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Step 19Add batteries and safety features
The next step is to add the lead acid batteries. You'll need to mount the batteries in some fashion. I welded some angle iron to the frame to create a battery tray, but a wooden platform would work just as well. Secure the batteries with some sort of strap. I used bungee cords.
Wire all of the battery connections with 14 gauge wire. Since I'm running my motors at 12 V (and the relays are only rated to 12 V) I wired my batteries in parallel. This is also necessary since I'm under-volting my 24 V motors; a single battery cannot put out enough current to spin both motors.
Safety Features
Since we're dealing with high current batteries and a large robot, some safety features need to be implemented. First, a fuse should be added between the +12 V terminal battery and the relays. A fuse will protect you and the batteries in the event that the motors attempt to draw too much current. A 30 amp fuse should be sufficient. An easy way to add a fuse is to buy an inline fuse socket. The batteries I used (salvaged from an imitation Segway donated to the CMU Robotics Club) came with an inline fuse socket, which I reused on my robot.
Emergency Stop This is, perhaps, the most important component of the robot. A robot this large and powerful is capable of inflicting some serious damage should it get out of control. To create an emergency stop, add a high current on/off switch in series with the wire coming of off the +12 V terminal in between the fuse and the relays. With this switch in place, you can immediately cut power to the motors if the robot gets out of control. Mount it on the robot in a position where you can easily turn it off with one hand - you should mount it on something attached to the frame that rises at least 1 foot above the top of the robot's legs. You should not, under any circumstances, run your robot without an emergency stop installed.
Wire all of the battery connections with 14 gauge wire. Since I'm running my motors at 12 V (and the relays are only rated to 12 V) I wired my batteries in parallel. This is also necessary since I'm under-volting my 24 V motors; a single battery cannot put out enough current to spin both motors.
Safety Features
Since we're dealing with high current batteries and a large robot, some safety features need to be implemented. First, a fuse should be added between the +12 V terminal battery and the relays. A fuse will protect you and the batteries in the event that the motors attempt to draw too much current. A 30 amp fuse should be sufficient. An easy way to add a fuse is to buy an inline fuse socket. The batteries I used (salvaged from an imitation Segway donated to the CMU Robotics Club) came with an inline fuse socket, which I reused on my robot.
Emergency Stop This is, perhaps, the most important component of the robot. A robot this large and powerful is capable of inflicting some serious damage should it get out of control. To create an emergency stop, add a high current on/off switch in series with the wire coming of off the +12 V terminal in between the fuse and the relays. With this switch in place, you can immediately cut power to the motors if the robot gets out of control. Mount it on the robot in a position where you can easily turn it off with one hand - you should mount it on something attached to the frame that rises at least 1 foot above the top of the robot's legs. You should not, under any circumstances, run your robot without an emergency stop installed.
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