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I'm looking to see if assembling my own USB hub is an option. I need to charge 20 devices via Micro USB at once. Data transfer is not needed.

Is anything stopping me from getting a 5V 20A power supply and wiring up 20 Micro USB cables in parallel? Does any protection circuitry need to be added?

Thanks!

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  • \$\begingroup\$ Do you care what will happen when you get a short on one port? \$\endgroup\$ – Transistor Jul 22 at 22:11
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    \$\begingroup\$ Most devices won't charge very fast unless the "charger" uses one of the expected rate signaling methods, such as a resistor network on the data lines. \$\endgroup\$ – Chris Stratton Jul 22 at 23:28
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Is anything stopping me from getting a 5V 20A power supply and wiring up 20 Micro USB cables in parallel

Not really. If you want something simple, just put a 2-3 A resettable polyfuse on each VBUS wire on your board, and use good grade full-sized micro-B cables. The simplest way to provide your devices with up to 1.5 A, short D+ and D- wires together and leave them floating (in each cable). This connection will inform attached devices that the power source is "Dedicated Charging Port", aka DCP (which is an adoption of Chinese Federal Standard). Most devices understand this "charging signature" and will take about 1 A from the ports (up to 1.5). So you might need a 30-Amp power supply.

If your devices are not using "fast charging", you can leave D+ and D- unconnected, and devices will take no more than 500 mA (if they are good-behaving devices).

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Add current limiting to each port to prevent smoking the cable or downstream device when you plug it in. Lots of solutions for this from TI, On Semi, Maxim, etc.

More: For a charger I would recommend the regular A host receptacle connector. Micro is generally for endpoints or OTG devices where space is at a premium.

Revise and extend: information about Battery Charging Port (BCP) and its issues: https://www.maximintegrated.com/en/app-notes/index.mvp/id/5801

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