Slow cooker and inverter ? (1 Viewer)

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Jun 3, 2021
326
254
Funster No
81,675
MH
Hymer B680
We have a small slow cooker rated at 120 watts and am wondering if we can use it with our inverter while off grid, the inverter is a 1000 watt modified sine wave and we have 2 x 130 AH batteries along with 2 x 100 watt solar panels, I'm informed that to cook a stew it would have to be on for about 6 hours, would this flatten the batteries or damage the inverter?
My wife uses her hair dryer rated at 1200 watts with no noticable problems but only for about 10-12 minutes.
 

funflair

LIFE MEMBER
Dec 11, 2013
19,752
31,869
Guisborough
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29,351
MH
MORELO palace
Exp
since 2012
You have a bit of a mix of units there with watts, hours, minutes and ah, when doing the calculations it is easier to keep the units roughly the same so lets say that your battery bank is 260ahx12volts so that is 3,120 watt/hour or a more useable capacity of around 1600 watt/hours to flat as of course you can't use the full capacity of lead acid without damaging them.

Whether you can use for slow cooker for 6 hours depends a lot on what the sun is doing, with no sun 120watts for 6 hours is 720 watt/hours so taking inverter inefficiencies into account that is half of your available battery capacity, now let's assume the sun is out for all the 6 hours and making at least 120 watts from your 200 watts of solar so you can see that the picture would be completely different.

Now looking at the hair dryer 1200watts for 12 minutes so 1/5th of an hour is only 240 watt/hours, so even though the load is a lot bigger than the slow cooker it's time that is as important.

So to try to answer your question, would the slow cooker flatten the batteries? no but it could take a big chunk out that the solar may or may not put back in, would this damage the inverter? no it shouldn't but I have very little experience with modified sine wave jobbies other than I took one straight off our first van as it just didn't do what I wanted it to.

Rather than a straight yes/no answer I have tried to give you a bit of background to enable you to do the mental calculations on a day to day basis taking into account the sun/solar as it has such a big bearing on the answer.
 

Puddleduck

LIFE MEMBER
Jan 15, 2014
12,501
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Scottish Borders
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29,703
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Without at present
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On and off for many years.
A brilliant answer funflair, thank you very much for the great details.

We use our slow cooker via a small inverter a lot. The 120W is pretty much the maximum it will draw, I always bring the liquid to the boil and add it hot to the slow cooker and the cooker is always on the low setting.

Our slow cooker comes into it's own when traveling (in a bowl in the sink) - or when we are out and about kayaking or cycling. It's great to come back to a hot meal. When kayaking / cycling we will usually be on a site with EHU.

For those who don't know it is possible to do baked potatoes and even roast meat in a slow cooker. Potatoes are rubbed with oil and salt, wrapped in foil and put into the cooker without liquid. Make sure they will fit before you prepare them. A roast goes into a roasting bag and then into the cooker. EHU probably a good idea of you are doing this.

The plate on our slow cooker says 90W and our inverter is just a 200w Lidl special.
 
Apr 27, 2016
7,100
8,360
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
To add a bit more about the solar, 200W will produce about 60Ah (60 x 12 = 720watt-hours) on an average summer day, and more like 80Ah (80 x 12 = 960Wh) on a good sunny day. In Spring and Autumn a lot less, and in winter hardly enough to charge a phone.

As far as I know, slow cookers don't have a thermostat, so it will be using power constantly. Not like a fridge that turns on and off, and is on for maybe 50% of the time. Is 120W the low power setting, or the maximum power as shown on the product label?
 

Puddleduck

LIFE MEMBER
Jan 15, 2014
12,501
44,667
Scottish Borders
Funster No
29,703
MH
Without at present
Exp
On and off for many years.
To add a bit more about the solar, 200W will produce about 60Ah (60 x 12 = 720watt-hours) on an average summer day, and more like 80Ah (80 x 12 = 960Wh) on a good sunny day. In Spring and Autumn a lot less, and in winter hardly enough to charge a phone.

As far as I know, slow cookers don't have a thermostat, so it will be using power constantly. Not like a fridge that turns on and off, and is on for maybe 50% of the time. Is 120W the low power setting, or the maximum power as shown on the product label?
Pretty sure there is no thermostat but putting any liquid in at boiling (or near to) means you don't have to use the high setting for an hour and then turn it down but you can just use the low setting.

On ours the 90W is the maximum load (eg at high power). I don't know off hand what the low power setting draws and it's dark outside so I am not going out to have a look - and it might not even say anyway.

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Last edited:
OP
OP
H
Jun 3, 2021
326
254
Funster No
81,675
MH
Hymer B680
To add a bit more about the solar, 200W will produce about 60Ah (60 x 12 = 720watt-hours) on an average summer day, and more like 80Ah (80 x 12 = 960Wh) on a good sunny day. In Spring and Autumn a lot less, and in winter hardly enough to charge a phone.

