# get heat from battery (question)?

hi i want to convert 9v battery or 12 volt battery into heat, i mean to get a heat from the battery to warm something up, it not important if the heat is not too much?? is it possible?

Energy in a battery can be converted to heat. Use a resistor. Current is voltage/resistance. Current times voltage is heat in watts. If you dump a 12V battery into a 2 Ohm resistor you will get 6A of current and thus 12(V)*6(A) = 72 Watts of heat.

zhirantaha:
hi
i want to convert 9v battery or 12 volt battery into heat, i mean to get a heat from the battery to warm something up, it not important if the heat is not too much??
is it possible?

Seems like an expensive way to do it. A battery won’t last long if you draw enough current to make it hot. Why not use a normal heating element?

johnwasser: Energy in a battery can be converted to heat. Use a resistor. Current is voltage/resistance. Current times voltage is heat in watts. If you dump a 12V battery into a 2 Ohm resistor you will get 6A of current and thus 12(V)*6(A) = 72 Watts of heat.

... and a very smokey resistor ...

Make sure your resistor can handle the power, or it will burst into flames. A little ¼W one wouldn't be suitable ;)

You can make your own heating element using Nickel Chromium (NiChrome) wire. A good source for this is from an old electric heater, surprisingly enough :)

i couldn't what you all said please explain it clearly!

can i get a enough heat by 9v battery and normal heating element??

zhirantaha: can i get a enough heat by 9v battery and normal heating element??

Enough heat for what? You'll get better answers if you tell people what you're trying to do.

fungus:

zhirantaha: can i get a enough heat by 9v battery and normal heating element??

Enough heat for what? You'll get better answers if you tell people what you're trying to do.

for water!

How much water? What temperature increase do you need?

the amount of water is less than 2 L and change the temperature up to 25c from 10c

zhirantaha: the amount of water is less than 2 L and change the temperature up to 25c from 10c

Over how long a period? (i.e., how fast do you want it to heat up?)

zhirantaha: the amount of water is less than 2 L and change the temperature up to 25c from 10c

How many joules of energy is that? How many are in your battery?

Answer: Over 120Kj of heat needed, only 18Kj in a 9V battery. You'll need about 15 batteries to do it.

the time as fast as it can

fungus: Answer: Over 120Kj of heat needed.

120,000 Joules = 33.333 Watt-hours

A 100 Watt heater would heat the water in 1/3 hour (20 minutes). Do you need faster heating?

200 Watts would take 10 minutes.

2,000 Watts would take 1 minute.

20,000 Watts would take 6 seconds. :)

20,000 Watts would take 6 seconds.

…annnd a 9V battery would take 10 days. XD

9V at 150ma = 1.35W
333Wh/1.35W = 246hours

John_S:

20,000 Watts would take 6 seconds.

...annnd a 9V battery would take 10 days. XD

9V at 150ma = 1.35W 333Wh/1.35W = 246hours

Make that 15 days - you're forgetting the time taken to swap the battery every 15 minutes.

Also, if you go too slow, you will be losing heat faster than the battery can put it in. Theoretically a 1.35W heater should be able to boil water. Realistically it won’t even come close for any substantial amount of water.

John_S: Also, if you go too slow, you will be losing heat faster than the battery can put it in. Theoretically a 1.35W heater should be able to boil water. Realistically it won't even come close for any substantial amount of water.

Oh, yes. All those times assume perfect insulation.

33.333 Watt Hours from a 12V battery would be about 2.8 Amp Hours. You can get that size sealed lead-acid battery for under \$20. Unfortunately that battery is rated 2.9 Ah at 20 hours. Without perfect insulation there is no way you are going to heat the water over 20 hours and get the same temperature rise. I think you will need a significantly larger battery, like a car battery. You can then buy a 200W car immersion heater to turn the charge in the battery into heat: http://www.langtoninfo.com/showitem.aspx?isbn=8000692729878&gclid=CI3EqfrQ1LMCFUOK4AodA0YARA

johnwasser: I think you will need a significantly larger battery, like a car battery. You can then buy a 200W car immersion heater to turn the charge in the battery into heat: http://www.langtoninfo.com/showitem.aspx?isbn=8000692729878&gclid=CI3EqfrQ1LMCFUOK4AodA0YARA

Car batteries aren't great for deep cycle use (but can provide rapid heating, most will provide several kW for a short period). Fortunately they are usually around 35 to 45Ah, which is a big margin.

Say 400A for 40s (assuming battery voltage drops to 8V or so due to internal losses) would give 120kJ and be about 20% discharge depth or so. Stupidly thick copper wiring would be needed (10mm or so)

A more reasonable 50A for 200s (this time about 12V) would mean more practical heater element and connecting wires (4mm diameter or so)

Alternatively a deep-cycle lead-acid battery at 20A for 8 to 10 minutes... Capacity of 10Ah or more ought to be sufficient for a deep cycle.

I'm curious now why the OP wants to heat up 2L of water as fast as possible with a battery.