I recently got into PCB design with KiCad and am a beginner. I am trying to make a portable phone charger, but for some reason keep getting this error:

Electrical Rules Checker error message

I'm assuming it is caused by the fact that I'm improperly using the two USB ports in order to charge/use as a portable device, but I'm not entirely sure. Any help would be greatly appreciated. Here is the schematic for reference:


Here are also the datasheets for the protection IC and charger:

Charger: http://ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf

Protection IC: https://www.diodes.com/assets/Datasheets/AP9101C.pdf

  • \$\begingroup\$ You are not permitted to use an edit to entirely change the nature of the question being asked, especially not after the original question has received an answer. Your improper edit has been rolled back. Additionally, the sort of broad open-ended design review question you were trying to turn this into is not really a fit for this site. \$\endgroup\$ Jun 23, 2020 at 1:35
  • \$\begingroup\$ I guess I'm in the wrong place then. I will figure it out myself. \$\endgroup\$
    – user255932
    Jun 23, 2020 at 2:09

2 Answers 2


J1 pin 5 is Ground. U4 pin 6 is Vbat which connects to P+ in the bottom right drawing. However, the bottom left drawing shows P+ connected to Ground, which is probably not right.

I'm a bit surprised that you didn't get a complaint about one net having two names: Vbat and P+ in the bottom right drawing.

  • \$\begingroup\$ I'm not entirely sure but that does make sense. These are the data sheets that I got the applicational example from: Protection IC: diodes.com/assets/Datasheets/AP9101C.pdf Charger:ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf \$\endgroup\$
    – user255932
    Jun 22, 2020 at 15:26
  • \$\begingroup\$ The typical application for the APC9101C shows a battery between P+ and Ground - your circuit shows a short circuit. When you fix that, you'll probably get a complaint about two names on the same net - Vbat and P+ - most CAD programs won't accept that. \$\endgroup\$ Jun 22, 2020 at 15:50
  • \$\begingroup\$ I added a battery and surprisingly there was no complaint about two names on the same netlist. However, what would be considered a good value for the battery that I'm using? \$\endgroup\$
    – user255932
    Jun 22, 2020 at 16:38
  • \$\begingroup\$ KiCAD allows to put multiple labels to the same net. The net ID is safed/handled separately. \$\endgroup\$ Jun 22, 2020 at 18:35
  • \$\begingroup\$ @ChristianB.: Thanks - I used Altium at work, which didn't allow multiple names on a net. From force of habit, I haven't tried multiple names in my limited use of KiCAD. \$\endgroup\$ Jun 22, 2020 at 18:49

The warnings in kicad are there to get you as a designer to check on them. It does not mean its wrong. Just usually that would be an issue with no other context.

In this situation if you know that this is not an issue for you. Then you can ignore it. Later development builds of kicad even let you hide errors you know are not an issue.

E.g. having a tristate microcontroller pin connected to an output would flag an error. But if I know that pin will only ever be an input as a designer. I can either ignore the error or change the pin definition to suit my specific use case.

The rule checking in the pcb layout is more clear cut. And generally those should not be ignored.

  • \$\begingroup\$ Oh okay, I see what you are saying. Thanks for the help. \$\endgroup\$
    – user255932
    Jun 22, 2020 at 15:15
  • 1
    \$\begingroup\$ If you know the pin will only ever be an input, then as the designer you should mark it as such on your schematic, and failing to do so means your schematic is incorrect and will convey inaccurate information to anyone who reads it. This includes yourself. Being the designer doesn't make you immune to lapses in memory or other mistakes. The example you give is not in any way caused by lack of context, it is an example of KiCad correctly giving an error because your schematic is incorrect. There is no missing context here, only an inappropriately designated pin function. \$\endgroup\$
    – metacollin
    Jun 23, 2020 at 0:19
  • \$\begingroup\$ I completely understand the schematic is easily one of the most crucial parts of the PCB board. I've only been using this program for like 3 weeks and I know I'm probably making some pretty stupid mistakes, but that's how you learn. \$\endgroup\$
    – user255932
    Jun 23, 2020 at 1:13
  • \$\begingroup\$ Metacollin. Kicad as software has no context if that is a valid circuit, just that power output to power output = display warning. E.g 2 power OR controllers with the outputs tied would flag the same error. But in that case would be a valid circuit. Its still up to the designer to make sure that warning is not a problem. \$\endgroup\$
    – Reroute
    Jun 23, 2020 at 2:18

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