[FTC]: Broken Fuse/Broken (Tetrix) Battery?!?!?!

Chief Delphi,

About a half an hour ago, our team was going to test out the electronics connections (battery pack, on/off switch, samantha, motor controllers, etc). When we flipped the switch to the “on” position, the lights turned on for two seconds, and then died. We kept turning it on, but none of the components (samantha, controllers, etc) worked.

We have wired the red wires together and the black wires together. Previously, this setup worked.

We are now trying to find the cause of this problem and the solution. We have ruled out the power of the battery because the charger says it has full power.

Could this be a fuse? What would the cause be? How do we fix it?


The Charging Champions

Sounds like a blown fuse (if the fuse is blown the charger will show fully charged). The fuse is under the black cover on the battery and is a 20a ATM fuse. EX: http://www.walmart.com/ip/Cooper-Bussman-ATM-20A-Blade-Fuses-5-Count/20971324

If the lights turned on momentarily then shut off, I’d be willing to bet that the main fuse did blow.

There should be an inline fuse holder on the positive lead of the battery. Open that up and take a look at the fuse inside. It’s easily replaceable. You can buy packs of 5 for about $3 on Mcmaster-Carr with the part # 7460K517 or at your local hardware/automotive store for under $10.

Did you turn the power on while the robot was enabled(NXT was sending motor commands?) If the robot was not enabled, check your wiring as there may be a short somewhere along the system, causing the fuse to blow.

Here’s what I’d do to check the electrical system:

  1. Unplug all but the first device in the chain
  2. Power on.
  3. If power does not die, power off and connect the next device in the system.
  4. Repeat 2-3 until your entire system is tested.

If power cuts out after you connect a device, then the problem lies in that device.

One other thing I’d check is your battery connection. The Tamiya battery connectors have given my teams some weird problems if they weren’t seated properly.

Another check is to get a multimeter and check to see if there’s voltage across the battery outputs. If not, blown fuse.

Also, you can use the multimeter to check to see if the + and - on your robot are shorted (i.e., check for a short between the two prongs on the connector that the battery plugs into on your robot). Then you can disconnect things until they’re not. This is another way to find the short without having to keep plugging in the battery and possibly shorting out more fuses.

Multimeters are pretty cheap at RadioShack and similar places.