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Testing batteries mAh with multimeter

Discussion in 'New Members Forum' started by Mikenekro, Dec 19, 2014.

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  1. Mikenekro

    Mikenekro Full Member

    Dec 19, 2014
    Kenosha, WI, USA
    I just signed up for ECF but have been vaping for about 2 years and using mech mods for almost 3 months now.

    I wanted to test my batteries mAh on my multimeter just as an experiment. I used 2 settings on my multimeter to try and calculate this. The DCV setting for testing the before and after volts. The mA setting to drain the battery and also a stopwatch to record the time it took to drain x amount of volts.

    I didn't fully drain the battery because I wanted to see if it would work this way. I also used a cheap battery which I do not use. Xtar 18650 30A 2100mAh 3.6V. Supposed to be a VTC4 cell but I doubt that due to the rapid rate it discharged at.

    So I started the test at 4.19V on the DCV setting.

    Then I switched to the mA setting, moved the red positive pin to the 300mA hole on the multimeter, put the multimeter pins on the positive and negative of the battery and started my stopwatch.

    After 6 mins I stopped, recorded the volts left and multiplied the difference by 10 to get the volts dropped after 1 hour. (Volts left 4.13V, difference of 0.06V, multiplied by 10 0.60V, 3.59V after 1 hour.)

    I know this is probably not accurate because I only measured over a 6 minute timeframe but just wanted to test it.

    This would mean it would take about 2 hours to get down to 2.50V and about 7 hours to get to 0V (I know you do not do this).

    I took the 7 hours to get to 0V and multiplied by 300 (mAh setting on multimeter) to get 2100 mAh rated by the battery.

    I just want to know if I had done this right.

    If not, what did I do wrong?
     
  2. Warpigs

    Warpigs Vaping Master ECF Veteran

    Mar 27, 2014
    USA
    Welcome to ECF! I bought 7 VTC4's. I love them. Much better than the other batteries I was using the past 580+ days.
     
  3. Ryedan

    Ryedan ECF Guru Verified Member ECF Veteran

    Mar 31, 2012
    Ontario, Canada
    Here's a video on measuring amps with a DMM: How to Use a Multimeter: Measuring Current.

    As you can see, you're not doing it quite right. I've never tried metering a battery with my meter set to amps, but I'm surprised you didn't burn out the fuse or the meter.

    You need to put a steady amp drain (varying load to keep the amp draw constant) on the battery and record the voltage as it drains. You could put a resistive load on the battery but that would be a diminishing amp draw as the battery drains, but it's better than nothing. The gentleman who runs this site knows what he's doing and here is his setup: How is the test done and how to read the charts. I have a hobby charger that tells me the number of mAh it put into the battery when it's finished charging and they are not that expensive. I think you can get one for around $50.

    In any case, I suggest you stop just trying something until you know if it is safe to do that way. If you do manage to short the battery and the meter doesn't blow, the battery could.
     
  4. Mikenekro

    Mikenekro Full Member

    Dec 19, 2014
    Kenosha, WI, USA
    Thanks for the help. I have only tested ohms and volts through my meter so wanted to try something new. But I'll take your advice and learn more about it before trying again.
     
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