Hello, my name is Eric O’Hara and I work along side with the Cazenovia HS Electrathon Team. My Engineering Design and Development project was to assist the team by discovering the correct Amp/Hr rating of their Yellow-Top batteries. This process included teaching myself how to use our new equipment that we were able to purchase by selling our own manufactured parts. The CBA (Computerized Battery Analyzer), as I discovered, was much more efficient than our other methods on calculating the Amp/Hr rating.

We could check to see if our gear ratio matches up with desired Amp/Hr rating by actually driving the car. It was unlikely however that we would be correct on our first try, or second or third. This process would require to guess-and-check and take up many trials that could extend to days.

The Batman or PakTrakr meter that most contestants use in their cars does not actually tell you the Amp/Hr rating of your battery. It requires you to tell it the Amp/Hr rating of your battery based on its label, and it will determine how much current should be drawn based off of that. But how do you know if the Amp/Hr rating you inserted is accurate? You don’t.

Finally, we are able to build and use a Light-Bank. Each light bulb is about 2Amps, so as they start to dim out it forces you to have to do the math. It’s also required that you use your own stopwatch to time the test yourself, so you should know by now your data is not accurate.  If that’s not enough, the changing temperature of the bulbs changes the current, making your data not only non-constant but also inaccurate.

The CBA we use simply eliminates all of these issues. We are able to determine the Amp/Hr rating without having to do the math, the current always remains constant, and the test immediately terminates as soon as it reaches the ending voltage (in this case being 10.5V).

 See the following test procedure. Word document attached

Determination of the C1 AmpHour Rating of Yellow-Top Optima Batteries using the Computerized Battery Analyzer 

Primary Purpose:

The purpose of this test is to use the Computerized Battery Analyzer (CBA) to determine the C/1 AmpHour rating of a 12V Yellow-Top Optima Battery.

Secondary Purpose:

To answer the following questions:

            Do batteries last longer after cycling them 5 times?

            Do all similar batteries have the same AmpHour rating?

            Do batteries’ capacities increase over five charge/discharge cycles?

Materials Required:

• The Computerized Battery Analyzer (CBA)
• Power Cable
• AC Adapter
• USB Cable
• Yellow-Top Battery
• Magnetic Temperature Probe
• CBA Amplifier

Safety Precautions:

• Never use battery that has poorly insulated or frayed wiring or exposed parts.
• Never connect a battery with reverse polarity.
• Never test a battery near flammable materials.
• Never allow a battery to reach a temperature too hot to touch.
• Recharge your batteries immediately with an appropriate battery charger after you have completed the test.
• Never test or charge batteries while unattended.
• Have fire extinguisher nearby.
• Never allow metal parts or wiring of battery to come in contact with metal heat sink.
• Don’t touch CBA shortly after high power test.

Initial Conditions:

       Leave the battery off the charger after being charged for exactly a half-   

hour before starting the test. This will affect the initial voltage of each test  so they are more similar.

       Connect USB to computer before connecting battery.

       Make sure batteries are already completely charged.

       Make sure battery is isolated, meaning that it isn’t connected to anything else while going through testing with the CBA.

       Operate CBA in cool and dry location.

       Make sure cooling fan isn’t blocked or jammed.

       DEACTIVATE SCREEN SAVER OR SLEEP MODE, for the test will     

automatically terminate if either activates.

Procedure:

1. Attach Power Cable into CBA module (DO NOT PLUG POWER CABLE INTO WALL SOCKET UNTIL INSTRUCTED TO DO SO)
2. Attach AC Adapter into the CBA Amplifier
3. Connect CBA Amplifier to the  CBA, make sure colors match up (red wire to red input and black wire to black input). (DO NOT CONNECT ANY BATTERIES TO THE CBA AMPLIFIER UNTIL INSTRUCTED TO DO SO)
4. Connect Power Cable into wall socket.

Steps 1 -4 above are documented in detail in the CBA III Software Manual ©2010

    5.   Open “West Mountain Radio CBA III” program

    6.   When beginning a new test, determine the type of battery (Yellow-Top: Lead Acid), the capacity (convert mAh to Ah if necessary), and voltage.

    7.   Check the box next to “Graph Temperature”

    8.   The test type is Discharge. Be sure to insert at what current you wish to test at.

    9.   For Optima Red & Yellow Top batteries, be sure the cut off voltage is at 10.5V. It is a 6 cell battery.

    10.   There is one amplifier to be used.

Steps 5-10above are documented in detail in the CBA III Software Manual ©2010

    11.   Before clicking start, connect the Optima battery into the CBA Amplifier using a 13mm wrench to loosen and tighten the clamps (polarity does matter, positive with red and negative with black).

    12.   Attach the Temperature Probe directly to the battery. Be sure it is well insulated so outside temperatures do not affect it.

