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Battery Chargers

Batteries are often referred to as the heart of a renewable energy system. By monitoring your battery and performing periodic maintenance, it is possible to prolong its life and correct small problems before damage occurs.

Always use caution when handling batteries. Wear gloves, goggles and old clothes. Battery acid will burn skin and eyes and destroy cotton and wool clothing. (Polyester is a good fabric to wear around batteries.)

Battery State of Charge
Knowing a battery's state of charge allows us to answer the two questions foremost in our minds, "How do I know when my battery is charged?" and "How do I know when it║s time to charge my battery?"

1. An amp hour meter is a simple and accurate way to determine battery state of charge and it simplifies battery maintenance. The cost of an amp hour meter will be easily recovered in extended battery life and improved efficiency of your electrical system║s operation.

2. A volt meter provides a useful measure of system and battery voltage. However, it is only an approximate indication of the state of charge of a battery. The best time to read battery voltage, is when it is at rest. That is, when no charging or discharging is taking place, and has not for several hours. Battery voltage will fluctuate as charging takes place and as loads are turned on and off.

3. Another way to determine a battery's state of charge is with a hydrometer. A hydrometer measures the density of the battery electrolyte. A fully charged battery will have a higher concentration of acid and a higher specific gravity reading. The extra time, potential for contamination and hassle of a hydrometer tends to make people avoid their hydrometer.

A battery that is constantly discharged will have a much shorter life than one that is regularly charged. If your battery is always discharged you must either increase the charge rate or reduce the loads.

Battery Maintenance
Battery maintenance should be performed every three months. It is very simple and will only take a few minutes to complete.

1. Check the connections and make sure that they are clean and tight. If there is corrosion on the battery terminals, clean them with baking soda, water and a wire brush. You must not allow water or foreign matter to enter the cells, especially soda.

2. Check all electrolyte levels and top up with distilled water. When batteries are at rest, the fluid level should be to the bottom of the split plastic ring or 1/2" above the plates. If water levels are constantly low the voltage of the charge controller is probably set too high. Do not add water to batteries when they are discharged, they may over flow when brought to a full charge.

3. If you are having problems with your battery use a hydrometer to check the specific gravity of each cell in your battery bank. A fully charged battery will read approximately 1.265 on the hydrometer. If any cells are noticeably different from the others (0.02 or more) you may have a weak cell which is an indication of impending battery failure. Equalizing your battery may eliminate the problem.

4. Equalize your battery (non-sealed, lead acid batteries). This needs to be done more frequently when a battery is kept in a partially discharged state or is experiencing deep discharge cycles. Equalizing should be performed for at least two hours when the cell voltage is raised above 15 volts in a 12 volt system. A longer period (up to 48 hours) is necessary when equalizing at between 14 and 15 volts. Audible gassing (bubbling) is an essential indication that equalizing is taking place.

When a battery is discharged lead sulfate forms on the lead plates. If a battery is not fully recharged the sulfate remains on the plates and hardens until a normal recharge will not remove it. This reduces the capacity of your battery by sealing off some of the surface area of the plates.

Even with proper charging some of the cells may accumulate lead sulfate. Equalizing a battery removes the sulfate from the plates and the gassing that results stirs up the electrolyte which tends to stratify. Stratification concentrates the sulfuric acid at the bottom of the cell and corrodes the plates. Distilled water should be added to the battery after equalization has taken place and voltage is back to normal.

Please read the section on Battery Chargers for more information on charging a battery.

Battery Chargers

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