Battery Leads Coming Loose

[bbuncher12]

To connect our batteries to the battery leads, we use a small bolt and locknut and torque them down to make sure that the battery leads do not come lose, then we cover the lead and connection to the battery in heat shrink tubing. However, we have been having issues with the leads becoming loose and flopping around because the bolts are not holding well. What methods do you use to keep the battery leads attached to the battery, and do you try to avoid this problem? Thanks!

[lpickett]

Battery leads will eventually loosen with the constant vibrations of playing the game. We do not use heat shrink so we can retighten the connections. You just need to have a system to check these on a periodic time frame. Just use black and red electrical tape to cover the terminal and bolts to protect from accidental sparking. You can also use nylock nuts. These are the ones with the plastic lining inside that grips and stays tight longer. The heat shring should only be used on the ends of your wire and lug terminal. We solder our connectors and crimp to ensure a good connection, then we use black and red heat shrink found at the local automotive supply store to cover the connection and make for a neater looking cable.

[adciv]

We usually use Crimp-on lugs. You need to have a decent crimper due to the force required. Typically we've noticed two reasons for leads coming loose. The first is the leads were not tightened enough. The second is people picking up batteries by the leads rather than the body.

[bbuncher12]

@lpickett: Good to know we aren't the only ones, we'll try out using electrical tape and soldering them, thank you!

@adciv: Yeah, we've had a lot of trouble with people picking them up by the leads, they just don't pay attention Are you suggesting crimping the leads directly to the terminals, or something else?

[Dad1279]

Originally Posted by bbuncher12

@lpickett: Good to know we aren't the only ones, we'll try out using electrical tape and soldering them, thank you!

@adciv: Yeah, we've had a lot of trouble with people picking them up by the leads, they just don't pay attention Are you suggesting crimping the leads directly to the terminals, or something else?

We crimp/solder the leads to lugs.

Every team member/parent/mentor needs to know NEVER pick up the batteries by the cables. Rule #2 right behind wearing safety glasses.

[jee7s]

FRC 2789 crimps leads as well. We've found that Home Depot carries the Thomas and Betts line of compression lugs, and they work very well. If you do crimp, don't fall for any "heavy duty" language on the packaging...that usually just means a thicker wall on the lug and hence bad compression.

To crimp, we use McMaster# 7061K12 plus an arbor press (no, we don't hit it with a hammer to compress like the instructions suggest). If you go this route, make sure you crimp into and out of the face of the lug. Going sideways means you don't get the right geometry since you aren't pressing into the split part of the lug.

After crimping, we could solder, but we find it isn't necessary. We do heat shrink over the shank of the lug, but not over the whole connection.

To attach to the battery, we use a nut-bolt combination (McMaster# 91241A773 and 96278A411) that includes a spring-type lock washer and a toothed washer (both are captive so nothing gets lost). AND NO OTHER WASHERS! Extra washers on battery terminals may feel like a good thing to do, but in the end they just provide extra surfaces for slip to occur at, and that causes all sorts of bad news when vibration starts.

We've had a great deal of success with this, when the fastening is done correctly.

Also, if you get that crimp tool and some 6AWG wire (preferably welding cable style), then you can purchase the un-assembled APP disconnect from Andy Mark and make your own battery cables. Our BOM cost on these is about $6.75, which is less than half the cost of the pre-assembled cable. This also means you get just the right lengths for the run from the robot side of the disconnect to the main breaker and PDB. VERY CONVENIENT! (Particularly when done with welding cable)

[Jon Stratis]

We crimp and solder our leads into the compression lugs. After that, we attach with a lock nut, bolt, and star washer to help prevent twisting. Cover the whole thing with heat shrink.

In our 7 years, we've only had a couple of batteries come loose (we check them a few times each year - at kick off, before each competition, and before our fall program starts)... when that does happen, we take off the heat shrink and check all the hardware. If anything isn't working like it should, it gets replaced and we get everything tight and reapply heat shrink.

It's also extremely important NOT to pick up the battery by the leads! This can cause internal damage to the battery that will stop it from working properly, and kill the battery! This isn't something that should be "people not paying attention"... this should be pounded into everyone's heads so much that if anyone even sees someone else do it warning bells go off.

