Batteries; Deep Cycle Solar
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Batteries; Deep Cycle AGM (Sealed) & Flooded Lead Acid (Vented)

deep cycle batteries
  • Highest Performance & Dependability.
  • The two types of common usage for battery based energy storage are off-grid and grid-tied. Off-grid applications are used where a customer chooses not to connect to the utility grid or the utility grid is not available. These include remote cabins or off-grid homes. Grid-tie systems are used where a customer lives in an area with frequent or extended power interruptions as a result of poor weather or unreliable grid electricity. Grid-tie battery based solar systems can fulfill the above mentioned requirements and as an added benefit export excess power produced back to the utility grid.
    When considering the size of your battery bank it is critical to determine the daily energy load requirements. Battery manufactures rate the life of their batteries not based on years but based on level of discharge and the frequency of cycling. Higher battery discharge will result in shorter cycle life. In reverse, a smaller discharge percentage will extend the expected cycle life of the battery as the battery will provide more charge/discharges.

Click the Tab Above ⇑ Battery Tips & Basics, Videos and Battery Articles to Learn More.

battery Note: Battery Shipment Within the Continental USA Only (48 States)

Battery Bank Sizing

battery An off-grid battery bank should be large enough to deliver a minimum 3 days of power with a discharge of no more than 50% of the battery banks total capacity. Less than 3 days and your charge and discharge number of cycles may shorten the life of the battery bank.

Battery bank sizing is the capacity to store electrons and is expressed in amp hours (AH) and at the rate the battery will charge or discharge not the physical size of the battery. Be careful when you are considering the Ah capacity of a battery and compare batteries that are advertising a 20 Ah discharge and not more (An apples to apple thing). Choose the 20-hour rate when sizing and selecting batteries.

Off-grid or backup battery banks can be made up of many small batteries which are connected in series and or parallel to give you the wattage (Volts X Amps) capacity needed. As a rule of thumb, battery banks with lower voltage (large cells) are going to last longer, take less work to maintain but are going to cost more initially. Keep your battery bank the same age, size and brand. Mismatched batteries will cause the smaller ones to have to work harder and the larger ones to coast and sulfate. (That's a bad thing)

Though both methods of calculations, (Watts Vs. Ah), will get you to the same conclusion, here is an example of a battery bank sizing calculation using Ah.

  • 6,000 AC Wh Average daily load ÷ 0.9 Inverter Efficiency = 6,667 Wh/day.
  • 6,667 Wh/day ÷ 48 DC system volts = 138.9 Ah per day.
  • 138.9 Ah per day X 1.11 battery temperature derate multiplyer x 3 days of autonomy ÷ 0.5 DOD (Depth of Discharge) = 925.1 total system Ah.
  • 925.1 total system Ah ÷ 325 Ah individual battery capacity = 3 parallel battery strings (rounded up from 2.85)
  • 48V system voltage ÷ 6V battery voltage = 8 batteries in series
  • 3 parallel strings X 8 batteries = 24 total 325 Ah batteries needed for the system.

This Ah battery calculation shows that a battery bank of 24 325 Ah batteries will provide ample energy storage in this example to meet the daily requirements, inverter loss, cold temperature inefficiency and days of autonomy while keeping the DOD (Depth of Discharge) above 50%.

Multiple Parallel Battery Strings. How Many Are OK?

battery Multiple parallel battery strings are only good up to a certain point. 1 string is ideal. 2 strings are okay. 3 strings are tolerable. More than 3 strings is just BEGGING for trouble! Tiny resistance differences between strings are unavoidable, and electrons being the supremely lazy things they are will always try to take the route of least resistance. With 2 or 3 strings battery string imbalances can usually be kept within control. But with more than 3 strings it’s inevitable that some strings will end up doing all the work, and some will do next to nothing. Neither condition is good for battery life expectancy.


