Hydrometer Measurements Questions

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marsofold
marsofold Solar Expert Posts: 45 ✭✭
in Off Grid Solar & Battery Systems #1
I bought the hydrometer made by Brady (Item#: 2F011-C98-77-2-3) and sold by our forum sponsor. Sucked up some battery fluid, lifted up the device and looked at the reading: 1.22. Not good ( should be 1.27). A few seconds later a cluster of bubbles surges up from the bottom as a little fluid dribbles out in a glass jar below. Now the reading is 1.275. A few seconds later again some fluid dribbles out, and the reading is now 1.29. Why does this thing seem to be sensitive to the liquid level within? There is no external mark on the glass chimney to indicate what the proper fluid fill level should be. Actually no written instructions at all came with the unit. As a sanity check I also tested with a cheapo $5 automotive battery checker of the floating ball type, which had all four balls floating (100% charge) and unlike the expensive glass unit was not at all sensitive to the fluid fill level. What am I doing wrong or did I waste $48 on it? Thanks for any help...
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
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    Re: Hydrometer Measurements Questions

    The gizmo in the glass should float. One problem is if your too much acid in the tube, the gizmo can float too high, and hit the top of the tube, giving a false reading. Fill the tube, then blow some out until you are sure it is floating freely. The level of the acid relative to the number is the SG.

    Tony
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
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    Re: Hydrometer Measurements Questions

    Funny you should mention it... I spent an hour this morning looking online for refractometers. I've had it up to here :grr with hydrometers. In addition to your problem I find that the glass float gets sticky. Also, my hydrometer dribbles acid onto the batteries.

    Most of the solar installers I know carry a small refractometer. You can buy them at auto parts stores or online for under $50. NAWS doesn't seem to carry them :cry:

    The ones that work for coolant also work for battery electrolyte. If you do google search, search for 'electrolyte refractometer'. Make sure the one you buy has dual scales... one scale will be for coolant and will marked with the freezing point, the other scale will be SG.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4
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    Re: Hydrometer Measurements Questions

    Just a few more cents ..

    Until you do get a Refractometer;

    Fill the glass Hydrometer tube and expel the electrolyte two times, and take your reading on the third fill.

    Keep the tip in the Vent Well (the opening in the top of the batt with the cap) while taking the reading -- acid dribbles back into the batt. Use a flashlight if necessary to get a good view of the marks on the float.

    Make certain there are NO air bubbles sticking to the float or inside the glass tube. If there are some bubbles, GENTLY ding the lower rubber stopper/fill tube against the vent well to cause the bubbles to be dislodged.

    As stated above, make certain that the float is not sticking to the sides of the glass tube, that the hydro is level, that the float is not hitting the top stopper, and that the float is actually floating.

    Sticking bubbles are often caused by sticky acid residue remaining on the inside of the glass tube and float. ...

    A hydrometer MUST BE RINSED/FLUSHED AFTER EACH USE, with Distilled Water. This rinses the acid out of the hydro, and avoids the build up of the sticky crap, which allows air bubbles to adhere to the guts of the hydro -- acid is inherently sticky. If the hydro has been sitting for an extended time, rinse once before use. SG readings should be temperature compensated if the electrolyte temps a are more than about 10 degrees F off of the Standard Temp of 77 (or 80) degrees F speced by batt manufacturers. Ten degrees F makes only a couple of points difference on the reading, IIRC.

    The single best thing that one can do IMHO for reliable SG readings is to Rinse twice after measuring SGs. The sticky residue is very difficult to remove if it is allowed to build up.

    Thanks vt for the ref to local Reftactometer in Auto Stores. I do not do on-line commerce (yea, I know that am very backward here), so local sourcing is a big help.

    Just opinions, 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.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #5
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    Re: Hydrometer Measurements Questions

    I have both hydrometer and refractometer. The refrac gives incorrect readings of the sg if you use distilled water to "zero" it as per the instructions (low). What I have is a baby food jar of 1.265sg electrolyte (as measured by my hydrometer) to use as the zero point...that's the only way the refract reads correctly. I just use the hydrometer now. The refract works, just too much trouble when it's reference is taken from the hydrometer anyway.

