12v kettles

[Alicia]

So we are kitting out out MH and thinking of a 12v kettle- do they suck the life out of your leisure battery?? Is it worth it for a cuppa or shall I just go straight to wine??!

 

[David and Sally]

Forget it. They take forever to boil.

 

[funflair]

Straight to wine as you will be waiting a long time for a 12v to warm up, not boil just warm up

 

[Gaston aires]

Low wattage camping kettle through an inverter. Well worth having an inverter for other things as well.
Phil

 

[Vipar]

Use gas

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[Eddystone]

Stick to gas for boiling water.

 

[Yorick]

My pal had a 12v jobby in his truck that plugged into cigarette lighter. Was fairly quick when I went out with him once

 

[two]

Yes (it will suck the life out of your batteries, slowly).
Yes (stick to wine).
If you really want to make a cuppa, get a gas kettle.

 

[Neil S]

Whistler kettle on gas far better

 

[Off da Grid]

If you shake the water for long enough the molecules will bash together and heat the water for free, stick with gas or some form of fire.

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[Grummyb]

My pal had a 12v jobby in his truck that plugged into cigarette lighter. Was fairly quick when I went out with him once

Of itvwas on arrival it was probably 24volt not 12

 

[EML]

Some O-level sums, if you're old enough to remember them...

2 mugs of tea is about 500ml. The energy required to heat 500ml of water from 20C to 100C is 500x80 calories, or about 160kJ. This is the only important number - it doesn't matter if you're running from 12V or 240V, or anything else, so ignore the previous comment about using an inverter (in fact, you need maybe 10% more energy if you're running off an inverter). 160kJ is about 3.7Ah, if you prefer Ah (you shouldn't, they're pretty useless).

So can you get 160kJ out of a leisure battery, in a relatively short time, without causing problems? Start with the power consumption of your kettle. 12V kettles seem to come with heating elements of about 100W to 150W, judging from what's on amazon. You need as much power as possible, so say 150W. 160,000/150 = 1067s, or about 18 minutes. So you can boil 2 mugs of water in about 18 minutes with a powerful 12V kettle. If you do have an inverter, and you can find a mains kettle which has a power rating (significantly) below the power rating of your inverter, you could get your tea quicker (but this doesn't use less energy overall). It looks like you can buy "low power" mains kettles at 750W (so you'd need a 1kW inverter, which is expensive). This will boil your water in 160,000/750 = 3.5 minutes.

To find the current required from the battery, the worst-cast scenario is the 750W kettle (say 850W after taking into account losses). A 12V battery has to provide 70A (for 3.5 minutes) in this case. Should be Ok, but I wouldn't do it. For the 150W 12V kettle, the battery has to supply 12.5A for 18 minutes, which is Ok.

In either case, you're taking 3.7Ah out of a battery which has maybe 100-120Ah capacity. If you've got lead acid, then the available capacity is much less, of course, and you're probably taking 10% of the usable stored charge just for 2 mugs of tea.

In short, use spirit or gas, unless you've got lots of solar hanging around doing nothing.

 

[deleted79651]

Some O-level sums, if you're old enough to remember them...

2 mugs of tea is about 500ml. The energy required to heat 500ml of water from 20C to 100C is 500x80 calories, or about 160kJ. This is the only important number - it doesn't matter if you're running from 12V or 240V, or anything else, so ignore the previous comment about using an inverter (in fact, you need maybe 10% more energy if you're running off an inverter). 160kJ is about 3.7Ah, if you prefer Ah (you shouldn't, they're pretty useless).

So can you get 160kJ out of a leisure battery, in a relatively short time, without causing problems? Start with the power consumption of your kettle. 12V kettles seem to come with heating elements of about 100W to 150W, judging from what's on amazon. You need as much power as possible, so say 150W. 160,000/150 = 1067s, or about 18 minutes. So you can boil 2 mugs of water in about 18 minutes with a powerful 12V kettle. If you do have an inverter, and you can find a mains kettle which has a power rating (significantly) below the power rating of your inverter, you could get your tea quicker (but this doesn't use less energy overall). It looks like you can buy "low power" mains kettles at 750W (so you'd need a 1kW inverter, which is expensive). This will boil your water in 160,000/750 = 3.5 minutes.

