Deep Cycle Batteries

Deep Cycle Batteries

Solar batteries provide energy storage for solar, wind power, or other renewable energy systems. A solar battery is just a deep cycle battery -batteries for solar panels are designed for the prolonged, repeated, and deep charging/discharging cycles needed to store and distribute energy generated by intermittent renewable sources like solar panels. For this reason, car batteries cannot be used as solar power batteries.

Grid tied systems do not need batteries unless you want to maintain power during utility grid outages. But for off grid systems, deep cycle solar batteries are essential and will likely be providing 100% of your electricity. This makes correctly sizing a solar battery bank among the most important steps of off grid system design - watch our video below for more.

Find more information on deep cycle batteries below, on our blog, in our DIY Solar Resources Library, or by talking with our energy storage experts at 877-878-4060.

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Solar Batteries

Solar batteries are an important part of any solar energy system, allowing the energy from the sun to be stored and used later. Charging solar batteries is not as complicated as it may seem, but there are certain things to consider before doing so. This post will provide an overview of how to charge a solar battery, types of solar batteries, how long solar batteries typically last, whether you can charge solar batteries without a charge controller, and how much they cost. Read more below to get started with solar battery storage.

How to charge a battery from solar panel?

If you want to access renewable energy after the sun goes down or during a power outage, you will need to invest in deep cycle batteries. Deep cycle batteries are specifically designed to provide reliable and efficient power in solar and other renewable energy systems, while car batteries are not. 

Deep cycle batteries differ from car batteries in several ways. First, they are designed to discharge and recharge multiple times over long periods of time without being damaged. Car batteries, on the other hand, are meant to start a vehicle and then quickly recharge. When it comes to selecting a deep cycle battery for your renewable energy system, lithium batteries are a great choice. They offer several advantages over AGM (absorbed glass mat) batteries. Lithium batteries last longer, require less maintenance, and are better suited for high-temperature climates.

It is also important to make sure that the battery bank voltage matches the solar array voltage in your system, unless you plan to use an MPPT charge controller. An MPPT charge controller will allow you to use a higher voltage battery bank than your solar array, resulting in more efficiency and greater power production.

Overall, deep cycle batteries are an essential component of any renewable energy system. Selecting the right battery for your needs is key to getting the most out of your system. With proper selection and maintenance, you can ensure that your system will continue to provide reliable power for years to come.

How long do solar batteries last?

When properly cared for, solar batteries can last up to twenty years.Solar batteries are an important part of any solar energy system. Without them, energy generated by the solar panels would be wasted. However, understanding how long they will last is key to making sure you get the most out of your investment. Lithium-ion batteries are the most popular type of solar battery, and they are known for their longevity. This makes them a great choice for larger solar energy systems. Flooded lead acid batteries are also popular, but they tend to have a shorter lifespan. With proper care, they can last between five to ten years. Sealed lead acid batteries tend to have the shortest lifespan, typically lasting less than five years. It's important to note that the lifespan of a solar battery is not just determined by its type. Factors like temperature, use cycles, and the quality of the battery itself all play a role in determining how long a solar battery will last. That's why it's important to buy good quality batteries and keep them at optimal temperatures for maximum lifespan. In addition, it's important to make sure you have enough solar batteries for your energy needs. If you don't have enough batteries, you won't be able to store all the energy produced by your solar panels and will likely end up wasting energy. Finally, having a good battery maintenance plan in place is essential for keeping your solar batteries in top condition. Regularly checking and testing your batteries can help you detect any potential issues before they become serious problems.

By understanding how long solar batteries last, you can make sure you get the most out of your investment in a solar energy system. With proper care and maintenance, you can ensure your solar batteries last as long as possible and give you years of reliable energy storage.

Can you charge solar batteries without charge controller?

You should always use a charge controller when charging solar batteries. When it comes to charging solar batteries, there are many different types of solar charge controllers. The three primary types are 1- or 2-stage solar charge controllers, 3-stage and/or PWM solar charge controllers, and maximum power point tracking (MPPT) controllers. Charge controllers for electric vehicles and golf carts may also be used for charging solar batteries. The most commonly used charge controllers range from 4 to 60 amps of charging current, but newer MPPT controllers can achieve upwards of 80 amps. This makes them very efficient for large-scale solar arrays. Without a solar charge controller, the battery may overcharge, reducing its lifespan and performance. For this reason, it is highly recommended that you use a solar charge controller to safely and efficiently charge your solar batteries.

How much do solar batteries cost?

Solar batteries are very affordable, with costs ranging from around $20 to over $5,000 depending on the capacity and the technology. It's important to not just look at the cost per unit, but also the total cost of setting up a battery bank. This means taking into account any installation fees, additional hardware, and other costs. When looking at the cost of a solar battery, it's also important to consider the cost per cycle. This is the cost of one full cycle of use. Depending on the technology and size of the battery, a cycle may last anywhere from hundreds to thousands of cycles. If you're planning on using your solar battery for a long time, this cost-per-cycle should factor heavily into your decision-making. Taking all of these costs into account can give you a better understanding of the true value of a solar battery.

In this video you will learn how to correctly size a solar battery bank.

Solar Battery Bank Sizing Tips

We strongly recommend watching the solar battery bank sizing video above, but some of the key takeaways are:

diagram of solar batteries connected in series and parallel
  • Connecting batteries in series (positive terminal of one battery to negative terminal of the next) increases voltage but keeps amp-hour capacity the same.
  • Connecting batteries in parallel (positive to positive, negative to negative) increases amp-hour capacity but keeps voltage the same.
  • Limiting the number of parallel battery strings minimizes the problems from uneven charging/discharging between strings.
  • Don't use batteries of different voltages or ages in the same battery bank. In fact, using multiples of the same exact battery to create your bank is recommended.
  • You can convert back and forth between a battery’s Ah and Wh (or kWh) by using the battery’s voltage since Watt-hours = Amp-hours x Volts.
  • Caveats about that the energy storage capacity number you got from our kWh calculator:
    • The number provided by the calculator is your daily energy use. A battery bank based on that number will only provide enough power for one “day of autonomy”. It’s a good idea to double or triple your battery bank’s capacity and consider incorporating a generator into the system to ensure you’ve got enough power for prolonged periods of no solar/wind power generation.
    • The recommended Depth of Discharge (DoD) on the deep cycle battery model your bank uses must be accounted for. For example, many lead acid batteries recommend discharging no deeper than 50% to get the most cycles out of them - meaning you should plan to only ever use half their rated capacity. Pay close attention to recommended DoD when comparing battery options to use for your bank.
    • Ambient temperature and the efficiency of the system’s inverter also affect how a solar battery bank should be sized.
    • If you expect your daily kWh use to increase soon (electric vehicle purchase, more people living in the house, etc.), consider oversizing your battery bank. Expanding a deep cycle battery bank later can be done in some cases, but is generally not recommended.

After determining the capacity and voltage of your battery bank (12V, 24V, or 48V DC), you can start thinking about the specific deep cycle batteries that will make up the bank. Need help making those determinations? Call us at 877-878-4060 or request a free off-grid solar power system quote.

Types of Solar Batteries

A deep cycle solar battery is the only kind of battery that makes sense for a solar or wind system, but what about the different types of deep cycle batteries - lithium, flooded lead acid, AGM, and gel? Which kind is best?

While it’s true that each different cell chemistry has its pros and cons, it’s also true that lithium batteries are easily the best choice for most solar panel systems. Compared to all the other chemistries, lithium batteries are deeper discharging, longer-lasting, lighter weight, safer, and maintenance-free. Yes, they are more expensive up front than the other types, but in the long run, the cost per kWh cycle is the best metric to look at - and with both longer cycle life and deeper Depth of Discharge than the alternatives, the cost per kWh cycle you’ll get from a lithium solar battery bank is unbeatable - and you won’t have to replace them as often.


Flooded Lead Acid

Sealed AGM

Sealed Gel

Upfront Cost High Low Moderate High
Cost per kWh Cycle Lowest Low Low to moderate Moderate
Expected Lifespan 10+ years 3-5 years 4-5 years 5-6 years
Max Recommended DoD 80% 50% 50% 50%
Regular Maintenance None Watering, equalizing, cleaning None None
Best Applications All renewable energy systems Full-time residences with committed, hands-on owners willing to do regular maintenance and replacement Part-time residences with intermittent use Part-time residences without many high-surge loads
Worst Applications Projects on a tight budget Part-time residences with intermittent use Systems requiring deep discharges Systems requiring high-amperage charging and discharging

Adding Solar Batteries to a Grid Tied System

If your solar power system is connected to the grid, it will shut down during grid outages as a safety precaution for the workers who will be repairing the utility equipment. To keep a grid tied solar system online during a grid outage, you will need to add a battery bank and a second inverter to create what is known as a hybrid solar system.

This video explains the two main ways to add battery storage to an existing grid-tied solar system.

Adding batteries to a grid-tied solar system is becoming increasingly popular - especially in areas where the utility grid is unreliable due to excessive demand (rolling blackouts) or frequent extreme weather events. For a new hybrid solar system or to retrofit an existing grid-tied system with battery storage, use our battery backup power system quote.

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