Converting Watt-hours to Amp-hours

  • Batteries are rated in Amp-Hours (Ah)
  • To convert Wh to Ah, divide WH by the battery voltage; 9500Wh/day ÷ 48VDC = 197.9Ah/day
  • Round up to 200Ah - This example system will use about 200Ah from the 48V battery bank, on average, each day
  • If this were a 24V system, it would be 400Ah/day
  • If this were a 12V system, it would be 800Ah/day


What Size Battery Bank Voltage?

battery Whenever possible, use a higher voltage battery bank such as 48V over 24V battery banks. (IE: 8 - 6V batteries = 48V battery bank) Your equipment will run cooler which means a longer life for things like refrigerator condensers etc. If your solar panel array is higher than 2,000 watts, we strongly recommend you employ a 48 volt battery bank.


Rated Battery Capacity in Ampere-hour (Ah)

battery Battery capacity is the measurement of electrical storage and is often expressed in Ampere-hours (Ah) but also can be expressed in watt-hours (Wh). An Ampere is the unit of measurement for electrical current and means a Coulomb of charge passing through an electrical conductor in one second. The Capacity in Ah relates to the ability of the battery to provide a constant specified value of discharge current over a specified time in hours before the battery reaches a specified discharged terminal voltage at a specified temperature of the electrolyte. The voltage at the terminals is highest at the beginning of a discharge cycle and gradually falls.

As a benchmark, the battery industry usually rates batteries at a “Discharge Rate” C/20 Amperes corresponding to 20 Hour discharge period. The rated capacity in Ah in this example will be the number of Amperes of current the battery can deliver for 20 Hours at 80ºF (26.7ºC) till the voltage drops to 1.75V / Cell. i.e. 10.5V for 12V battery, 21V for 24V battery and 42V for a 48V battery. For example, a 100 Ah battery will deliver 5A for 20 Hours.

How Can You Squeeze More Years (Cycles) Out of Your Battery Bank?

battery This starts with the design. Minimize the number of strings of batteries by using higher Ah 6V or 2V batteries. Having fewer strings can help distribute the charge equally across the battery bank. Make sure your battery connections are at opposite corners of the battery bank. This will also help equalize the charge and discharge distribution across the battery bank. The last tip involves rotating your batteries within the series strings can help with more evenly distributed charges between cells. Use this opportunity once a year for your Saturday exercise routine and not only will you be in better shape, but you will save some money by extending the life of your battery bank. (Ok, we threw in the exercise part in to see if you were paying attention.)

Battery Energy Storage, Its About the Chemistry and the Plates.

battery We all know from high school that chemical reactions slow as it gets colder. A cold battery will not hold as much energy as a warmer battery. On the converse, a cold battery will last longer that one stored in an area that is unusually hot. That being said, the larger the surface area of the battery plates, more electrons will be allowed to react at one time creating more amps. Car batteries are thin platted which means there is more surface area for the electrons to react but they draw down very quickly. Deep cycle batteries use much thicker plates and have less surface area so they produce power over a longer time frame.

How Temperature Affects the Storage Capacity of Batteries.

battery Local temperature is a significant consideration when sizing a battery bank for a solar system. The capacity of a deep cycle battery to store energy is reduced in cold temperatures and shortened in high temperatures. Mother earth is a great insulator in high or low temperatures. If you bury the battery bank in the ground, you can increase the battery banks capacity at colder temperatures and lengthen the life of batteries at high temperatures.


Fullriver AGM Deep Cycle Batteriesagm

Fullriver battery manufacturing has been one of the leading battery products distributed in America for over 18 years. AGM deep-cycle batteries are well suited for off-grid sites or grid-tie backup because they require no maintenance and are practically freeze proof. With the sealed, maintenance-free aspect of all Fullriver AGM batteries, you can simply "Set it" and Forget it".

fullriver MODEL VOLTS Amp Hour
(20Hr Rate)
6 VDC 224 AH 66 LBS agm canadian solar fla 4
BP9DC4006 AGM L-16
6 VDC 415 AH 123 LBS agm canadian solar fla 4
BP9DC11502 AGM
2 VDC 1150 AH 126 LBS agm canadian solar fla 4

battery Batteries Ship in about 5 Business Days After Funds Clear. (Subject to Seasonal Increases (Up to 20 Business Days +))

Myth Vs. Fact. Batteries should not be stored on a concrete floor.

batteries Myth - This false notion has been around since about WWI and just never seems to die. In the early 1900's battery cases were made of wood products and sealed with asphalt. The battery acid would slowly leak and often formed a discharge circuit through the acid pool around the battery case. Plastic battery cases solved that problem.


