Learn About Solar Batteries

Whether you are interested in checking out solar power for your main home, cabin in the woods or bug out spot, unless you are independently wealthy and don’t care about cost, there are things to research in order to make an informed decision before buying. I, personally, become overwhelmed when too much new information is thrown at me at one time, therefore, I’m going to research the topic as if it were intended for me. If I can understand it, you won’t have an issue at all. Let’s learn about solar batteries.

The first thing to learn is batteries are not the same and may have totally unequal life and performance expectancy, even when labeled with nearly identical specifications. Choosing the wrong battery for your solar system could lead to frustrating downtime, lower than expected performance and/or expensive repairs or modifications.

Materials and Manufacturing Matter a Lot

Simply put, a battery produces electrical current through a chemical reaction that converts the stored chemicals into electrical energy. That’s enough science. The important part is this whole process begins with the lead itself and the cost of lead has went through the roof since 2006. Since lead comprises 60% – 80% of a battery’s cost there is a push to use less lead and more additive formulation and lead-oxide production in order to keep costs down.

All American battery manufacturers use recycled lead, so there is a common baseline for all batteries, the difference begins with the amount of lead used for the battery and quality of manufacturing.

  • Some manufacturers use expanded metal and stamped grid production because they are quicker, but these methods tend to embed impurities and porosity into grid wires. In contrast grids which are produced by gravity casting contain no impurities and nearly zero porosity, therefore producing plates that provide extended life and improved reliability.

  • Active lead materials are applied to plates in a process known as pasting, and there are dozens of variables involved in paste mixing and application which significantly affects the battery performance. Conventional systems rely on manual hand pasting, which is as good as the operator that day, while others employ a computerized system which eliminates any variables.

  • Once the grids are pasted they are cured in specialized ovens, set at specific temperatures and humidity, in order to bond active lead materials to the grid for better performance and longer life. Be sure your battery was built with plates cured in such ovens.

  • After curing, the battery plates are stacked in groups and are connected by fusing the plates together with a lead strap, which creates a parallel circuit between the plates. Many companies still utilize the strap-assembly process, where workers manually attach lead lugs to a strap and burn them together using a torch and lead stick, or by manually pouring molten lead around a jig, This process, which began in the early twentieth century, produce weaker connection points.

  • In contrast other companies employ a cast-on-strap (COS) assembly system which fuses the battery plates simultaneously at the optimal temperature. This method insures strengthened connections, resist cracking and improves battery life, as well as reduces corrosion, increases current and reduces maintenance.

  • Following assembly, batteries are charged for the first time in a process called formation that converts lead sulfate and insures maximum capacity. Some companies speed up this process by using higher currents, which cuts production time and costs, but doesn’t fully activate all the usable material, which negatively affects performance and life expectancy. In contrast low current formation results in longer battery life.

Why did I run you through a quick tutorial of battery assembling? I wanted to demonstrate a few of the differences which make one battery better than the other although they are rated the same. By being able to recognize quality and compare manufacturing techniques and materials you are better equipped to know what type of battery you actually need and how much to spend to get it.

You’ll need to choose a voltage for your solar system, which can be 12, 24, or 48 volt. The higher the voltage the less energy loss, although most off-grid homes use a 12 or 24 volt battery system. Is it possible to use a car or truck battery? Yes, for short bursts of high energy, but they are not intended for a deep discharge, and more than likely you’ll require a deep-cycle, lead-acid battery which permits partial discharge and deep slow discharge.

Understanding Different Battery Types

Lead-acid batteries are made for specific applications, therefore not all of them are suitable for usage in a renewable energy system. For instance, automotive and commercial batteries deliver short burst of power and stay charged most of the time making them unsuited for long term usage with a solar system. Uninterrptable power supply batteries (UPS) are designed to provide electrical energy for short term emergency situations, but won’t last under continuous discharge and charge cycles.


Deep-cycle batteries are capable of delivering electricity for a long time, several days, because they are designed for constant charge and discharge cycles. The deep-cycle battery and renewable energy battery are very similar, but the RE battery is fine tuned for specific renewable energy applications required for solar power.

Flooded batteries are the most commonly utilized battery in renewable and grid-backup systems. They are easy to maintain, long-lasting, reliable and most importantly affordable. Valve-regulated lead-acid (VRLA) batteries are maintenance free, but usually more expensive. Again, the quality of materials and quality of construction methods will dictate the reliability of the battery. Ask questions. Do research on the manufacture.

Best Solar Batteries?

Batteries used in solar power systems (renewable energy systems) are made out of one of the three chemical compositions; lead acid, lithium or saltwater. Lithium ion batteries seem to be the most popular choice for solar panel systems, but other battery types can be more affordable at a small loss of ability.

Lead Acid Batteries

Lead acid battery technology has an established track record as they have been used in off-grid energy systems for decades. As with everything there are pros and cons, but this is the least expensive option and like I said, it has a proven track record for reliability and energy storage.

Lithium ion Batteries

The majority of new renewable energy technologies favor some form of lithium ion chemical composition, because they are lighter and more compact than lead acid batteries and tend to have a longer life span. However, they are quite a bit more expensive than the lead acid option.

Saltwater Batteries

Saltwater batteries are a relative new comer, which contain saltwater electrolytes instead of heavy metals. The main advantage is a saltwater battery can be easily recycled while heavy metal batteries require special disposal, which is great for the environment. However, the technology by being relatively new, is untested.

How Long Do Charges Last on a Solar Batteries?

That is a one of those it depends question and answer. There are many variables involved which can effect that calculation. The best way to explain is to use a hypothetical example.

Based on the US Energy Information Administration, the average U.S. Household consumes @30 kilowatt-hours (kWh) of energy per day. The typical solar battery can deliver 10 kWh of capacity per day. Based on those numbers, 3 batteries will power your entire household for 24 hours. However, nothing is that simple.

In reality due to fluctuations in operating draw, batteries will not be able to operate at 100% capacity, but is actually closer to 90%. So your 10 kWh just went to 9 kWh of useful capacity. Ultimately, if you’re pairing your batteries with a solar PV array, one or two batteries can provide sufficient energy during the nighttime hours when the panels are not producing, but may require 3 or 4 batteries to power the household during the daytime activity. It is also essential to have additional batteries in reserve to provide power during extended cloudy weather conditions when your solar panels produce no power. A solar battery or solar installer representative will be able to offer a more definitive answer to your particular situation. However, you will require a bank of batteries, whether it be 3 or 10.

From what we’ve learned about solar batteries is their lifespan is between 5 and 15 years. Currently if you buy a battery today you can anticipate you’ll need to replace the battery at least once, if not twice, to match the 25 – 30 year lifespan your PV system will last. Or you can learn the simple method to recondition batteries and never have to worry about replacing them.

However, everything associated with solar power system technology, cost down, productivity up, improves as the demand for solar energy increases. As we learn about solar batteries it can be reasonably expected battery life span will increase with technological advancements.

On a parting note; batteries for a solar energy system are not cheap, but if you view the expense as an investment which could pay big dividends in energy cost savings, then it takes on a different light.