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Thank you for the great forum, Safe Driving over the weekend. Sincerely Jason

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Just now, Richard Mackay said:

ThIs has got to be an ad for LFP batteries!  (It's fine if the PV panels are pumping power into the system..)

There should be a law against using the most sophisticated energy we have available for heating water!

It's been all down hill since the flint and dry grass.

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1 hour ago, plonkster said:

 

I run my normal 2kw kettle from my inverter. The LFP batteries can handle it 🙂

 

 

The more efficient charging of lithium batteries makes extra energy available . Boiling a kettle or 2 is hardly noticed .

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To boil water quickly on gas you need one of those cheap ugly aluminium kettles. They boil very quickly as they are thin metal and the aluminium conducts heat very well. Ours last about 1 year before they start leaking from the spout and get converted into a flower pot, but they are very quick on a gas hob.

The other thing we have is a wood stove so once that is going in winter, you always have a hot kettle on the hob. Helps to humidify the dry winter air a bit as well.

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On 2020/03/21 at 9:39 AM, Tsa said:

@DeepBass9 thanks. Out of interest, what are the specs of the plate on high and low settings and how long does it take to boil on low vs high? How many litres? 

Its one of these https://www.takealot.com/salton-single-induction-cooker/PLID46915693?gclid=CjwKCAjw3-bzBRBhEiwAgnnLCq0yenDQI0UFjKkMCRdmxIE3NyxXGZGPFcxhOadj41jplVt4Y7nFlBoC5IkQAvD_BwE&gclsrc=aw.ds

On full power it is 2kW so plenty fast enough, and the lowest setting is about 400W. Induction is efficient as the container is heated directly, so it will be the same as an immersed element in a 'normal' kettle. Is works on any steel container, but not aluminium, copper or brass. If a magnet sticks to the pot it will work, so even those baked enamel pots and kettles work, or cast iron.

I have a big flat bottomed potjie pot (no legs) which works great for stews etc on the 'hotpot' setting on the induction plate.

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18 hours ago, DeepBass9 said:

Its one of these https://www.takealot.com/salton-single-induction-cooker/PLID46915693?gclid=CjwKCAjw3-bzBRBhEiwAgnnLCq0yenDQI0UFjKkMCRdmxIE3NyxXGZGPFcxhOadj41jplVt4Y7nFlBoC5IkQAvD_BwE&gclsrc=aw.ds

On full power it is 2kW so plenty fast enough, and the lowest setting is about 400W. Induction is efficient as the container is heated directly, so it will be the same as an immersed element in a 'normal' kettle. Is works on any steel container, but not aluminium, copper or brass. If a magnet sticks to the pot it will work, so even those baked enamel pots and kettles work, or cast iron.

I have a big flat bottomed potjie pot (no legs) which works great for stews etc on the 'hotpot' setting on the induction plate.

Excellent, thanks for the detail. Will do some investigation and shopping. If you had to guess, how long does it take to boil water, say 1 or 2 liters at the low setting of 400W, or whichever setting you usually use. 

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1 hour ago, Tsa said:

If you had to guess, how long does it take to boil water, say 1 or 2 liters at the low setting of 400W

Depends on ambient water temperature and efficiency of the cooker. Induction cookers are 84% efficient according to the US energy star people. Let's assume ambient water is at 15°C, so you have to heat it by 85°C. You need 1.16*85 ~= 100Wh (you can use that as a rule of thumb, 100Wh for each liter). Divide by 0.84 to account for efficiency, so you need 120Wh to get the job done. Divide "Wh" by "W" and you should get h, so 120/400 = 0.3, or 18 minutes.

So that is my guess, about 18 to 20 minutes.

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19 hours ago, DeepBass9 said:

Induction is efficient as the container is heated directly, so it will be the same as an immersed element in a 'normal' kettle.

Sadly not the case. Even though you gain a good 10% in the energy transfer into the utensil, some of the heat energy still fails to enter the water and instead goes from the utensil into the environment without ever entering the water. Hence my number above of 84%. With the element-in-water setup, the heat literally has to go through the water to reach the outer container before it can go off into the environment. Of course a small amount can take a shortcut to the container wall because the element is attached at the back.

It's also another reason those flat-plate kettles (where the element is below the water) will be less efficient than element-in-water kettles.

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On 2020/03/23 at 9:22 AM, Richard Mackay said:

There should be a law against using the most sophisticated energy we have available for heating water!

If your'e using DC to heat your water then this isn't as bad as using AC. DC is a more basic form of electricity so it's ok to use it for this.

However the pain of generating AC power puts it into another league..

 

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11 hours ago, Richard Mackay said:

If your'e using DC to heat your water then this isn't as bad as using AC. DC is a more basic form of electricity so it's ok to use it for this.

Well, if you insist, there are camping kettles available that run from 12V... Usually not very powerful, since they have to run from car batteries, and often from cigarette lighter plugs that have 15A fuses. I think they boil one cup at a time, and it takes around 10 minutes.

🙂

 

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Isn't there one that plugs directly into the PV array?

This concept isn't that far fetched: The Geyserwise Dual system's PV circuit is DC. The PV panels feed a MPPT which then feeds DC to the lower voltage element in the geyser.. 

 

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3 hours ago, plonkster said:

Well, if you insist, there are camping kettles available that run from 12V... Usually not very powerful, since they have to run from car batteries, and often from cigarette lighter plugs that have 15A fuses. I think they boil one cup at a time, and it takes around 10 minutes.

🙂

 

Probably easier to put a tin cup on the exhaust manifold!

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