connect the arduino with batteries and control it with bluetooth

I'm making a car controlled by bluetooth and when I connect it to a USB it works but when I connect it to batteries the bluetooth doesnt work. why?

You have not provided any useful information with which to help you.

You have not even told us what battery you are using.

...R

I'm using arduino uno r3 and I want to connect to it 2 18650 batteries

Where are the batteries connected? Where are the motors and bluetooth module connected? What is driving the motors and what motors are they? A circuit diagram would be useful.

Steve

yoelku:
I'm using arduino uno r3 and I want to connect to it 2 18650 batteries

I thought you said you had already connected it to the batteries?

Make a pencil drawing showing how you have everything connected and post a photo of the drawing.

Post the program you are using.

...R

What pins does the BT use

I connect on the arduino anathor board called sensor shield and it has places to input vcc and gnd and there i connected the batteries and the bluetooth is connected: the tx to the rx in arduino and the rx to the tx in the arduino

yoelku:
I connect on the arduino anathor board called sensor shield and it has places to input vcc and gnd and there i connected the batteries and the bluetooth is connected: the tx to the rx in arduino and the rx to the tx in the arduino

What part of Reply #4 is hard to understand?

If you have any additional hardware post links to the relevant datasheets

Help us to help you.

…R

What battery
What car
What shield
What is so hard about giving details