    If you make the last "suck up" of electrolyte slowly, less bubbles develop on the float in my experience. For light in the battery box a good head strap led light is mandatory kit. One had for the hydrometer bulb, the other for pulling caps and writing down the values. Once you have a good headlight you use it for many jobs, and you always know where it is....on top of the battery box.

    Ralph
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  • larcal
    larcal Registered Users Posts: 53 ✭✭
    #6
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    Re: Hydrometer Measurements Questions

    Heh Vic, hope you're still around. Maybe this is my problem. Is this sticky residue obvious because it is sticky to your finger or is it hard to detect? Maybe it's there and I'm just not detecting it. How do you remove it without getting some other agent in there like kerosene, alcohol, even soap? Having trouble. do you recomend refractometers? Just now learning about them. Thanks.
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  • larcal
    larcal Registered Users Posts: 53 ✭✭
    #7
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    Re: Hydrometer Measurements Questions

    Ralph, It's nuts isn't it. any idea why they all say to use water when it doesn't work? I don't want to use a hydrometer even just to get a reference as I don't trust them, so how low is the reference using water? Would you say that even with such low readings the refractometer is useful because it would still reveal variations between cells? which is mainly what is important to me. as far as what a full reading is I could just take a refractometer reading when battery in float and call that sg "full"
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #8
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    Re: Hydrometer Measurements Questions

    Hi larcal,

    Well, the stickiness seems to build up over a period of time. It is difficult to reove. I would NOT use any petroleum solvent.
    You need clean only the glass parts. I would try to use some dish detergent, and perhaps a small brush for the float part. Ideally, some detergent and a bottle (really a test tube) brush if you can find one. Let the parts soak in warm detergent rich water, scrub well, rinse, rinse ... rinse ... rinse with clean water each time, then rinse several times with new distilled water. Basking soda is mildly abrasive, but am superstitious about using baking soda on things that contact the electrolyte. This sticky stuff is very dificult to remove. You will notice, when the glass is clean, the electrolyte wets the glass. When the glass is sticky, the electrolyte does not flow onto the glass. You will also notice that stickiness of the main glass tube causes small air bubbles to stick to it. I have never tried an alcohol, but this might work. Please let us know how you are doing. Good Luck, Vic

    Rinsing several times after each use, with distilled water really helps. 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.
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #9
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    Re: Hydrometer Measurements Questions

    A hydrometer MUST BE RINSED/FLUSHED AFTER EACH USE, with Distilled Water. This rinses the acid out of the hydro, and avoids the build up of the sticky crap.


    Great Info ..



    VT
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  • larcal
    larcal Registered Users Posts: 53 ✭✭
    #10
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    Re: Hydrometer Measurements Questions

    Thank you so much Vic. Long ago when I set this system up I read all the early Homepowers and trouble makers like Richard Perez, Steve wiley etc. and never saw such good, knowledgable info as you have presented here. You're an expert! Will at least get everything washed this weekend and then try again weekend after that. Can I ask again though, is this stickiness at a level that is detectable by touch or is it more subtle? Did extensive research late into night on Refractometers so can pass on what I learned, in case anyone interested. First level is those that don't have auto temp compensation like the Robinair 75240. Next level does have like Extech RF40 and I think it's worth it to get that for around $75.00. Reads up to 1.3 sg. The best do a sg reading up to 1.4 instead of 1.3 and there are certain batteries/situations where that could be useful. Cheapest in that category is Reichart Duo Chek for $140.00 and I'm thinking it's stupid to chinse on battery care so maybe but I just really don't want to right now. Gonna try make hydrometer work, then maybe get Extech to check my work. Trouble is that even if you get everything real clean and do everything just right you can't be 100% sure of your accuracy. Damn float allways leans. but your advice should help a lot. I have a freas #1 which doesn't have nubbins to help prevent sticking/leaning so maybe try and upgrade that. Didn't know before. I've allways just mainly equalized frequently like Richard said and watched my voltages and hoped for the best. Not good enough. Appreciate you letting me know about stickiness if you get a chance, tho the other signs you gave are very good.
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