Fuse on battery keeps blowing

Hello everyone, So I have a 12v battery from tetrix which also has a 20 amp fuse on the wire. I am using 2 mdd10a motor drivers made by cytron techologies. I am making a robot for a class which uses 4 DC motors and is controlled by an arduino UNO and an r/c reciever/controller, I got everything working and put it on the robot and was driving it around for like 20-30 min with no problems. However, I am now having a problem with the fuse blowing on the robot every time I turn it on. It is strange to me because the fuse blows before I try to use the motors at all. As soon as the battery is turned on the fuse blows. It seems like the problem would be a short circuit somewhere but I have scoured the robot and can't see anywhere that has exposed wires touching. Do you guys have any other ideas as to why this is happening?

I have scoured the robot and can't see anywhere that has exposed wires touching

I'd say you need to go through the wiring with an ohm meter.

Maybe also post a schematic of your circuit, although if it was working it's probably not inherently incorrect. And even some photos?- perhaps someone can see something you can't.

alright when I go to class tomorrow I think I will take some pictures (although it is somewhat messy) and I will draw a circuit diagram. How would I go about checking everything with the ohm meter?

But your key diagnostic process imo, is to go through it with an ohm meter, looking for continuity where there ought not to be any.

If a 20 Amp fuse is blowing... that's a serious short circuit. Does the fuse blow with no robot connected?

Do you mean with the battery unplugged from anything? Because if so I was running low on fuses so I didn't try that

Yep with it unpowered

What could have happened to the battery that would cause the fuse to blow even with it unplugged?

Do you mean with the battery unplugged from anything? Because if so I was running low on fuses so I didn’t try that

If running low on fuses… turning on the battery source with no load connected would be good to try. Would expect fuse not to blow. And then can focus on the robot side after that.

Large capacitor has short circuited or a motor flyback diode has shortened or your h-bridge has failed and is trying to drive both forward and reverse circuits at the same time.

Hi, Can you post a picture of your project so we can see your layout, plugs, ESC etc.

Thanks.. Tom... :)

So i have discovered something internally is wrong with one of my motor drivers. I can use the other one fine but as soon as I attach the second it blows the fuse. I have been testing and using the motors for a few days but not with a lot of continuous use. Do you think the product is defective possibly or would it have been something I did? Because the other one is still fine.

Hi, Can you post links to data for your driver and your motors, as well as circuit diagram?

Thanks.. Tom... :)

Ok here are links to the parts
Motor drivers- http://www.robotshop.com/media/files/pdf/user-manual-mdd10a.pdf

Motors- http://www.tetrixrobotics.com/Motors/TETRIX_DC_Gear_Motor


The hand-drawn circuit appears ok to me. I would first disconnect the circuit entirely from the battery. Then use your multimeter (in DC volts setting) to measure battery voltage..... to ensure the voltage is the expected ballpark area.

Then disconnect all motors from the drivers. And measure the resistance of the coils of each motor....to make sure everything is ok.

Make sure actual wiring is all correct.

Connect the positive terminal of a relatively large electrolytic capacitor to the +ve supply rail of arduino, to ensure it has fairly clean supply voltage.