USB-C Adapter – No Voltage Under Load

usb-c

I have bought a usb c pd board (12V) (https://www.aliexpress.com/item/4000460866867.html) and such a GnA usb c charger (https://www.amazon.de/-/en/UGREEN-Charger-Supports-Compatible-MacBook-black/dp/B091BRJSRN). Additionally I have a Li-Ion Battery Pack 3S with BMS.

I thought that it should be possible that I just wire them up as you would normally do. But after I did so, nothing happened. After some time I figured out that if you connect the battery after you connected the usb c cable, everything works fine.

So I mesured and found out that my usb c charger takes approximately 1-2 seconds to reach 12V.

But why is that so?

Do you have an idea how to wait until it reaches 12v?
I have tried:

  1. Putting a self-made coil in series (didn't change anything)
  2. Use a Relai which triggers at 11V (worked but after it was triggered once the battery started keeping the relai open)
  3. Use a Relai plus a Mosfet (as Diode) (worked as expected but dropped the voltage by 0.6V so that I wasn't able to charge my battery to 100%)

Best Answer

Do not connect lithium batteries directly to power supply output. Stop immediately what you are doing before either the batteries or power supply is damaged, and please understand that damaged batteries may be dangerous and can explode or burst into fire. You also don't know if they have been damaged already, so it may not be wise to keep using them, it might be a good idea to recycle them properly.

You are missing a critical component in your system, a lithium battery charger, which takes in power from the power supply and uses it to charge the lithium batteries safely.

No, your power supply is not a lithium charger. No, a BMS is not a lithium charger either. You need a lithium charger between power supply and the battery pack.

What most likely happens is that when power supply tries to give 12V, too much current flows into batteries and the charger shuts down due to overcurrent situation. Also since batteries output more than 5V, the output may go into overvoltage shutdown mode before the power supply even outputs 5V. This is just plain wrong usage of power supply and battery.

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