Hydrometers, how do you use them

G'day Jim,
the numbers represent "Specifig Graphity"

Here are tow links that explain about Hydrometers,
Cheer, Mike

I would be looking for around 1280 from a fully charged in good condition battery. It refers to specific gravity and that about all I know. We still measure our batteries in Substations with hydrometers and they hold 1250-1280 after three years.

Jim,
Im not expert but i was surfing at the time i read your question and this is what i found....
Using a hydrometer to measure the specific gravity of the electrolyte. The more charge on the battery, the more sulfuric acid there is in the electrolyte and the higher the hydrometer float will be on the scale. A fully charged battery has a specific gravity or about 1.265

SPECIFIC GRAVITY
Specific gravity means exact weight. A "Hydrometer" or a "Refractometer" compares the exact weight of electrolyte with that of water. Strong electrolyte in a charged battery is heavier than weak electrolyte in a discharged battery. By weight, the electrolyte in a fully charged battery is about 36% acid and 64% water. The specific gravity of water is 1.000. The acid is 1.835 times heavier than water, so its specific gravity is 1.835. The electrolyte mixture of water and acid has a specific gravity of 1.270, usually stated as "twelve and seventy."



SPECIFIC GRAVITY - EXCESSIVE CELL VARIATION READINGS
Variation in specific gravity among cells cannot vary more than 0.050. The variance is the difference between the lowest cell and the highest cell. A battery must be condemned for excessive cell variation if more that 0.050. In the example below, the highest SG reading is cell #1 (shown in green) while the lowest SG reading is cell #5 (shown in blue); the difference is 0.070 which requires battery replacement. Cell #5 if failing.

Cell #1 Cell #2 Cell #3 Cell #4 Cell #5 Cell #6
1.260 1.230 1.240 1.220 1.190 1.250

Many factors contribute to cell variation; for example, if water was just added to that cell, the cell is then diluted with water resulting is a lower specific gravity reading. Recharging the battery would correct this false reading. In some cases if a battery that has cell variation slightly over the specification and is only about 50% charge, charging the battery at a slow rate of charge (5A) may reduce the cell variation, thus saving the battery.

SPECIFIC GRAVITY READINGS
By measuring the specific gravity of the electrolyte, you can tell if the battery is fully charged, requires charging, or must be replaced. It can tell you if the battery is sufficiently charged for a capacity (heavy-load) test. The battery must be at least 75% charged to perform a heavy load test. (The heavy load test will be discussed later). In other words, each cell must have a specific gravity of 1.230 or higher to proceed.

CELL READINGS - PERCENT CHARGED
1.270 100%
1.230 75%
1.190 50%
1.145 25%
1.100 0%

If the battery is less than 75% charged, it must be fully recharged before proceeding. If the battery is 75% or higher proceed to a heavy load test. A battery not sufficiently charged will fail because it is discharged.

Fairdinkum mate ...it just goes on and on and on....hope that helps
Ange

Jimbo.
You can also use your hydrometer to see how much alcohol is in your home brew! Tony

Just bought one also, says this on the back.

Charge scale:

1.265 = 100%
1.245 = 75%
1.190 = 50%
1.155 = 25%
Below 1.155 = 0%

Cheers

Evening Jimbo.

Mate I respectfully suggest that you get your son-in-laws GMC gennie in the first instance.

Strap,clip,attach the 12V outlet to the subject battery and fire up the gennie in the second.

Take out the cell caps and watch the show begin.

It will start to bubble after about 5mins and if you test it you will find it is pumping in anything between 14 - 16 volts.

Maaaaaaaaaaaaaaaate the white build up crappola on the plates disappears and the battery starts thinking along the lines of a 'teenager' again.

Good idea to turn it off at this point and continue with a regulated battery charger, however this depends on the the individual battery being ' rejuvenated'.

The end result is just phenomenol.

I rejuvenated a Deep Cycle wet cell battery in this manner about two weeks ago..

It didn't matter if it failed as it was on the way out anyway.

Holds 12.8V - 13.00V now.

Regards

Ken Robinson

As one of the guilty party that advised you to buy a hydrometer, here is another reference from the Windsun WEB site.

State of Charge
State of charge, or conversely, the depth of discharge (DOD) can be determined by measuring the voltage and/or the specific gravity of the acid with a hydrometer. This will NOT tell you how good (capacity in AH) the battery condition is - only a sustained load test can do that. Voltage on a fully charged battery will read 2.12 to 2.15 volts per cell, or 12.7 volts for a 12 volt battery. At 50% the reading will be 2.03 VPC (Volts Per Cell), and at 0% will be 1.75 VPC or less. Specific gravity will be about 1.265 for a fully charged cell, and 1.13 or less for a totally discharged cell. This can vary with battery types and brands somewhat - when you buy new batteries you should charge them up and let them sit for a while, then take a reference measurement. Many batteries are sealed, and hydrometer reading cannot be taken, so you must rely on voltage. Hydrometer readings may not tell the whole story, as it takes a while for the acid to get mixed up in wet cells. If measured right after charging, you might see 1.27 at the top of the cell, even though it is much less at the bottom. This does not apply to gelled or AGM batteries.

Jimbo,

Becareful about using 'general values' for specific-gravity readings

eg: Exide Extreme : full charge = 1.275 = 12.80V [o/c]
..............................50% = 1.230 = 12.35V [o/c]

These values are from the Exide chemist, as you can see they don't match values quoted elsewhere in this thread. Maybe an idea to contact your battery manufacturer for specific values?

Another poster has outlined Equalisation [I do it once a year..BUT I LEAVE THE CAPS ON] You need to keep a record of the SG from each cell to track the performance of your battery.

Cheers

Wok

Wok
Yes we get the battery's and acid from the warehouse on site (if their not nil stock, that’s an insiders joke for all the miners out there) fill them up with acid then install them, I've had the Auto lecy install some solar panel on the roof of their shed and run some wires to a positive and negative bus bar through a BP regulator, if we get the chance we will make some battery's up of all sizes and have them sitting on the solar power until they are required, usually no longer than a couple of days, works well.
As for the acid type why don’t you ring Yuasa / Century head office and ask for some technical help, they were very helpful for me, years back.
Stew