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I have a powerbank with a 20,000 mAh capacity, from which I can power different devices.

The devices include an LED strip and a Raspberry Pi Zero W (RPI Zero W).

The LED strip consists of 60*5 LEDS = 300 LEDS, and will roughly draw 4.5 A with 50% PWM.

The Raspberry Pi requires about 170 mA.

The powerbank has 3 output ports, one capable of drawing 2 A, and the other two capable of drawing 1 A.

Would it be possible to somehow extend the current draw from these USB ports? I could put them in series, such that I would have one port with 4 A, but how would that affect voltage? I need to power both my Raspberry Pi, and the LED strip.

Would the USB port be able to handle such a high current draw?

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It is very likely that all three USB ports in your powerbank are internally connected in parallel. You can try to check continuity between VBUS pins on all three connectors using a DMM.

Remember that ports do not "draw" current, loads do. The designated port capability simply means that different ports have different "charger signature" on D+/D- connector pins, so the plugged devices can decide which current they can take. If loaded with a smaller resistor (non-intelligent) load, each port is likely to supply much more current, up to physical capability of the design of internal DC-DC converter inside the powerbank.

However, one need to remember that USB contacts also have a limited contact rating, usually 1.5 A. So to get more current without melting USB connector you should try to make a cable assembly with three USB plugs in parallel, so the load current will be at least some way distributed across all three connectors.

Finally, "any way i can test it" - yes you always can. Just connect your load, and see if your LED rig is still powered with 4.5-5V, and connectors do not melt or smoke. You can start with 20% PWM, and increase the load until you run into the limit.

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"... 3 output ports, one capable of drawing 2 A ...".

No, the load draws, the power-bank supplies.

I could put them in series, such that I would have one port with 4 A, but how would that affect voltage?

Series connection (if it were possible) means you would have 5 + 5 + 5 = 15 V and the smallest of the currents, 1 A. That is not what you mean. What you are suggesting is that you wire them in parallel.

Would the USB port be able to handle such a high current draw?

Probably not. You can't predict which output will provide the majority of the current. The device may have current limiting on each port and shut them down but if it is a cheap device it may just parallel all the 5 V outputs and have no protection. 4 A is more than the contacts will be rated for.

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  • \$\begingroup\$ Yes, I meant parallel but wrote series instead.. Do you have a data sheet for usb connector rating? I can't seem to find contact rating.. \$\endgroup\$ – nano Jul 28 '18 at 8:50
  • \$\begingroup\$ any way i can test it? \$\endgroup\$ – nano Jul 28 '18 at 8:50

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