# COMMUNITY : FORUMS : BURNING QUESTIONS

## Battery Powered Water Heater

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. :)

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steveastrouk4 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.
whiskeysausage (author)  steveastrouk4 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.
4 years ago
6 wouldn't be too bulky, and you'd not destroy the batteries doing it.
whiskeysausage (author)  steveastrouk4 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?
4 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
whiskeysausage (author)  steveastrouk4 years ago
Does gauge of the nichrome wire matter? Or is it pretty much trial and error at this point?
4 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.
4 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
whiskeysausage (author)  steveastrouk4 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.
4 years ago
You SHOULD be able to heat shrink it tightly to the metal tube too.
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