Charging cell fone with 4s 18650 pack

[PfloydBham]

I am something of a novice so can I get some advice? I built a plastic ammo box battery with 18650 cells from modems as a 4s configuration which charges to 16.8 volts. I put a small socket in the lid which has two USB charge ports and a small volt meter as well as a cigarette lighter socket and an on/off switch. I intend to power led lights that run in 10 to 30 volt range so the 16.8 volts is workable with them. But, I really do not know much about how the chinese USB ports are regulated. Is it likely that I can plug a fone or tablet into the USB safely, or will the voltage be too high? Any thoughts would be appreciated, thanks.
Pink Floyd

 

[snoobler]

You need 5V for the USB ports. Most 12V to 5V converters should work.

I use this one to convert my 5th wheel's 13.8V to 5V to power a Blink camera wifi module:

Amazon.com

 

[PfloydBham]

Thanks, very helpful. I followed the link and learned a lot about available products. I guess I need to just test the output of my particular USB ports. If they are around 6 volts instead of 5 v. If so, I probably need to use a small buck converter between the battery pack and this particular fixture. I noticed amazon has several small boards like the one you use that can be attached to the inside of the can for any future battery boxes. This is my first little project from scratch and it has really been cool to make something like this that actually works. I can't believe how much I don't know and it is basically impossible to talk to somebody locally. Thanks
Pink