Can I Charge My Phone and Battery Pack Simultaneously with a Power Bank?

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Discussion Overview

The discussion revolves around the challenges of charging a phone and a NiMH battery pack simultaneously using a custom-built portable power bank. Participants explore the technical aspects of the charging circuitry, voltage levels, and current requirements, while seeking solutions to ensure both devices can be charged effectively when connected to a power supply.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes their setup where the power bank charges only the NiMH battery pack and not the phone simultaneously.
  • Another participant points out a potential issue with having both 5V and 2.5V on the same line, questioning the design.
  • Concerns are raised about charging NiMH batteries with a constant voltage source, suggesting they should be charged with a constant current source to avoid overheating and potential hazards.
  • A suggestion is made to separate the charging circuit for the NiMH batteries from the power supply to prevent overload.
  • One participant proposes lowering the 5V to match the battery pack voltage of 2.5V and then stepping it back up to 5V, which is challenged as unnecessary.
  • Another participant mentions that the phone may require a signal to draw more than 0.1A, indicating a possible issue with USB communication.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate charging method for the NiMH batteries and the design of the power bank. There is no consensus on the best approach to resolve the charging issues, and multiple competing perspectives remain throughout the discussion.

Contextual Notes

Participants highlight limitations in the current design, including potential overload conditions and the need for proper charging circuits. There are also unresolved questions regarding the phone's charging behavior and the implications of using different voltage levels.

Akmalidin
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Hello,
I have built a portable power bank to charger my phone when necessary.
But I have a problem with it. When I charger the power bank, it is charging only my battery pack which is NiMh, it is not charging my phone at the same time.Therefore, I want to ask ,how I can make my system , so it charges my phone and battery when it is plugged to power supply.When the batteries in pack are full, they are charging my phone. So please let me know your opinions.The schematics is given in pic.
IMG_20160910_111657.jpg
 
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Akmalidin said:
Hello,
I have built a portable power bank to charger my phone when necessary.

I see a problem in the middle section ... do you see it ?Dave
 
Nope I don't see it. Could you be more specific?
 
5V and 2.5V on the same line ??
 
yes, the buck converter outputs 5v and it is connected to battery.Two battery gives out 2.5 volts.So when I measured the middle point, it showed 2.5v. What can we do about it?
 
It looks to me like you are charging the NiMH batteries with 5V. I wouldn't...
 
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Yes I am charging with 5v .Why would not you do that?
 
Akmalidin said:
yes, the buck converter outputs 5v and it is connected to battery.Two battery gives out 2.5 volts.So when I measured the middle point, it showed 2.5v. What can we do about it?

you shouldn't have 5V and 2.5V coming together at that point

Akmalidin said:
Yes I am charging with 5v .Why would not you do that?

cuz you are likely to cook them
there should be a separate line to a correct charger circuit for the NiMH's. The NiMH output voltage total should be 5V and then a separate switching circuit to switch between the 1st 5V supply and the battery pack before going to the phone the second 2.5 to 5V converter isn't needed
 
Last edited:
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What if I lower the 5v to 2.5v as the battery pack voltage and step it up to 5 v?
 
  • #10
Akmalidin said:
What if I lower the 5v to 2.5v as the battery pack voltage and step it up to 5 v?

that's a bit pointless because as I said in my last post you don't need the second converter, just a waste of space and resources
increase your battery pack capacity to 5V is a much wiser move. I really don't see the point of a 2.5V battery pack
 
  • #11
Read up on the charging requirements for NiMH cells before going any further.

You aren't really meant to charge them from a constant voltage source. They should really be charged by a constant current source. Any kind of medium/fast charging also needs charge control (eg circuits to stop over charging when the battery is full). Overcharging a NiMH cell can sometimes cause them to overheat. That can cause the heat shrink insulation around the cell to split leading to short circuits and fire. Been there, done that.

Sometimes it's easier, cheaper and safer to just to buy one.
 
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  • #12
The way its wired now the buck converter is probably pushing too much current into the NiMH pack causing an overload. The buck converter goes into current limiting mode and that's why voltage drops to 2.5V. So you're using the boost converter because the buck converter is overloaded. That's a crazy thing to do. There should be a charging circuit on the 12V line for the NiMH pack and only the buck converter to power the phone.
 
  • #13
https://e.mail.ru/attachment/14741015700000000579/0;1 I added couple of batteries to make battery pack 4.8 v. But still it is not charging my phone. I even tried to charge my phone from a buck converter which outputs 5 v and connected to power supply. My phone was only getting 0.1A .But when I connect only battery pack it was sucking 0.6A .Why phone is taking only 0.1 A?
 
Last edited:
  • #14
This is the way I connected my phone and buck converter. Still cannot understand, why my phone is taking only 0.1 A.Please let me know your feedback.
IMG_20160917_113911.jpg
 

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