Electronics > Projects, Designs, and Technical Stuff
DIY cheap powerbank (technical suggestions R welcome !)
ym58:
Actually, I just received this morning the new PCB from HK (via Istanbul !!!)
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I am just quite upset :( coz it worked for 30min in discharge mode (one piece of fully charged Lipo connected to B+/B- and a 4R/100W resistor load connected to the USB-OUT 2.1A output).
The LCD was then just working fine, with a nice '95%, 5V-2.1A' message (with percentage decreasing smoothly) and I effectively measured a 1.2A discharging current with my DC clamp ammeter ...
Then, all of a sudden, it just stopped and now it's dead :-- and the LCD does not even light any more!
I tried to reverse the process and charge another half-charged Lipo thru the microUSB, the LCD lights up correctly and gives a coherent percentage (57%, i.e. the charge state of the current LiPo) but actually it does not charge at all the battery, the current is near to zero ... no way, the PCB is dead !
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Since I had ordered another one to another supplier, I must now wait another couple of days/weeks before I can resume my tests.
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However, I made a pic of the dead PCB and indicated the chips references, just in case someone would got a clue whether this PCB (in working condition ;)) could possibly charge LiPos with currents > 1A ... ?
edavid:
Why not charge each cell with a separate TP4056, and combine the outputs with some big Schottky diodes? You'll lose a little capacity that way, but at least it will work.
ym58:
--- Quote from: edavid on August 06, 2016, 03:06:41 pm ---Why not charge each cell with a separate TP4056, and combine the outputs with some big Schottky diodes? You'll lose a little capacity that way, but at least it will work.
--- End quote ---
A TP4056-based circuit will only handle the CHARGE of the LiPos( or Li-Ions).
What I want is a reversible circuit (exactly as those cheap ones described earlier in the thread) that can not only CHARGE but also manage the DISCHARGING (with correlative protection) of the LiPos into the external load (smartphone, iPad, tablet ... you name it).
Actually, I think they call this a BMS, for Battery Management System.
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And also, my bottom line was to make a funny prototype with what already exists ans sells a few bucks, instead of designing something that will eventually cost more than a real 20000mAh LiPo-based powerbank (around 25€-35€) !
Kilrah:
--- Quote from: ym58 on August 06, 2016, 04:26:35 pm ---instead of designing something that will eventually cost more than a real 20000mAh LiPo-based powerbank (around 25€-35€) !
--- End quote ---
Good luck then, since I don't even actually know of any "real" powerbank that does what you want (charge at >1A).
ym58:
--- Quote from: Kilrah on August 06, 2016, 04:35:50 pm ---Good luck then, since I don't even actually know of any "real" powerbank that does what you want (charge at >1A).
--- End quote ---
At least, that one does (amongst dozens) :
https://www.conrad.de/de/logilink-powerbank-12000-mah-1040721.html
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Let's make a quick calculation if you will :
This 12000maH PB (powerbank) claims it can deliver 12Ah (ouch :clap: !)
That means that it either includes ONE 12A LiPo or TWO 6A LiPo (in parallel) ... I dont really think it could be more than TWO (see the thickness).
Then 1C for each battery is either 12A (1 batt) or 6A (2 batt) but not less !
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Therefore, the charging current (I said CHARGING, not DISCHARGING ) should NORMALLY be either 6A or 12A to stay within the frame of NORMAL charge cycle diagrams (that is a few hours charging, generally less than 6hrs depending on the battery technology and manufacturing quality).
Then, if you are right (see your quote), that would mean that it takes that PB MORE THAN TWO DAYS to get charged ... no way :palm: !
CONRAD.DE could not possibly be so dumb to include such a poor device in their listed products !
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Don't forget that even if a wall socket can deliver only 1A to the PB's micro USB charging connector, some internal switch-mode circuitry is intended to increase this current !
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