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I have made a bench power supply from an old PSU and added a USB port connected directly to the 5V rail (leaving the data pins disconnected).

When I connected a TP4056 charging board (like this), the TP4056 smoked and blew up.

I am trying to understand if the board was defective (or I messed up with the wiring) or if the USB must not provide more than 1A (the 5V rail of the PSU provides something like 25A).

As far as I know it does not matter how many amps the USB can provide since the connected device always draws what it needs, but I like a confirmation from someone more expert than me :)

Cheers

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    \$\begingroup\$ If you connected the USB port straight to the power supply it will deliver 25 Amps with no problem. Normally there is a chip in between that regulates the current. Three guesses: 1) you accidently used the 12 Volt; 2) you swapped plus and minus; and 3) the battery was faulty. \$\endgroup\$ – JvO Mar 19 '17 at 12:44
  • \$\begingroup\$ The port is providing 5V and the polarity is correct. It could be the battery then, maybe was trying to draw too much? I noticed that even after I disconnected the USB, the board was still heating up, so it must be from the battery. \$\endgroup\$ – Ema Mar 19 '17 at 12:57
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    \$\begingroup\$ Or a faulty chip... hadn't considered that one yet. \$\endgroup\$ – JvO Mar 19 '17 at 13:52
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    \$\begingroup\$ I doubt that faulty battery could cause damage to TP4056. Most likely you plugged something wrongly. \$\endgroup\$ – Chupacabras Mar 20 '17 at 11:34
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    \$\begingroup\$ Normal battery chargers always limit input current even in case of dead shorted battery. I would guess that "TP4056" from NanJing Top Power ASIC Corp., likely being an illegal reverse-engineered copy of LTC4056, does not have any of the protective features. So the result should be expected with unlimited input power. \$\endgroup\$ – Ale..chenski Mar 20 '17 at 17:42
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USB ports are supposed to limit current somehow. This can be totally disconnecting power for a while when overcurrent is detected (like a resettable fuse), or current limit. However, no device should rely on this.

Being able to providing more than the maximum normal current should be OK, as long as the device is working properly. Most likely, your output wasn't supplying 5 V. Check it with a voltmeter.

Of course you should have done that before plugging in something that could get smoked by the higher voltage.

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  • \$\begingroup\$ Just checked and the port is supplying 5V. Coming from a PSU is also very stable. So I guess was the charging board to be defective. \$\endgroup\$ – Ema Mar 19 '17 at 12:55
  • \$\begingroup\$ Current limiting is not relevant, how would the TP4056 pull more than it needed? It would only pull more if the voltage was above 5V. It's certainly either wrong polarity or 12V lulz. \$\endgroup\$ – user2497 Aug 3 '17 at 17:43

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