loading

we all face problems from the fake capacity of power banks ,

mainly the power banks have pretty good circuits but the cells they give are very bad .

Here i am showing how to retrofit a cheapy power bank 1$ with good cells 18650 .

i n many countries the higher capacity power banks cost more

so we can use some good reliable cells and a damn cheap PB to make a reliable

usable device .

Step 1: The Refit

Grab a 2 cell power bank at low price ,

desolder wires

new cells sometimes come seperate ,

so need to scratch with sharp object and solder cells in parallel

install in to the case .//

Step 2: The Safety Cut Off

The litiums must cut at 4.2V ...

DANGER : some of the power bank charger circuits DONT cut so how to know ?

Well charge the cells for 1-2hours , monitor voltage

if it is crossing 4.2 , the cut is not there

So , instead of using OPAMPs etc , we can have a simple circuit like this to cut off

select zener as zevervolt + 0.7+0.7=4.2V zener can be 2.7V

<p>Thanks for this circuit, it looks like it might do for something that I have been wanting to build.</p><p>Do you have any thru-hole replacement for the MOSFET? The only places with the IRLML2502TRPBF show it as a surface mount device. Thru-hole would be a lot easier to solder.</p>
<p>I am ordering another common Logic level mosfet SI2302... any logic level mosfet with 1-2AMP current capacity will work </p>
<p>If I apply more than 5V at the input, any problem ?</p>
<p>some really nice and cheap circuit exists how take care of all the charging process. By example the mcp78831 <a href="http://ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf" rel="nofollow">http://ww1.microchip.com/downloads/en/DeviceDoc/20...</a></p><p>It&acute;s not easy to solder on protoboard, but still possible. I guess you should be able to find PCB or kits for it. Something else to be aware of when using lithium batteries is over discharge and over discharge current. Some batteries integer such protections but you will also find PCB or even battery holder with integrated protection.</p>
<p>some issues with the special chips are 1)chip itself will cost like another powerbank 2)pcb + wiring will take 10-15$ or many painful diy hours 3) many of the chips cant do 1AMP charging many need 6V as input 4)yes difficult to procure in many parts of the world </p>
Yes it'a true. The chip on the picture only allow 500mA, is not easy to solder (but only takes minutes) and cost one dollar...add another one for the capacitors resistors and led...
<p>thatz a great build ... grabbing the caps in a SMD bulk bag it can be done in 'some' countries ... here in india people in small towns are not so fortunate .</p><p>but now a days the mosfets are available online all over the country .</p>

About This Instructable

2,237views

32favorites

License:

More by aaaaoooo:good powerbank from 1$ powerbank case Almost free good looking soldering stand 30seconds Nailpolish PCB 
Add instructable to: