9V battery gets hot during [Ampere] checking test

[EARNEST]

Hi guys,
I am new to electronics...so I dont really know a lot of things.
Anyways, I'll appreciate if you guide me here. I was messing around with my multimeter, decided to check how many amps 9V energizer has. So, I've had my settings on A -- -- (DC), appropriate polarities leads were connected, the ground lead was in COM port, the red positive was into 20A max slot...and then I've noticed that my battery gets super hot in few seconds.

P.S. here is my MM
http://images.gittigidiyor.com/1929/TT-TECHNIC-M-890-G-F-DIJITAL-MULTIMETRE__19299424_0.jpg

20Amax with COM = 10 sec max, each mins, unfused

[Ripthorn]

The reason why is that your ammeter is a series test that has no significant internal impedance.  You are therefore shorting the positive and negative sides the battery.  This is like sticking it in your pocket with your keys.  It gets warm because there is so much energy transfer going on due to there being no external resistance.  You can actually look up the mAh rating for a lot of batteries I think.  Though a battery will put out a ton of current if you want, it just might not last very long.  You can use one to power tubes, but they suck it dry pretty quick.

[Pablo1234]

You cant test your battery like this. Basically amps are a result of voltage and a path to ground. Think of your meter from one side of the battery to the other side as a 30 foot diameter pipe (it has very low resistance in Amp setting) and the 9 volts is equivalent to city water pressure. Current or Amps would be the quantity of water flowing through the pipe (Meter) and with no resistance its basically flooding the streets which will cause kids on a hot day to run in the streets and cause a car accident. This in turn will bring the fire department and local police to The vicinity and your local drugdealer will get mad because you had the cops knocking on his door because you opened a water main in the streets.

If you really want to test a battery (This will ruin the battery but give you an idea of how long it will last in an application(also depending on type, brand and age)) you need to do an amp hour test. This is where you would connect a battery to a load(Resistor) of a known value and measure the voltage across this every 5 min or something until it hits 7.5V's. This isn't a great test to preform and it wont give you to much useable data but its a good leason in internal battery resistance and direct results of ohms law and such.

[EARNEST]

I see, thanks mate. Is there a way to measure Amps in more "friendly" environment? Or maybe there are some special purpose Ammeters? Also, I have vintage A/V meter, Norma 188AV, made in Germany. Maybe that one will be good to measure it...?

[EARNEST]

Hm...Thanks, Pablo1234, i didn't really wanted to check mAh, I just wanted to see the current of the battery Such a newbie, sorry

[Pablo1234]

no worries man, I just getting silly. We all where their at some point. Basically the only way to test how much amprage your battery has is to empty the thing out and measure how much came out of the battery over time. That amp hrs.

Their really isn't much of a use other then a learning experience in trying an amp hr test for that reason. Measuring voltage will tell you if the battery has potential to discharge electrons or not. This is really all that would matter. Now measuring current draw from your device to see how much juice it sucks is more practical. plug one terminal into your pedal and then hook your amp meter up to the other terminal of the battery and the pedal. Turn the pedal on and play through it and you will have measured the consumption of amps from your pedal. then you can look up the mAH of the battery and determin how long the battery will last in that device.

[EARNEST]

I think that thing i had in mind when I tried to get Amps:

Now measuring current draw from your device to see how much juice it sucks is more practical. plug one terminal into your pedal and then hook your amp meter up to the other terminal of the battery and the pedal. Turn the pedal on and play through it and you will have measured the consumption of amps from your pedal. then you can look up the mAH of the battery and determin how long the battery will last in that device.

thanks a lot!

[zachary vex]

This site has some interesting information on how many milliamp hours are available in different types of nine-volt batteries:

http://www.powerstream.com/9V-Alkaline-tests.htm

The thing about current to remember is that it's about hunger... your circuit is hungry and asks for a certain amount of current.   That's where you insert a current meter... in series with the circuit you're curious about, to see how much current your battery is feeding the circuit.

After you measure the current your circuit draws you can calculate battery life using information from that site above... let's say it's 30 ma (which is kinda high).  If you're using a Duracell coppertop, according to that site, you've got 310 mAH available, so 310/30= 10.3 Hours of life.  If you did an empirical test (hook it up and let it run until the pedal dies) you'd get a different number... but it's a useful approximation.

It's not terribly informative to connect a current meter directly to a battery and see how many electrons it can deliver... the battery voltage drops to nothing because it's a dead short (that's what current meters are, approximately... dead shorts) so you're not seeing anything useful from your measurement.  It's like trying to measure motor torque at zero RPM... not very helpful info, because motors are usually put to work while they're turning.  By connecting a dead short across your 9V battery you're measuring something akin to "cold cranking amps" which is not something you'll experience inside a guitar pedal.  Well, not one that I've seen.  8^D

[R.G.]

By connecting a dead short across your 9V battery you're measuring something akin to "cold cranking amps" which is not something you'll experience inside a guitar pedal.  Well, not one that I've seen.  8^D

Ok, how about Ken Stone's V8 Simulator:
http://www.cgs.synth.net/modules/v8.html

[Paul Marossy]

This site has some interesting information on how many milliamp hours are available in different types of nine-volt batteries:

http://www.powerstream.com/9V-Alkaline-tests.htm

Wow, that Nuon battery kicks every other batterie's butt. I've never even heard of that brand. And the Panasonic "Super Heavy Duty" battery sucks, but I see that it's a carbon-zinc type and not an alkaline battery.

I don't use batteries for any of my effects, they are expensive and end up in a landfill somewhere. The only time I use 9V batteries is for my guitars that require them.