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Sorry for such a newbie question. I am still trying to find my feet. I know that a battery cannot be charge and discharge at the same time as I find this:

No, a battery can't be charged and discharged at the same time. If a battery is connected to a charger delivering 1 A and a load drawing 3 A, then the battery will be discharged at 2 A. There is no simultaneous charging and discharging going on

on here:

https://findanyanswer.com/can-you-charge-and-use-a-battery-at-the-same-time#:~:text=No%2C%20a%20battery%20can't,charging%20and%20discharging%20going%20on.

But I have just purchased this:

RAVPower Portable Charger 20000mAh 60W PD 3.0 USB C Power Bank 2-Port Power Delivery Battery Pack High-Capacity External Battery

from here:

https://www.amazon.co.uk/gp/product/B083J2YKRL/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Does that make a difference? Can I charge and discharge at the same time? I forgot to order the PD plug so I cannot actually test that at the moment.

Any guidance even just to tell I am stupid? :)

Thanks

NB To add more info. This is my User Case:

I have an enclosure with a raspberry pi. It is connected to a usb power bank. I have an external port where I can plug the usb power bank to an external charger. At the moment when the battery runs down I charge it by connecting a power source to this charger. I also turn the Pi off via SSH command. It charges OK. I was only wondering if I could avoid that step of using software to turn device off. So, scenario is:

  • Raspberry Pi is running and powered by usb power bank
  • The usb power bank runs out of charge
  • The raspberry then powers off
  • I plug an external power supply to recharge this usb power bank
  • As soon as it does the raspberry pi starts up again.

So i am now in the situation that the Raspberry pi is running and the usb power bank is charging at the same time.

I figured it MAY be able to work because you recharge a phone this can also be the same scenario?

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  • \$\begingroup\$ I don't even understand how someone can think this is even possible, what's your idea about this process? What do you want to happen? How could it magically charge and discharge? Will the battery be empty or full after this procedure? \$\endgroup\$
    – pipe
    Oct 10 '20 at 8:04
  • \$\begingroup\$ @pipe Hi, I am a complete newbie with electronics as my question and your comment proof! :) I have augmented my question with the user case. Thanks for spending time commenting \$\endgroup\$ Oct 10 '20 at 8:29
  • \$\begingroup\$ I have a GP battery pack that I wanted to use in the same scenario; I contacted GP about having it connected to a charger while a load was connected at the same time. I got a straight and precise answer; maybe RAVpower will answer your question as well. \$\endgroup\$
    – ocrdu
    Oct 10 '20 at 10:18
  • \$\begingroup\$ @ocrdu Thank you. I will \$\endgroup\$ Oct 10 '20 at 11:40
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schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. A rough schematic.

As usual, the Amazon products don't come with proper datasheets and that's why we don't recommend them as a source of components.

The quote in your question is mine, I think, from someone else's question. What I am saying is that the battery can't be charging and discharging at the same time. Either current is going in or coming out. It can't be going both ways.

In Figure 1 it should be clear that if you have power in on the left and power out on the right that one of several things can happen:

  • If the output current required is less than the that which can be supplied by the input source then there is power available to charge the battery.
  • If the output current is greater than the input supply can provide then the battery must make up the difference and will be discharged.
  • If the battery is fully charged then the output will draw current directly from the input.

I've kept this very simple. In practice there will be a boost converter to step the battery voltage up to whatever the output voltage is supposed to be and it should shut the output off to protect the battery before it goes flat.

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  • \$\begingroup\$ Thanks for explaining. I figured that that if more power going in than the target needs that the power bank would charge (albeit slowly). I was concerned it would damage the battery though. I am glad I decided to add a software off switch when charging then.. \$\endgroup\$ Oct 10 '20 at 9:50

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