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Newbie Question 18650 Powerbanks

BangkokScott

Jun 25, 2021
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Hello,

DIY powerbanks

Questions- What is the best 18650 batteries for making your own powerbanks, I bought shells from China based store on the internet.

thanks
 

Audioguru

Sep 24, 2016
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Here is an 18650 battery bought from ebay. It is one of many fakes that are sold:
 

Bluejets

Oct 5, 2014
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Just be aware that video is from 2012 so whomever sold those could be gone by now.
Obviously still a possibility but who would know unless one does the same operation.
I've had 18650's from Ebay that work just fine for long periods of time now.
 

Audioguru

Sep 24, 2016
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Here is the same brand name last year as 8 years ago, Ultrafire.
It is labelled with 3 times the capacity of Name Brand more expensive batteries but it is a lie. It tested at 1163mAh.

Another cheap lightweight 18650 Chinese battery was opened 3 years ago and it was almost empty inside.

Another cheap Chinese 18650 battery measured 353mAh.

And another, and another and another.
 

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BangkokScott

Jun 25, 2021
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High quality ones, brand type.

Possibly low to no quality.
With many companies outsourcing the manufacturing of products, how can I ever know that its not a cheap Chinese "knock-off".

I checked ebay and find almost the exact same shells, are there any known high quality companies (or brand names) that produced high-end shells?
 

Audioguru

Sep 24, 2016
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Samsung (Korea) and Panasonic (Japan) make high quality 18650 cells and real ones are sold by reputable dealers. Horrible knock-offs are sold by '"sellers" on all the Chinese websites. Frequently the fake one has less weight but looks better than the real one.
 

BangkokScott

Jun 25, 2021
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so....is weight (of the 18650s) the best way to know if its fake of not?


I bought Samsung 18650 25R, but I still get barely one recharge of my iPad (8 cell charger)
 

Harald Kapp

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Nov 17, 2011
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I bought Samsung 18650 25R, but I still get barely one recharge of my iPad (8 cell charger)
How is your powerbank constructed? A single 18650 cell with a USB powerbank adapter PCB (charging the 18650 cell, delivering 5 V on a USB port)?
The Samsung 18650 25R cells have a capacity of 2.5 Ah @ nominal 3.7 V. That's 9.25 Wh. You may be able to use ~ 80 % thereof (to prevent deep discharge of the cell and includibg losses of the step-up converter). That leaves you with ~7.4 Wh for charging the iPad.
An iPad battery I found has 6.6 Ah @ 3.7 V, equivalent to 24.4 Wh. Your single 18650 cell could charge this iPad battery by ~ 1/3 of the capacity.
You will need at least 3 or more 18650 Cells of this type to fully charge this type of iPad battery.
Numbers will vary depending on your specific iPad.
 
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