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Batteries are basically devices that store electrical energy as chemicals. And despite dating back to at least the 18th century, batteries are still by far our easiest and most efficient means of storing energy. They are made from electrochemical cells, each having an anode and a cathode, that transform, at a very high efficiency, chemical energy into electrical energy. Rechargeable batteries, which are of interest to us here, can reverse the chemical reaction and turn electrical energy back into stored chemical energy.


Battery types and their various chemical compositions are too many and diverse to mention, but each battery is usually specified by, among other things, its voltage and capacity. The voltage is usually intrinsic to each cell (and thus depends on the number of cells). The capacity is the maximum amount of electrical energy (or amps at the given voltage) that can be stored in or retrieved from the battery at normal operating conditions.


Despite their wide presence and everyday use, batteries are still very much “misunderstood” devices among most people. And there are probably no greater misunderstandings and false information flying around than about battery life. The first misunderstood fact is that batteries do not have a specific lifetime in years or months, but their life is given by the number of cycles they can perform before their capacity starts dropping below a certain level. And even that number is not constant but is largely affected by many factors including the depth of discharge, storing temperature, maintenance (for flooded batteries), and charging and use habits…etc. Regular batteries will usually last around 500 cycles while being discharged 20 to 30% of their capacity on a regular basis, while some deep-cycle batteries can exceed 2500 lifetime cycles for as much as 50% daily discharges.

Hence the expected life of a battery is far from constant and is not even reliant on the type of battery alone. How you use a battery will have the biggest effect on how long it will live. A deep cycle battery that is properly cared for in a well-designed renewable energy system will usually last at least 5 to 7 years.



Batteries in Renewable Energy


Batteries are one of the most important components of most renewable energy systems. That is because most renewable energy sources tend to be unreliable and constantly varying. Solar energy in particular is ever changing because of clouds, the weather and obviously night and day time. And while some applications such as solar pumping will not require batteries, any back up power application needs an energy storing mechanism.


Batteries for renewable energy applications need obviously to be rechargeable, but also heavy duty and deep cycle to with stand very deep discharges on a daily basis and even more. The usual types of batteries used for renewable energy applications are the AGM, the Gel and the typical flooded battery, each with its slight advantages and disadvantages over the other. The first two are valve regulated and require little maintenance, while the flooded type need regular watering and equalization. All those batteries are a variation of the Lead-Acid technology. Lithium Ion batteries are sometimes used for very specific tasks but their cost is still too high to justify any popular use despite their obvious advantages.


From all the deep cycle batteries on the market, Trojan Batteries, the ones used here at Control Panel, remain the outstanding brand with the best durability, efficiency and lifetime cycles. Below is a small summary on how to care for your Trojan Battery.



Battery Maintenance Tips

-          Make sure there is enough space between batteries to allow for minor battery expansion that occurs during use and proper airflow to keep battery temperature down in hot environments.

-          Depending on the local climate, charging methods, application, etc., Trojan recommends that batteries be checked once a month until you get a feel for how often your batteries need watering.

-          Do not let the plates get exposed to air. This will damage (corrode) the plates.

-          Do not fill the water level in the filling well to the cap. This most likely will cause the battery to overflow acid, consequently losing capacity and causing a corrosive mess.

-          Do not use water with a high mineral content. Use distilled or deionized water only.


1.       Open the vent caps and look inside the fill wells.

2.       Check electrolyte level; the minimum level is at the top of the plates.

3.       If necessary add just enough water to cover the plates at this time.

4.       Put batteries on a complete charge before adding any additional water.

5.       Once charging is completed, open the vent caps and look inside the fill wells.

6.       Add water until the electrolyte level is 1/8″ below the bottom of the fill well.

7.       A piece of rubber can be used safely as a dipstick to help determine this level.

8.       Clean, replace, and tighten all vent caps.


-          Never add acid to a battery.


·         Clean the battery top with a cloth or brush and a solution of baking soda and water.

·         When cleaning, do not allow any cleaning solution or other foreign matter to get inside the battery.

·         Rinse with water and dry with a clean cloth.

·         Clean battery terminals and the inside of cable clamps till shiny.


-          Avoid locations where freezing temperature are expected. Keeping a battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to a battery’s plates and container.

-          When storing, avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 80° F (26.6º C) accelerate the battery’s self-discharge characteristics.


1.       Completely charge the battery before storing.

2.       Store the battery in a cool, dry location, protected from the elements.

3.       During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less.

4.       Completely charge the battery before re-activating.

5.       For optimum performance, equalize the batteries (flooded) before putting them back into service.


-          Charge only in well-ventilated areas.

-          Tighten all vent caps before charging.

-          Do not charge a frozen battery. Avoid charging at temperatures above 120° F (48.8° C).

-          Do not leave batteries deeply discharged for any length of time.

-          For every 18° F (10° C) rise above room temperature (77° F or 25° C), battery life decreases by 50%.

-          If you store your batteries for an extended period of time, be sure to charge them fully every 3 to 6 months.

-          Lead acid batteries will self-discharge 5% to 15% per month, depending on the temperature of the storage conditions.

-          As a general rule of thumb, the total amps from your PV panels should be sized between 10% and 20% of the total amp-hours (Ah) of the battery pack.

-          Equalize your batteries at least once per month for 2 to 4 hours, longer if your batteries have been consistently undercharged.




Batteries remain potentially very dangerous devices and should be handled with extreme care. They are made of toxic chemicals that should never touch bare skin. That is why it is advisable to always wear protective gloves and goggles while handling batteries. Ingestion of battery chemicals can be harmful and even deadly. Batteries are also prone to leakages of those harmful chemicals and will overflow if watered too much or over charged. Batteries may even explode if exposed to flame or extreme heat or even if aggressively overcharged. Always be cautious when handling batteries. If in doubt, contact a technician for help.

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