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| Internal Parts of Battery |
Tools to use: Hydrometer, Battery Cell Tester, Multi-tester
The level of the electrolyte should be about 1/8" below the bottom of the filling wells. If the electrolyte is above the bottom of the well, it may be forced out when the battery is charged. If the electrolyte is allowed to fall to below the top of the plates, the battery will be damaged. If the level of the electrolyte is low, refill it with distilled water only. Regular tap water has minerals which may coat the plates and reduce the battery's capacity.
Distilled Water:
Distilled water is water that's been heated to cause it to evaporate into water vapor. The water vapor is then condensed back into liquid water. The distilled water is free of all impurities including minerals that would coat the plates of the battery and therefore reduce its capacity to produce electrical current.
Cranking Amps:
Cranking amps is the spec that tells you how much current a battery can produce for 30 seconds at a temperature of 32° F and not have the voltage on any of the individual cells drop below 1.2 volts (7.2 volts for a 6 cell automotive battery). This may also be known as MCA or marine cranking amps.
Cold Cranking Amps:
This is the same test as cranking amps but is done at 0° F. The CCA spec is especially important if you live in a really cold climate. Since the chemical reaction that produces electrical current in the battery slows down as the temperature drops, the battery can produce less current at colder temperatures (especially below freezing). When comparing the current capacity of batteries, make sure that you have some standards to qualify the current ratings. If you see the current rating without CA or CCA, you don't know how the battery was tested and the current rating is virtually useless.
Reserve Capacity:
The reserve capacity is the time that a battery can produce 25 amps at 80° F before the individual cell voltage drops below 1.75 volts (10.5 volts for a 6 cell automotive battery).
Deep Cycle vs Standard Battery:
1. A normal lead-acid battery will be damaged if it is completely drained (even if it's only one time).
2. A deep cycle battery is designed to survive being drained multiple times.
3. Deep cycle batteries have more reserve capacity but have less cranking amps for a given size.
4. A standard battery would have more total surface area on its plates when compared to a deep cycle battery of equal size. This extra surface area provides more area for the chemical reaction to take place and therefore produce a higher output current.
5. The electrolyte in a deep cycle will be a slightly more concentrated sulfuric acid than a standard battery.
Gel-cell Batteries:
Gel-cell batteries use a thickened (gelled) electrolyte that will not leak out like a liquid electrolyte. Many of them can be mounted in virtually any position. These batteries may be suitable for some applications but for engine starting, other batteries should be used. Gel-cell batteries can not produce as much current for long periods of time as standard liquid electrolye batteries.
Recombinant Gas Batteries:
RG batteries have only 2 long thin plates per cell. They are constructed much like an electrolytic capacitor. The plates are separated by a fiberglass mat material designed to hold the electrolyte. These long thin plates have significant amounts of surface area (compared to standard batteries). This extra surface area allows the battery to produce significantly more current than standard batteries of similar physical size. Optima® is one manufacturer of RG batteries. If you're going to add batteries to your system and the batteries will be in the vehicle's trunk or passenger compartment, RG batteries won't vent flammable hydrogen gas or corrosive gasses into the vehicle.
At one time or another most of us have gone out to go to work or to the store and when we go to start the car. Nothing happens. Dead battery. Now Murphy's Law stipulates that when a battery dies, it will be in the most inconvenient place and time. If you have a set of jumper cables it's not too bad. You can usually find someone willing to give you a jump-start. A lot of times you need to call a tow truck to get you started or towed to a shop and have the problem repaired.
CAUTION: BATTERIES CONTAIN SULFURIC ACID. ALWAYS WEAR EYE PROTECTION WHEN WORKING ON A BATTERY. BATTERIES PRODUCE HYDROGEN GAS, DO NOT SMOKE OR CAUSE SPARKS THAT MAY IGNITE THE GAS AND CAUSE AN EXPLOSION.
The battery is only one link in the chain that makes sure you can start your car when you turn the key. As in any chain, it's only as strong as it's weakest link. Let's take a look at the charging system and some ways we can keep it strong and healthy.
There are three main parts to the charging system, the Alternator, the Voltage Regulator and the battery. We're all most familiar with the battery, so let's start with that.
Car batteries are of a lead-acid type. Most of the world production of lead goes into car batteries and an estimated 95% of all car batteries are recycled so the lead can be used again and again. The positive plates in a battery are made from lead dioxide and the negative plates are made from metallic lead. The electrolyte inside the battery is a sulfuric acid solution. As the cell discharges, the acid electrolyte is consumed producing water and both electrodes change into lead sulfate. When the cell is recharged, the process reverses. A 12-volt battery has six cells connected in series making a total of 12 volts.
There are several ways to test a battery to see how good it is. The quickest and easiest is the load test. A predetermined load is placed across the battery terminals and held for ten seconds. At the end of the ten seconds the voltage across the terminals is measured and this voltage determines how good the battery is. If the voltage stays above 11 volts, the battery is good and healthy. If the voltage drops between 9 and 11 volts, the battery is determined to be borderline. It will be okay in warm weather, but may fail as the temperature drops toward freezing. If the voltage drops below 9 volts, it's no good.
The way we test the batteries state of charge is with a battery hydrometer. A hydrometer measures the specific gravity of the acid solution. The higher the specific gravity, the more charge in the battery. A fully charged battery will have a specific gravity of 12.75. A weak battery will have a specific gravity of 12.50 or 12.25. A discharged battery will have a specific gravity of 12.00 or less. When you check the battery, you need to check each cell. All six cells must have the same specific gravity. If five cells test at 12.75 and one tests at 12.25, you have may have a bad cell. Charge the battery for about 30 minutes and test again. If the low cell does not come up, it's bad and you need a new battery. Some variance is allowed between cells but if it is a large variance, you may have battery problems.
The individual cells can also be tested with a voltmeter. Take a coat hanger and make two lead extensions about six inches long and attach them to the meters test leads. Touch the positive lead to the positive terminal and stick the negative lead inside the cell next to it. It should read about 2.1 to 2.3 volts. Now insert the positive lead in the first cell and the negative lead in the second cell. Proceed down the line until you get to the last cell. Here you will put the positive lead in the last cell and the negative lead on the negative terminal. All the cells should read the same, or within 0.2 volts. If one reads 4.0 or more, you have a shorted cell and the battery is no good. If you get a very low reading or a zero reading, the cell is open and again the battery is no good.
Before you do any battery testing, you need to start with a fully charged battery. If it is not fully charged, then any test results you get mean nothing. So always check the specific gravity before you do anything. Also make sure the terminals are clean and tight.
Now some batteries are sealed so you can't do a cell test or check the specific gravity. In this case all you can do is charge the battery for about 30 minutes and do the load test. In sealed batteries you will usually see the "green eye." What this is, is a built in hydrometer. Don't trust it. I have seen hundreds of bad batteries with green eyes telling me they are good.
A little bit about working with batteries. Whenever you disconnect a battery, ALWAYS disconnect the negative cable first. This will prevent sparks that may cause the gasses inside the battery from igniting. Wear safety glasses, batteries contain sulfuric acid and it can splash if you are not careful. If it comes in contact with your skin, wash it off with plenty of water. Take off any rings or jewelry when you work on a battery. I worked with a technician who was taking a battery out of a car and the wrench he was using slipped and touched both terminals. The battery shorted and his gold wedding band was, literally, welded to his finger. He was fortunate that the doctor at the emergency room was able to remove the ring and save his finger.
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