heating element is on it draw 0.52A, and when it's off it draws nothing. If it were on all the time (a Duty Cycle of 100%) then it would consume .052AH every hour that it runs. If it's only on half the time (50% Duty Cycle), then the power consumption would be 0.26AH every hour that it runs.

Hopefully this help clarify rather than confuse.
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Old 23-02-2014, 07:39   #6
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I would estimate your 180 watt panel giving you 50 to 60 amp hours a sunny day. which is enough for the slow cooker but what about your other loads. And also there's a problem of the day starting out nice and turning cloudy. If you have the room I would suggest making an insulated box a pressure cooker can fit into. And slow cooking that way.
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Old 23-02-2014, 07:47   #7
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re: Amps, Watts and Volts Required For Slow Cookers

I would suggest a Dutch oven on a portable induction plate which can be used for many more things… saves some space.

p.s. this requires an induction plate that lets you select the desired temperature, of which there are plenty, incl. the cheap one from TV ads.
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Old 23-02-2014, 12:01   #8
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re: Amps, Watts and Volts Required For Slow Cookers

Folks thanks for the replies. Dave for the suggestion, would that add a bit of a kick to a dish

I am not to worried about going into deficit with the house bank because we only use about 30-40 AH a day, although I did buy SWMBO a TV for Christmas so that's probably put the kabosh on being energy efficient. Also it won't be every day so the panels can pick up the slack on the following day.

At present by early afternoon I am wandering around the boat looking for stuff to charge up rather than waste half a day of sunshine. Also being 50 deg N does make a difference. Panels don't get hot, sun is up early and whilst the panels don't give full wack early in the morning any charge they do give goes straight into discharged batteries so it does all help.

Nick thanks for the suggestion of the Dutch Oven, we also have a small pressure cooker on board which is more likely to be used and gives us an alternative option using gas and a variety to cooking.

So the maths checks out and it looks like a plan, lets see what happens in the real world.

Pete
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Old 23-02-2014, 12:46   #9
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re: Amps, Watts and Volts Required For Slow Cookers

Hi Pete, your math checks out.

As discussed elsewhere, electric-powered heating appliances are usually a poor use of battery energy when away from the dock... but if you truly have an excess of solar charging capability at midday, I can't see the harm in channelling that into your crockpot

Seems a practical thing for a daysail, if you've properly prepared the food and immediately start heating it. So that implies you have proper refrigeration for the raw ingredients. Letting something sit at or near room temp without heating is a recipe for food poisoning as Dave points out.

We've had success with preparing (fully cooked) curries, chili, sauces etc onshore and freezing them in a bag. They go into a cooler with other stuff and freezer packs etc, where they thaw gradually, and are good for up to two days as long as they remain properly cool til used. Bag contents go into a saucepan, and it takes 10 -15 min on a small butane stove to reheat.
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Old 23-02-2014, 13:26   #10
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re: Amps, Watts and Volts Required For Slow Cookers

Yes we have a good fridge and tend to buy fresh cut meats and veg as we need them, it would be rare to be away from shops for more than a couple of days. We do freeze things like milk at the start of the voyage but there is only so much you can do. With France 12 hours away there isn't much need for anything else. hence we buy fresh local produce often and that is part of the fun on holidays searching out the local farm shops or family butchers who survive on their reputation.

The advantage of a slow cooker is it can be left to its own devices if you go out for the day. That would probably worry some folk, bit like leaving a yacht at anchor unattended, but I am okay with it.

Pete
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Old 23-02-2014, 13:33   #11
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re: Amps, Watts and Volts Required For Slow Cookers

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Originally Posted by goboatingnow View Post
And botulism

Dave

Dave's got a good point here.

No actual experience but I suspect that a slow cooker could in the right circumstances make you very sick as it never gets the meat hot enough, especially at 120 watts and also takes it through the dangerous bug generating temp very very slowly.

However, I like Mr Ds thermal cooker as it does a similar job but instead of slowly cooking the meat, you put it on the induction hot plate on high for about 5 mins until nearly boiling, then turn it off and leave it for 5 hrs in the thermal outer vacuum pot that retains the heat like a thermos.

Then do the whole procedure again for say another 4 hrs. The meat will be tender, just like a slow cooker with the following advantages....

1 the meat got rapidly taken through the dangerous 40 to 60 degree temp very quickly, killing dangerous things.

