Best Batteries for Solar Power Storage

Best Batteries for Solar Power Storage

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One of the main reasons people set up a solar backup system in their homes is for use in case of an emergency. In many emergencies, the electricity from the power grid is no longer accessible. A backup will ensure you remain relatively comfortable while being able to run basic loads in your home.  Electricity needs what we call the load in the set up. An automatic transfer switch will switch your power from the grid to the storage backup in case of a black out. It is important to note that a solar battery backup cannot power your entire home.  It should however keep your critical loads running like lights or refrigerator running in case of a blackout. During the day the power bank can power your critical loads in case of emergency and during night time it can power important house loads.

 Best for Off Grid System and Grid Tied SystemsBest of Grid Tied SystemBest for Small Off Grid Sytem

Product NameBattle Born LiFePO4 Deep Cycle BatteryWeize 12V 75AH Deep Cycle BatteryVMAXTANKS AGM Battery
Voltage12V12V6V
TypeLithium-ionSLA AGMFlooded
Battery Capacity100Ah75Ah225Ah
MaintenanceNo maintenanceLittle maintenanceHigh Maintenance Required
Dimensions and Weight12.8 x 6.9 x 9 inches ; 29 pounds10 x 8.9 x 6.7 inches; 47.2 pounds9.5 x 7.3 x 11 inches; 77 pounds

Terms Used in Batteries

Terms Used in Batteries

Voltage

Large systems use small voltages typically 6v while small systems use higher voltages. Most small solar power systems use 12v.

Battery Rating

Batteries are rated in Ah (amp-hours). This is a measurement of the current output over time. Voltages are fixed but according to type of battery. However capacity is relative to the type of Battery, this is usually printed on its side.

Capacity (Power)

Battery Capacity or power is measure in in Kilowatt hours.  This gives the total storage capacity derived from Voltage and amp hours. Capacity (Watt hours) = Voltage x Ah

Cycle Life

Every time a battery is discharged and recharged this is called a cycle. Cycle life is the number of times a battery can be charged and discharged. This is used to calculate the life of battery.

Depth of discharge (DOD)

DOD is measured as a percentage of energy that can be pulled out of Battery during each cycle.

Efficiency

Batteries are not 100% efficient; Lithium Batteries have 95-98% efficiency while lead Acid batteries have a 80-85% efficiency rate.

Deep Cycle

Deep cycle batteries are designed to produce a steady amount of current over a long period of time. While regular batteries (for example a car battery) are made to provide a large amount of current over a short period of time. For example when you’re starting your car you only need that short burst of power to get the motor running and once it’s running the alternator takes over from there and gives the motor all the power it needs

Lithium Ion Deep Cycle Battery

Lithium Ion deep cycle battery best option for domestic grid connected homes. It is commonly used in battery storage appliances from phones to laptops.  It has a higher density of energy compared to Lead Acid batteries. This means that you get more power with smaller lithium ion battery than you would with a lead acid battery of the same size or even bigger. Lithium ion batteries can tolerate huge temperature changes and can be use between 320 – 1000 F.   Lithium batteries have a long lifetime can last up to 10 years and do not require maintenance. However Lithium batteries have higher upfront costs and must use a controller as it poses a slight risk of fire in case of overcharging. 

Lead Acid Battery

Lead Acid batteries are the common types of batteries we find in Cars, tractors and sub marines. There are two types; Flooded Lead Acid batteries and Sealed Lead Acid batteries. 

Flooded Lead Acid Batteries

Flooded Lead Acid batteries are an old school deep cycle battery. They are high maintenance and need to be stored in a place with good ventilation as they emit gas. They are referred to as flooded as because it needs to be submerged in distilled water regularly.   It is an economical option for off grid systems but need hands on maintenance.

SLA AGM Battery

Sealed Lead Acid Batteries (SLA)

Sealed Lead Acid batteries are the better option if you don’t intend to do regular maintenance.  They are two types of Sealed Lead Acid batteries; AGM (Absorbed Glass Mat) and Gel batteries. They are fairly similar   Lead Acid batteries are mainly used indoors as they are not tolerable to outdoor temperatures.  You will also need a lot of space as you need an array of batteries to up capacity. They are easily recyclable as capacity has been built over the years

AGM batteries, or Absorbed Glass Mat, are the non-spill type that you find (normally) as small 10 amp hour alarm system back-up batteries. This type of battery is also available in larger capacities for solar applications, and have advantages, such as a bit more available energy per pound of battery, and are safer because there is no electrolyte (battery acid) to deal with, there are also disadvantages such as cost, and, for some, the fact that they are ‘maintenance free’ means that once they are done, there is not much you can do.

Gel type batteries are another option, and unlike AGM, are a bit more forgiving as far as ruggedness goes, and are a great option for solar, or other alternative energy setup. They however come with a higher cost.

These can be great for an off grid system that you don’t visit regularly and battery bank for grid tied systems.

Car Battery

The WORST type of battery you can use for alternative energy applications is the standard car battery. They will ‘work’, and some will argue that given the cost and availability, they are the best for someone just starting out, and in some limited way, I agree. For someone in a garage that just wants to tinker with a 100 watt inverter to run a couple lights and that’s all they will ever want out of their system, I would say yes, grab any battery (A deep cycle if you can get you’re hands on one), a cheap inverter and panel hooked into a controller (usually available as a set) will do just fine, and for a couple hundred bucks, you have a working system.

car battery

Golf Cart Battery: Best Battery for Small off grid use

6V Deep cycle batteries are one of the best types of batteries out there for long extended use in a solar system or without any type of charger nearby. A pair of 6V batteries running together to create a 12V battery bank can last up to three times longer than a single 12V deep cycle battery. On top of that they have a longer life span than a 12V battery and are made to be used for long periods of time.

A typical golf cart battery costs about the same as a 12 volt car or deep cycle battery.  You will need two of them to run on a 12V inverter. This will seem to doubles the cost right up front, compared to a 12v battery and a waste of money. It actually isn’t. A set of golf cart batteries can run for much longer and they are designed for this type of use, so, at double the cost, I got 4 times the capacity.

VMAXTANKS 6 Volt 225Ah AGM Battery