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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. 

Comments

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steveastrouk
steveastrouk

8 years ago

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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whiskeysausage
whiskeysausage

Reply 8 years ago

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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steveastrouk
steveastrouk

Reply 8 years ago

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

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whiskeysausage
whiskeysausage

Reply 8 years ago

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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steveastrouk
steveastrouk

Reply 8 years ago

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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whiskeysausage
whiskeysausage

Reply 8 years ago

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

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steveastrouk
steveastrouk

Reply 8 years ago

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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steveastrouk
steveastrouk

Reply 8 years ago

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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whiskeysausage
whiskeysausage

Reply 8 years ago

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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steveastrouk
steveastrouk

Reply 8 years ago

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

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sachinram92
sachinram92

6 years ago

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
Kiteman

8 years ago

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
whiskeysausage

Reply 8 years ago

How fast can a AA discharge?

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steveastrouk
steveastrouk

Reply 8 years ago

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

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whiskeysausage
whiskeysausage

Reply 8 years ago

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