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Batteries

The battery bank is the heart and the most important part of your system and should be treated as priority. They are expensive, but try not to cut corners and invest all you can in good batteries. In a later stage one can always ad more solar panels, install a more powerful inverter etc., Adding new batteries to an older bank is money thrown out of the window. The Deep Cycle Batteries are a key component of renewable energy systems requirement for electricity storage it is heavily relied upon for the reliable operation of the solar system. A battery bank can provide a relatively constant source of power when the grid is down, or during periods when your photovoltaic system is not producing power. These batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates – not sponge. This gives less surface area, thus less “instant” power like starting batteries need. Although these can be cycled down to 20% charge, the best lifespan vs. cost method is to keep the average cycle at about 50% discharge.

Even though batteries are not one hundred percent efficient, they are predictable and stable enough to provide for reliable long-term service as they normally discharges slowly over hours or days before being recharged base on system engineering.

Deep cycle batteries used in renewable energy applications are designed to provide many years of reliable performance with proper care and maintenance however proper maintenance and usage will play a major role in achieving maximum battery lifespan.

There are three main types of batteries that are commonly used in renewable energy systems, each with their own advantages and disadvantages. Flooded or €œwet€ batteries are the most cost efficient and the most widely used batteries in photovoltaic applications. They require regular maintenance and need to be used in a vented location, and are extremely well suited for renewable energy applications. Sealed batteries come in two varieties, the gel cell and Absorbed Glass Mat (AGM) type. The gel cell uses a silica additive in its electrolyte solution that causes it to stiffen or gel, eliminating some of the issues with venting and spillage. The Absorbed Glass Mat construction method suspends the electrolyte in close proximity with the plate€™s active material. These batteries are sealed, requiring virtually no maintenance. They are more suitable for remote applications where regular maintenance is difficult, or enclosed locations where venting is an issue.

At Carisol you can rely on us for the best in batteries that the industry has to offer.

The quality of a battery is determined by their plate structure and the lead alloy. The capacity of a battery, the amount of current it can store, is expressed in Ampere/hours (Ah). However, the slower one discharges a battery, the more amperes one can drain from it. The discharge time is called C and expressed in hours. 100Ah at C10 means one can drain max. 100A in 10 hours. The same battery could be sold as a 150Ah battery when discharged in 100 hours, 150 Ah-C100.

Therefore, and apart from its quality, to find the cheapest battery with a capacity X, one has to take into account this C-value, and only compare batteries with the same C value. A second important question is the life span of a battery. This life span is highly determined by its internal construction: Which type of lead and how are the plates configured. A standard car battery has very different plates than a battery made for a fork-lift or truck (traction battery). The expected life span is often expressed in the number of charge/discharge cycles. All quality batteries have such a classification, if not mentioned, ask for it!

Our main brands are:

TROJAN BATTERY – Clean Energy for Life„¢

Trojan Battery Celebrates 85 Years of Providing Clean Power to the World. With over 85 years of experience, Trojan Battery Company is the world’s leading manufacturer of advanced deep-cycle battery technology. Long-lasting, reliable and clean, customers all over the globe know Trojan deep-cycle batteries deliver superior power to any renewable energy application. Trojan€™s proprietary Maxguard® Advanced Design Separator and exclusive Alpha Plus® Paste Formulation deliver longer life and enhanced performance making Trojan Deep Cycle batteries an excellent choice for uninterrupted solar power applications even in the harshest of environments.€™

ROLLS SURRETTE BATTERY – Rolls Battery – One Mean Battery

Surrette stand firm with their batteries offering some of the longest warranties in the industry, average life expectancy of these batteries are known to be well over twelve years. The Surrette Battery Company established in 1935 has been a trusted name in deep cycle batteries for well over 50 years. Their quality workmanship has earned them a solid reputation in the battery industry as one of the worlds€™s most rusted and reliable batteries on the market. Surrette Rolls batteries environmentally conscious rugged, dual container construction sees each cell encapsulated in its own inner container made with a high grade, polypropylene shell and its own heat bonded cover, the cells are then further protected with a second, high-density, polyethylene outer container. These safety measures allow the battery to still be operable should the outer container break, eliminating the hazard of a toxic sulfuric acid spill. Surrette Rolls cells also feature double insulated positive plates, the first layer utilizes a thick woven glass mat, which then is sealed in a non-destructible micro porous polyethylene envelope, this protective envelope reduces the possibility of separator misalignment, cracked separators, or shorting at the bottom or sides, it also allows the sediment chamber to be eliminated, creating more space for liquid at the top of the battery, thus lengthening periods between watering.

Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

Bulk Charge: The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no “correct” voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.

Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since its main purpose is to keep an already charged battery from discharging. PWM, or “pulse width modulation” accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called “pulse width” because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

Battery Bank Sizing Worksheet

How much storage would like your battery bank to provide base on the number of hours or days your system will have to provide power without solar input?

Batteries should not be completely drained (ever), neither is good for them to be consistently undercharged. It is best to size your battery bank so that it gets full capacity charged.

