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  • Specific gravity measurement

    Hello

    Can anyone recommend a good brand of hydrometer for measuring lead acid batteries?

    I have recently purchased two different testers, and they do not agree. The one has a scale that goes down to 1.000. I suppose I could cool some distilled water to 4 degrees C and check the calibration that way. But, the scale itself is not very easy to read, so even this may not be an accurate method.

    Ideally, I would like to buy a tool that I know is accurate, straight out of the package. Any suggestions?

    Thank you.

  • #2
    Easy peasy. OTC 4619 Professional Battery Hydrometer or Deka
    Last edited by Sunking; 11-19-2018, 04:46 PM.
    MSEE, PE

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    • #3
      Originally posted by CMcD View Post
      Hello

      Can anyone recommend a good brand of hydrometer for measuring lead acid batteries?

      I have recently purchased two different testers, and they do not agree. The one has a scale that goes down to 1.000. I suppose I could cool some distilled water to 4 degrees C and check the calibration that way. But, the scale itself is not very easy to read, so even this may not be an accurate method.

      Ideally, I would like to buy a tool that I know is accurate, straight out of the package. Any suggestions?

      Thank you.
      OTC 4619 is nice but no temp compensation comes with temp gauge to calc offset reading, complicated. EZ-RED made in USA It's simple stupid to use and Temp compensated. Friend has Golf cart biz Thats all he uses.
      Last edited by Paul Land; 11-19-2018, 04:40 PM.

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      • #4
        Originally posted by Paul Land View Post
        OTC 4619 is nice but no temp compensation comes with temp gauge to calc offset reading, complicated..
        Hogwash, it has temp comp. Complicated perhaps for Millennial's or younger generations who were not taught simple math in school. To hard for the little darlings, it takes them out of their Safe Space.

        MSEE, PE

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        • #5
          Originally posted by Sunking View Post
          Hogwash, it has temp comp. Complicated perhaps for Millennial's or younger generations who were not taught simple math in school. To hard for the little darlings, it takes them out of their Safe Space.
          Giddy-Yuppi

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          • #6
            Originally posted by Paul Land View Post

            OTC 4619 is nice but no temp compensation comes with temp gauge to calc offset reading, complicated. EZ-RED made in USA It's simple stupid to use and Temp compensated. Friend has Golf cart biz Thats all he uses.
            Thanks Paul, I found the OTC 4619 is sold by a local auto supply store. I will check tomorrow if they have one in stock.

            I also see I can get the EZ-RED on Amazon, if the OTC is not available.

            Thanks again.

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            • #7
              CMcD regardless of what hydrometer you chose, do not get too hung up on what the tells you with respect to either low or high. What you are mostly after is Balance. You want all cells reading the same specific gravity or EQUAL. When you see a spread of .030 between lowest and highest, time to EQ. To EQ you apply a EQ charge until specific gravity rise stalls and all cells are equal. When done the specific gravity will be above 100% of 1.275. Just be aware it can take up to 24 hours, and you need to check every hour.
              MSEE, PE

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              • #8
                Originally posted by Sunking View Post
                CMcD regardless of what hydrometer you chose, do not get too hung up on what the tells you with respect to either low or high. What you are mostly after is Balance. You want all cells reading the same specific gravity or EQUAL. When you see a spread of .030 between lowest and highest, time to EQ. To EQ you apply a EQ charge until specific gravity rise stalls and all cells are equal. When done the specific gravity will be above 100% of 1.275. Just be aware it can take up to 24 hours, and you need to check every hour.
                As I said at the beginning, I have two testers. Not the same brands as Paul suggested. The problem is their accuracy. One of the sticky posts in the category said to take your reading after about the third draw of electrolyte, to sort of mix it up a bit, to get a better reading.

                I have one tester that the same style as the EZ-RED. It reads 1300 on every cell. I think it calibrated too low, and is just stopping at the top of its range every time.

                The other tester looks like the OTC. The problem with that one, is the float rubs on the side of the glass chamber. When I take my third draw, I get one reading. If I do a fourth draw, I get a different reading. If I draw the tube half full, I get a different reading. Three quarters full is another reading. If I draw more or release some fluid, the float tends to stick a bit to the side, and does not move freely. There seems to be a bit of friction causing some resistance on the float's movement. I can get more than .030 spread on different readings in the same cell.

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                • #9
                  OK I get it. Part of the problem is likely your technique.

                  1. Perform measurement immediately after a full charge cycle. This is important because acid is heavier than water, and the electrolyte will stratify between charges leaving water on top. After a complete charge the batteries will bubble and gas mixing the electrrolyte.

                  2. Flush hydrometer with distilled water. Use a cup to hold distilled water, and fil and drain tube a couple of times before you start and in between cell measurements.

                  3. Draw electrolyte 3 to 4 times. Fill hydrometer, forcefully squirting electrolyte back into cell a few times. Again this is to mix the electrolyte.

                  4. On 4th or 5th draw only fill hydrometer until the Float just floats.

                  5. This is where you might have got inaccuracies. Once filled thump and flick the hydrometer making SURE you get all the air bubbles off the hydrometer and to release any contact friction. Make sure hydrometer is plumb bobbed by holding the hydrometer with a light grip pressure on the bulb as close to the end as possible.

                  MSEE, PE

                  Comment


                  • #10
                    Originally posted by Sunking View Post
                    OK I get it. Part of the problem is likely your technique.

                    1. Perform measurement immediately after a full charge cycle. This is important because acid is heavier than water, and the electrolyte will stratify between charges leaving water on top. After a complete charge the batteries will bubble and gas mixing the electrrolyte.

                    2. Flush hydrometer with distilled water. Use a cup to hold distilled water, and fil and drain tube a couple of times before you start and in between cell measurements.

                    3. Draw electrolyte 3 to 4 times. Fill hydrometer, forcefully squirting electrolyte back into cell a few times. Again this is to mix the electrolyte.

                    4. On 4th or 5th draw only fill hydrometer until the Float just floats.

                    5. This is where you might have got inaccuracies. Once filled thump and flick the hydrometer making SURE you get all the air bubbles off the hydrometer and to release any contact friction. Make sure hydrometer is plumb bobbed by holding the hydrometer with a light grip pressure on the bulb as close to the end as possible.
                    Thank you for sharing that pearl of wisdom.

                    I thought my new hydrometer was defective...... Turns it was a defective operator.

                    When I was on the road full time I didn't have any problems. I suspect that driving the bus daily kept my electrolyte mixed. Now that I have been stationary for a considerable period my readings have gone crazy.

                    Note to self: mix electrolyte before taking SG reading

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                    • #11
                      My system has been operating for 5.5 years now, in the beginning I was using a Deka temp compensated hrdyo to do the EQ with and I did that for the first 2 years, then I got tired of it the tiny lines etc and I bought a simple float needle type and used that from then on to now. Agree with SK on not reading it until you have "swished around" the electrolyte 4 or 5 times. Now I just run the EQ until all the cells are the same on the same hydro. Keep a log book and number your cells, that way you'll be able to track when it is getting time to replace.
                      1150W, Midnite Classic 200, Cotek PSW, 8 T-605s

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                      • #12
                        Thank you Sunking. I am getting much better readings. I finally feel confident, now that the reading are more consistent.

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