ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Can I Use a Car Battery for My Solar Power System?

Updated on February 20, 2020
Mpfana Manu profile image

Mpfana Manu is a mechatronic engineer who's working in green energy electronics products. He's currently working on solar technologies.

Can you use a car battery?
Can you use a car battery?

It's pretty tempting right? A car battery looks very much like a deep-cycle battery and looks very capable of fitting perfectly in your solar power system. But do not fall for the temptation, car batteries cannot be used in a solar power system because of particular reasons you're going to learn in this article.

You're also going to learn the consequences of including a car battery in the battery bank of your solar system and how to maintain your battery bank so that it last longer.

Batteries are the heart of every solar electric system, especially when you're off the grid. If you can take good care of them, you can easily increase the lifespan of your solar system before it starts tripping.

And also considering the amount of money you cashed in to buy all the batteries in your battery bank when the system was installed, you ought to diligently protect that investment. Replacing a failing battery in your power bank with a car battery is not an intelligent move. In fact, it will throw the initial investment down the drain. Here's why.

Why a car battery can't fit in a battery bank of a solar system

Car batteries are designed to release lots of electrical power in an instant. They can discharge almost half of all their stored energy in a few seconds. This is good when they're installed on a car because a car only demands significant electrical energy when its engine is starting (except for electric cars of course).

Battery bank
Battery bank | Source

But when it comes to a solar system, batteries are required to give a slow and steady electrical power output for a lengthy period of time. And also, batteries should have the ability to discharge up to 80% of the stored electrical power without significantly changing the rate of discharge.

Car batteries can't do that. Use a car battery until it's 70% discharged and you're most probably going to have a hard time recharging. Most of them need an electrical boost to start recharging normally when they've been discharged over their limit.

A totally discharged car battery may never recharge again especially when it spends a long time before getting recharged. This is how some car batteries die. When it's installed in a car, it quickly gets recharged by the car's alternator when the car is revved. But when it's installed in a solar system, it'll swiftly suffer a premature death and the solar system will start tripping.

There's another more horrible reason why a car battery is bad news for your solar system. You know a big solar system doesn't run on a single battery. If a single car battery is to be installed among deep-cycle batteries making up the whole battery bank, it'll ruin all of them as itself also gets ruined.

The characteristics of a deep-cycle and a car battery are very different. And as a result of that, when the batteries are connected in series/parallel one battery will discharge/recharge faster/slower. The overall effect will be that all the batteries will reach a compromise level of performance at which they work as one power bank.

That level of performance will be ridiculously low compared to the performance of a normal battery bank. The battery bank will deliver much less energy than it took when it recharged or it may never fully recharge or it may stop delivering power before getting even 50% discharged.

What exactly happens to the overall battery bank depends on the type of car battery and how it's connected (series/parallel) in the battery bank.

What is worse is that even when you remove the car battery and replace it with a proper deep-cycle battery, the battery bank will still behave as if the car battery is still in use. It's in the nature of batteries to adapt, so all your batteries would have been crippled by the car battery while it was still in use.

The only option you'll be left with is to replace all the batteries in your battery bank. That's hundreds, if not thousands, of dollars worth of an investment forfeited.

What is the best way to replace batteries of a solar system?

Now that you know how horrible it can get if you connect a car battery in your power bank, it's obviously necessary that you also know the right thing to do when a single deep-cycle battery needs to be replaced.

If your battery bank was initially set up by someone who had done his homework very well, all the batteries must have been of the same size and model. If one battery needs to be replaced, here's what you do.

  1. Check the model and size of the batteries making up your battery bank and write it down.
  2. Calculate the age of the battery bank from the time it was initially installed. This is the age of all your batteries. Note it as well.
  3. Recharge all the batteries to their maximum capacity before replacing.
  4. Buy/get a second-hand deep-cycle battery of the same model, size and age, and install it in the battery bank.

Battery manufacturers and DIY shops do sell second-hand batteries. If you intend to get it from a manufacturer, you can also sell the broken battery that you want to replace and then buy the second-hand battery. The model, size and age will make sure that you get the battery with the same characteristics as the rest of the batteries making up your power bank.

Someone might ask what happens if you buy a new battery of the same model and size. The answer is nothing happens to your power bank, it continues working as it used to. But the new battery would quickly adapt and start behaving as the rest of the old batteries.

So all of its improved and better properties as a new battery would be waisted after several cycles of charging and discharging. That is money waisted since brand new batteries cost more than second-hand batteries. The most cost-effective way is to just get a second-hand battery similar to those in your power bank.

If it happens that you cannot find the exact model of the battery that you need, I advice that you consult a battery manufacturer/engineer and ask which other model has almost the same characteristics as the model of the rest of the batteries in your power bank.

You can compromise on the age but it's safe to get a battery that is newer or of the same age as your other batteries. But do not compromise on the size. Get the exact size as the one you're replacing.

Tips to maintain your batteries so that they last longer

  • If your batteries are flooded lead-acid batteries, check for the liquid level every month and add distilled water accordingly. If your battery bank recharges more frequent than once per day, check the liquid levels after every two weeks.
  • If your batteries are connected in parallel, use a multimeter to check for the voltage across adjacent batteries. There should be no difference in the voltage readings. The maximum voltage difference that you can live with is 0.7V. You can balance the voltages using a battery charger. A voltage difference that is higher than 3V indicates that a battery is failing. Replace the battery before it affects the whole power bank. You can do these voltage tests every month but if the system recharges and discharges frequently, you should also do it frequently.
  • After every month or two, you should shuffle the batteries. Those that were in the middle should be shifted to the ends. And those that were at the ends should be shifted to the middle.
  • Check the inter-connecting cables and make sure all connections are tight and intact. Apply a layer of petroleum jelly on all connections to prevent water ingress.
  • The battery bank should not be placed directly on the ground/floor. Make a wooden frame on which all the batteries can fit together. The frame should keep the batteries off the ground so that they don't get cooled by the ground/floor especially in winter.
  • If your charge controller can set the limit to the extent of discharge of your batteries, keep that limit as low as the system will still strive. Batteries that recharge after discharging 50% of their stored energy last longer than those that recharge after discharging 80% of their stored energy.

Conclusion

Do you know what I did? I translated the complicated chemistry that happens when a car battery joins a solar battery bank into words that I hope can be understood by everyone, even folks who did no chemistry. If there's any part that's still hard to understand, don't hesitate to complain in the comments section and I'll be more than happy to help you out. If all is clear and understandable, then cheers.

Comments

    0 of 8192 characters used
    Post Comment
    • Brenda Arledge profile image

      BRENDA ARLEDGE 

      4 days ago from Washington Court House

      Your article is very informative.

      You are a good writer.

      Thanks for sharing.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://maven.io/company/pages/privacy

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)