Those new to the solar world have the same question when they see the price of batteries. “Can I use car batteries for my solar system?”
Let me save you a lot of headaches and money with one word, no. However, they can be used for some small, infrequently used solar systems.
Here are some of the things we’ll be covering in this article
- Types of batteries
- How Batteries work
- Car Batteries with solar
- The best battery for your solar system
This guide will save you time and money – ensure you get the right battery for your solar panel setup.
All Batteries Are Not Made the Same?
Before discussing why a car battery is not suited for solar applications, it is necessary to know a little about how a battery works.
There is a lot of chemistry involved in battery operation. This is a highly simplified explanation of how a battery provides electricity.
How Batteries Work
Lead Acid Batteries rely on an exchange of ions between sulfuric acid and lead plates to produce current. Acid strength and lead plate configuration determine the power produced by the battery.
See also: How Does a Solar Battery Work? An Ultimate Guide to Understanding Solar Energy Storage
How Are Batteries Rated?
Batteries are rated two ways A Car Battery is designed to produce a high current for a short period. Several thin layers of lead are used to create a large surface area for ion exchange. Such a configuration creates a high Cold Cranking Amps rating on car batteries. The Cold Cranking Amps (CCA) defines the number of amps the battery can provide for 30 seconds while maintaining at least 7.2 volts. The range for this value is usually between CCA 300 to CCA 600. While most car batteries do not specify an Amp Hour rating, the average range is 60 – 70 amps at 20 hours. Deep Cycle Batteries are designed to produce a lower current for a long period. They use fewer, thicker lead sheets to create a smaller, more stable, longer-lasting surface area. This configuration provides the higher Amp Hour rating required in deep-cycle batteries. The Amp Hour (Ah@20hr) rating of Deep Cycle batteries ranges from 100 to 400 amps @ 20 hours. The battery will provide the specified number of amps for 20 hours. All batteries experience normal wear. A car battery in a solar application suffers faster normal wear since the plates are not designed to provide prolonged current. There are two basic wear factors. The lead plates shed small flakes during charge/discharge cycles. The material will eventually wear away as lead is shed from positive plates, causing an open connection. At the same time, the lead being shed falls to the bottom of the battery case as a brown sludge. If material builds up enough, it can bridge several plates causing an internal short. Both of these conditions will result in a dead battery. Flooded Lead Acid batteries’ life depends on regular care and maintenance. There are three basic maintenance factors. All batteries can suffer from these factors. Deep discharge is the greatest enemy of even a well-maintained car battery. Prolonged load on a car battery can not only cause accelerated wear but can also cause plate damage. Plates can overheat and warp. This will cause an instant failure of the battery. Since reading this article, you have probably been looking at batteries. You have noticed a wide variety of batteries on the market. Many of these are special-use batteries and can be easily eliminated from your search. Car batteries are not suited for solar applications. I must confess that they do have a small range of use. Car batteries are perfectly suited for light-duty solar applications. I use a car battery for a solar garage door opener system. The car battery is suited for such an application because it draws a fairly high current a few times a day for a short period. PROS CONS Top rated car battery from Amazon; Another style of lead-acid battery is the Multi-Purpose battery. As you might suspect, they are a sort of hybrid battery. They are the same size and voltage as a car battery but are designed to produce current for a longer period without damage. The CCA ratings tend to be lower than a typical car battery. The Ah rating of these batteries generally remains in the 60 – 70 Ah @ 20-hour rate. Such a battery may be a better option for a light-duty solar system. PROS CONS Deep Cycle batteries are the best option for a real solar power application. Designed to withstand repeated deep discharge, recharge, and prolonged current draw, these batteries are your best bet when designing a solar system. There is a wide variety of configurations available in the Deep Cycle market: 12 volts, 6 volts, small, and large. They all have a purpose. If space is an issue, 12-volt batteries with 100 Ah @ 20 hr ratings are commonly available. Higher Ah units are available, but with more capacity, the size increases. PROS CONS The L16 Lead Acid battery is a standard in off-grid solar applications. These units have ratings of up to 400Amps @ 20 hrs. They are 6-volt batteries, so they usually need to be used in pairs to create 12 volts. They are big and heavy but have life spans of up to 10 years. For an off-grid home, these are a good place to start. PROS CONS Here’s a power 200Ah deep cycle battery – Renogy on Amazon; The batteries are the most expensive part of the project when setting up a solar system, whether in an RV or an Off-Grid Home. They can also be the Achilles Heel if not chosen wisely. They will not get you through the night if there is not enough Amp Hour capacity. Low capacity will also shorten the lifespan of the batteries due to the high depth of discharge. Inexpensive car batteries may ease the pain today, but they will cost you tomorrow. Improper battery construction and chemistry will reduce your system’s effectiveness and shorten the battery’s life. Your best course of action is to do some research before you shop. There are many good websites with information and calculators to help you determine how much battery capacity you need. Find a reputable solar supply or battery shop if research is not your strong suit. They will work with you to evaluate your needs and find the best battery for your situation. I can promise that the battery will not be a car battery. Sources:
Why Batteries Fail
Normal Wear
Battery Care and Maintenance
What Battery Do You Need For Solar Panels?
Are Car Batteries Good For Solar Panels
Multi-Purpose batteries
Deep Cycle Batteries
Variety
How To Choose The Right Battery For Your Solar Panel