Trojan Deep Cycle Flooded Lead Acid Batteriesagm

When failure is not an option and reliable power is absolutely essential, you’re in Trojan territory. Specifically engineered to support renewable energy systems with large daily loads that cycle regularly, high-capacity power when you need it the most. Founded in 1925, the Trojan Battery Company is a world leading manufacturer of deep-cycle batteries. From deep cycle flooded batteries to deep-cycle AGM batteries, Trojan has shaped the world of deep-cycle battery technology with more than 90 years of battery manufacturing experience. USA Manufactured in California & Georgia

trojan MODEL VOLTS Amp Hour
(20Hr Rate)
trojan WTY MIN
BP4001937 FLA
6 VDC 225 AH 67 LBS agm canadian solar fla2 YR 4
BP4001968 FLA
6 VDC 420 AH 114 LBS agm canadian solar fla5 YR 4
BP4001920 FLA
2 VDC 1110 AH 119 LBS agm canadian solar fla5 YR 4

battery Batteries Ship in about 5 Business Days After Funds Clear. (Subject to Seasonal Increases (Up to 20 Business Days +))

A Little Love During the Planning Stage, Will Help Your Batteries Live Longer.

battery Deep cycle batteries need a little love to squeeze every life cycle out of their service life. Sulphation, which is irreversible, is caused if the battery is not sufficiently recharged after each discharge. What happens over time is Sulphation crystals grow and can no longer be completely transformed back into lead or lead oxide. In the course of the operating period, the active mass decreases and the dischargeable capacity falls. The lower part of the battery cell is particularly affected by sulphation since a full charge is rarely attained there. You can avoid this by matching your daily solar impute during the shortest days of the year with your energy budget so your batteries are fully charged each day.

Rolls Surette Deep Cycle Flooded Lead Acid Batteriesagm

Surrette Battery Company Ltd. Established in 1935, Rolls is proud to be one of North America’s leading lead-acid battery producers and Canada’s only remaining independent battery manufacturer. Located in Springhill, Nova Scotia, Rolls produce a wide range of Rolls-branded premium deep cycle batteries for use in Renewable Energy and Railroad applications. Rolls flooded and sealed AGM & GEL VRLA products are internationally recognized for their dependability, outstanding quality and industry-leading manufacturer warranties.

fullriver MODEL VOLTS Amp Hour
(20Hr Rate)
6 VDC 428 AH 123 LBS agm canadian solar fla7 YR 4
BP4002113 FLA L16
2 VDC 1124 AH 120 LBS agm canadian solar fla7 YR 4
BP994860 FLA
2 VDC 4860 AH 570 LBS agm canadian solar fla10 YR 4

battery Batteries Ship in about 5 Business Days After Funds Clear. (Subject to Seasonal Increases (Up to 20 Business Days +))

OutBack Sealed AGM Energy Storage Systemagm

roof rackOutBack's new EnergyCell RE high-capacity battery employs a modular design concept with an integral racking system that can be installed more quickly and easily than most Valve Regulated Lead Acid (VRLA) batteries of this size. The included racking system is deployed with four cells per shelf so a 48 VDC system typically uses six shelves. The 1600RE is three modules per shelf and eight high. Terminals and connecting plates as well as clear safety covers are also included.