To find the current required from the battery, the worst-cast scenario is the 750W kettle (say 850W after taking into account losses). A 12V battery has to provide 70A (for 3.5 minutes) in this case. Should be Ok, but I wouldn't do it. For the 150W 12V kettle, the battery has to supply 12.5A for 18 minutes, which is Ok.

In either case, you're taking 3.7Ah out of a battery which has maybe 100-120Ah capacity. If you've got lead acid, then the available capacity is much less, of course, and you're probably taking 10% of the usable stored charge just for 2 mugs of tea.

In short, use spirit or gas, unless you've got lots of solar hanging around doing nothing.

I only drink coffee ... But I'd use gas anyway in our Brunhilde which is our wee ohm from ohm ... Steve, proving again that what he knows about physics plus tuppence would be insufficient to purchase a penny bun ...

Steve

 

[David and Sally]

So we are kitting out out MH and thinking of a 12v kettle- do they suck the life out of your leisure battery?? Is it worth it for a cuppa or shall I just go straight to wine??!

OK, if you had put your 12v kettle on when you posted you would be pouring the tea about now! But, would have a flat battery!

 

[deleted79651]

OK, if you had put your 12v kettle on when you posted you would be pouring the tea about now! But, would have a flat battery!

But the flat battery would enable me to close the compartment lid ... I'm sure I read about it on one of those lithium threads

Steve

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[68c]

But the flat battery would enable me to close the compartment lid ... I'm sure I read about it on one of those lithium threads

Steve

I'm growing old, took me a few minutes to get that.

 

[Scattycat]

Tried a 12v kettle.
Personally, we now use a small saucepan, although we do have a small electric kettle when on hook-up

 

[funflair]

Some O-level sums, if you're old enough to remember them...

2 mugs of tea is about 500ml. The energy required to heat 500ml of water from 20C to 100C is 500x80 calories, or about 160kJ. This is the only important number - it doesn't matter if you're running from 12V or 240V, or anything else, so ignore the previous comment about using an inverter (in fact, you need maybe 10% more energy if you're running off an inverter). 160kJ is about 3.7Ah, if you prefer Ah (you shouldn't, they're pretty useless).

So can you get 160kJ out of a leisure battery, in a relatively short time, without causing problems? Start with the power consumption of your kettle. 12V kettles seem to come with heating elements of about 100W to 150W, judging from what's on amazon. You need as much power as possible, so say 150W. 160,000/150 = 1067s, or about 18 minutes. So you can boil 2 mugs of water in about 18 minutes with a powerful 12V kettle. If you do have an inverter, and you can find a mains kettle which has a power rating (significantly) below the power rating of your inverter, you could get your tea quicker (but this doesn't use less energy overall). It looks like you can buy "low power" mains kettles at 750W (so you'd need a 1kW inverter, which is expensive). This will boil your water in 160,000/750 = 3.5 minutes.

To find the current required from the battery, the worst-cast scenario is the 750W kettle (say 850W after taking into account losses). A 12V battery has to provide 70A (for 3.5 minutes) in this case. Should be Ok, but I wouldn't do it. For the 150W 12V kettle, the battery has to supply 12.5A for 18 minutes, which is Ok.

In either case, you're taking 3.7Ah out of a battery which has maybe 100-120Ah capacity. If you've got lead acid, then the available capacity is much less, of course, and you're probably taking 10% of the usable stored charge just for 2 mugs of tea.

In short, use spirit or gas, unless you've got lots of solar hanging around doing nothing.

I have been through the numbers using specific heat capacity of water as 4.2J/kg/K and get to 168kJ so close enough to your number, I then took this to 46.6 watt/hour which you could easily call 50 Wh with a few losses from the kettle and an inverter if going that way, so 50Wx60 = 3kw kettle for 1 minute would do the job or put another way 3000/750 for your low power kettle = 4 minutes so again not far away from your 3.5 minutes.

Again rounding up a bit I would call it 4ah from your nominal 12v batteries.

In conclusion that is not a lot of power and can easily be put back with solar but the thing to watch out for is the peak draw which comes down to the wattage of the kettle and for a 2.2kw which I find boils in good time the peak amps will be around 180A which might be a bit much for Some set ups.

Anyway in interesting waste of 30 minutes thanks EML

 

[138go]

You can't beat a gas hob!

 

[Yorick]

Have a nice cold beer instead

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[138go]

Have a nice cold beer instead

With breakfast?

 

[Yorick]

With breakfast?

Depends what time you have breakfast.