I'm not sure if this is the right place to post this but if anyone can provide any help it would be appreciated. Please keep in mind I am no expert when it comes down to power and electrical stuff

I am working on a project (Making a costume) that will require the use of fairy lights also known as string lights. The project I'm working on requires 16 separate strings and each string has its own small battery pack which contains 2 cr2032 3v batteries and a on/off switch. So a total of 32 cr2032 3v batteries

These are the lights I purchased.

So for testing purposes I tested this with 4 fairy lights and 1 9V battery. Note I have tried wiring 2 strings to 2 AAs and the brightness was not there. Not to mention having to carry around 32 AAs would be a bit tedious. Attached is an image of how I wired it up in series and parallel. wiring

  1. Series wiring - LEDs would not light up

  2. Parallel wiring - LEDs would light up however the battery slowly started getting hotter and hotter.

My question is, what would be the easiest way to wire all of these into 1 switch safely. Please keep in mind that this will be part of a costume so I'd like to keep weight down to a minimum. Note that carrying 4 9V batteries is alot ligher than 32AAs. I'm just not sure how I would wire them. And if resisters are needed, what size and where would they be inserted?

New Image wiring:

New Image

  • 2
    \$\begingroup\$ Note that both button cells and 9v batteries have poor energy density and high cost, so they should be used only when form factor makes them necessary. AAs have such higher energy density that you likely can use smaller mass, add a voltage converter and pay it's losses, and still come out on top. \$\endgroup\$
    – K H
    Jan 7 '19 at 21:02
  • \$\begingroup\$ As a compromise, you may wish to consider "fake" AAs and 9vs. There are AAAs, AAs and 9V batteries available now that actually have a 3.7V li-ion cell and a voltage converter inside them, giving much higher performance than an actual alkaline 9v. These batteries include a microusb input for charging them. \$\endgroup\$
    – K H
    Jan 7 '19 at 21:05
  • 1
    \$\begingroup\$ a 9V batttery contains six 1.5V AAAA cells .... way less power than AA or even AAA cells \$\endgroup\$
    – jsotola
    Jan 8 '19 at 1:10

The 2nd is correct, all LEDs in parallel. Two CR2032 make 6V. Use a 4AA battery pack to drive the LEDs. Put the switch in series between the battery+ and the LED+.

  • \$\begingroup\$ Thanks for the info about wiring them in parallel. In regards of the batteries, I am using 16 strings, which with your reply I would need 64 AA batteries which is a bit much to carry. What other options do I have? Also noted, while wired in parallel with the 9v battery and 4 strings the battery started getting hotter which is kind of a concern. \$\endgroup\$
    – Freqz
    Jan 7 '19 at 19:30
  • 3
    \$\begingroup\$ I think the battery got hot because you either shorted it out with the switch (which your 2nd drawing shows), or were drawing too much current from the battery.The lights only want 6V, not 9V. One 4xAA pack should be fine, or one 4xC on one 4xD if you want longer on time. \$\endgroup\$
    – CrossRoads
    Jan 7 '19 at 19:34
  • \$\begingroup\$ Just one battery pack for all the light strips in parallel. \$\endgroup\$
    – CrossRoads
    Jan 7 '19 at 19:36
  • \$\begingroup\$ You are right about the switch wiring. I just changed it to per your suggestion and its good. \$\endgroup\$
    – Freqz
    Jan 7 '19 at 19:40
  • \$\begingroup\$ So what you are saying in regards of the battery, if I were to use 4xD sized batteries I will be able to power all 16 strings? If so would it be any difference if I were to use 8xAA since I already have a holder? \$\endgroup\$
    – Freqz
    Jan 7 '19 at 19:41

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