fullriver MFG
VOLTS Amp Hour
(20Hr Rate)
04001180 800RE 48 VDC 672 AH 2,262 LBS agm canadian solar fla
04001181 1100RE 48 VDC 960 AH 3,797 LBS agm canadian solar fla
04001182 1300RE 48 VDC 1,148 AH 4,330 LBS agm canadian solar fla
04001183 1600RE 48 VDC 1,378 AH 5,082 LBS agm canadian solar fla
04001184 2000RE 48 VDC 1,716 AH 6,580 LBS agm canadian solar fla
04001185 2200RE 48 VDC 1,836 AH 6,870 LBS agm canadian solar fla
04001186 2700RE 48 VDC 2,288 AH 8,600 LBS agm canadian solar fla

battery OutBack Batteries Ship in about 20 Business Days After Funds Clear. (Subject to Seasonal Increases)

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Related Items; Grid-Tie, Off-Grid & Wind Turbine Off-Grid Packages

Solar Energy Storage for Off-grid or Backup.

Batteries for off-grid or grid tied solar powered systems are containers of electrical energy or a collection of electro chemical cells connected together in series. Electro chemical reactions produce a flow of electrons from the negative terminals to the positive terminals inside the battery. Factors affecting the capacity of a battery and how much energy you can expect to reap from the system includes the quality of active material and electrolyte concentration, the number of batteries, type, design and size of the battery plates. If you have ever asked "what is a deep cycle battery", Blue Pacific Solar® energy consultants have put this page together for you to help you understand and make an informed buying decision.

Solar panels produce electricity but without the proper battery storage, the electricity produced is wasted or given back to the utility company at much lower rates than you are buying it for. If your solar panel system is off-grid, you will need to select the correct battery bank wired together with the proper cable size to store electricity to use later. Grid-tied systems also can utilize battery banks to store power for days when the grid goes down during blackouts.

Rechargeable deep cycle batteries are a group of cells that store power using a chemical reaction as the catalyst. Each battery cell has a specific voltage output depending on the battery technology which is separate from the cell size. Batteries used for solar panels are similar to car batteries but constructed differently so they release their energy slowly rather than in a burst which is what car batteries do. Every cell in a deep cycle battery has either a single positive plate with a negative side or multiple positive and negative plates. The plates sit in a electrolyte solution, either gel (AGM) or liquid. This solution allows the negative and positive particles to flow between the plates. As the battery bank is discharged, the lead oxide becomes lead sulfate the sulfuric acid becomes water. In a fully discharged battery there is a very watery acid solution where the positive and negative electrons don't go away, they change into a different form and are stored in the lead sulfate solution.

In solar rechargeable batteries during the charging cycle, the sulfate breaks up forming lead oxide and the water solution becomes a strong acid again. Hydrogen gas is produced which can vary with the different battery technologies used by the various battery manufactures. Electrons are forced back into the plates where they started and the whole process is repeated when a load is provided to draw out the electrons again.

The most common battery used in off-grid solar systems are lead acid batteries because they are usually the least expensive. The downside to flooded lead acid batteries is the monthly maintenance over say sealed AGM batteries. Absorbed Glass Mat (AGM) is the latest in off-grid battery technology. Sealed AGM batteries completely eliminate the hassles of flooded lead acid battery maintenance. There is no liquid acid in the AGM battery. All of the acid is absorbed into the compressed glass matting in the cells. They are completely Non-Spillable, so they can be shipped by UPS or LTL freight with no hazardous warnings or extra fees. Blue Pacific Solar's AGM batteries re-combine the oxygen and hydrogen as the batteries charge and discharge to make them truly maintenance free. No liquid ever needs to be added, No leaks, spills or vent tubes. (Cheaper) Flooded lead acid batteries have a liquid electrolyte inside the container that floods the battery cells. The flooded lead acid battery typically has a cell cap that is removed once a month and check. There are automatic battery watering systems that are available now to help alleviate that monthly chore, but they are not cheap by themselves.

