#22:
Author: mark75, _files/icon_minipost.gif "Post") Posted: Sat Jun 26, 2010
11:39 pm
go to your local auto parts
store and get a motorcycle sized hydrometer. usually about $5-6, less than
$10 anyway.
fully charged battery/cell
should be 1.26-1.28
a Volt/Ohm or Multimeter is a good
investment too.
a cheapy from Harbor Freight, Radio Shack, etc. is all
you need.
Hydrometer (Specific Gravity) – How to Test a Battery
Dec 13
2009
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Battery Hydrometer
Battery Hydrometer
Here at BestBatteryTips.com we get
asked this question numerous times in a week. “What is a Hydrometer, and
how do I test my battery with one?”
A hydrometer is a float-type
device used to measure the concentration of sulfuric acid or ( The
Specific Gravity) of a battery electrolyte (”battery acid”). After reading
this post you can easily and accurately determine a non-sealed battery’s
State-of-Charge. A hydrometer is a glass or plastic container with a
rubber nozzle or hose on one end and a soft rubber bulb on the other.
Inside the barrel or container, there is a float and calibrated
graduations used for the Specific Gravity measurement. We are going to
explain step by step procedure on how to use a battery hydrometer, to find
out and know the condition of your battery.
Rubber Gloves
Rubber Gloves
Safety Goggles
Safety Goggles
Remember, Safety first!! Always wear rubber gloves, and goggles
before performing any maintenance or while handling batteries. Its a good
idea to wear goggles over safety glasses, because of the seal goggles
gives you around your eyes in case of an explosion.
If the fluid
in the battery (electrolyte) is above 115 degrees, let the battery cool
down before proceeding forward.
If the battery has been charged in
the past 5 hours, you will have to remove the surface charge to get a
accurate reading. There are a couple of ways you can accomplish this. Put
the battery in a car and turn on the high beam lights for 5 minutes, and
then wait 10 minutes. You can let the battery sit at room temperature for
6 to 12 hours to allow the surface charge to dissipate.
Battery
Hydrometer Example
Hold the Hydrometer vertically, squeeze the
rubber bulb on the end of the Hydrometer and insert the other end of the
Hydrometer with the rubber hose on it in the battery cell closest to the
positive post or flag post. Then release the rubber bulb and the
electrolyte will then begin to be sucked up into the Hydrometer. It may be
necessary to tap on the Hydrometer to remove any air bubbles that are in
the Hydrometer, these bubbles can interfere with a accurate reading if not
removed. Once you get a reading then you press the rubber bulb to force
the electrolyte back into the cell of the battery. It is recommended to
take several reading of each cell for accuracy. When you get two different
readings of the same cell, average the two readings for a accurate
specific gravity. At eye level and with the float steady, read the
Specific Gravity at the point the surface of the electrolyte crosses the
float markings. The Specific Gravity reading should be between 1.100 and
1.300.
Repeat the process for each individual cell. The Specific
Gravity reading should not have a difference of more than 30 “points”
(.030) between the lowest and highest reading or 10 “points” (.010) below
the battery manufacturer’s recommended temperature value with the battery
fully charged. If so, try and equalize the battery by following the
battery manufacturer’s procedures. If equalizing does not help, replace
the battery.
When finished taking all of your Hydrometer readings,
be sure to rinse the Hydrometer out thoroughly with water.
Specific Gravity vs. Temperature
at Various States-Of-Charge
(SoC)
for a Wet Low Maintenance (Sb/Ca)
or Standard (Sb/Sb) Car
Battery Table
Electrolyte Temperature (Fahrenheit) Electrolyte
Temperature (Celsius) 100% SoC 75% SoC 50% SoC 25% SoC 0% SoC
120°
48.9° 1.249 1.209 1.174 1.139 1.104
110° 43.3° 1.253 1.213 1.178 1.143
1.108
100° 37.8° 1.257 1.217 1.182 1.147 1.112
90° 32.2° 1.261
1.221 1.186 1.151 1.116
80° 26.7° 1.265 1.225 1.190 1.155 1.120
70° 21.1° 1.269 1.229 1.194 1.159 1.124
60° 15.6° 1.273 1.233
1.198 1.163 1.128
50° 10.0° 1.277 1.237 1.202 1.167 1.132
40° 4.4°
1.281 1.241 1.206 1.171 1.136
30° -1.1° 1.285 1.245 1.210 1.175 1.140
20° -6.7° 1.289 1.249 1.214 1.179 1.144
10° -12.2° 1.293 1.253
1.218 1.183 1.148
0° -17.8° 1.297 1.257 1.222 1.187 1.152
For
example, if the electrolyte is at 20° F (-6.7° C), the Specific Gravity
reading would be 1.289 for a 100% State-of-Charge because the liquid is
more dense at the colder temperature. At 100° F (37.8° C), the Specific
Gravity reading would be 1.182 for 50% SoC and a reading of 1.104 or lower
at 120° F (48.9° C) would indicate a discharged battery. |