[fb39ca4]

If you have a good soldering iron, I recommend soldering them.

[bbuncher12]

Thank you all so much, we will experiment around with these suggestions! But yeah, it is extremely annoying when people pick up the batteries by the wires, we put up signs, remind people constantly, and have had several announcements about it before meetings, but there's always that one person who forgets or is in a hurry who picks one up by the wires

[James Tonthat]

Originally Posted by jee7s

To crimp, we use McMaster# 7061K12 plus an arbor press (no, we don't hit it with a hammer to compress like the instructions suggest). If you go this route, make sure you crimp into and out of the face of the lug. Going sideways means you don't get the right geometry since you aren't pressing into the split part of the lug.

We use the same crimper and but with a hammer, I don't think we've ever had any issues with the wiring mechanically coming out. We just make sure we're doing the crimping on a solid concrete floor.

These are the type of crimps (McM#7113K249) that we use. We also use #4 AWG wiring instead of #6. It's a highly stranded car audio wiring that we use. Something very similar to this Stinger Pro Translucent Red

Andy has pretty good pricing on the SB50 connector and terminals but we buy ours through Powerwerx along with our other APP products. (Warning: the other colors have different connector geometries so only buy red.) We use to use this crimper for the SB50 connectors but I'm not sure if we do it any more. I'll have to check in with our electronics students.

[Mike Marandola]

We crimp our leads. Like some others have said, with the heavy vibrations and the constant swapping of the batteries, a lead is bound to come loose eventually. To prevent this we have a checkout sheet that our pit manager fills out before every match. On this sheet there is a checkbox for making sure the battery connections are tight. So I would say the best way to make sure your connections don't loosen during a match is to check them before you head to queue.

[apb2390]

Adding another $0.02 here, we tend to use either screw terminal lugs or hard crimps. I crimp using a square end punch and a hammer, or a phillips screwdriver in a pinch.

Well-crimped leads don't come loose. I've tested this by hanging a 6-inch length of 6-gauge wire with crimped lugs on the pyramid and hanging 130 lbs (myself) on it. Sat there for about 3 minutes, nothing came loose. Hung some additional weight (somewhere around 220 lbs) on it, still no sign of breakage.

[Tristan Lall]

• Use good quality finely stranded wire. (I like welding cable. Car stereo cable is fine if insulation durability isn't a huge concern.)
• Use the right terminals for the wire. (I like to use the solid copper, tin-plated crimp sleeve terminals designed specifically for the wire gauge, with a #10 screw hole.¹)
• Use a a high-quality crimping tool. (Last time I bought one of those, it was less than $40 CAD. $65 is the best price I could find today; they're often well over $200 now. Consider the style Home Depot currently sells, but be aware the results may not be satisfactory due to the differently-sized crimping dies.)
• The barrel of the terminal can usually accommodate two crimps with the tool. The whole process is completed within about two minutes (once you get used to stripping fine-stranded wire with a utility knife, without nicking the conductors too badly), and I've never had one fail.
• The same procedure applies to Anderson SB50 and SB120 terminals; use the sleeve-type (not stamped) ones, and crimp once.

¹ FIRST has often supplied ones with a Ø0.25 in screw hole. These don't fit the provided battery screws nicely.

[Tom Line]

Something we've found that helps immensely is to bend the two leads so they are pointing toward eachother. Where the leads cross, we zip tie them together with a huge ziptie. Then we zip tie them above that so they are in a single lead.

We used to put a hole in 'handle' piece of the battery to zip tie the wires, but we've been told that any modification of the battery is illegal, so we don't do that any more.

Here's a sketch.

[Jon Stratis]

Originally Posted by Tom Line

We used to put a hole in 'handle' piece of the battery to zip tie the wires, but we've been told that any modification of the battery is illegal, so we don't do that any more.

Yes, that is illegal, and a huge safety concern. What happens if your drill goes a little too far when making that hole? You drive right into the battery, causing damage and a potentially dangerous situation (battery could internally short and catch on fire/explode, it could leak/spray battery acid, etc) For the sake of everyone's safety, there is a blanket safety rule against any modification of the battery beyond attaching the leads with appropriate fasteners.