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

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

 

Battery Sizing

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.

Model	Item #		Volt	Amp Hour (20Hr Rate)	Data Sheet	WTY	Size L X W X H	WT (Lbs)	Price
AGM DC105-12	BP9DC10512		12V	105 Ah		7 YR	12.25" X 6.75" X 8.5"	67Lbs		Qty
AGM DC200-8	BP9DC20008		8V	200 Ah		7 YR	10.25" X 7.25" X 11.75"	88Lbs		Qty
AGM DC224-6A	BP9DC2246A		6V	224 Ah		7 YR	10.25" X 7.06" X 9.75"	66Lbs		Qty
AGM DC260-12	BP9DC26012		12V	260 Ah		7 YR	20.51" X 10.59" X 8.66" (8-D Battery Type)	172Lbs		Qty
AGM DC400-6 L-16	BP9DC4006		6V	415 Ah		7 YR	11.65" X 7.08" X 16.75"	123Lbs		Qty
AGM DC1150-2 L16	BP9DC11502		2V	1150 Ah		7 YR	11.61" X 7.05" X 16.18"	126Lbs		Qty

 

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.

Model	Item #		Volt	Amp Hour (20Hr Rate)	Data Sheet	WTY	Size (L X W X H)	WT (Lbs)	Price
T-105RE	BP4001937		6V	225 Ah		2 YR	10-3/8" X 7-1/8" X 10-7/8"	67Lbs		Qty
L16P-AC	BP4001968		6V	420 Ah		5 YR	11-5/8"X7-1/8"X17-11/16"	114Lbs		Qty
IND9-6V	BP4002026		6V	445 Ah		5 YR	15-3/8"X10-1/4"X24-1/4"	220Lbs		Qty
L16RE-2V	BP4001920		2V	1110 Ah		5 YR	11-5/8"X7-1/8"X17-11/16"	119Lbs		Qty

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.

Model	Item #		Volts	Amp Hour (20Hr Rate)	Data Sheet	WTY	Size (L X W X H)	WT (Lbs)	Price
S-550	ROLLS-S-550		6V	428 Ah		7 YR	12.5 X 7.125 X 16.75	123Lbs		Qty
S-1380	BP4002113		2V	1050 Ah		7 YR	13.25 X 7.125 X 16.75	115Lbs		Qty
2-KS-33PS	BP9900162		2V	1766 Ah		10 YR	13.25 X 8.31 X 24.81	208Lbs		Qty
2-YS-31PS	BP9900182		2V	2430 Ah		10 YR	15.5 X 9.25 X 31.81	285Lbs		Qty

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.

Model	Item #		Volts	Amp Hour (20Hr Rate)	Data Sheet	WTY	Size (L X W X H)	WT (Lbs)	Price
AGM S6-275	BP9942755		6V	250 Ah		7 YR	10.25 X 7.125 X 10.75	77Lbs		Qty
AGM S6-460	BP9946055		6V	415 Ah		7 YR	11.75 X 7.125 X 16.75	123Lbs		Qty
AGM S2-590	BP9945905		2V	550 Ah		7 YR	9.5 X 6.75 X 14.5	77Lbs		Qty
AGM S2-945	BP9949455		2V	880 Ah		7 YR	16.25 X 6.865 X 14.5	118Lbs		Qty
AGM S2-1275	BP9911805		2V	1150Ah		7 YR	18.75 X 6.875 X 14.5	123Lbs		Qty
AGM S2-2375	BP9923755		2V	2200Ah		7 YR	19.25 X 14.75 X 15.125	286Lbs		Qty

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.

Cycle 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.

 

 

 

Article on Battery Systems Maintenance and Repair / Home Power Magazine

Article on Battery Blunders and How to Avoid Problems / Home Power Magazine

Article Choosing Batteries / Home Power Magazine

Article Homemade Battery Box / Home Power Magazine