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How To Pick Out The Best Battery For a Solar Panel System, Battery Bank, or Off-Grid System

Have you ever wondered how to pick out the best battery(s) to your solar panel system (or off-grid energy system)? Or have you wondered what makes one deep cycle battery better than another?  If so, this article will answer these questions and give you specific things to check on before purchasing your new battery (to ensure you get the most bang for the buck)!

When choosing a battery (or batteries) for your solar panel system, there are three categories of batteries which work best.    We’ll do this in two parts:

Part 1)   Instantly compare the three main kinds of solar batteries (lead acid, saltwater, and lithium).   And,

Part 2)   Assess the elements of batteries, such as: depth of discharge, capacity and power, efficiency, battery life, and manufacturer.

By the end of this article you will know exactly how to pick the best battery to your own solar panel system!

So let’s begin…

So the first decision to make is the type of battery that will fit your system.

Lead acid batteries are the most commonly used rechargeable battery in the world. They’re also one of the longest-used and most reliable batteries in existence.  Compared to the other batteries we will discuss in this report; they are the cheapest option but you exchange price for some battery life and depth of discharge.  But for homeowners needing a great deal of storage for a lesser price, or whether you are just making the transfer to a solar panel system, lead acid batteries may be an excellent option.  They’re the sort of battery we use in the majority of the battery banks in our solar panel systems.

Saltwater batteries are more expensive than lead acid batteries, but also have a greater lifespan.  Unlike lead acid batteries, saltwater batteries are basically brand new to the market and remain both somewhat untested and more difficult to come across.  Of the 3 kinds of batteries, saltwater has the best depth of discharge, which means you’ll find the most output per charge before needing to recharge.

Lithium batteries are the most expensive and the longest lasting of the three types of solar batteries.  Their depth of discharge is less than that of a saltwater battery, but more than that of a lead acid battery. Comparing all three choices, the lithium ion battery is probably the highest rated, but also the most expensive.  A good example of a lithium battery is the Tesla Powerwall.

Part 2) Assess the elements of batteries.  Once you’ve picked the best battery type for your solar panel or off-grid system (that meets your system’s needs), there are elements to research to find the ideal battery to your system.  

Cost

Price is probably one of the more obvious components.  But the old saying,”you get what you pay for” holds true when buying batteries as well.  In some instances though, certain batteries could be overkill for your system so the most expensive battery might not be the best choice always.

Battery Life and Warranty

For many systems, a battery will cycle every day, meaning it will drain and charge regularly.  With every cycle, the battery’s ability to hold the same charge lessens slightly.  So one component to consider is the guarantee on the battery which guarantees a certain number of cycles of useful life.  But keep in mind that when you use the maintenance and reconditioning methods we teach you at the EZ Battery Reconditioning application, you can extend the life of your batteries.

Length of Discharge

Depth of discharge is how much you can drain the battery down before needing to recharge the battery without harming its life.  Certain solar batteries can be depleted further than others, allowing for more use between charging.  Basically, a battery with a 90% depth of discharge per cycle provides more battery power per charge compared to a battery with less.

Ability and Power

Measured in kilowatt hours (kWh), capacity is the amount of energy a battery can store over time. The more capacity a battery has, the more power it can store.   Power is how much energy that a battery can provide at a given moment.  A battery with a high capacity and higher power can run a massive system for several hours; a battery with low capacity and high power can run a large system but only for a short time.

Efficiency

Efficiency is the amount of energy used compared to the quantity of energy it took to save energy.  Batteries require power to charge and efficiency compares the energy taken to control a battery together with the amount of energy that the charged battery produces. 

Manufacturer

This might not be a component most would consider, but it’s something to focus on.  Like other technology, there are both trusted brands and startup brands.  A trusted brand comes with known flaws and advantages; a startup brand can perhaps have better technology, but can also have unknown technological difficulties.  Based on your system demands, you may decide to go for a well-reviewed company or one that is brand new to the market.