Before we get more into battery types, we need to say a few words about battery DOD or depth of discharge. This is an important topic when planning for any off-grid solar system because it affects not only if your home or cabin will have enough power to see it through the night, but also days without any sunshine. The average depth of discharge (DOD) is the amount of energy that is drawn from a battery bank each day. The electrical load that is drawn during the winter is usually higher than during the summer simply because of the shorter days. That is an important consideration, but no less important is the fact that in most locations, winter has the shortest days and the most days without sunlight or minimal sunlight. Days of autonomy or days without sunshine are expressed in the amount of time a fully charged battery system can supply power without further charging. We have customers ask repeatedly about how much much power will I need, but the truth is that answer always lies with each individual customer to control. The depth of discharge (DOD) is not only controlled by the owner, but is also conversely related to the lifespan of any flooded lead acid or AGM battery system. Batteries do not last forever and at some stage of your solar panel system, grid tied or off-grid, you will need to replace them. Every time you discharge and recharge a battery you cycle that battery the same as if you were driving your car and putting miles on the engine. After a number of cycles, the chemical reaction inside the battery cell will start to break down and eventually the battery will need replacing. A typical battery life cycle may look like this: 20% DOD = 1600 life cycles; 40% DOD = 1200 life cycles; 50% DOD = 1000 life cycles; 80% DOD = 350 life cycles. The life cycle of your battery bank is always controlled by the owner so hence the life of the battery is a function of the owners ability to control their home or cabin energy demand. You should always install a large enough battery bank that you will never discharge your batteries beyond 50%.

This page is not about charge controllers, but you cannot have a discussion about batteries without taking a quick look at the charge control process. A charge controller is a the piece of equipment that does exactly what the name implies, controlls the rate of battery charge. This process is mission critical to ensure the life of your investment and to maximize your life cycles. Simply put, the charge controller role in a solar system is to control the current (amps) and voltage from the solar array to your battery bank. Depending on the charge controller you select, it is sometimes necessary to set the the charge set points on the controller to match your batteries. The three main levels of recharging a battery are bulk charge, absorption charge and float charge. The first stage of charging that occurs when the sun comes up and wakes up your solar panels (system) is the bulk charge stage. This happens first thing in the morning after the batteries DOD has been drained down from the previous day or usage. The bulk charge stage of recharging your batteries is to push as many amps as possible back into the battery bank from your solar system and quickly get the voltage back up in the process. This is similar to filling a glass with water in that when the glass is empty you turn the faucet on full then slowly close the valve when he glass gets full. Same fundamental principle in battery charging only when the battery starts to accept the higher amps being pushed at it, it tends to heat up. Many solar charge controllers also have a temperature probe that is connected to the negative terminal of one of the batteries in the bank. When the probe senses the battery is heating up, it will act as one of the several controls switches to slow down the recharging of your batteries.

The next stage in the process of solar rechargeable batteries is the absorption stage. When your battery bank reaches it's manufactures voltage set point of nearly charged, most of the material in the batteries has been changed to its original form and the amps must be slowed down to limit the amount of overcharge applied. This occurs around the 80% level of DOD. During the absorption stage the battery charge amps slowly tapers off working towards the final stage of the battery charging process. The float stage is the final stage for solar powered batteries and is the process where the controller keeps the batteries in a full state of charge.

Now that we have covered the basics of batteries we can get to the real heart of the off-grid and backup systems, the battery bank. A battery bank is a group of batteries wired together with series or parallel connections (or a combination of both) to provide a specific overall voltage and power capacity. Though the size of the battery bank voltage is often determined by the inverter, for larger inverters and larger loads it is recommended that battery banks be sized for 48 volt rather than the 12 or 24 volt option available with most solar systems. By engineering larger volt battery banks you can usually lower the amps required for the solar system inverter. The lower a system amps are the lower the size and cost of conductors, fuses, disconnects and other balance of system components of a bimodal or off grid battery system. When choosing the type of battery you should consider: sealed or unsealed, allowable depth of discharge (DOD), charging characteristics of the inverter and charge controller, maintenance requirements cost and transportation costs. Additionally, it is recommended that when engineering a battery bank you connect your batteries in as few parallel strings as practical. The primary reason is slight voltage differences and lead to inconsistencies in the charge received by each string eventually causing, in some extreme cases, inconsistent charging.

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