[Hugh Meyer]

WinDnDustT,

I would highly recommend the west mountain CBA tester. It gives a good solid indication of the state of the battery under test. We purchased one several years ago and it has given us data that takes the guess work out of knowing the state of the battery.

We test our batteries at least once per year during build season, so we have fresh data on our complete inventory before competitions start. I compare the results to previous years to decide if a battery will be used for competition. By looking at the discharge curves as they change from year to year we can tell when a battery is nearing end of life. Bad batteries go to the recycler and marginal batteries are marked “Not for Competition”. Only good ones are used for competition.

Throughout each event we log the state of charge before the match using the battery beak tester. Attached is a copy of what we do. I have several years of log data and so far have not found the internal resistance to be much of an indicator of anything useful.

Since we got the battery beak the first year it came out we have not had a battery fail in a significant way. We do have some that are getting higher than normal. I have been told by the people that make the battery beak that an internal resistance in the range of .035 is a trashed battery. Haven’t seen that yet, but we have some getting up to .028. In an odd sort of way I am hoping to see a failure this season just so I can see what the internal resistance is when they fail. Most of our batteries measure in the range 0.015 - 0.025. These batteries perform fine.

One thing that is important, but not mentioned so far in this thread is the state of your connections. In our FRC world by far a much more significant issue is the connections that people make. It is extremely important that you make good tight clean solid connections throughout the circuit. When you test a battery your measurement is only as good as your weakest connection. Since you are not a rookie team I assume you know this but I wanted to mention it just to be sure others reading understand the importance of good connections.

Attachment 1 is our log template that we complete at competitions.

Attachment 2 is our inventory data sheet that shows battery history. You can see when we got our beak tester where that data starts to populate.

Attachment 3 is a log sheet completed.

Seeing a team go dead in a match because of a dead battery is really sad. More than once I have heard a team declare they unintentionally went out with a dead battery. ALWAYS know the state of your batteries!! The beak tester and CBA tester are great tools!

-Hugh