Our team has experienced our battery cables coming loose at the ends that are screwed to the actual battery from teammates forgetting to not carry the battery by the wires and being pulled on when removing the battery from the robot. Are there any solutions to relieving stress on these battery cables? What are the best nut/washer combinations to screw the cables to the battery. Which is better, heat shrink or liquid electrical tape?
The #1 thing you can do right now is to make sure they don’t pull on the battery by the wires. I hate to just say “Just don’t do that”, but… don’t do that. Other than that, 900 put together a pretty comprehensive battery guide that answers your questions.
Don’t carry the battery by the wires. Ever.
Seriously, if it’s a recurring problem that people are carrying the battery by the wires all the time, that’s a safety hazard for both your team and the battery itself. That should be drilled in as something never to do under any circumstance. No one wants a dropped 12+ lb battery on their foot. Any solution you could get here won’t eliminate the stress you put on your batteries.
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Applying stress on the battery terminals can crack the seals around the terminals and allow the battery acid to leak out. It can also break the connection between the terminal and the plates inside, leaving your robot dead on the field.
You can try telling your team members that if other teams see them picking up the batteries by the cables, the team may get put on the DNP list (Do Not Pick) because no one wants an unreliable robot.
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At some point loose terminals won’t matter because the bolt will pull through the connection tab. It happened to 3674 in Galileo Finals 3. The take away from this is to never move your battery by the wires, however sometimes terminals do get loose due to vibrations and unintentional strain put upon the terminals. Knowing that, 1817 checks each and every battery before it goes into the bot and if it wiggles at all it is taken out of the rotation until it can be tightened back down.
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#1 Carrying batteries by the cables will break the connection internally in the battery no matter what you do. Just don’t
#2 900’s paper is great. Even if you don’t go to the heavier cables Nord-locks are the bomb.
#3 even with the Nord-locks we have our battery specialist (yes that is an important job) untape and check connections on a regular basis during competitions.
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We’ve always had a strict rule of no carrying batteries by the wires, however that season was because of poor battery placement in the robot. Each time we replaced the battery we had to pull the wires across the robot to connect them. The result was the terminal on one of our batteries snapped straight off in the finals of our division.
We now check our terminals before/during each event, and try to put a little more emphasis on good battery placement within the robot.
I would say that y’all need one person whose (sole?) job at competitions is to make sure the batteries are properly handled. (And in the shop as well.) This includes being the person to set up the batteries and terminals, the person to charge the batteries, the person to put the batteries in the robot…
Anybody else doing any of those jobs gets trained by the Battery Person. Anybody doing any of those jobs WRONG… er, I leave the results of that sort of action to the Battery Person’s imagination, and hopefully said culprit isn’t permanently harmed by said Battery Person (or minions of same).
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I would agree to stress to not carry the batery by the cable. It losens the bolts and nuts / screws that hold it together and also put alot of un nessicary strain on the battery terminals and crimps/soldered on things
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If the kids won’t listen to the safety argument, hit them with the winning argument.
No elite teams mess around with batteries. They put serious care into them as they’ve learned that being lax or sloppy with batteries loses matches.
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If the kids won’t listen to the winning argument, hit them with the pizza argument.
One battery killed by stupidity costs $40-50 to replace. That is 4-10 pizzas, depending on your preferred supplier. I’d rather eat pizza.
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Its been said, but don’t carry the battery by the wires, and make sure that anyone that does handle batteries knows that.
We always use nuts and screws and wrap it with a ton of electrical tape. That seems to work (make sure the you tighten them as much as possible).
As many have said, just don’t carry or even lift them by the wires. Make sure all the team members know about the “handles” built in to the top of the batteries between the terminals. There is enough room to get fingers on one side and your thumb on the other side of the battery. Teach team members to lift by these rather than the wires. (Note, this battery was selected for this image by color/visibllity of the handle; I have never purchased this brand.)
The simplest method of insuring that the battery terminals stay put is to add a single #10 external tooth lock washer between the battery terminal and the wire terminal. This simple addition prevents the two terminals from rotating and causing the locking hardware to loosen. The lock washer also breaks through the surface crud on the two terminals.
All batteries of this size are manufactured with posts inside the battery so that optional terminals may be added as needed. At manufacture, the external terminal is added, soldered in place and then the red or black epoxy is added. By picking up the battery by the wires, the internal connection between the battery post and the external terminal will break. This will lead to excessive voltage drop internal to the battery, and that leads to brownout. Eventually, the battery will fail to provide current even though it may measure a full 12 volts when checked with a voltmeter out of the robot. Generally there is no warning to this failure as others have reported.
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Ebay webbing works fine for a handle that you can use if your team tends to run a flat orientation and can’t get to the normal handle.
On-brand Panduit edge clips per 33’s recommendation, I haven’t found anything cheaper.
Yes, those are nordlocks with nylon nuts (900’s recommendation).
Make sure both the bolt head and nut turn while you’re tightening, in order to get the nordlocks fully mated.
Not shown: lightly sanded both the contact & terminal with 200-grit and wiped with IPA afterward to remove oxide & grime before installation
If I was going to skip one thing in our setup, I’d skip the Nord locks - they take the removal effort from “Trustworthy, Firm, and Sufficient” with just the nylock up to “Bring Me Thor’s Hammer” if you get them installed correctly.
(Of course, you can also read that comment as a ringing endorsement of Nord Locks if you prefer…)
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