get heat from battery (question)?

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. :slight_smile:

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: Item detail page

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: Item detail page

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.

But not to the temperature of tea...

i'd go to a camping store and buy a small gas bottle :slight_smile:

cjdelphi:
i'd go to a camping store and buy a small gas bottle :slight_smile:

I thought of that (or a gasoline camp stove) but what if flames/combustion are not allowed?
Perhaps an exothermic chemical reaction.

johnwasser:
Perhaps an exothermic chemical reaction.

Powdered iron, powdered magnesium, salt. Just add water to start the reaction...

You could get it to 21 degrees by leaving it stood on the side.

thanks all for the replays :slight_smile: