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Batteries; Deep Cycle AGM (Sealed) & Flooded Lead Acid (Vented)
Trojan, Rolls Surette, FullRiver, & OutBack
Deep cycle flooded lead acid and AGM batteries are the most common battery used in off-grid and home backup installations. Energy storage for both applications are required because energy generation and consumption do not coincide. Choose here from a wide selection, best wholesale prices for the DIY customer.
- Battery Cables with Lugs:
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Note: Battery Shipment Within the Continental US Only (48 States)
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?
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?
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.
FullRiver AGM Deep Cycle Batteries
Fullriver battery manufacturing has been one of the leading manufactures in America for over 18 years. AGM deep-cycle batteries are well suited for telecommunication and remote off-grid sites because they require no maintenance and are practically freeze proof. Fullriver deep-cycle batteries are ideal for applications that require sealed batteries with heavy duty cycling capabilities with a power range of 50 AH to well over 1,000 AH.
How Can You Squeeze More Years (Cycles) Out of Your Battery Bank?
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.)
Trojan Deep Cycle Flooded Lead Acid Batteries
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, the industrial line delivers 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 85 years of battery manufacturing experience.
Trojan batteries have been used in off-grid power systems in remote cabins for the past 25 years with great success. Because of their low initial cost and long life, they are affordable true, deep cycle batteries. The T105 battery in remote home system where they are cycled down 20% every day they can last 3 to 6 years. The L-16 battery is a heavy-duty cousin of the golf cart battery with much thicker lead plates and nearly twice the capacity. Trojan’s Renewable Energy (RE) Series (L16RE-2V, L16RE-A, L16RE-B and T105-RE) is a line of technologically advanced lead-acid deep cycle batteries, optimized for renewable energy applications such as solar, small wind, and micro hydro. They have heavier duty separators and plates designed for longer life and their warranty has been extended to two years free replacement and 60 months additional pro-rated on the L16s and 36 months pro-rated on the T-105.
A Little Love During the Planning Stage, Will Help Your Batteries Live Longer.
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.
Myth Vs. Fact. Batteries should not be stored on a concrete floor.
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.
Rolls Surette Deep Cycle Flooded Lead Acid Batteries
Rolls Battery Engineering is one of Americas leading lead-acid battery manufacturers; covering a full range of batteries for railroad, marine, wind and solar applications. With a history of battery production since 1935, Rolls has a stellar reputation for manufacturing durable, reliable and easy to maintain batteries. Rolls solar batteries are known for their high cycle life because they have the thickest plates in the industry, a large liquid reserve, and a tough double-wall construction. Rolls stands behind their batteries with some of the longest warranties in the industry, up to 10 years on certain models. The life expectancy for these deep cycle batteries is known to be in the 15 to 20 year range. Rolls Surette is indeed one mean battery.
Rolls Surette FLA batteries ship ship in 5 to 7 business days after funds clear.
How Temperature Affects the Storage Capacity of Batteries.
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.
Rolls Surette AGM Deep Cycle Batteries
Rolls AGM Battery Engineering is a company who's off-grid and backup battery design is legendary in the solar industry. With a history of battery production since 1935, Rolls has a stellar reputation for manufacturing durable, reliable and easy to maintain batteries. Rolls stands behind their batteries with some of the longest warranties in the industry. Rolls Surette is indeed one mean battery.
Rolls Surette AGM batteries ship direct from the manufacture. Current lead time is 4 to 6 weeks.
Battery Sizing; Depth of Discharge Vs Battery Lifespan
Different types of batteries have different lifespans but you play a big factor in how long that is starting with the decision on the size of the battery bank. To even begin to consider this it is critical for you to spend some time on how much power you need in one day (Daily Load). Desired Daily Depth of Discharge (DOD) in percentage means batteries will last longest with shallow daily DOD, and are worn out faster with deeper daily discharges. Aim for 10-20% daily DOD, with only rare discharges of more than 50% DOD for best battery life.
Battery manufactures do not necessarily think in terms years but rather in terms of cycle life. Every time you discharge and recharge your battery bank you have completed one "cycle". After a certain number of cycles the chemistry inside the batteries will break down and become weaker and weaker until they will need replaced. Battery manufactures will often times show this on the data sheet but typical figures that you will see for cycle life will look like this:
- 20% Depth of Discharge -- 4,000 Cycles
- 30% Depth of Discharge -- 3,000 Cycles
- 40% Depth of Discharge -- 2,000 Cycles
- 50% Depth of Discharge -- 1,600 Cycles
- 60% Depth of Discharge -- 1,400 Cycles
OutBack Sealed AGM Energy Storage Systems
The new OutBack Integrated Battery Rack Systems are a standardized solution built from the industry’s most proven technology and materials in the field of renewable energy management and storage. As consumer and commercial interest builds in grid-interactive and stand-alone renewable power systems, OutBack is available with a full line of EnergyCell Batteries as well as integrated racking and cabinet options. OutBack Power Technologies is a leading designer and manufacturer of reliable power electronics for solar energy applications including solar, wind, micro-hydro, and battery based energy systems. OutBack's' products have been installed in homes, businesses, industrial and government facilities around the world.
OutBack Energy Storage
|Item #||20 Hr Rate||Battery Bank||Watts Energy Storage||Price|
|OutBack Rack w/ 200RE||BP9890050-1||178 AH||48 VDC||8,544 Watts|
|OutBack EnergyCell 800RE||4100190||672 AH||48 VDC||32,256 Watts|
|OutBack EnergyCell 1100RE||4100191||960 AH||48 VDC||46,080 Watts|
|OutBack EnergyCell 1300RE||4100192||1148 AH||48 VDC||55,104 Watts|
|OutBack EnergyCell 1600RE||4100193||1378 AH||48 VDC||66,144 Watts|
|OutBack EnergyCell 2000RE||4100194||1716 AH||48 VDC||82,368 Watts|
|OutBack EnergyCell 2200RE||4100195||1836 AH||48 VDC||88,128 Watts|
|OutBack EnergyCell 2700RE||4100196||2288 AH||48 VDC||109,824 Watts|
Rated Battery Capacity in Ampere-hour (Ah)
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.
Battery Energy Storage, Its About the Chemistry and the Plates.
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.
Battery interconnect cables for battery banks and inverter connections. Choose a length of battery cable that is slightly longer than the run between terminals in the battery bank. You should be cautions about choosing battery cables that are too long because tight bends in the cables can cause cracks in the cable insulation over a period of time creating a safety hazard. How do you choose the right size of battery cable for your battery bank? Generally, the larger the cable size, the better the performance. But larger cable are more expensive. Cable size is mainly determined from the length the battery cable needs to be and the amount of power in amps that the cable must carry.
Batteries AGM Flooded Lead Acid Deep Cycle Rolls Surette, FullRiver, OutBack and Trojansolar energy storage for off-grid or home backup.
Batteries for off-grid or grid tied solar powered systems are containers of electrical energy or a collection of electrochemical cells connected together in series. Electrochemical 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 Solars' 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.
|Marine||Gelled Electrolyte||Absorbed Glass Mat (AGM) Deep Cycle Battery||Flooded Lead Acid Deep Cycle|
|Construction||Thicker plates than automotive, but not as thick as deep cycle. Considered a hybrid battery.||Electrolyte is gelled by adding silicon dioxide to the electrolyte.||Electrolyte is in an absorbed glass mat which means the liquid is absorbed into a fiberglass mat that is sandwiched between the plates.||The liquid electrolyte is sulfuric acid and water solution.|
|Properties||Moderate to low water loss, low self-discharge rate.||No Maintenance. Spill Proof. Must be charged at a lower rate to prevent excess gas from damaging the cells||Low maintenance. Spill Proof. Can withstand deep discharge. Highly efficient, no water loss. Low self discharge rate. An additional benefit of AGM batteries is they can be shipped as normal freight.||Low maintenance, robust charges well with low current, can withstand deep discharge. (Safety WARNING: Extreme caution should be used when storing and filling lead acid batteries. Additionally, flooded lead acid batteries have to be shipped marked hazardous material and require special handling by the trucking company.|
Range in aH
|60 - 260 aH||10 - 130 aH||100 - 3300 aH||400 - 2430 aH|
Life Cycle (Approximate)
| 20% - 1000
40% - 500
| 30% - 800
50% - 300
| 30% - 3000
50% - 1000
| 30% - 4500
50% - 1200
Note: This battery comparisons shown here are for the purposes of general considerations regarding the characteristics of batteries often used in off-grid and home backup designs. You should always compare specific manufactures specifications for detailed comparisons.