2 The induction hob was on full for maybe 8 mins so used V little energy.... Can't be bothered doing the energy comparison but should be better than the slow cooker.
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Old 23-02-2014, 13:46   #12
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re: Amps, Watts and Volts Required For Slow Cookers

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Originally Posted by Fuss View Post
Dave's got a good point here.

No actual experience but I suspect that a slow cooker could in the right circumstances make you very sick as it never gets the meat hot enough, especially at 120 watts and also takes it through the dangerous bug generating temp very very slowly.

However, I like Mr Ds thermal cooker as it does a similar job but instead of slowly cooking the meat, you put it on the induction hot plate on high for about 5 mins until nearly boiling, then turn it off and leave it for 5 hrs in the thermal outer vacuum pot that retains the heat like a thermos.

Then do the whole procedure again for say another 4 hrs. The meat will be tender, just like a slow cooker with the following advantages....

1 the meat got rapidly taken through the dangerous 40 to 60 degree temp very quickly, killing dangerous things.

2 The induction hob was on full for maybe 8 mins so used V little energy.... Can't be bothered doing the energy comparison but should be better than the slow cooker.
I don't know how the OP's cooker performs or the ones you have used..but every one of mine for the last 30 odd years will boil on high within hours and on low by around hour 6...the fancier ones with more settings...I can't say ...but the on, low, high ones I'm used to will get the ingredients plenty hot to avoid getting you sick.
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Old 23-02-2014, 14:01   #13
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re: Amps, Watts and Volts Required For Slow Cookers

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Originally Posted by Fuss View Post
No actual experience but I suspect that a slow cooker could in the right circumstances make you very sick as it never gets the meat hot enough, especially at 120 watts and also takes it through the dangerous bug generating temp very very slowly.

However, I like Mr Ds thermal cooker as it does a similar job but instead of slowly cooking the meat, you put it on the induction hot plate on high for about 5 mins until nearly boiling, then turn it off and leave it for 5 hrs in the thermal outer vacuum pot that retains the heat like a thermos.
My Mom had a crockpot, and we have an inexpensive one too... and I don't recall ever having any illness from it. But my Mom and my wife are both excellent cooks, and good cooks know that you brown your meat before it goes into the crockpot... and yes you start out in high to get the boil happening quickly.

I haven't seen a thermal cooker before... thanks for that. It sure looks more efficient, practical and safer than a slow cooker, especially for use on a boat. I would definitely go for one of those over a slow-cooker.

But it doesn't help Pete use up his leftover electricity at midday...
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Old 23-02-2014, 14:10   #14
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re: Amps, Watts and Volts Required For Slow Cookers

Quote:
Originally Posted by Fuss View Post
Dave's got a good point here.

No actual experience but I suspect that a slow cooker could in the right circumstances make you very sick as it never gets the meat hot enough, especially at 120 watts and also takes it through the dangerous bug generating temp very very slowly.

However, I like Mr Ds thermal cooker as it does a similar job but instead of slowly cooking the meat, you put it on the induction hot plate on high for about 5 mins until nearly boiling, then turn it off and leave it for 5 hrs in the thermal outer vacuum pot that retains the heat like a thermos.

Then do the whole procedure again for say another 4 hrs. The meat will be tender, just like a slow cooker with the following advantages....

1 the meat got rapidly taken through the dangerous 40 to 60 degree temp very quickly, killing dangerous things.

2 The induction hob was on full for maybe 8 mins so used V little energy.... Can't be bothered doing the energy comparison but should be better than the slow cooker.
Wouldn't slow cookers be sued out of existence if they made people sick?
Maybe do some research on slow cookers.
Range 60-240 W.
Slow Cookers and Energy Usage

Slow cooker safety
Slow Cookers and Food Safety : Preparing Safe Meals : Preserving and Preparing : Safe Meals : Preserving and Preparing : Food Safety : Food : University of Minnesota Extension

Doing some rough calcs the 120 W slow cooker should be able to heat 2 liters (or quarts) of water to 140 degrees F in a little over an hour, so less than the 2 hour limit on leaving food out.
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Old 23-02-2014, 14:17   #15
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re: Amps, Watts and Volts Required For Slow Cookers

It's 120w because it's tiny, the next size up is about 180w and upwards depending on size. At home it produces just enough to feed 2 or 3. Don't have the instructions in front of me but I think they cook at about 180 - 200F depending on setting.

Wifey is fussy about food, indeed I am worried about a fairly ripe French Camembert in the fridge at the moment

However, your point is valid.

Pete
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