Battery Fill Can

Batteries often times need water added to them over time. However there seems to be some confusion in what it is to put in them when its time. Never use tap water to fill battery cells, I can’t stress that enough. Tap water is full of natural salts and minerals that can’t be seen with the naked eye. These salts and minerals attach themselves to the lead plates in the battery, and reduce the ability of the battery to produce and move electrons. Manufactures recommend using distilled water for any filling of the battery cells that might be necessary. Distilled water has been removed of all impurities.

Battery Cutaway

How do you know when to fill a battery or battery cells? When you take the cell cap or caps off the top of the battery and you see the lead plates above the water level. The water level inside the battery should just cover the top of the lead plates inside. If the lead plates are visible, pour distilled water into the cell or cells until the lead plate or plates are covered. Due not over fill the battery cells, the batteries were designed for the electrolyte level to just cover the lead plates to allow for expansion inside the battery if necessary. During battery activity, some of the water through chemical action breaks down into hydrogen and oxygen gases that may evaporate from the battery. The result of this process is a low electrolyte level. The battery must be filled as described above.

Maintenance Free Battery

Maintenance free batteries do not have access to the electrolyte levels. The manufactures build maintenance free batteries with higher electrolyte levels to give for evaporation and expansion of gasses. No maintenance is required on these types of batteries.

Always remember to wear safety goggles, and wear rubber gloves when conducting maintenance on batteries.

All product names, logos, brands, and other trademarks featured or referred to within BestBatteryTips .com website are the property of their respective trademark holders.

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

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.

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

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.

Batteries which are at less than 75% state-of-charge need recharging before proceeding with any further tests. Observe that the battery does accept a charging current, even though it may be small in amperes, when the charger is switched on.

If the state-of-charge is 75% or higher, the battery should be given a high-rate load test. Typically, the high-rate load tester will discharge a battery through an adjustable carbon-pile resistance and indicate the terminal voltage as the discharge proceeds. After 15 seconds the battery voltage will not drop below a specified value if the battery is in good condition and if the current is set at about 50% of the Cold Cranking Amps (CCA). The minimum acceptable voltage reading will vary as battery temperature decreases. Read and follow the manufactures instructions for the tester.

Batteries which have a low but uniform specific gravities in each cell and which clearly require an extended recharge may have become deeply discharged through accidentally leaving a car door open overnight. It may also be the result of undercharging caused by regular driving in heavy traffic patterns or by a fault in the vehicle charging system. This may be nothing more than a slack alternator/generator drive belt, but system should be checked out before the battery is returned to service.

Batteries which have suffered as a result of considerable overcharging may show extremely low electrolyte levels, black deposits on the underside of the vent plugs or black “tide-marks” on the inside walls of the container from about one inch below the cover. If these signs are present, the voltage regulator/generator setting must be checked and reset according to the manufacturer’s instructions before a battery is returned to service, modern car batteries in which electrolyte levels have to be adjusted frequently are clearly receiving too much charging current.

Below is a batteries state of charge when hooking a volt-meter to the battery.

• 12.75 & Above      100% Charged
• 12.60 to 12.74      85 to 100% charged
• 12.40 to 12.59      75 to 85% Charged
• 12.20 to12.39        50 to75% Charged
• 12.00 to12.19        25 to 50% Charged
• 12.00 & Below       Fully Discharged

Over Charged Battery

Helpful Resource: Exide Technologies

Superior Battery Manufacturing Company Inc.