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How to test a 9v battery using a multimeter?

Discussion in 'Miscellaneous [BG]' started by kurosawa, Mar 14, 2001.

  1. I'm going to be using one 9v battery to drive two 9v devices wired in parallel, so I will probably need to check the battery frequently.

    1) What's the test procedure using a digital pocket multimeter?

    a) under load

    b) battery disconnected

    2) What measurements should I be looking for in each case?


  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Just check the battery itself without any load. The voltage measured may be higher than it actually is (e.g. 9.4V) but it usually over 7-7.5 V is ok at least for some hours of use.

    Check the DYI part in this arcticle for a cool tip on this...


    Measuring the consumption is done with load. Plug a cable into your bass and connect the meter in series with battery and circuit, using the mA setting. Just disconnect one battery pole from the battery connector and put the meter in between.
  3. Thanks, JMX! That'll do it!
  4. notduane


    Nov 24, 2000
    Dang JMX, ya' beat me to it. In a pinch, you could ask your
    drummer to stick it on his/her tongue: if they get a sudden
    attack of incontinence, then you're good to go! :D
  5. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    My, why didn't I think of that one laugh.

    That's the best method of course. But be careful, drummers have been known to sponteanuously combust while checking batteries.

    cf.: This is Spinal Tap
  6. sn0wblind


    Apr 20, 2000
    Ontario, Canada
    That's how I check the juice of my 9volt batteries, if there aint much effect, I throw it out, and make a trip to the store, If I only remember to buy recharble one's!!!!
  7. Good idea, notduane, except after using his tongue to check the mains, my drummer doesn't have enough sensitivity in his tongue to tell if a 9v is dead or not.


    After reading a few serious replies, I feel obliged to post this product safety warning: the "winky" emoticon at the top of this post indicates it is a joke. Nobody should check the mains on any continent with his tongue.
  8. notduane


    Nov 24, 2000
    Your band got a keyboard player?

    They gotta' be good for somethin'.

  9. Jeez, I test 9-volts with my tongue all the time(and 110 circuits with my fingers). Now you've made me feel inferior, like a drummer :(.....:D Of course when you have 15 UHFs on a show, getting the meter out is a bit time consuming, so onto the tongue they go :p
  10. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Be careful not to do that on tour in Germany!!

    230V/16A may be even too much for a Spacegoat :eek:
  11. Yep, I think I'll stay away from the 230 volt stuff. That might hurt a bit.:D That reminds me...I was tying in to a very old 110/220 100 amp service once...Live (when I was young and stupid (er)). anyway, Mr. flathead screwdriver slipped out of Mr. set screw and crossed two hot lugs. BOOM! Melted the screwdriver, blew me out of my shoes and across the room. My right arm was numb for a week.:p
  12. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    Its not voltage that kills,its amps.Anyone who has ever been zapped by a spark plug wire on a car or lawnmower has been zapped by 20,000-30,000 volts.It only takes 100mA (1/10 of an amp) to kill.Bottom line, of course, is to be careful around any electrical stuff.

    Kurt,would it be possible to get an AC adapter so you could plug your device into the wall instead of using batteries?Could save you the cost of replacing batteries,or the hassle of having it crap out at the worst possible moment.Just a thought.
  13. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    The 16A would do you in, not the 230V....
  14. Yes, while it is current that kills (as little as 100mA through you will do) voltage is an important factor. 16 A at 230 volts is certainly more dangerous than 16 A at 110 volts, because there is more potential energy there. The current that will flow through something is a function of the voltage (potential) and the resistance of the material its flowing through, not what it says on the circuit breaker. So if your body resistance was 1000 Ohms (it ain't and everybody's is different, but 1000 makes for easy math......):D At 110 V, about 110mA would flow through you, at 230 V 230mA would. So if the possible current is the same (16A or 15A here) the higher voltage is more dangerous. A spark plug won't hurt you because it's max current is limited to a very low level. Your resistance is dependent on your body chemistry and can change rapidly. Especially if you start sweating :p

    My favourite electrical advice is "Don't lick big Capacitors.":D:D
  15. notduane


    Nov 24, 2000
    Back in tech school, we had some OLD radar gear donated by
    a local airport. Among the goodies was a 2 Farad cap -
    `bout the size of a breadbox, terminals shorted to prevent chargin' .
    Teach used to threaten "troublemakers" with havin' to sit on it :p .
  16. 2 FARADS? Oh my God. That would charge up in free air and blow you to kingdom come!!! I'd say they kept the terminals shorted! I blew the tip off a screwdriver with a 4700 microfarad one...2 FARADS?!?!! :D:D
  17. Hey, about how mains voltage can kill you:

    Frequency seems to be a factor too, so I've read. 50 or 60 cycles is about as deadly as it gets. If the mains frequency were more like 500 cycles it'd be much less deadly.
  18. Alright in a parallel circuit the voltage is the same through-out. The current varies though.

    No load, a decent battery should measure around about 10 Volts on a DMM

    On the DMM, switch the dial to V 20. as you are measuring voltage under 20 volts.

    Its as simple as putting the red on the positive and the black lead on the negative anywhere within the circuit you create.


    Oh BTW, its the that amps kill people. I hate these idiots who do those tricks like "Man gets shocked by 30,000 volts and is not harmed", well durr, the amps were probably 0.0000000001 mA. oh well.
  19. Oh and on the frequency thing, yeah, but Mains is 50 cycles per second here in Australia. It can still kill because the Peak voltage our the wall is around 339 volts. the reading they give to you (240 in my case) is onlt the RMS value (Root Mean Square) In america i think you have @ 60 Hz?? unsure but its still the same principle.

  20. 30000 v at 0.0000001mA certainly won't kill you, but neither will 100A at 1 volt because there isn't enough potential energy to overcome your body's natural resistance. So it's kinda wrong to say that current kills but voltage doesn't, you need a combination of both if you want to get killed :p It's the amount of current that actually passes through your body to ground that kills, and current is solely dependent on what the circuit draws, which is dependent on your resistance. Ohm's law and yada yada yada. :D:D

    In North America it's around 110 volts RMS at 60Hz, I'm not sure what peak is.

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