Help! Why was it shorted?

I ran the DRC, soldered the resistors, and connected the 30pins esp32 in the middle. However, when I connected the battery:

  1. I did not even turn the switch to ‘on’
  2. The battery blew up.
  3. The 5v voltage regulator/boost converter’s LED did not light up the whole time (I tested the regulator before hand, and it worked.)
  4. It was shorted however the voltage divider in parallel was not hot at all.

I am so confused. Why did it happen?
Though I have to say that the battery I used was once shorted. However, that shouldn’t be the problem because I have used that same 18650 3.7v 3400mA battery in other projects which worked fine.
ShortedPCB_2.fzz (75.4 KB)

Wait a minute. I tested another blank unsoldered board, and even without anything, the two pads of the battery are still shorted.

The likely reason the battery blew up is that it is connected backwards. It is always a good bet to route schematic to make sure breadboard and pcb are correctly routed. In this case they are not which schematic makes clear the battery positive terminal is connected to the regulator ground terminal which is obviously wrong.

as we see here the battery positive terminal is connected to the - input of the boost regulator. That will power the boost regulator in reverse and very possibly short the battery which would produce the result you describe. There are a number of other odd things about this circuit, but this is likely the cause of your problem. I would advise using a proper part (rather than headers) for the ESP board so you get proper pin labels that are more easily checked. There likely is a Fritzing part for whichever ESP this is as I have made a variety of ESP dev kits for people over the years.

Peter

Thanks for spotting that.
However, it looks like it is wired correctly in the PCB view.
Also I tested a blank PCB with nothing soldered onto it and it seems like the 2 terminals of the battery are shorted.

That doesn’t appear to be the case in your uploaded circuit. There may of course be an error in the board (or a solder bridge) causing a short but the board appears correct other than the battery is connected backwards to the inverter. Here I rigt clicked on the - battery terminal. As we see it does not connect to the positive terminal of the battery directly.

It is possible that you have connected the -OUT of the boost converter to the positive of the battery but that doesn’t appear to be correct either. Here I add a wire (circled in green) to connect the In- pin to the Out- pin as is usually the case in boost converters, then right clicked on the switch terminal which will light all nets connected to the switch (and to the positive of the battery, if the switch is closed) but that still doesn’t short the battery.

I would guess you either have a solder bridge on your board, your board wasn’t made correctly or the converter being backwards has the effect of shorting the battery. You might try putting an ohm meter across the battery terminals (without the battery in place) and see if that shows a short. Then trace the paths (or unsolder the boost converter) and see if it clears.

Peter

Is this the ‘exact’ sketch that was used to create the gerber files used to create the PCB? Do you have the gerber files that were sent to the production house? Use a viewer to check the gerber copper layers to see if you can find a short from plus to minus.

Visually compare the gerber output to the blank PCB.

You can also try direct visually tracing on the blank PCB. If the ohm meter shows them shorted, there is a problem somewhere on the board. Finding it is the challenge.

Good catch! I missed that. It obviously is not the same gerbers as the gerbers generated from his sketch do not show a short between the battery terminals (as there shouldn’t be as there is a switch between the positive battery terminal and the circuitry. This is the gerber output from the posted sketch displayed with gerbv. There is no obvious short. So either the boards were made wrong (which I find unlikely) or the wrong gerbers were supplied.

Peter