Hydrometer

System
System Posts: 2,511 admin
I would like to know if there is a good hydrometer on the market. Most I have seen in the auto parts stores look very cheep.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hydrometer

    Our host sells gear that they stand behind:

    NAWS Battery Maintenance Accessories for $26-$36 each:

    wind-sun_2092_2081187Freas HD98C Precision Hydrometer Set

    wind-sun_2092_2082913Freas HD99M Precision Hydrometer

    wind-sun_2095_891008Brady 10" Precision Battery Hydrometer
    1.100-1.300 Specific Gravity Scale

    -Bill

    PS: Other than as a moderator for spam--I have no connections with NAWS or anything in the solar business...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Hydrometer

    The HD99M and the HD98C. The 98C comes with a thermometer, are the Hydrometer's the same? And why would I want a thermometer?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hydrometer

    You would have to contact NAWS for the details about their products...

    Regarding Temperature--Lead Acid battery chemistry is fairly dependent on temperature. And the density of the acid is temperature dependent.

    From the Trojan Battery Website (more on batteries vs temperature at link):
    How do I account for temperature when taking my gravity readings?
    Temperature will affect specific gravity readings. As temperature increases, the electrolyte solution expands and as temperature decreases the electrolyte solution contracts. As a result, it is a good practice to temperature correct specific gravity readings. Here are the relationships Trojan recommends using:
    For every ten degrees above 80oF add 3 points to the hydrometer reading.

    Example: @ 90oF the hydrometer reads: 1.250 The actual reading: 1.250 + .003 = 1.253
    For every ten degrees below 80oF subtract 3 points from the hydrometer reading.

    Example: @ 70oF the hydrometer reads: 1.250 The actual reading: 1.250 - .003 = 1.247

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Hydrometer

    Just a bit of trivia to add to Bill's explanation: in addition to temperature, electrolyte SG is also subject to altitude.
    That's usually not a significant issue for most people. :p

    It is important to get a good hydrometer to start with, take readings with your new batteries fully charged, and write down the results. Compare future readings to this to see how your batteries are holding up. Equalize only when necessary: usually greater than 0.010 difference between any two cells.

    If you break your original hydrometer, buy another just like it. There can be significant differences in the readings given by two different hydrometers from the same cell at the same time.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Hydrometer

    Several things:

    The first Hydrometer I bought, when ordering batteries about four years ago was a Freas with the built-in thermometer. However, the volume of the bulb seemed too small for the volume of the glass tube, so it was almost impossible to pull enough electrolyte into the tube to float the float. It bordered on useless. So replaced it with a Freas unit w/o thermometer. Did buy an electrolyte thermometer -- a separate glass thermometer which works quite well.

    Recently, my SG seemed to have inched up, so bought one additional Freas 99M, and the Brady. (BTW, all of these were supplied by the generous host of this site). I was surprised to find that the Brady unit had a built-in thermometer. This Hydro/Thermo works well.

    One observation, tho, On the Pilot cell, the Brady reads 1.250, the new 99M reads 1.265, and the old Freas (99M I think) reads 1.280.. All of these readings are after the traditional 4 (or more) pulls, and exercising great care to keep the float from sticking to the sides of the tube, and not hitting the stopper at the top, AND over a very short time period while in Float.

    It is possible that the old Freas has become 'unclean', and somehow this might cause some surface tension, and might cause the float to mis-read SGs, altho, have tried to compensate for any misreads due to surface tension by reading while filling the tube slowly, and reading it while expelling electrolyte slowly, but still the old Freas still reads higher than the other newer ones.

    Hope this is not a Hijack.

    Freas has said to, "wash the hydro in warm water, and continue until it is 'not sticky'. Do not use a bottle brush". Tolerance is quoted as + / -- one minor division. Was unable to get a spec on repeatability, however. One minor division may be 10 points IIRC ( am not at the off-grid site to see).

    I guess that I will either have to weigh a measured amount of electrolyte (and compare it to an identical volume of H20), and compare this ratio to the readings from the various hydros, or it might be OK to take readings on commercially available 1.265 bulk electrolyte (altho this has its own tolerance). I love science ... but ...

    This is my recent experience. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • sawmill
    sawmill Solar Expert Posts: 93 ✭✭✭
    Re: Hydrometer

    I also bought the Freas with therometer. The bulb is too small to draw enough liquid for a reading. The only way you can use these hydrometers is after the first bulb squeeze, remove it and turn upside down and allow the liquid drain to the bulb, squeeze while upside down and reinsert in the cell with the hydrometer lying horizontal across the battery you might get enough for a reading after two or three squeezes with the above method.

    If you are near retirement age when starting to check 36 to 48 cells you will pass the magic number before getting through using this hydrometer. An electric pump for drawing the electrolyte would be needed to make this an usable instrument.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Hydrometer

    Hello sawmill,

    Yes, I did just that for perhaps one round of 24 cells, but was concerned that the rubber might be contaminating the electrolyte with any impurities in the rubber. So stopped using it altogether, altho, it should still work fine for taking a temperature reading, as the float needs not float to do that. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    Re: Hydrometer

    Vic,
    On your last pull of electrolyte do you do it slowly and make sure there are no bubbles sticking to the float? I've learned over the years that bubbles stuck to the float will raise your sg reading by.01 sometimes!

