Electronics > Projects, Designs, and Technical Stuff
DIY cheap powerbank (technical suggestions R welcome !)
NottheDan:
Looking at the linked pdfs they quote a charging current of 200-1600mA and a charging time of 15 hours at 1.5A.
Though, looking at a 19600mAh powerbank of the same brand they only vie a charging time of 12 hours at 1A. And the 20000mAh one gives 10 hours at 2A.
ym58:
--- Quote from: NottheDan on August 06, 2016, 05:51:23 pm ---Looking at the linked pdfs they quote a charging current of 200-1600mA and a charging time of 15 hours at 1.5A.
--- End quote ---
Thanks Dan, shame on me I did not even look at the specs in French :-[ (I only sticked to the second .PDF, less precise ...!).
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So, 'Max 15 Heures sous 5V 1.5A' is not THAT bad.
But still, how come one can't find any cheap chip ;) that could deliver higher constant currents to charge LiPos (or Li-Ions) ... how can the mainstream market possibly accept such poor charging time performances ?
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Any LiPo (or Li-Ion) can be TECHNICALLY charged within a few hours with a proper CC (constant current) equaling its 1C capacity.
How can we, customers, accept specs stating 15Hrs to charge a 5-ounce battery ?
Kilrah:
--- Quote from: ym58 on August 06, 2016, 05:35:00 pm ---Then 1C is for each battery is either 12A (1 batt) or 6A (2 batt) but not less !
--- End quote ---
Nothing requires you to charge a Li battery at 1C, it's the maximum you can do on normal cells. The cell count in the powerbank is also irrelevant, it's the energy capacity that matters.
About your Conrad powerbank:
Pack "rating" (not always realistic, let's assume it is) is 12Ah @ 3.7V so 44.4Wh, so 8.8Ah equivalent @5V. They say "up to 15h", 8.8/15 =.... 0.6A.
So this one also charges at the usual 600mA (losses ignored, it will probably actually draw about 7-800mA or so).
The reasons for the low charge speed is a mix of convenience, cost, size and "no need for more".
Having an USB charge port allows not supplying a proprietary charger (expensive, inconvenient to carry around for the user). But given that you have to assume the user might use any USB charger, including one that might not be rated for >500mA, and a charge controller that handles that actively is too much to ask from the cheap manufacturers.
Then a 5-10W charge circuit would start to get pretty big compared to the power bank itself. Lastly, as we can see, that's how things are and nobody complains, most will actually rather want a cheaper powerbank than a more expensive one that charges faster... most people have them in their bag just in case "for emergencies", once back home it's not a problem to charge it all night. There are some that charge faster, but of course they cost more.
Even I who have been using standalone Li-Pos for more than a decade and have universal chargers have never found the need to spend the 5 minutes needed to crack open my powerbanks to wire them to a fast charger, I just plug them to an usb charger laying around and forget them there for a while.
NottheDan:
Random thought: Having you looked into the balance chargers available to RC model enthusiasts?
ym58:
--- Quote from: blueskull on August 06, 2016, 06:27:57 pm ---https://www.amazon.com/Xiaomi-20000mAh-External-Battery-Portable/dp/B01A89C3K2/ref=sr_1_3?s=wireless&ie=UTF8&qid=1470507890&sr=1-3&keywords=xiaomi+power+bank
Spend some more money for better quality. Xiaomi is one of the best Chinese personal digital gadget manufacturer.
When they say their products passed CCC/CE/FCC, they mean it.
Warning: Chinglish.
--- End quote ---
Apparently, this one is QC2.0 certified, that's a big step forward compared to my cheesy stuff ;) !!
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Besides, reviews are not all good, is Xiaomi experiencing QC problems or is it just coincidental ?
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BTW, your Chinglish's quite good, way better than my froglish :-DD !!!
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