What Is The Best Battery For Your Solar Power System?

trojan batteryDeep-cycle, lead-acid batteries are widely used in renewable energy and grid-backup system, and are ideally suited for these applications because of their long, reliable life and low cost of ownership. There are many companies that sell deep-cycle lead-acid batteries, so it is important to understand the technologies and other performance factors that affect overall operation and battery life.

Types of Deep-Cycle Battery Technologies

Deep-Cycle Flooded Lead Acid (FLA) Batteries
Deep-cycle flooded batteries are the most popular type in use today in renewable energy systems, and contain electrolyte which fully submerges the plates of the battery. There are several benefits to using flooded batteries, such as lower cost, longer life, easy maintenance, good performance when operating at partial states of charge, and a long, proven history of use.

Deep-Cycle Valve-Regulated Lead Acid (VRLA) Batteries
Deep-cycle VRLA batteries, which include AGM and gel technologies, are designed to eliminate the need for water addition and can be used and installed in any position. They are engineered so that oxygen created by the positive plates during charging can migrate to the negatives plate where it is reduced to water, significantly reducing water loss.

Factors Affecting Cost of Ownership
When buying a deep-cycle battery, there are several factors that should be taken into account to determine the total cost of ownership over the life of the battery.
Price: A battery with a low price is always attractive, but if this is obtained at the expense of quality and battery life, the cost over time will be high because of the need for frequent battery replacements. That’s why it’s important to consider issues other than price when making the decision.
Capacity: A battery’s capacity is very important since it is the measurement of the amount of energy stored in the battery.
Voltage: The battery bank voltage must be considered to ensure it matches the system requirements. The battery bank voltage is often determined by the inverter specifications if installing a DC to AC system, or by the voltage of the loads in a DC system.
Brand: Choosing a battery from a reputable company is important. Because many companies sell deep-cycle batteries, choosing a company that focuses on deep-cycle technology with a proven history of manufacturing deep-cycle batteries means you will benefit from the company’s expertise.

The Most Important Consideration – Cycle Life
While the factors above are important, the most critical consideration is cycle life, which measures the number of discharge/charge cycles the battery can provide before capacity drops to a specified percentage of its rated capacity. Batteries from different manufacturers may have the same capacity and energy content, and be similar in weight, but design, materials, process, and quality influence how long the battery will cycle.

Battery Ratings
The nameplate rating on a battery is the fully developed capacity; therefore, testing a battery immediately after it is purchased is misleading since it may take up to 100+ cycles for it to reach its full capacity. Beware of a battery that promises full capacity at the time of purchase or one that reaches full capacity after only a few cycles. Batteries with a 100+ cycle warm-up will always outlast a battery touting a high initial capacity.

As the solar market grows worldwide, the importance of implementing deep-cycle batteries as the energy storage component for renewable energy systems is critical. Because the battery bank in a solar application often represents a considerable percentage of the overall equipment cost, careful attention to proper selection and maintenance of batteries is more important than ever in maximizing return on a deep-cycle battery investment.

By: Dean Middleton, Director of Sales for Renewable Energy at Trojan Battery


  1. micWeekly says:

    I wish some North American companies would develop or import supplies of nickel-iron batteries for solar arrays. 100+ year life span, non-toxic highly abundant materials and less prone to damage if electrical short occurs, the only trade off is a slightly lower voltage and different but safer electrolyte.

  2. Robert Ford says:

    Prius and batteries are a step in the right direction period. Technology is getting better and better every day, more efficient and less impacting to the earth. Im proud of our society now, imagine how much impact they had on the earth in the mid 20th century without even being aware of it. Batteries are a must for solar systems, if you don’t have them than your getting ripped off by the power company on your night time use (when your actually home)

  3. Thanks to Trojan for the sales pitch. How about environmental impact as a factor? It’s a serious consideration for those of us trying to implement renewable energy systems. It would be good to have an article and discussion on the impact of this part of any off-grid/backup system. It’s frequently the most difficult part of the system to justify to a client.

    • Get a life wacko. Thank you for the information Trojan! This product is beneficial in many ways, as an added plus it availability helps the environment..

      • Patrick James Furman Sr. says:

        wacko? you seem to be the wacko not wanting to discuss the effects of lead based bateries. Even though I chose trojen, I would like the discusion on environmental impact.

        • Pissed off says:

          OMG I don’t see you wacko’s talking about the effects of the Prius on the environment. Get a freaking life…

          • While there is no question that – most – current Hybrid vehicles have a greater imbedded carbon footprint than traditional vehicles, one cannot deny the technology that Toyota – and others – have developed.

            Solar arrays need batteries, and this article helps us to understand the options.

          • No question according to whom? My Tesla charges on solar. My two Chevrolet Volts charge on solar as well. Where’s the impact? Oh, and the battery packs go back to ABB and are turned into whole house battery backup units. There is a question….where are you getting your “facts”!?!

          • FlyOnWall says:

            That is the whole issue you simpleton. The electric cars are trojan polluters. The electricity generation is usually via gas/coal plants. Get informed.

          • Anyone who still opposes solar and electric vehicles is an idiot, plain and simple. Even though we still have to generate most of the electricity in a coal/gas plant, the fuel that is being burned produces far more power than a internal combustion engine ever could. They take the waste heat and run it back through again to increase efficiency to 60% versus the 20% your car’s engine can do. We just have to be good with recycling the batteries and eventually we will be able to completely remove our dependence on fossil fuels. Electric vehicles are the first step of the process.

        • Ummm lead based batteries are not a big environmental impact, lead occurs naturally in the environment and 99% of lead is recycled which makes it less of a mining impact and a great example for recycling programs.

    • Lead acid batteries are one of the easiest products to recycle – the only component that can’t be recycled is the paper liner between the plates. That’s pretty low impact in my opinion.