Charger for 12V battery & calculation of watt

sunhuxAsked:
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serialbandConnect With a Mentor Commented:
You could just use a 12 Volt socket.

http://www.ebay.com/sch/i.html?_nkw=12+volt+socket

http://www.autozone.com/autozone/accessories/Electrical/12-Volts-Socket-Adapter/_/N-25ne

http://www.amazon.com/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3A12%20volt%20socket

That Rayovac battery seems to only provide 7.2 Ah which means you only get about 86.4 Watts (12x7.2) out of it.  Based on one of the amazon reviews, it took them 35 minutes to boil 20 oz. of water from their car with a draw of around 10 Amps.  Assuming that the 10 Amp draw is correct, you would only get one use out of each battery.  It's only good enough to boil clean water.

Is there a reason for using electric instead of a standard fossil fuel powered camp stove?  If you're using it for camping, they would be much lighter.  The propane, kerosene or Alcohol would also get lighter as you used up your fuel as well as get your water to a boil sooner.  Even a bunch of candles would provide more heat.
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JohnConnect With a Mentor Business Consultant (Owner)Commented:
That particular battery is not rechargeable (I use the 6 Volt version in an emergency lantern).

For a rechargeable battery, you need something like:

http://www.amazon.com/American-Hunger-Lantern-Rechargeable-Battery/dp/B003WHDOKG

And then any reasonable 12 volt charger will work such as the one below:

http://www.amazon.com/CTEK-Multi-12-Volt-Battery-Charger/dp/B000FQBWCY

Chargers come in many varieties and the above is just one.  At the bottom of the first link, there are other rechargeable batteries as well

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sunhuxAuthor Commented:
Forgot to ask one last question:

http://www.amazon.com/Roadpro-12V-Hot-Pot-oz/dp/B000667QL4/ref=sr_1_1?ie=UTF8&qid=1387987622&sr=8-1&keywords=battery+powered+kettle
  Can I just cut off the car lighter charger of the above hot pot & then
  use the Rayovac battery (with crocodile clips) to charge/heat up the
  hot pot?
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Tony GiangrecoConnect With a Mentor Commented:
Yes, that should work, but as the previous expert mentioned, that battery is not rechargeable. It will only work a set number of times. Based on how often you use it, you will drain that battery and it will be dead.

Replacing that battery with a rechargeable battery will be much more cost effective if you plan on using the Hot Pot regularly.
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JohnConnect With a Mentor Business Consultant (Owner)Commented:
Yes. It is a one way street. That is, once you cut off the plug, it would not be safe to try to put it back on. But cut off close to the plug and then carefully strip the insulation, attach clips and insulate with good electric tape.

I have looked and cannot find the power draw of the hot pot but the rechargeable battery I pointed to should power the hot pot.

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sunhuxAuthor Commented:
http://www.amazon.com/CTEK-Multi-12-Volt-Battery-Charger/dp/B000FQBWCY

Would the above charger work in my country as the input power in
my country is 230-240 Volt.

I'm looking at the charger below but it did not specify the input voltage:
http://www.amazon.com/Black-Decker-BM3B-Battery-Maintainer/dp/B0051D3MP6/ref=sr_1_3?ie=UTF8&qid=1388073211&sr=8-3&keywords=12V+charger

The model below specifically mentions it could support 240V input
but it's a costlier charger:
http://www.amazon.com/Battery-Tender-022-0150-DL-WH-Waterproof-Charger/dp/B000CITKCE/
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JohnConnect With a Mentor Business Consultant (Owner)Commented:
You would have to ask Black and Decker about the first one, but the second one looks like a better unit.

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sunhuxAuthor Commented:
We ever sparked a mini fire/blaze when using fossil fuel
thus battery is preferred.
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sunhuxAuthor Commented:
Wife is afraid of fossil/propane/kerosene fuel for fear of catching
fire or explosion
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Tony GiangrecoCommented:
serialband brought up some interesting facts about the warmer.  How often do you intend to use it? Do you realize, if you don;t insulate the alligator clops and leaders very well, the assembly could short out and provide a few minutes of fireworks?
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sunhuxAuthor Commented:
So can I say 12V 7Amp battery would last 1 charge only to
boil 20 oz of water?
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sunhuxAuthor Commented:
Thank TG, I'm aware of the sparks if the alligator clips touches
each other : have seen those car batteries clips touching each
other causing sparks.
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serialbandConnect With a Mentor Commented:
That's assuming the reviewer of the electric hot pot is correct about the 10 Amp current draw from a larger car battery.  You may need a bigger battery for it to output that much current.  The smaller battery has a smaller plates and therefore smaller current capacity.  86.4 Watt Hours doesn't seem like a whole lot of energy to boil 20 oz of water.  You can try to look up how much energy is needed to boil 20 ounces of water.  30 minutes seems to be a long time to wait for hot water.

Whether you use electric or gas, there's always a chance for fire.  Does your wife cook?  You should never leave a burning stove unattended, even an electric one.  With the gas camp stoves, they'll at least be done sooner.
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Tony GiangrecoCommented:
This question is outside of the norm for EE.  Is this an assignment you are working on or real life experience? Tell us what made you decide to ask this question....
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JohnBusiness Consultant (Owner)Commented:
@sunhux - Thanks, and I was happy to help you with this.


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