Check your Anderson battery connectors

The students are still recovering from the regional, so just in case anyone else is experiencing power lost on defenses or robot to robot impact, I know there are posts out there already to check your radio and roborio, but just to share our findings and avoid someone else figuring this out the hard way.

sadly, it took the entire regional to get to the root cause, which really frustrated the team…

Anyway, if you are experiencing power lost and reboot on impact, after checking the radio power and roborio, give your Anderson battery connect some twisting and pulling. we were able to reliably cause a reset when we did this. we are still trying to figure out exactly what is wrong with the connector (weak spring? wear and tear? too much cable movement?) but what we did find is that just within the 10 or so connectors we had with us at the regional, there were at least 3 lug designs and possibly 2 housing designs (not sure if it was a tolerance thing or a design change). we’ll be contacting Anderson to get more information, but one thing that comes to mind is weather they are backwards compatible. These connectors all came the way assembled and were never taken apart till the issue was found. I’m also not sure whether andymark assembles these or if they came assembled with cable from Anderson, so will try to up date this as we figure out more details.

There are two terminal part numbers, a “low detent” and a “high detent” one. Last year, all the pink battery cable assemblies in the Kit of Parts came with high detent terminals. If two of those got connected together, disconnecting them was ridiculously difficult. But all terminals are compatible, and unless one is bent or otherwise damaged they should not cause problems.

The spring strip inside the connector housing is potentially an issue. If the terminal is not snapped securely in place against the spring, there can be a poor electrical connection that is susceptible to vibration or impact.

I have observed numerous cases where a team wanted to blame the Anderson connector for intermittent power but eventually discovered that the true culprit was a loose bolt on the battery terminal.

Thanks for the information Alan, I’ll say that it was the last thing we considered checking. We even started pounding on the robot with a rubber mallet and dropping the robot from 6 inches off the ground to replicate the problem. loose battery connection was actually common with my all girls team (they don’t tend to have the hand/arm strength to get it really tight. so it was the first thing we checked. but we were literally able to poke with a finger on the red wire right outside the Anderson housing on the robot side and see the robot reset. We also confirmed that the connector was fully snapped into the detent. like I said, the goal is to get the information out there, not necessarily placing blame as there could be many reasons that failed. but it was hard to troubleshoot so would like people to be aware that it is a potential thing to check.

we have had problems before as well when the battery cable bolts where not properly attached to the PDP (no washers or not tight enough) although this is a very easy fix it was tricky to spot without knowing where to look

I’ve been amusing myself going through some old batteries, load testing and checking resistance with a Battery Beak. Newer batteries had 0.018 ohm resistance. There were several marked “Practice Only” with 0.030 ohms resistance that dropped down to 0.018 ohm once I swapped out the battery cable and cleaned up the mating surfaces of the terminals with a wire brush.

548 had battery Anderson issues in one of our elims matches at Southfield. In our case, one of the battery-side pins partially slid out of the housing. This is the first time we have experienced this issue as far as I know. If you have sharp turns in your leads right next to the connector (you shouldn’t) make sure the wires do not pull out of the housing.

This is some great advice. I was the FTAA at the NYC regional last weekend and whenever a robot would lose communication with the field, the FTAs and I would wiggle-test as much of the power pathway as we could trying to find something loose. I can recall a few situations where robots had either loose Anderson connectors or loose connections between the battery and the wires. We were able to reliably cause reboots by wiggling the cables around, which is what happened during the match when the robot hit a defense.

We’ve had similar problems at each of the bolt connections (main breaker, battery, and PDP), but never at the Andersons. About two-thirds of our connections are factory, and the other third are hand made in house, but tested after crimp and install. A properly crimped and seated Anderson connection (whether the battery or power pole style) will actually make better connection when stressed almost up to the point that it separates.

We also had a power outage after the jumping the rock wall. Upon inspection, the pink Anderson connector we had installed on the robot did not have the terminal fully captivated by the spring clip and slipped back. We have no idea if it was due to original assembly or being stressed.

The way the anderson connectors work, it was almost certainly an incorrectly installed crimp in the connector housing. I have been using the SB50 connectors for years now in situations much more stressful than FRC and I have never seen or heard of a crimp coming out of the connector housing once properly installed. The one failure mode I have seen that was not entirely user error is the wires breaking where they go into the connector from fatigue. To combat this is pretty simple. Bolt the robot side of the connector to something in the robot that doesn’t move like the frame. (there are already holes for 6-32 screws in the connector housing just for this)

Yup that was us, luckily Mark (The FTA spotted it during our first match on practice day) after that we had 2 rio reboots which ended up being a battery cable hitting the red button on the breaker.

Pre match wiggle your alliance partners cables around JUST DO IT. If they tell you they lost comms one match do it more. If they blame it on a field fault but, there was not a replay it was not a field fault it was them. On Sunday I started doing it, and it did make a difference. There was one particular alliance partner who wouldn’t let me do it saying I wasn’t qualified because our alliance was seeded low and ironically enough they lost comms that match TWICE.

More than 9/10 times it is a loose connection at the other end of the battery cable wire…either the terminal on the battery is loose, or the terminal on the power wiring at the 120a breaker or the PDP is loose. (and in the old days, it would be one on the complicated distribution terminal blocks).

A RI caught a slightly loose breaker connection on our robot in the pre-Elims reinspection…thanks!

What seemed to be the problem for us (which we found out before our third last match) is that the cause for our radio to reboot was the webcam. I was told by another team WPILib’s webcam support was the problem, and oddly enough turning off our webcam seemed to fix everything. We played like madmen during the last 3 matches and not a single “no robot communication” came up. Just to throw that out there is the leads weren’t the problem.

We saw two different issues. We have one Anderson sb50 which is “loose” with one connector but not others. Not sure why yet, i need to investigate at next chance. We also had an alliance mate whose breaker bolts were less than finger tight.

I think everyone is discovering how good their wiring is this year.


I’ve watched about 130 matches from the side of the field this year. None of them were replayed due to communications-related field faults.

Nothing is certain, but so far in 2016 robot communication problems => problem is on robot.

Things I’ve seen that cause “communication issues”:

  • loose wires at breaker
  • loose wires at battery terminals
  • radio barrel connector came out
  • radio wire at robot came loose
  • tinned wire on radio connector at robot broke off
  • forgot to reconnect Ethernet cable
  • something bumped the red button on the circuit breaker
  • loose fuses in PDP

Things I haven’t seen:

  • dodgy Anderson connector (others have seen this)
  • loose wires at PDP

So I found this… from here

We have been using both pink and red ones, any chance this is a problem? or are the pink ones specific to FRC and the below does not apply?

SB Powerpoles are Color Keyed
A unique feature of the SB Series Powerpole housings are that they are keyed to only mate with the same color housing. For example, a gray color will only connect with the same gray color SB housing. The Red color will only connect to a red colored connector, etc. The exception for SB50 is the black housing which also mates with the gray housing.

This feature can be used to color code different voltages or systems and prevent accidental connection.

Read more:

The pink sb50’s we have been using are really red sb50’s. From what I hear Anderson had too much pink plastic and donated pink versions of their red power poles to First.

So you are telling me that it’s really lightish-red?

Yup. The blue box under R36 says that the pink connectors from the KOP can mate with the red connectors.

How were you using the webcam in conjunction with WPILib?
We had one, and then two webcams, but we were just streaming them through the router, not doing anything with WPILib.
Martin Haeberli
(de-)mentor, FRC 3045 Gear Gremlins (formerly SWAT)