    13.   Place the battery clamps on the battery terminals (polarity does matter, positive with red and negative with black)

    14.   Click “Start” to begin the test.  Be sure that current draw is 31 Amps. The test will automatically terminate when voltage has reached 10.5V

    15.   Never leave the room while a test is in process.

    16.   Save the Test results in an easily found location on the computer.

    17.   Print the test results as a PDF. Print the test results, 3 hole punch, and save in binder.

Attachments
 CBA Yellow-Top Testing Procedure.doc [43 KB]

We are revising outr testing procedure, and the data shown below may not be accurate, as the batteries may not have been fully charged.  We are also in the process of verifying the accuracy of the tester. We are looking into it now, and will post more information soon.

Though our spreadsheet and procedure suggests that we should do five tests for each battery, we found that it would not be necessary. After having done four tests for each battery the data that we would have received on the fith test could be easily predicted in most cases.

Some of the batteries actually do last a bit longer after each charge and discharge, even though it’s for just a few more seconds, which some may see as insignificant.

The capacity/AmpHr rating for the batteries didn’t seem to have much of a pattern. However, the AmpHr rating data all remained within .5Amps of the average, so there was little to no change.

 What surprised me the most is that the average AmpHr rating for all four of the Optima Yellow-Top batteries ranged from 28.8 to 33. Note that we tested each test and each battery with the exact same current, being 31Amps. I don’t know why the AmpHr ratings of the batteries would be different as such. We can only conclude that the AmpHr rating can vary significantly in even brand new batteries.

Below is a graph that shows all four batteries overlayed on the same graph. Notice the difference in the AmpHour rating of the four batteries. All batteries were purchased at the same time, from the same vendor.

Attachments
 Y1 05 19 2010 c.pdf [65 KB]
 Yellowtop test spreadsheet.xls [18 KB]
 Y4 05 20 2010 c.pdf [65 KB]
 Y3 05 19 2010 c.pdf [66 KB]
 Y2 05 19 2010 c.pdf [64 KB]

Well the data is in! We have tested the Optima D35's, both yellow and red tops, sorry for the delay, but we needed the time to do the following:

1. Recertify our tester: It was sent back to the manufacturer and recertified accurate to +/- 0.01 V and +/-0.01 Amp.

2. Acquire two Brand new Optima Red Top D35's to add to the data. Thanks to Dave at Interstate Battery in Syracuse NY for loaning them to us!

3. Rewrite the test procedure to incorporate different types of charging techniques used by different teams. Note that some of the fields in the data table below are left blank on purpose due to the proprietary nature of the information.

It has taken us over 4 months to get this straight, and we have learned a ton about batteries:  how they're made, how to test them, and how to charge them. Thanks for being patient, and here's the data:

From carefully analyzing the data in the previous post (and summarized above) we have drawn the following conclusions:

1. All batteries are NOT created equal. From the factory, the batteries can have a C1 rating that can vary by up to 3-4 Ahrs from battery to battery.  Choose wisely; if you have a choice.

2. Both Reds & Yellows are green directly from the factory; They do NOT hold an optimal charge, and get better over time. (see data in the previous post)

3. Both Reds & Yellows improve with age; to a point. What is that point? We don't know, as we haven't reached it yet. It could be as many as 10 to 15 charge/discharge cycles for the yellow tops. (Thanks Dave!)

4. How you charge the batteries does have an effect on the final Ahr rating, but when charged similarly, the yellows and the reds overall differ by less than 1Ahr at a C1 rating.

5. The discharge curves for the two diferent batteries have almost exactly the same profiles.  See the attached files as well as the graph below.

In the chart above, the red & green lines represent the factory yellow tops, and the black & blue the factory red tops. As you can see the curves are exactly the same with the C1 Ahr rating averages differ by less than 1 Ahr.

6. Contrary to popular belief, the Red's and Yellow's C1 rating differ, on average, by LESS THAN 1Ahr. See chart above. (Have I stressed this enough?)

Popular thinking was that because the batteries had a C20 rating difference of 4 Ahrs (see specs here), it was assumed that electrathon racers would be able to go either much further, or much faster in the given hour. This would be a huge safety concern to me as a teacher, as my top priority is safety for my students. This was proven not to be true as shown by the data.

Since we use the batteries in one hour, you cannot apply the C20 rating.

We have tested old, not so old, and brand new batteries, and have come to the above conclusions. Please see the posts previous to this for the Testing Procedure we used, as well as the test set up.

This data does not take into account any different driving "styles", just the cold hard facts about the two batteries: Optima Red & Yellow Tops.

In closing: because the Yellow tops will have a much greater life span than the Red Tops, and do NOT give a significant difference in Ahr rating for one hour, I strongly recommend moving to the Yellows for cost savings and recycleability alone. They may cost a bit more but will last 5x's (at least; I'm being conservative, as we have not tested this) as many charge/discharge cycles.

Special Thanks to Dave at Optima Batteries in Syracuse, NY for his expertise and the loaning of the brand new batteries!

We would love to hear your comments!

Attachments
 2010-11Optima C1 Data.pdf [118 KB]
 2011 01 19 Y6 c.pdf [63 KB]
 2011 01 19 R10 c.pdf [62 KB]