Remember when you are sizing a solar panel array you are dealing with watts per hour that you need to produce with batteries you are dealing with amps per hour that you need to store.

Battery Boxes – Carisol provides a complete customize beautiful metal battery racks solution of every colour, shape and size to suit all applications.

What are the different battery types?

A. The most common type of battery in renewable energy installations is the lead acid battery. Batteries based on a different chemical process are available and will probably play a role in the future. For now they remain too expensive. Nickel-Cadmium, Nickel-Metal-Hydride, Lithium-ion etc. based batteries are already common place in portable electronics and even used in hybrid cars.

Why lead acid battery?

A. A perfect battery should be cheap and indestructible, it should be able to store much energy per Kg. weight and very efficient in accepting and releasing this current and able to keep this charge safely stored for many months. Plate technology, lead composition and the presentation of the acid are important determinants of these qualities. Plates made of pure lead have very good cycle qualities and a low self-discharge rate. But pure lead is soft and easily deformed. To make the plates of a pure lead battery sufficiently strong they have to be thick, resulting in a very heavy battery. By using lead-alloys one can avoid this disadvantage. Lead containing a small amount of Antimony results in a much stronger metal. Batteries constructed with this material are lighter due to their thinner plates. A negative quality is that the material degrades more easily during deep discharges and stimulates gas formation during the charging phase. Calcium-lead is also stronger than pure lead, but it gasses much less than antimony-lead during the charging cycle. Compared to Antimony-lead it resists less well deep discharges. Calcium-lead batteries are preferably used when shallow cycling is guaranteed (No more than that 25% DOD). The material is often used in VRLA (Valve Regulated Lead-Acid) batteries (See maintenance free batteries) as it gasses much less than Antimony-lead.

What does plate has to do with the battery?

A. The more robust, the heavier the plates, the longer a battery will live. The strongest batteries use tubular plates, while cheaper ones have thin, flat plates.

What does electrolyte do in the battery?

A. In vented-flooded-lead acid batteries the electrolyte is a straight forward, watery solution of sulfuric acid. It is liquid as water. These batteries have to stand upright as spilling of the electrolyte can cause serious problems. Particularly during the charging phase, gassing occurs in all types of batteries. In the vented ones, this mixture of hydrogen, oxygen and water damp will escape, and cause a slow, but steady loss of water. These batteries need periodical topping up with distilled water (Never use battery acid). Certain brands provide caps with a build in catalyst which recombines the hydrogen and oxygen into water, which will drips back into the battery. The net loss of liquid is therefore less and the topping up frequency is reduced. But it is a good habit, whatever type of battery you have, to look at them once in a while. The least one should do is keep them clean and free of dust. In applications where periodical inspection is truly a problem (as in remote unmanned stations), there is a choice of €œmaintenance free€ batteries. In general they are far more expensive than the equivalent vented battery. The VRLA battery (Valve-Regulated-Lead-Acid. The cells of these batteries are closed with a cap containing a catalyst which recombines a large part of the hydrogen and oxygen back into water which drips back into the cell. There is still a security valve to release excess of pressure if that might occur. In Gel batteries the electrolyte is changed into a jelly by mixing in a silica gel. Gel batteries have generally a slightly longer life expectancy than vented batteries and are completely closed. They can be installed in any position. In AGM (Absorbed Glass Matt) batteries the electrolyte is absorbed by special glass mats used as separators between the plates. Some of these batteries can be stacked in any desired position, which can be useful. As said before, all batteries produce gas, also maintenance free batteries. Gassing occurs particularly during the charging phase and , as these batteries are sealed, overcharging can cause explosion due to excess gas formation. (Vented batteries, on the contrary, will benefit from periodical overcharging, called equalizing)

How long will my battery last?

A. The expected life of a battery is best expressed the number of charge/discharge Cycles a battery can sustain before it suffers a significant loss of capacity. A commonly used standard is the IEC Cycle, where the controlled discharge is halted when the voltage of the cells is 1.67V (which equals in practice a total discharge). Others use terms such as 25%, 50% or 100% DOD, which stands for Depth of Discharge.

Which battery should I buy?

A. Any batteries built for the purpose €œsolar€ storage battery. The cheaper version is also based on flat plate technology, but these plates are thicker and heavier than those used in car batteries. The battery is therefore suited for cyclic use. They have often an IEC cycle rating of 400 to 500 (which means, if treated well, a maximum life span of 4 to 5 years). They come in 6 or 12 V blocks. The largest ones have a capacity of 250 Ah and can be as heavy as 70 kg. The best batteries, the most expensive ones, use tubular plate technology. Their life span, expressed in IEC units is 1000-1500, and they can live up to 20 years. The larger ones are often 2 volt cells. For a 12 V bank you need minimal 6 and for a 24 volt bank 12 of these units. True industrial traction batteries as used in fork-lift trucks etc., have a similar, very solid construction. Deeply discharged each working day and forcefully recharged during the night requires a very solid construction. Hence, if used with care in solar applications, they are nearly indestructible. They are very expensive. Quality golf cart batteries are reasonably robust and are an alternative for the smaller solar installations. To keep your batteries as healthy as possible one should never leave it discharged. A low state of charge promotes sulphation, the formation of lead-sulphate crystals on the plates. A sulphated battery will lose a large part of its capacity. Always recharge batteries as soon as possible and avoid deep discharges. If possible never use more than 20% of their capacity. For example, you should extract no more than 4.8 kW from a 24V, 1000Ah bank. The average temperature of the battery is an important, often forgotten factor in their life expectancy. This is particularly important for those of us who live in warmer countries. A battery with an average temperature of 35ºC will break down much earlier than one kept at 20ºC. Batteries should therefore be housed in a cool, well ventilated place.

