Doubts making a power bank

Discussion in 'Power Electronics' started by Rafael Grossi, Aug 18, 2016.

  1. Rafael Grossi

    Thread Starter New Member

    Aug 18, 2016
    Hello friends,

    I was looking for a cheap power bank to buy, but I've thought make one could be a nice idea. But many problems came in mind.

    There are many kind of DIY power bank modules selling in the internet. Look:


    My idea is buy one module and use some 18650 batteries. Nice. Or not?

    Well, I asked to sellers How many batteries can I use in each module. One told me 4, other told me there isn't a limit. What do you think? Many batteries will taken a long time to charge, but it's ok. But, will the module show the correct state of charging? Can the module deal with different charging state of each battery?

    I extended my doubts to the problem of connecting batteries in parallel. When the module is off, the problem of one good battery charge a bad battery and it creates a great current could occour? Will I need to connect resistors among batteries? Would it occour even with protected batteries?

    So I'm afraid to create a bomb instead a power bank.
    There are some DIY power banks selling too. Look:


    The first problem I found in this product is my protected 18650 batteries don't fit the space for batteries. Protected batteries are bigger. But, my fear about parallel batteries wouldn't occour with this power bank too?

    Maybe one solution is give up my idea and buy a better DIY power bank, like this:


    It isn't cheap as I want but maybe it's saber. And I don't explode my house.

    I would like to ask your opinion. Is my idea to create a power bank from a module a bad idea? Could it bring me problems? What care do I need to take?

    Thanks guys!
  2. DickCappels


    Aug 21, 2008
  3. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    There is so much info to figure out just to build a simply power bank.. Building or buying is up to you ..The chinese build millions or if not billions of power banks with non protected cells every year .. Also most power banks use only parallel cell configurations.

    I will post alot more when I get home