Suggestion on What to use on battery Terminals
 

Hello Chief Delphi community

I wanted to ask, what does everyone use to protect the terminals on the battery, do some use electrical tape or shrink wrap? What do you, ladies and gentleman use on your battery terminal to protect or cover them?

Re: Suggestion on What to use on battery Terminals
 

Terminals on the batteries need to be checked often to make sure that they are tight. That is why we use electrical tape instead of shrink wrap.

Re: Suggestion on What to use on battery Terminals
 

For our battery terminals, we use locking nuts to help ensure they won't come loose, and some heat shrink. These get checked multiple times per season (beginning of the season and before every competition) to make sure they haven't come loose. If any do (we've only had a couple that have over the past 6 years), we cut away the heat shrink and completely redo the connection (with new heat shrink as well!).

Our feeling is that heat shrink is slightly safer, as it's harder to accidentally remove than electrical tape. That said, there's nothing wrong with using electrical tape, so long as you ensure everything is covered and make sure the tape doesn't start pulling up!

Re: Suggestion on What to use on battery Terminals
 

Before using heatshrink we assemble the terminals in a special way. The use of an external tooth star washer between the terminals and the addition of locking hardware will insure that the termination will never come loose. If the terminals cannot move, the hardware (even locking hardware) will not come loose. I am a big fan of keps nuts (lock washer is integrated in the nut) and battery terminals are only one place they are useful. They are available from McMaster.

Re: Suggestion on What to use on battery Terminals
 

Doesn't that have a negative effect on the electrical impedance of the connection? Do you use any special alloy for the hardware to minimize any potential effects?

Re: Suggestion on What to use on battery Terminals
 

PAR - The nut and bolt aren't involved all that much in the electrical pathway. The electricity will primarily flow from the battery terminal through the lug terminal on the end of the battery connector. This is due largely to the large surface area connection between the two, which makes it a much, much more efficient conductor than going "out of your way" to travel from the battery terminal, through the head of the bolt, down the bolt, into the nut, and finally into the terminal on the end of the battery connector.

True, any time you have conductive materials attached together, all of the materials involved will conduct some electricity. But in this case, it's not enough to make it noticeable. Essentially, you have a current divider circuit, with the two sides of the circuit having significantly different resistances. Play around with that, and see how changing each side of the circuit can change the overall current through the circuit.

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

Is their a specific size of heat shrink that has to be used?

Re: Suggestion on What to use on battery Terminals
 

Jesus,
It depends on the size of the terminal you are trying to insulate. It will likely be somewhere between 1/2" and 1".

Re: Suggestion on What to use on battery Terminals
 

If you look at the specs for heat shrink, it'll specify an inside diameter both before and after shrinking. You'll want to get some that is big enough to fit over everything, including the nut and bolt, but that will shrink down to a snug fit without splitting. I've seen students use the wrong heat shrink a few times... it looks good, then they put the heat gun on it, and it splits because it tries to shrink too small for the wire it's around!

Re: Suggestion on What to use on battery Terminals
 

Thank you Mr. Al Skierkiewicz for the advice and suggestion

Thanks again Chief Delphi Community for the advice and input, it greatly appreciated, as i have so much to learn

Re: Suggestion on What to use on battery Terminals
 

Thanks Jon Stratis, i will keep that in mind so that it won't happen and end up ripping it

Re: Suggestion on What to use on battery Terminals
 

Another couple factors to consider to prevent the nototrious heatshrink split:

1. Buy good heatshrink. The ES200 line from Tyco (http://www.strancoproducts.com/downl...ta%20Sheet.pdf) has an amazing 4:1 shrink ratio and is pretty rock solid

2. When cutting the HS from a longer length, make sure the cut is straight and contiguous. Any aberration along the cut will likely cause a tear. This commonly happens when cutting a larger diameter HS with a pair of side cutters, where you can't cut across the width with one full cut. We typically use a pair of stout scissors or, odd as it sounds, a heavy duty paper cutter (good for getting precise lengths).

Re: Suggestion on What to use on battery Terminals
 

This is a quote of an earlier post, but no matter. If you'd need to check your terminals and want to use shrink wrap, I'd suggest clear shrink wrap. I don't have much experience with wiring a robot, but I know that using electrical tape is unreliable because it's not exactly the stickiest tape on the market...
I use it all the time and reccomend it to you! :)

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

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

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

Three words: Giant heat shrink.

Re: Suggestion on What to use on battery Terminals
 

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!

Re: Suggestion on What to use on battery Terminals
 

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.

Re: Suggestion on What to use on battery Terminals
 

Thank you, that makes a lot of sense.