diff --git a/640.md b/640.md
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--- a/640.md
+++ b/640.md
@@ -169,6 +169,13 @@ Motors are connected to each individual motor connector on the board. You should
 ![640 motors](/images/motors640.png) 
 
 ## Connecting the power
+
+The power supply for your motors is connected to the connector on the far right of the board. The 640 board can take between 2V and 11V for the motor power supply. It motor power supply is kept apart from the Raspberry Pi supply so that any voltage drop caused by the motors doesn't damage your Raspberry Pi or cause it to reboot.
+
+There is a polarity protection mosfet on the 640 board to protect the motor drivers, so if you find that your motors aren't moving, then check that you have the battery connected the right way around.
+
+![640 battery](/images/battery640.png) 
+
 ## Connecting your RC receiver 
 
 # Programming the 640
diff --git a/images/battery640.png b/images/battery640.png
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Binary files /dev/null and b/images/battery640.png differ