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Battery Testing: Our Team would like to share our downloadable study with your team!

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  • Battery Testing: Our Team would like to share our downloadable study with your team!

    Our team has completed an exhaustive battery testing regiment and we would like to share our experience with your team. Teams accrue batteries over time, but which ones are good for competitions? Newer doesn't always equate to performance.

    To better understand battery performance in a competition environment, students researched and implemented four industry standards of battery test. They then tested sixteen of the team's batteries with three performance benchmarks. The batteries were then ranked from first to worst and a strong correlation was found between not only battery age but the number of charge and discharge cycles a battery goes through. Finally, an engineering report was written so that other FIRST teams would benefit from our findings.

    In the 2014 competition season, our robot had a complete failure during a critical qualifying match while on the field. The team did an in-depth analysis of the failure and the cause was determined to be low battery voltage, which reset the robot’s processor and shut all functions down. This was a surprising finding – as we were using a new battery that was checked before being placed in the robot.

    This finding provided the incentive to pursue the following questions:

    1. How do we really know how our batteries will perform in a competition?

    2. Are there industry standards for battery testing?

    3. Can we perform regimented testing and rank our batteries?

    4. What are the characteristics of the FIRST lead acid batteries and can we better understand how to measure them?

    5. Is there a way to log battery performance while the robot is actually running?

    We answered these challenges in this report, and we hope it can also help you.

    The pdf of the report is attached to this post. A link is also available below:
    Testing and Analysis of FIRST Robotics Batteries.pdf
    http://the-charge.com/uploads/3/3/5/..._batteries.pdf

    Thank you for time.

  • #2
    Re: Battery Testing: Our Team would like to share our downloadable study with your t

    That's an excellent report (based on my 30 years experience in electrical engineering). Nice work!

    A couple of thoughts/questions:

    Would your battery evaluation method have correctly predicted the battery that failed during your 2014 competition?

    My favorite quote from the report is this one: "The findings of the report were both revelatory and elucidating." You might have overshot your audience with that choice of words, though.

    It would have been good to give some justification for giving equal weight all three of your measured battery parameters. That's essentially what you did by basing the overall rankings on the average of their rank for each individual parameter.

    It would have been nice to see a calculation of the total energy provided by the battery during the recorded simulated test run. Accumulating the product of voltage and current would have done the trick. It would have been interesting to see a comparison of the battery capacity vs. the energy used in a typical match. I realize that is out-of-scope for the intended purpose of evaluating battery performance. But a bit of analysis on whether these batteries are a good match for the demands of the FRC contests, that would be interesting as well.

    It would have added a lot of value if there was an appendix with technical specs and design details for the custom logger and the dynamic battery loader.

    Great report, thanks for posting it here.
    FIRST LEGO League Mentor and Referee/Head Referee since 2011.

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    • #3
      Re: Battery Testing: Our Team would like to share our downloadable study with your t

      Dear Tom,

      Thanks for the response.

      I do believe that our analysis would have flagged the battery back in 2014. If you look at our compiled list, several 2014 batteries were rated very poorly, and I'm highly certain that one of them was the culprit.

      As far as equal weighting, that's a fair question. As a first go-round, we thought that this would be satisfactory. Currently, we're tracking our battery performance during competition season, and I believe when we analyze how they did, we can then go back and say whether the weighting was reasonable.

      Calculating the battery energy would have been possible, since we know the instantaneous power consumed via current and voltage at any point in time. A simple integration algorithm would give the power consumed. In fact, we could post process the Excel outputs to get that.

      The students in the electrical team thought that too much emphasis on the battery logger and dynamic loader would shift the focus away from the study, we could always produce another document, or perhaps a "makeable" on building those separately.

      Thanks again for the feedback - the kids worked hard and its great to see that others might benefit from their efforts!

      -RM

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      • #4
        Re: Battery Testing: Our Team would like to share our downloadable study with your t

        Just wanted to update with our abstract:

        Testing and Analysis of FIRST® Robotics Batteries

        FIRST robotics batteries were tested and ranked to determine which batteries would provide maximum power for the robot in a competition. This need was identified by Team 2619, after a failure of the robot during a competition was due to an underperforming (although relatively new) battery. Sixteen batteries were analyzed and systematically ranked from first to worst using industry standards, so the team would know which batteries would perform the best during the competition season. Many veteran FIRST robotic teams gain a collection of batteries over time and it is often problematic to choose the best batteries to take to a competition. Three specific engineered test criteria were used to analyze battery performance. These were: 1 – high current drain time, 2 – low current drain time and 3 –internal resistance. An Excel spreadsheet was then generated for the final rankings and recommendations that were ultimately presented to the team. Finally, the top ten batteries were benchmarked using a dynamic battery loader that simulated a FIRST robotics competition. The tests conducted were derived from the following industry standards: IEC 60254-1 [1], SAE-J240 [2], SAE-J537 [3] and UL-2054 [9]. This study was designed and executed by the electrical sub team of FIRST (For Inspiration and Recognition of Science and Technology) Team 2619, “The Charge” which is the robotics club of Herbert Henry Dow High School (Midland Public Schools), Midland, Michigan, USA.

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