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Battery Powered Water Heater Answered

I need some help. Well, I'll be honest, I need a lot of help. 

I am trying to heat 1 liter of water running through a small tube that holds 8ml of fluid up by 12C, with a maximum temperature of the heater reaching 60C, and the entire liter needs to be heated within 30 minutes. 

In my experiments, the tube holds 8ml of fluid while passing along the 'heater' core, and will pass by the core in a total of 10 seconds.

So 8ml heated by 12C in 10 seconds is the limiting factor and multiply that out to cover 30 minutes. 

The good news, I have managed to accomplish this feat by wrapping the tube around a curling iron rated at 80W x 110V.
End result is 12C rise in output fluid, so I know the theory is completely possible. 

However, here's the kicker, the entire system needs to run off of battery power. 

So the 2 big questions are: what material should I use as the 'heater core' since I can not use a standard curling iron, and what battery system/configuration should I use (needs to be universal purchase ie, AA, AAA, D, C, 123, 9V, etc)

Any help would be greatly appreciated both to my personal safety as I tinker in the garage, and to my wife's sanity as she watches me play with water around plugged in curling irons. :)

Thanks in advance. WS. 

15 Replies

user
steveastrouk (author)2013-04-13

Mathematically, I make the total energy required 1 x4200 x 12 Joules. Delivered in 30 minutes, or 1800 seconds = 50400/1800 = 28Watts.

Entirely tractable, you could do it with AA batteries, or you could use a cordless drill battery. If you go for AA, you are going to be on 2.8 Ah batteries, and you can JUST survive for that kind of discharge rate, for one shot, at 30 minutes.

Me, I'd use a drill battery. You'd get 14V at 5Ah, or a LOT more energy for your money.

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user

How many AA's do you think it would take? And there would be 2 thermometers attached to the device, so should I add another battery?

But I like your idea of a drill battery. It might have to be a smaller version, but I think you got me on the right track. Thanks for that.

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user

6 wouldn't be too bulky, and you'd not destroy the batteries doing it.

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user

So I hooked the batteries up to a copper foil as the heating element, and only the batteries heated up. Is there a better heating element I could use?

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user

Yes, copper foil is pretty useless. You need to find a resistance to deliver 28W from 9V, that would be 2.7 Ohms. If you are really serious, you could buy nichrome resistance wire, and wind a short coil of that around a pipe, alternatively

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user

Does gauge of the nichrome wire matter? Or is it pretty much trial and error at this point?

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user

It matters a lot. Your profiles doesn't say where you are in the world, but in the UK, its easy to get some nice thin stuff which is insulated too, so making the resistor is simple.

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user

Just over 0.5 metres of 0.375mm enamelled nichrome, wired in two parallel strands will do what you want - you can wind it straight onto a metal tube

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user

awesome. I just ordered some and should have it by the end of the week. I will let you know how it goes.

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user

You SHOULD be able to heat shrink it tightly to the metal tube too.

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sachinram92 (author)2015-02-25

hey!! I would like to know if this attempt of yours was successfull. We are also trying a similar experiment wherin we connect around 6 1.5V AA batteries to heat up some amount of water in less than 10min. will this be achievable and can you provide us some more details about the specifications of nichrome wire to be used.

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Kiteman (author)2013-04-13

Simple, you need a battery that can deliver 80W for half an hour.

If my rusty calculations are correct, you aren't going to get that with a convenient set of small batteries - I think you'll need a bank of around 80 AA cells.

You might be able to do it with a lead-acid battery, though, like a car battery.

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whiskeysausage (author)Kiteman2013-04-13

How fast can a AA discharge?

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user

Very, very fast, but you ruin the number of cycles it can accept.

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user

This application would be just a "one shot whambam thank you ma'am" application for the batteries. No recharging is expected.

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