Properly reading a battery hydrometer

Bet I can see tons of errors in all this using my 20X loupe. Chum Lee is IMHO most correct. If a .00000001 gravity resolution is necessary it's a horse of another color.

Look, if you are after ultra precise resolution, Freas, sells an EXPANDED SCALE hydrometer. Use it with reading glasses and whatever parallax is seen in the meniscus will be insignificant.

Take an exact 10 ml extraction and place it on a .01 digital gram scale. There are precision measures that positively cannot accept 10.01 ml. Adjust for temperature and there you are: Mother Fletcher's Do It Yourself Specific Gravity Laboratory.

While you're playing Professor Zharkoff, keep in mind small but significant stratification variances within the cell.

Once again, most of you guys are resplitting previously split hairs. Whats most important in taking hydrometer readings is the overall average of all the results. If you check all the cells the same way at the same time, say 30 minutes after charging, the readings should all be within +-10% of each other. (hopefully in the green zone) If they are not, then you need to do further investigation or an equalization. After that, if full charge voltage is still off and the the cells still show major discrepancies in specific gravity, THEN, you may have a problem.

Geezo! In my 5 years of automotive technical training, which was prior to my 5 years of engineering school, which was prior to my 35+ years of field experience, I've never seen more anal retentive neurotic behavioral thinking! Relax guys, enjoy the day! Chances are you're fine.

Chum lee

NinerBikes wrote:

SCVJeff wrote:
I know I'll get cr@p from the battery crowd here, but this "unclear" line has bothered me for years both on battery hydrometers, as well as the one I use floating in my salt reef tanks. There is friction glass to glass in the hydrometer tube as well as water creep on the probe, and the same water "creep" on my floating tank probe. In the tank I can look at it from below the water line and above and interpret two different readings.

In the salt tank I cured this issue with a Refractometer. For the batteries I just bought a HydroVolt and used it on my T-145's over the weekend. It tracks my glass tube hydrometer exactly without the tapping of bubbles and rattling around to zero out the glass on glass friction with a repeatable reading. It's simply a better mouse trap and no glass to break. Read the full .PDF sheet on it.

This is a small benefit to AGM batteries. No burnt acid hole in your clothes, no opening up, and pulling out the trays supported to check the readings on the two batteries in the back, no tearing apart all the cable connections and losing the copper washers or lock washers, and no corrosion forming on any of your copper connector cables, no matter how nicely they are hand made and sealed up.

And you don't have to lift them half or 1/4 or 1/8 as often, those gut buster lead slugs. :S :B Let me know if you need a hand, don't be afraid to ask, if you need help.

LOL! Don't try to explain all the advantages of AGM batteries, folks are fearful and resistant to change. Remember also that you can mount AGMS upside down under your dinette without venting, degassing, or worry. I like T-105s too, but under the seat of my Club Car!) :)

From Wikipedia:
When reading a depth scale on the side of an instrument filled with liquid, such as a water level device, the meniscus must be taken into account in order to obtain an accurate measurement. Depth must be measured with the meniscus at eye level (to eliminate parallax error) and at the center of the meniscus, i.e. the top of a convex meniscus or the bottom of a concave meniscus.

Manufacturers of glassware and other tools calibrate their measurement marks to account for the meniscus. This means that any instrument is calibrated for a specific liquid, usually water.

Here's what I use,, I have also found that filling the meter up with fluid from the cell then discharging it back into the cell one or two times gets rid of bubbles and gives a truer reading of the fluid tested.
It is something I was taught in mechanic school years ago.

MEXICOWANDERER wrote:
Hmmm one shot has the column doing a replication of the leaning tower of Pisa.

Hold the hydrometer so the interface is level with the eye.

Refractometers and questionable vision make for a problem

Exactly! I find it difficult to prevent the leaning tower of Pisa, or the bulb sticks to the side of the tube. On and on... Every now and then I can get it to float nicely vertical in the middle of the tube. Takes some work though!

Matt_Colie wrote:
All of this is why I bought a refractometer years ago and use it still. It does not require temperature correction and the number you get is where the line is. That's it.

Matt

Can you supply a pic or link of this instrument?

Hmmm one shot has the column doing a replication of the leaning tower of Pisa.

Hold the hydrometer so the interface is level with the eye.

Refractometers and questionable vision make for a problem

CJW8 wrote:
In this case read the bottom of the meniscus. The top of the meniscus is just surface tension of the glass and the liquid and is to be ignored.

That's exactly what I was wondering. It is more natural to look at the meniscus from above, but if you position your eyes so you are looking up at the meniscus from below, the reading is at least 5 or more points higher then when looking from above.

SCVJeff wrote:
I know I'll get cr@p from the battery crowd here, but this "unclear" line has bothered me for years both on battery hydrometers, as well as the one I use floating in my salt reef tanks. There is friction glass to glass in the hydrometer tube as well as water creep on the probe, and the same water "creep" on my floating tank probe. In the tank I can look at it from below the water line and above and interpret two different readings.

In the salt tank I cured this issue with a Refractometer. For the batteries I just bought a HydroVolt and used it on my T-145's over the weekend. It tracks my glass tube hydrometer exactly without the tapping of bubbles and rattling around to zero out the glass on glass friction with a repeatable reading. It's simply a better mouse trap and no glass to break. Read the full .PDF sheet on it.

I will look into the HydroVolt. My only concern would be that the design looks somewhat similar to the EZRed that I had before. Mex tested a whole box of those and got readings all over the place. However, if the HydroVolt is very accurate, that may be the way to go.