I am making a "simple" bluetooth speaker and have followed instructions from a Youtube video on how to assemble the components I have bought.

However... I am finding that the rechargeable li-po battery that I am using for power in conjunction with a protection circuit and voltage boost module doesn't seem to want to do so...

Could somebody tell me what would be the best way forwards?

This is the module I am using, and this the battery.

The battery is rated for 3.7V as written on the side of it, but when connected to this battery protection circuit it seems to drop to 3.4V (assuming for protection purposes?).

Given that I am working with 3.4V at FULL charge, I charge up an then switch the circuit on and adjust the boost module to output a steady 6.5V as per the Youtube video. I assume this is done such that as the battery is drained and the voltage reduces, the boost will remain above the 4.5V required to power this bluetooth amp board...

Could somebody please inform me if I am wrong about this?

Just FYI, the speaker works perfectly when I am powering through the micro-USB cable connected to a wall charger.

I am new to the world of hobbyist electronics, so my knowledge is limited.

Update (more info) I just had a quick test of the voltages throughout the system with my multimeter.

  • Battery terminals: 3.2V
  • Protection board output: 2.5V
  • Booster V-in: 2.5V
  • Booster V-out: Varying unstably between 3.5 and 4.2V (I did not have a capacitor connected across the V-out terminals at this time)

I have drawn a very rudimentary diagram to hopefully explain my layout: enter image description here

  • \$\begingroup\$ Ask a specific question, you'll get better answers \$\endgroup\$ – Voltage Spike Jun 10 at 20:02
  • \$\begingroup\$ There should be practically no drop in the protection module. Insert every wry, dire, or outright rude thing you've ever heard about eBay here -- if you buy from a flea market, expect flea-market quality... You need to find a better module. That sort of voltage drop is not inherent in battery protection circuits. \$\endgroup\$ – TimWescott Jun 10 at 22:55
  • \$\begingroup\$ @TimWescott - I understand completely. If there were an electronics shop nearby, I'd have gone there :-( I will have a go at re-soldering the protection circuit later to see if I can improve. I feel that it may be my crappy soldering that may have also inhibited progress, but I will investigate further and report back :-) \$\endgroup\$ – physicsboy Jun 11 at 5:41
  • \$\begingroup\$ @TimWescott - Your hunch is indeed correct. It looks like the protection circuit is a duff one. I tested the whole thing with a new battery connected to the circuit with no protection and it worked fine. Back to the internet I go to buy a new protection circuit! \$\endgroup\$ – physicsboy Jun 11 at 18:25

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