What efficiency should I expect from my batteries?

A. Do not expect that all the energy you put in a battery, will also come out. No process in nature is 100% reversible. Energy is lost as heat and in the generation of hydrogen gas. In calculating the size of your system, it is safe to assume a 10% loss in the charge and discharge process.

What is battery capacity?

A. The capacity of a battery is the total amount of electrical energy you can store in it, is usually expressed in Ah (=amp/hour). For a given battery this capacity is not a constant. It depends on the rate (=the speed) of discharge (the quantity of amps one drains per hour). During a fast discharge much less energy will be recovered than during a slow discharge. The capacity (= C) of the battery is often given in combination with the C value, C5, C10, C20 or C100, The C stand for the amount of hours in which the battery was discharged: 100Ah at C5. This battery has a capacity of 100Ah battery when discharged completely in 5 hours. Notice that the same battery could be sold as perhaps even as 200Ah in C100. One therefore should always compare capacities with corresponding C values. A cold battery gives less easy its charge away as a warm one. A warm battery therefor can deliver considerably more energy in a measured amount of time than a cold one (as some of us have experienced when starting their car on a freezing morning).

How do I care my batteries?

A. Battery care is important for all batteries the important points are: Their average temperature, choose the coolest possible place for them. The area must be well ventilated. Avoid temperature differences between bottom and top of the cell. A battery should be surrounded by air. They should not stand on a cold concrete floor, but placed on wooden support and provide air gaps in between the different units. Whole the battery should have more or less the same temperature. This to avoid stratification of the electrolyte due to temperature differences. Correct charging is essential. Most batteries come with specific instructions regarding the optimal charge conditions. Invest in a modern, electronically regulated charger. Many modern inverters come with a built in charger. Avoid deep discharges and never leave the battery in a discharged state. Vented batteries profit from periodical overcharging. During a short period of time, the voltage of the charger is kept over the normal limit of 2.4 V per cell (for example during 30 min) causing excessive gassing of the batteries. This process, called, equalizing, will equalize the electrical charge over the all the plates in their different cells, while the bubbling liquid helps cleaning the plates and will remix the electrolyte. Never have the electrolyte level drop below a marked minimum on the cell. If a plate is not covered with electrolyte it will cause serious sulphation and sometimes deformation of the plate.

What state of charge?

A. Depending on the type and brand of battery, the specific weight of the electrolyte of each cell of a fully charged battery could be 1,28gr/l. (in some batteries it is 1.26). After discharging this battery for 20% (thus 80% charge left) you will measure 1, 25 gr. /l., and if discharged for 40% (60% charge left) it is 1, 22 gr/l. If no charge is left the specific weight is about 1.140. Measuring this specific weight is an accurate but unpractical way to estimate the state of charge of your battery. It is also a way to check on the condition of the battery. If 5 cells indeed are 1.28 but one cell is 1.24 than that cells is corrupt (affecting the performance of whole the battery.) One need a good Hydrometer and it is a messy procedure and the system has to be rested for at least one, preferably 2 hours. (Otherwise there is not yet a steady equilibrium). Be very careful, sulphuric acid is aggressive and particularly dangerous for your eyes (it will eat holes in your cloth as well). Therefore use gloves and wear protective goggles. Always have a solution of baking soda at hand (to neutralize spilled acid). Easier, but less exact is the voltage method. Apart from anything else, every bank should always be connected to a voltmeter, which provides basic important information. To estimate the state of charge with a voltmeter, the battery bank should have been rested for at least one hour (better for two). Over a fully charged 12V battery the reading should be 12.7 V. At 20% and 40% discharge it should be respectively 12.5 V and 12.3 V. Measuring only 12 volts means that the battery is much more than half empty, and at 11.9 V only 20% of the charge is left. The best way to control the state of charge of your bank is with an amp-hour meter. They were expensive instruments in the past, but are much cheaper nowadays. They come as true amp-hour meters or as rather sophisticated instruments, estimating the State of Charge by measuring the balance between incoming and outgoing current, while incorporating voltage and temperature factors.

What is meant by parallel batteries?

A. Two 12 volt batteries in parallel means connecting + pole of Bat. A to the + pole of battery B and the €“ of A to the €“ of B. Result: A 12 volt bank with double capacity.

What is by series batteries?

A. Two 12 volt batteries in series means the + pole of Bat A is connected to the €“ pole of bat B, while the €“ of A and + of B is connected to the system. Result: A 24 volt bank with the same capacity as the original 12 V battery.