Good Powerbank From 1$ Powerbank Case

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 .

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 .//

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