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NOTE: I AM A TOTAL NEWBIE ON HOW ELECTRICITY AND CIRCUITS WORK, SO STEP BY STEP WITHOUT TOO MUCH COMPLICATED LANGUAGE WOULS BE GREAT

Hi, I'm currently a middle school student and wanted to perform a small experiment on battery life, but am stuck on the first step on how to set it up. Currently have 4 NiMh batteries and 4 Alkaline batteries with 4 of these Flashlights below, along with 4 multimeters. but am clueless on how to connect the multimeters to the batteries Whilst they are running (since I am recording the drop in voltage over time). Do I need external battery holders, and if I do how do I connect that to the voltmeter and flashlight? Thanks enter image description here Here's the multimeter I have (all same model)enter image description here If battery holders are necessary, I am considering theseenter image description here

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  • \$\begingroup\$ Can you include a selfie of the front of the MultiMeter? And ask around for bell-wire --- standard solid-conductor insulated wire --- around school : the science instructors, the industrial-arts (A/C repair) instructors. Or visit Mouser or Digikey : wire, solid, insulated. To measure the battery life, monitor across the two batteries, as the flashlight is on. You'll see high voltage 3.3 volts, when light if off; that should drop 10%??? when you first turn on the light; and slowly decline thereafter. \$\endgroup\$
    – analogsystemsrf
    Commented Apr 11, 2017 at 3:55
  • \$\begingroup\$ Please expand on what you mean by monitor and how the wire should be used \$\endgroup\$
    – blocktrocks101
    Commented Apr 11, 2017 at 5:12

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Welcome to the site and pleased to see that you're experimenting with electronics and electrical circuits.

It looks like your batteries are stacked one on the top of the other when they're inside the torch. If you could get two wires connected to the top of that battery stack and to the bottom, you could take them to your multimeter.

Then, as the batteries discharge into the light bulb, you can monitor the battery voltage and see it get lower and lower as the batteries go flat.

If you just push the wires into the space between the battery and the battery holder, they'll keep falling out so that's not the way forward. If you could scrounge some small strips of copper from school or buy some, you can solder a wire to each. Then you can push the copper in between the battery and holder at the top and bottom and connect those to your multimeter's voltage input terminals.

An AA battery is around 14 mm in diameter, so your copper strips would need to be 10-14 mm wide and maybe 40-50 mm long. Check carefully before using a different metal because it may have a higher resistance that'll affect your experiment and maybe spoil it.

I don't know what you have to hand but it's what I'd try and do. You can then easily move it from torch to torch.

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  • \$\begingroup\$ Hi, thanks for the great answer! Was wondering if I could do something with external battery holders to power the flashlight, the ones in the image above, as it already has a wire attached to it. \$\endgroup\$
    – blocktrocks101
    Commented Apr 11, 2017 at 8:38
  • \$\begingroup\$ You're welcome. You could use the battery holders but it gets harder to make suggestions, not knowing if you can solder or what you have to hand. Does the battery circuit make sense to you? Look it up on the interweb if not. After that, can you attach the battery block wires to the torch insides in place of the batteries? Much more tricky. I'd reconsider my answer above, it's far more flexible. \$\endgroup\$
    – TonyM
    Commented Apr 11, 2017 at 8:50
  • \$\begingroup\$ from what I understand, I simply have to get the wires to touch both the ends of two batteries and get that wire to the voltmeter, is that right? And sorry if this sounds really stupid but how would I go about soldering the copper and the wire? Just want to make sure I do it right, \$\endgroup\$
    – blocktrocks101
    Commented Apr 11, 2017 at 10:16
  • \$\begingroup\$ @blocktrocks101, You can solder to the edge of it but hold it in a vice. If it makes it easier, hammer the end of a nail through to make a wire-sized hole in the copper and put 5 mm of the wire through then solder. That's about the most I can suggest on all this. Out of interest, are you doing this on your own or with the school's help? If the latter, take these ideas to the relevant teacher to advance them. \$\endgroup\$
    – TonyM
    Commented Apr 11, 2017 at 11:23
  • \$\begingroup\$ Hi, thank you for all the help, but I have two more things I would like to enquire on: 1... once the wires are in place, do I use the voltmeter's terminals/pin/needle things and touch the other end of the two wires? \$\endgroup\$
    – blocktrocks101
    Commented Apr 12, 2017 at 10:55

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