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I'm trying to use this small (and awesome?) unit as a boost/step-up converter for my project. I need to give my ESP8266 12-E NodeMCU a 5v input from a 18650 battery. Since this powerbank already had 1x 18650 battery in it, I assumed doing this would be easy. I was wrong.

The circuit looks like this:

On the far right, you can see the micro USB input, which charges the battery (B+ and B-) at 4.2v. In the middle, you can see 4 solder pads. That is a regular female USB connector, which I desoldered.

Here's the weird issue: If I take my battery, which is at 3.8v at the moment, and I check the voltage on the USB in the middle (which would normally charge your phone), it will be at 3.8v as well.

Am I doing something wrong? Shouldn't it be 5v, so it would charge my other devices at 5v? You can see the complete unit here: https://imgur.com/a/7almr

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  • \$\begingroup\$ It is difficult (or impossible) to tell what this unit is from the picture. Do you have a link to where you bought it, or a model number/name? \$\endgroup\$ – Ron Beyer Nov 23 '17 at 21:34
  • \$\begingroup\$ @RonBeyer Yeah, I figured someone would ask. Nope, I don't know what kind of unit it is or where to get one today. It was inside a cheap, cheap, cheap 1 cell powerbank I got years ago. The album at the bottom shows the other side of the unit, which might help a bit. \$\endgroup\$ – MortenMoulder Nov 23 '17 at 21:37
  • \$\begingroup\$ Do you have a load connected, when you are measuring the Voltage? If I were making this sort of circuit, I would want feedback from the o/p load. With no load, you would just see the V i/p. Which IC device is on that board? Knowing what the IC is, you could get the data sheet, which should show a reference cct. \$\endgroup\$ – LateDev Nov 23 '17 at 22:22
  • \$\begingroup\$ Please post the schematic for this device. \$\endgroup\$ – Nick Alexeev Nov 23 '17 at 22:35
  • \$\begingroup\$ Thanks for the reply! Before I do anything else, do you think the voltage could increase, if I put some load on it? Is that actually a possibility? \$\endgroup\$ – MortenMoulder Nov 23 '17 at 22:35

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