Suggestion on What to use on battery Terminals

[Nate Laverdure]

The above are great suggestions for engineering solutions to mitigate the terminal-loosening problem. You might also want to employ some non-engineering solutions:

• Train personnel to pick up batteries two-handed, by the body of the battery, rather than by the cables. Carrying batteries by their leads will wrench the terminals loose and may also damage the more-delicate internal connections within the battery.
• Go through your team's stock of batteries and align all the leads in the same direction. Adapt charging racks and old robots to the new standard orientation. This will discourage heat-of-the-moment efforts to reorient the battery cables when connecting batteries. It may also lead you to consider the cable orientation more closely when designing battery holders on future robots.

[jwallace15]

Originally Posted by Jon Stratis

Trust me, when the terminals aren't tight, you can tell. Just grab the wire near the terminal and wiggle it - if it's tight, it won't move. In this case, IndySam was indicating electrical tape due to the ease at which it could be removed after a terminal was identified as loose, in order to tighten the nut/bolt, and then reapplied.

Ok. I understand what you (and IndySam) mean. However, I still wouldn't rely on the stickiness of electrical tape. Perhaps putting duct tape over the electrical tape?
Also, I don't use shrink wrap when securing power connections. I don't need to because the wiring I do conveniently goes into terminals. I don't use this on a robot either; my wiring remains stationary. I only use shrink wrap for wrapping wires when I solder two different wires together.

For a battery terminal? I agree that convenient access is important. But if you choose to go the role of electrical tape, I'd suggest securing the electrical tape with duct tape or something similar.

[Al Skierkiewicz]

James,
I recommend against duct tape because frequently the gray/silver types actually have conducting coatings.
Lifting batteries by the wires is also bad practice from a safety standpoint. The battery is actually designed to take a variety of different terminal types from posts to tapped blocks. As such, each of the terminals merely fit over round pins and solder/molten lead is then poured over the joint. The battery is finished with a colored filler, either black or red. Neither the internal joint nor the colored filler is designed to carry the weight of the battery.
Al

[sanddrag]

Originally Posted by Al Skierkiewicz

James,
I recommend against duct tape.

Yeah, we don't want to follow the path of American Motors in the 1980s (yes, they used duct tape on electrical connections). For those using electrical tape, you need to use the right kind. They are not all created equal. Use only 3M #33+ (black) or #35 (colors). Some folks argue you should not even allow anything else in your shop/inventory.

[rachelholladay]

Three words: Giant heat shrink.

[Jon Stratis]

Originally Posted by jwallace15

Ok. I understand what you (and IndySam) mean. However, I still wouldn't rely on the stickiness of electrical tape. Perhaps putting duct tape over the electrical tape?
Also, I don't use shrink wrap when securing power connections. I don't need to because the wiring I do conveniently goes into terminals. I don't use this on a robot either; my wiring remains stationary. I only use shrink wrap for wrapping wires when I solder two different wires together.

For a battery terminal? I agree that convenient access is important. But if you choose to go the role of electrical tape, I'd suggest securing the electrical tape with duct tape or something similar.

For most crimp terminals (the yellow/blue/red ones with the plastic housing), this is just fine, and it's what we do as well. In those cases, you're attaching the terminal to a Jaguar, Victor, or Spike, and the wiring is protected by 20/30/40A circuit breaker, should a short occur.

However, with the battery terminals, it's a different situation entirely. Even if none of your wire is exposed, the entire terminal is exposed, and it does NOT have any protection from a circuit breaker at that point.

So, if the terminals are exposed, you run a very dangerous risk. The battery can put out hundreds of amps (Al can probably give you a better upper-bound on the batteries than I can, he has more experience!). When surrounded by your typical aluminum robot with students using metal wrenches, pliers, and screw drivers, there is every possibility of shorting out the battery terminals if they aren't completely insulated. The result, in that case, is the terminals welding themselves to whatever shorted them. This is an extremely dangerous situation.

That is why inspectors are extremely cautious and strict when it comes to the battery terminals and the main power routing all the way up to the PD board. If you show up at one of my regionals and your batteries have uncovered terminals that I see, I will literally stand in your pit until you fix them. So please, make sure you completely insulate all connections that are NOT protected by a breaker, at minimum! These are the most dangerous connectors, and also generally the largest and most exposed ones on the robot!

[Al Skierkiewicz]

The battery is capable of 600 amps at full charge. No matter where the battery is or at what stage in wiring it might, one of the terminals should always insulated. Jon's practice at regionals is recommended for all inspectors and teams. I will watch you insulate bare terminals while I carry on inspection or I will do it for you.
600 amps flowing through the internal resistance of the battery (0.011 ohms) works out to nearly 4000 watts. Yes, it is enough to weld a dropped tool (or wire or a necklace, bracelet or watch band) in place across the terminals. The result is a lot of heat, possible flame, escaping gas and acid, ruptured case and in rare cases, explosion.

[PAR_WIG1350]

Originally Posted by Al Skierkiewicz

Alan,
While it might add a slight series resistance, the teeth of the star washer bite through any surface crud and oxidation on the lead battery terminal and when tight produce more contact surface than the terminal. AS the hardware tightens on the normal terminal it deforms and produces a cup shape. The ability to keep the terminals from moving is the distinct improvement here. We have batteries labeled as far back 2006 that we use for practice that have no issues with loose terminals.

Thank you, that makes a lot of sense.