help with DFRobot 4WD platform batteries overheating

[system]

Hello there,

I assembled a DFRobot 4WD mobile platform together with an Arduino Motor Shield (http://arduino.cc/it/Main/ArduinoMotorShieldR3) as per instructions on the rugcommunity website (http://www.rugcommunity.org/page/dfrobot-4wd-arduino-mobile).

After assembly, the robot works as expected, however, after using it for 2 mins or so, I turn it off and eventually smoke starts to come out it because the batteries are so hot they melt the plastic, this has happened twice now, and in one instance one of the batteries even leaked.
Does anyone know why this can happening, where might have I screw up?

Thanks in Advance,

H

[dc42]

So the batteries get hot when you switch it off. How have you wired the on/off switch? It sounds to me that you are shorting the batteries.

[system]

this is the on/off switch http://i.imgur.com/qLgwa.jpg and its wired to the batteries http://i.imgur.com/vsHwc.jpg, which then together go red to 'vin' and black to 'gnd' on the shield ( http://arduino.cc/en/uploads/Main/MotorShield_R3_Front.jpg.jpg )

[JimboZA]

I think dc's right- when you throw that switch it looks to me like you're shorting red and black together.....

If you need a switch just put it in red line between the battery and the Vin pin.

Jim

[system]

Hi Jim,

Thanks for your reply. Im afraid I dont understand what you mean by putting it in red line between the battery and the Vin pin. could you clarify please?

Cheers,

H

[JimboZA]

If you follow say the red line from the battery as it is, it goes to that join (which I guess is where it goes to Vin?), then goes to the switch. When you throw the switch it joins the red to black, so if you follow the black back out, it goes to the join then to the other side of the battery and you've shorted the battery.

So, take the black lead off the switch, you don't need it. Put the black lead from the battery into the board ground.

Then, undo the connection where you join the two red wires, and put the red from the battery onto the switch. Now you have a red wire from battery to switch, thru the switch and then put the far end of the other red wire from the switch, into Vin.

So now the black goes from battery to ground. The red goes from battery to Vin thru the switch so the switch will make or break the red line now.

[dc42]

You've connected the switch in parallel with the batteries, when it should be in series. Connect them like this:

1. Black wire direct from battery -ve to motor shield (not to switch at all)
2. One red wire from battery +ve to switch centre contact
3. Another red wire from switch outside contact to motor shield

[JimboZA]

..... as shown in the pic switch attached. What you had is shown in pic switch2...