HI all.
Well, the thing is i have this:
I use this with 4 batterys 1.5v
I try if works with a 5v power adapter, and yes it does.
So i think maybe put 1 18650 (i have some batterys from and old notebook). Somebody can tell me what module i can buy to put to charge this battery with a 5v power, and for this battery go up and give 5v??? (and some careful advice, i ear that this batterys are danger... i already put out of the notebook charger).
Or another idea???
Thanks.
What about the suggestion you already received on that page?
The thing is i dont want to buy 4 batterys, and also a charger for that.
Using something like this it will be bad???
I suppose i can put this into the "phone" (i dont know the word for that in english)
But, if i use the "phone", and the battery is draining... the battery can explode in that moment??? or that "power bank" will protect about this.
In the other hand, i cant charge and use at the same time dont?? or yes?
Thanks for your time.
I have to chuckle at that "power bank". 
"Power Bank"s are frequently a problem as because they incorporate a power converter to boost the 3.7 V LiPo battery to 5 V, they shut the converter off after a while if the 5 V is not being used and you often have to press a button to start it again.
They do not explode very often, otherwise there would be a backlash against the sellers. 
Whether you can charge at the same time as using the output is not clear - it may vary from model to model. There is a module available on eBay that I understand is specifically specified to do so.
Depending on what that "this" is exactly it may be perfectly happy with 3.7V. Did you try that already?
Lower voltage than rated is normally perfectly safe. It may simply misbehave or not do anything at all. Or maybe it works beautifully.
