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testing a deep cycle battery

How To Tell If A Deep Cycle Battery Is Bad

Investing in deep cycle batteries is a good idea. They’re powerful and long lasting but there is, of course, a simple caveat. You’ve got to take good care of them. You also need to know it is time to replace the deep cycle battery. If you are wondering how to tell is a deep cycle battery is bad then that part is pretty easy.

You will need to check the battery’s voltage after a full charging session.

If it’s not reaching full charge, there may be a chemical issue such as a dead cell but a little bit of troubleshooting on your part can help to rule out some common issues so that you can isolate the real problem.

Today we’ll talk about how that is done and give you some additional tips on troubleshooting as well as a simple way to extend the life of your current deep cycle batteries.

 Let’s start out with what you will need to properly assess your deep cycle battery’s charge.

What you will need and where your charge needs to be

First off we should tell you a little about the charge itself. While you might purchase a battery that is advertised as ’12 volt’ that is just not really an accurate rating of its voltage. A 12 volt battery, fully charged, is actually going to be about 12.6 volts or maybe a little higher.

With this in mind, to actually test the battery properly you are going to need 3 tools that you will be getting a lot of use from:

You can get these through your local hardware stores, automotive supply shop, or simply by ordering them online.

As you are handling batteries then you’ll also want to get some protective gear as well, such as some goggles and gloves if you don’t have a set already at hand. Once you’ve gotten these items then we are just about ready to get started.


Deep cycle batteries: Your Pre-check Check

Before you can do an accurate reading on your deep cycle battery’s health you need to attempt a full charge cycle. If you are not able to do this then you should let the battery sit for at least an hour after the last time that it has been used.

This will help to ensure that you can get a relatively accurate assessment of what state the battery is in.

We do recommend that you take advantage of this time to clean any grime buildup from the battery that you can and if you have any loose or broken terminals then you’ll want to mentally note this so that this can be addressed as well.

Speaking of damage, if the case has been compromised or even worse, leaking, then you will need to write this battery off and replace it at your soonest convenience.

A damaged case or a leaky battery should not be used to power anything as this an enormous safety risk.

Deep cycle batteries: Time for inspection

Now that your spot-checked, shiny-clean deep cycle batteries have had their charge cycle or have been sitting for at least an hour then you are ready to start. Your inspection will consist of 3 easy steps with the 3 tools we recommended:

  • Hydrometer – Your Hydrometer will measure the gravity of the acid in your battery fluid. You are looking for each individual cell to have a minimum reading of 1.225 and there should be no more than a 50 point discrepancy between the highest and lowest reading. The battery fluid should also be clear and you overall Hydrometer total should read 1.265.
  • DC Voltage meter – With a full charge, a 6 volt battery should be at least 6.4 on your voltage meter and a 12 volt should be at least 12.6. Higher is good, but anything lower can be signs that the battery is starting to wear out.
  • Battery Load Tester – For load testing, all of the battery cables must be removed from their terminals and when you apply your load tester you’ll want to send a 15 second load that is equal to 50% of the tested battery’s CCA rating. Your load tester automates things and will tell you if the battery meets the minimum passing voltage.

Now you know for sure whether or not the battery needs to be replaced. If it doesn’t then congratulations, but even if you have to replace it there is a simple thing you can do to help make sure that this or the next battery lasts a good, long time.

Consider extending your deep cycle battery life with Full Cycle charging

When you only charge your batteries every now and then, instead of giving them a dedicated time for a full cycle charge, then your battery may suffer from sulfation.

What happens is that there are tiny deposits of sulfate crystals that form inside the battery which are normally harmless – unless your battery is uncharged for long periods of time.

The sulfate crystals end up becoming more stable on the negative plates inside your battery and eventually this affects charging and overall performance.

By giving your batteries a scheduled time when they get a regular, full charge cycle this problem may be easily kept at bay.

Now that you know to tell if a deep cycle battery is bad just be sure to take advantage of this knowledge to schedule regular inspections and don’t forget the importance of full charge cycles.

A little care now will keep your deep cycle batteries running for a long, long time.

All the article on Oofgrid offer help and practical advice for using and purchasing a portable generator. However, We are enthusiasts and not qualified electricians. Always seek professional advice when working with electrical or Petrol appliances.