What Is The Best Battery For Your Solar Power System?

trojan battery

For an updated, more thorough version of this topic please click here. 


Deep-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

  • Jens Bauer

    @micWeekly: Two suppliers / manufacturers in Canada…


    -Thank you for posting information about the NiFe battery; this helped me a lot, and I will probably get those for my solar panels (when I get solar panels). :)

  • scrooge

    what about nickel iron batteries

  • Scrooge

    What about lead iron batteries

  • Steven Bushong

    I’ve deleted any comments that call specific users names. Personal attacks will not be tolerated.

    • Dennis Vines

      Would you guys have any specific recommendations for batteries?

  • Mobile hot dog cart man

    All I’m trying to do is find out what the best battery is for my solar panels to run my hot dog cart and All you people want to do is fight? wth thanks for nothing. Who cares about the damn cars. Stay on topic

    • Steven Bushong

      Hi there — thank you for reading. Beginning in January, Solar Power World will have a special section dedicated to batteries and off-grid technology — I hope this helps with your hot dog stand!

      • Roger Priddle

        Hello – your “special section” is just what I’m looking for! But I haven’t found it yet…
        I’ve been off-grid long enough that my lead acid batteries are getting tired – they can be recycled, and that’s good, and I’d be happy to get more of the same. Given that neither space nor portability are an issue what is the current thinking?

        My existing bank is 1600 AHrs @ 24VDC fed by 1650 watts PV.

        Any ideas?

  • Bob

    A suburban is greener than a Prius. When you consider a lifespan of twenty years the Prius will most likely need three battery replacements. Take into account that the ore for the batteries is mined in China, refined in Canada, and assembled in britan and then shipped back to china, what do you suppose the carbon footprint is for all of that?
    Last year our EPA shut down the
    Set us lead ore processing facility, now all prime lead comes from another country. Remember they never really proved that asbestos causes cancer and it’s a naturally occurring material that comes out of the earth just like lead does. Oxygen will kill you if you consume enough of it.
    The lead that affects the human body is not the lead that’s in batteries or bullets, it’s the chemical lead that the body can absorb.
    In Kalifornia we have prop 65 that makes every thing known to man cancer causing and hazardous. Everything is if you overdose on it. Vitamin D is good for you, but not in gigantic doses.
    My father worked in the foundry business his entire life, he’s now 93 years old. He poured stell, iron, aluminum, and yes lead. His father lived to be 92 and worked 364 days a year 16 hours a day. His one day off was Xmass. My father had to take him his lunch and dinner and shovel the coal while he ate to keep the laundry shutting down.
    In the Bay Area we have The Bay Area Air Quality Management District and they are shutting down the few (about ten) foundries left. The result will be 250,000, yes 1/4 million people out of work and they could care less. If they were really concerned about air quality the would do a cash for gas cars program to incentivize people to buy a new diesel or hybrid vehicle. You put ten of the diesel vehicles on the road for the same emissions as one of the new gas vehicles.
    Kalifornia does not care about business.

  • micWeekly

    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.

  • Robert Ford

    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)

    • Bizonberg

      not really…

    • Lorne

      Sounds good if companies were not profit driven, they will throw out toxic materials in the trash, to save a buck. Unless you work for or have done extensive research on a company(near impossible) you don’t know if they are protecting the earth.One can only hope they are.

      • FiendishThingy

        Lorne: “… if companies were not profit driven…”. All companies must be profit-driven or they go out of business. Private citizens are also profit-driven or we would not have any savings accounts to fall back on. Everyone needs profits to stay out of the red, so obviously everyone need to driven.

  • http://www.facebook.com/timmassons.page Tim Masson

    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.

    • Mike

      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.

        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

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

          • eddieo

            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.

          • http://www.brickellprincess.com/ Brickell Princess

            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”!?!

          • James

            The impact is in the construction. To build these vehicles is a greater impact when you go from material sources all the way through production and maintenance.

          • FlyOnWall

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

          • jon

            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.

          • sukamadicabiach

            oil is not a fossil fuel. that is a lie.oil is the blood of the Earth. it replenishes like when little blood taken from human. but because of the greed of money for oil companies Mother Earth is dying.

          • Xeno

            Wow… You could not be any more wrong. Have you even been through Ecology / Earth and Space in High School. Oil and any other natural gases can take many years to replenish.

          • Kenneth Kirkham

            Oil is not a fossil fuel as we were taught Oil wells that had been drained in the 1930’s have been found to be full producers again. Numerous scientists now understand that oil can be produced by methane and a bacteria. This occurs naturally. There is a good reason we now have greater oil reserves than in any time in history.

          • Matthew Broxson

            This is completely untrue. The reason we have the large deposits we do is due to environmental conditions that existed during the Carboniferous period. The small amounts that are produced now are insignificant and localized. No matter the volume, the process takes millions of years, but sure, in millions of years the earth will have produced a little bit more. You have to view it in context: our use is trillions of times more than what would be sustainable for this process. The wells that have come back into production is not because more was produced it is because the areas around those wells that dried allowed some of what was there to ‘diffuse’ through the stone to saturate the stone around the wells again. We only have oil reserves because we have been exploring more than ever before.

          • John Puccetti

            This whole issue is air pollution from burning fossil fuels.

          • Joe Smith

            So I can assume you don’t drive a car or use any products made from oil? If so, you shouldn’t run your mouth. And how many companies are not in the business to make money?

          • Steven Woodcock

            I’d love a solar powered SUV but there aren’t any just yet. Honestly even if there was I’d still have a problem –it wouldn’t be AT HOME to be charged by my solar panels when I’m at work.

            Now upon retirement it might become possible. I like a LOT the idea of having a truck that didn’t have all those bits hanging down underneath it since I live on a pretty rough gravel road.

        • Chris

          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.

    • Ernie

      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.