    Probably telling you stuff you already know. The hydrometer I use has small glass nipples in the lower part of the tube which keeps the float from dragging on the side of the tube...very nice. If the bulb is squeezed and released quickly the vacuum it creates results in bubbles on the float and inaccurate readings.

    Anyone else, just watch the last draw of electrolyte, do it slowly and repeat if there are any bubbles on the float.

    Ralph
  • jeffkruse
    jeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: Hydrometer
    sawmill wrote: »
    I also bought the Freas with therometer. The bulb is too small to draw enough liquid for a reading. The only way you can use these hydrometers is after the first bulb squeeze, remove it and turn upside down and allow the liquid drain to the bulb, squeeze while upside down and reinsert in the cell with the hydrometer lying horizontal across the battery you might get enough for a reading after two or three squeezes with the above method.

    If you are near retirement age when starting to check 36 to 48 cells you will pass the magic number before getting through using this hydrometer. An electric pump for drawing the electrolyte would be needed to make this an usable instrument.

    +1

    It works better when the SG is high. Forget out trying to measure a low SG :roll:
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Hydrometer

    Hi Ralph,

    Yes the last pull is very slow, as am trying to read it on the way into the tube, at rest and then again while it is being expelled. Do work very hard to make cartain the the float is not stuck to or touching the glass tube. My old hydro is not clean enough, as there are no air bubbles, but the glass is not well wetted by the electrolyte. With the new hydros the glass is readily wetted.

    I might feel that am being too obsessive, but SG readings ARE important.

    I'll need to clean house and try again. YES, the Freas hydrometers in the past three years or so seem to have bumps or stand-off nibs or ... These help.

    Will clean my aged hydrometers and report back ... And apologies for bending this thread, if not quite hijacking it ... Thanks Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Hydrometer

    We are looking for a decent wholesale source for the newer type of hydrometer (refractometer) that have finally gotten cheap enough to consider vs the bulb/tube type that has been around for 300+ years. So far not much luck though, having trouble finding a real distributor for any of the non-lab grade types, such as http://www.robinair.com/products/detail.php?id=1859
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Hydrometer

    Helo WindSun,

    Thanks for the link to the refractometer ... interesting.

    I may get two graduates [essentially precision made tubes with accurate scales, indicating the volume of a fluid ]. So weighing equal volumes of distilled water and electrolyte, and using the ratio twix the two, should allow one to check the accuracy of a hydrometer. Then one would know how much english to apply to a given hydrometer. That would be good enough for me right now.

    Have always wanted some probe-like want that would read out the SG directly, but of course this would be very difficult to make work.

    I do like the Brady hydrometer that you are currently selling. The one I just got from you folks has a built in thermometer and is very cleverly made. It works quite well.

    Thanks Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • System2
    System2 Posts: 6,290 admin
    Re: Hydrometer

    I bought the Brady Hydrometer. I now have some questions.

    People have spoken about temperature and I am wondering how close I have to be on this measurement. If I open the front compartment on my trailer and start testing immediately I'm sure the batteries are going to be much colder than the air out side the trailer. How should I get an accurate reading? Can I just rely on air temp?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hydrometer

    You should adjust your specific gravity readings by -.0.001 for every +3 degrees Fahrenheit. Note the signs--SG reading go down (less dense) as temperature battery temperature increases.

    So a +/- 0.005 SG adjustment (about as close as you can read the SG?) would be required for a -/+ 15F change in battery temperature.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Hydrometer

    Am I measuring the temperature of the electrolyte or just the air temperature?? And if I am measuring the electrolyte what do I measuring it with?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Hydrometer

    You want the temperature of the electrolyte--which is the temperature of the battery.

    When you use the hydrometer, you should pull the fluid in and out a few times so that the hydrometer is the same temperature as the battery/electrolyte.

    From the Trojan Battery Maintenance Manual (PDF download)
    Specifc Gravity Testing (fooded/wet batteries ONLY) 7.3.
    • Fill and drain the hydrometer 2-3 times before drawing a sample from the battery
    • Measure specifc gravity readings for all battery cells
    • Correct specifc gravity readings for temperature by adding 0.004 for every 10°F (5°C) above 80°F (27°C) and subtract 0.004 for every 10°F (5°C) below 80°F (27°C)
    • If every cell in the battery set is below 1.250 the batteries may be undercharged; recharge batteries
    • If any battery has a specifc gravity variation of more than 0.050 between cells equalize the set
    • If there is still a variation there may be a failed battery
    You can measure the battery temperature by inserting a glass/insulated thermometer into the cell (no metal inserted into a storage battery--or all sorts of fun and games may occur).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jprokos
    jprokos Registered Users Posts: 8
    Re: Hydrometer
    Just a bit of trivia to add to Bill's explanation: in addition to temperature, electrolyte SG is also subject to altitude.
    That's usually not a significant issue for most people. :p

    I know this is an older thread but I would love to know at what altitudes this variation in electrolyte SG comes into effect. And how does it effect SG, higher alt. = lower SG or higher alt. =higher SG? I am at about 7000 feet here in Nepal.

    In response to an earlier post on this thread. The Freas Hydrometer rate of draw is making me antsy and I am nowhere near retirement age. It definitely needs a larger bulb.