Little help with Conect Two 18650 with a usb charge

Hi everyone! I Have one question before I try one thing that maybe just have a result: :grin:

I get 2 portable battery charger with Flashlight: |500x281 |281x500

I open up and... Surprise: |500x281 (It have a 1W Led but it's not working anymore... so I Improvised one Haha)

18650 Battery of 4.2V (I have not measured the Usb Output but is 4.2v directly)

I Want to know it I can make it a Serial Battery to have 8.4v |500x221 (Yep, Paint for Quick things Haha)

Aaaaaand the really "Want to know thing"... I Can still use the Usb Output/input for charge the batteries? I gonna use the Power directly with a switch before the usb output but I want to use the Micro Usb input for Charging the batteries... |500x281 (Yep, Another Paint for Quick things Haha)

There are photos of the Usb Output/input: |500x281 |500x281 My Idea can be use?

If the batteries are equal (and has close to same charge status when you begin) it is OK to connect + to + and - to - (paralell) and charge from 4.2V (no more than 2A)

It they ar connected in series |-===+||-===+| you use 8.4V (max 1A)

Stop !!! if a cell tends to be warm.

knut_ny: If the batteries are equal (and has close to same charge status when you begin) it is OK to connect + to + and - to - (paralell) and charge from 4.2V (no more than 2A)

It they ar connected in series |-===+||-===+| you use 8.4V (max 1A)

Stop !!! if a cell tends to be warm.

Damn, Sorry, I'm try to say I Want to conect it in series Haha It will still Work?

thats 24V in your picture.. Go for 8.2v .. 8.4V

Aaaaaand the really "Want to know thing"... I Can still use the Usb Output/input for charge the batteries? I gonna use the Power directly with a switch before the usb output but I want to use the Micro Usb input for Charging the batteries...

no, you can't . You won't get the needed voltage from the usb charger - you could even damage the electronic charger, which might not like the extra volts on its output (depends on how it is designed ;-) )

knut_ny: thats 24V in your picture.. Go for 8.2v .. 8.4V

I know, It's just a Example.

alnath: no, you can't . You won't get the needed voltage from the usb charger - you could even damage the electronic charger, which might not like the extra volts on its output (depends on how it is designed ;-) )

How I can make it Work in that case without damage it? :C

MegaCorsair: How I can make it Work in that case without damage it? :C

you can't ! I can't see how you could charge 2x18650 in series with a 18650 usb charger