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I'm building an 18650 phone charger which follows this tutorial.

Block diagram

The 18650 battery is connected to the TP4056 module. Then I have that connected to a boost converter to step up the 2.8V - 4.2V (from the 18650) to 5V. The boost module has a USB output which I can then connect to my phone.

My problem is that after connecting my phone, I can confirm a correct 5V but it only draws like 60-80mA (confirmed with my multimeter.)

I initially thought maybe I had high wire resistance but it still doesn't draw much current.

What am I doing wrong here?

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    \$\begingroup\$ Technical note: you're building a phone power supply. The charger / charge controller is in the phone. Are you aware of charge negotiation? It's been asked many times here. \$\endgroup\$
    – Transistor
    Commented Nov 2, 2020 at 21:44
  • \$\begingroup\$ No I'm not but thank you for lead. I'll look into that. \$\endgroup\$
    – Tom
    Commented Nov 2, 2020 at 21:46
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    \$\begingroup\$ A lithium battery cell is 4.2V when fully charged and is 3.2V or less when it is dead. Your cell is only 2.8V so it is dead. A dead cell cannot produce much current. It also might be ruined from being discharged to a voltage that is too low. \$\endgroup\$
    – Audioguru
    Commented Nov 3, 2020 at 0:40

1 Answer 1

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Phone cannot detect how much it can draw current.

Commonly the two USB data pins are connected together at the supply, so that phone sees over standard USB cable that it can draw enough current to charge.

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