As far as I know, slow cookers don't have a thermostat, so it will be using power constantly. Not like a fridge that turns on and off, and is on for maybe 50% of the time. Is 120W the low power setting, or the maximum power as shown on the product label?
The label just says 120w so I guess that’s the max power, So looking at the comments am I I correct in assuming that on an average sunny day the batteries should hold their own ?
 
Apr 13, 2019
2,096
49,430
Nottinghamshire
Funster No
59,884
MH
Ci Coachbuilt
Exp
Since September 2018
You have a bit of a mix of units there with watts, hours, minutes and ah, when doing the calculations it is easier to keep the units roughly the same so lets say that your battery bank is 260ahx12volts so that is 3,120 watt/hour or a more useable capacity of around 1600 watt/hours to flat as of course you can't use the full capacity of lead acid without damaging them.

Whether you can use for slow cooker for 6 hours depends a lot on what the sun is doing, with no sun 120watts for 6 hours is 720 watt/hours so taking inverter inefficiencies into account that is half of your available battery capacity, now let's assume the sun is out for all the 6 hours and making at least 120 watts from your 200 watts of solar so you can see that the picture would be completely different.

Now looking at the hair dryer 1200watts for 12 minutes so 1/5th of an hour is only 240 watt/hours, so even though the load is a lot bigger than the slow cooker it's time that is as important.

So to try to answer your question, would the slow cooker flatten the batteries? no but it could take a big chunk out that the solar may or may not put back in, would this damage the inverter? no it shouldn't but I have very little experience with modified sine wave jobbies other than I took one straight off our first van as it just didn't do what I wanted it to.

Rather than a straight yes/no answer I have tried to give you a bit of background to enable you to do the mental calculations on a day to day basis taking into account the sun/solar as it has such a big bearing on the answer.
Nice answer 👍
 
Feb 2, 2022
315
530
Hartland, Bideford, Devon, UK
Funster No
86,664
MH
Ixeo 1744
Exp
I’m newbie
You have a bit of a mix of units there with watts, hours, minutes and ah, when doing the calculations it is easier to keep the units roughly the same so lets say that your battery bank is 260ahx12volts so that is 3,120 watt/hour or a more useable capacity of around 1600 watt/hours to flat as of course you can't use the full capacity of lead acid without damaging them.

Whether you can use for slow cooker for 6 hours depends a lot on what the sun is doing, with no sun 120watts for 6 hours is 720 watt/hours so taking inverter inefficiencies into account that is half of your available battery capacity, now let's assume the sun is out for all the 6 hours and making at least 120 watts from your 200 watts of solar so you can see that the picture would be completely different.

Now looking at the hair dryer 1200watts for 12 minutes so 1/5th of an hour is only 240 watt/hours, so even though the load is a lot bigger than the slow cooker it's time that is as important.

So to try to answer your question, would the slow cooker flatten the batteries? no but it could take a big chunk out that the solar may or may not put back in, would this damage the inverter? no it shouldn't but I have very little experience with modified sine wave jobbies other than I took one straight off our first van as it just didn't do what I wanted it to.

Rather than a straight yes/no answer I have tried to give you a bit of background to enable you to do the mental calculations on a day to day basis taking into account the sun/solar as it has such a big bearing on the answer.
Your clever and very helpful mr fun flair 👍
 

funflair

LIFE MEMBER
Dec 11, 2013
19,752
31,869
Guisborough
Funster No
29,351
MH
MORELO palace
Exp
since 2012
The label just says 120w so I guess that’s the max power, So looking at the comments am I I correct in assuming that on an average sunny day the batteries should hold their own ?
Basically yes you won’t be far off👍

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Apr 27, 2008
11,919
14,221
Eastbourne East Sussex
Funster No
2,327
MH
Hymer low profile
Exp
Since 1972
We used to use a slow cooker, in the sink, while driving, from an modified square wave inverter with no problem and no noticeable effect on the batteries. I think on a low setting they use very little lecky, after all you're only keeping it hot rather than heating it up.
 
Sep 29, 2019
3,180
7,310
Funster No
64,846
MH
Hymer Exsis
Exp
20 years
I can’t beat the comprehensive answer you have already had by funflair.

I have a similar setup and I find with ours, April to August is all good. Rest of year, don’t bother unless moving or have hook up. :)
 
Jan 27, 2023
44
65
Cirencester, UK
Funster No
93,636
MH
Wildax Solaris XL
Exp
Brand new
A different answer is that many slow cookers are very badly insulated. If the cooker has a thermostat and is wrapped in a thick layer of insulation then it will cook effectively while using very little power. Better still use the old haybox cooking approach.
 

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