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This is my first post here.

vivitern , 12-06-2017, 06:55 PM
DIY enthusiast especially in electronics
Err, I'm a DIY enthusiast especially in electronics. I'm actually building a portable Playstation 2 Slim with an IPS display, so that it would look like a Wii U controller. It's my first large electronic endeavor.
However, being portable, I'd need it to be powered by rechargeable batteries. I'm very confused on how to approach the power part of this project. I'll try my best to be detailed as possible! I look forward towards your answers!
The Little Details
Looking around, I concluded that a battery pack of 18650s (3S) would do a good job, it seemed straight forward too. Connecting three of them in series will produce a maximum of 12.6V. It's also a bit common, therefore a lot of information about the batteries can be found, and even be salvaged from laptop battery packs.
I have some details on the electronics included in the project so far:
Sony Playstation 2 Slim (Model 75003)
  • Operational Voltage: 8.5V
  • Power Consumption: 6 A Maximum
Innolux N070IDG (Yeh, I love nice screens )
  • Type: IPS LCD
  • Resolution: 1280x800
  • Size: 7 Inch Diagonal
  • Operating Voltage: 9-12V (Best at 12V)
  • Consumption: 190-210mA (full brightness) (Indicated from Bench power supply)
  • Display Interface: Includes Interface board of HDMI, VGA, 2 x AV.
PAM8403 Audio Amplifier ( datasheet sees attached below )
  • 2 Channel
  • Output: 3W output per channel at 4 Ohms.
  • Voltage: 5V

The Batteries
I managed to obtain 6 x 18650 Batteries from an old laptop. After some searching, it seems to be Sony SF US18650GR 2400mAH Li-Ion batteries. So i concluded that this seems good enough as a start, three of them.

The Problem
I wanted to use this 3S battery pack with a BMS. After I got the BMS, just as I was about to assemble the pack, i researched some more.
It seems that BMS's do NOT balance cells. I thought, since it has an under and overcharge protection, it will all charge the cells at 4.2V each, when the cell is full but the others are not, it will stop charging for that particular cell and continues on the cells that aren't full. But I seem to be wrong, and it can still be out of balance.
I was wondering.. most consumer devices we use, simply use a DC power charger/supply to re-charge devices, such as laptops or portable speakers, etc. For sure, they must've designed a balancing circuit inside the battery pack or in the device - or they aren't balance charging neither?
Most tutorials mention, that the use of a balance charger with a balance connector is the only way to maintain its performance. I find it rather inconvenient to carry around a balance charger and remove the battery pack from the device to re-charge it.
My question is .. is it possible to design a battery pack, that has necessary protection features such as under/over voltage and over current protection, and design it in a way that it charges through a simple DC barrel charger?
robertferanec , 12-07-2017, 11:14 AM
You may need to search for a chip. Try google for "charging chip li-ion battery" .. there are many chips, maybe you will find something what will be a good solution for you. Some of these circuits also include battery protection. This may not be what you are looking for, but here is an example: http://www.ti.com/power-management/b...tml#p1152=3;16
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