6 Things That Drain Your Boat Battery [And What To Do About It]

6 Things That Drain Your Boat Battery

Boating is a great pastime with so many qualities to enjoy. Being out on the open water is almost like a therapy for many of us. Unfortunately, when owning a boat, there are many things that could go wrong – on the water and off of it. 

6 Things That Drain Your Boat Battery

There are many things that drain your boat battery. The best way to figure out the issue is with the process of elimination. First, check if anything obvious was left on or any common issues are present. If not, you may need to perform a test. Hooking up a test light is a great way to narrow down the cause. 

While this seems like a straightforward solution, there are many common issues that could be draining your boat battery. Below is a list of 6 reasons you could be losing your power, as well as advice for detecting and fixing these issues. Once you have identified the source of the problem, you will be able to resolve the issue and return to the water worry-free as it was meant to be.

What Can My Battery Hold?

Before diving into the list of common issues found with drained batteries, it is important to understand what a battery holds and how long it can last. The reality is that your battery only has so much charge capacity, and this amount gets lowered every day, month, and year. 

If you have a brand new, fully-charged battery that did not discharge there would be plenty of space to run many of these list items without worry for over a year. That being said, this is simply not how batteries work. It is important to recognize how they do so that you can be more in control of your battery’s life.

The average battery (including boat batteries) will both lose capacity (how long it works from full-charge) and will self-discharge (drain its own power) on a regular basis. When considering the battery’s capacity, you can expect almost a 10% decrease in capacity each year for a standard battery. As for the topic of self-discharge, this number ranges anywhere from 2% all the way to 10% drainage per month. 

Unfortunately for summer-loving boat enthusiasts, warm weather is one of the causes of faster discharge. So, if you find that your battery has unexpectedly drained after a hot day, this could also be a possible cause.

Now that you understand that batteries are losing their charge and capacity on a regular basis, you will understand why things that may seem like microscopic, parasitic loads on the surface can actually be causing your battery to die. 

List of 6 Common Battery Drainings on Your Boat

Boating for a while, my friends and I have seen just about everything that causes boats to die unexpectedly. Sometimes these reasons are just simple mistakes, while other times these are real issues that need to get fixed. Regardless of the cause, I want to make sure you are prepared to deal with it if any of these types of problems come your way. 

6 Things That Drain Your Boat Battery

1. Radio/CD Player Was Left On

A radio/CD player left on has been found to be one of the most commonly reported reasons that boat batteries are losing their power. On a decent battery with a full charge, you can safely leave your radio on for several hours without fear. However, as your boat’s battery ages, this timeframe gets cut down.

Of course, leaving your radio on purposefully for several hours and accidentally leaving it on at a low (or nonexistent) volume when you are not intending to use it are very different things. If the radio is running all night, for example, there is a good chance that your battery will be gone by the time you get back to your boat in the morning. 

2. The Bilge Pump Automatically Runs

bilge pump

While the bilge pump is a great feature that can keep your boat in tip-top shape, it does come at a cost. Many bilge pumps turn on automatically each hour to check for water in the bilge. The only way to be positive that this is not the cause of your problem is to disconnect the bilge pump for a time and see if the battery is still being drained. 

By following this logic, you can be sure that if your bilge pump is disconnected and your battery still loses power or dies, your bilge pump automatically running is not the source of the problem. You should then check for other possible issues.

3. Your CO Detector

CO detectors (or any smoke and odor detector for that matter) can drain a good bit of power – as much as .3 amps per hour. While this may seem to be a minute power loss, it could drain even a new and in top-shape battery within a couple of weeks of non-use. 

A great way to prevent this is to disconnect the CO (or smoke/odor detector) and hook them up to separate batteries for a while to see if they could be causing your issue. If so, switch them out for a more energy-efficient option, or keep them off of your main power supply entirely.

4. Memory from GPS or Radio

Similar to cars, many boats hold memories on the radio and GPS. This is a great feature for remembering your favorite stations or knowing how to get you back to your truck while on the water. However, just like other technological advances, this feature also comes with a few risks. While this relatively small device may not seem like it would drain a lot of power, they still can. 

For a GPS or radio to keep their memory, the tiny bit of power used each time combined with an old battery or one that has not been charged recently can be all it takes to drain the power entirely.

It is likely that this one may be difficult to detect. You may try unplugging these devices and running the battery again without them, but you can more likely conclude this after you have tested other options and found them not to be the source.

5. Something was Left Plugged In

Small appliances onboard your boat can make your “out on the water” experience significantly more fun, but forgetting to take them off of the boat could cause an issue. As an example, if a phone was left charging or a speaker left plugged in, this could cause your battery to drain a lot faster than if this was not the case. 

To prevent this issue from coming up, make sure that you and all your passengers remove anything electronic from the boat before leaving it off for the night. You would hate for yourself or one of your friends to have screwed up the next day of fun due to simple forgetfulness.

6. A Defective or Old Battery

A defective or old battery is probably not one of the issues that you want to hear, but this is a real scenario for many people. If you have done proper testing and concluded that there is not a cause of your battery being drained – it is likely just a defective battery. 

Thankfully, if it is new, you should be able to get it exchanged wherever you purchased it from under warranty or protection. (Be sure to keep your receipt just in case.) If it is an old battery, it may just be time to replace it. 

Boat batteries can be a bit expensive, but they do last an average of 5- to 7-years. If you are purchasing a previously owned boat, be sure to ask how long it has been since the battery has been replaced so that you are aware of when to expect to replace it.

How to Identify the Battery Drain on My Boat? 

So, your boat battery has died and you are not sure why? By following these steps, you should be able to determine the source of the battery drain. From there, you will be able to address the issue and get back out on the water.

  1. Connect a Digital Multimeter to your boat’s battery. A Digital Multimeter is a common tool used by electricians to measure the values of electricity such as amps. To connect it to your boat’s battery, you will remove the battery’s cables and follow the Digital Multimeter owner’s manual for connection directions.

  2. Find the normal amp reading for your boat’s battery. You will use the owner’s manual for your boat’s battery to find out what a normal range is. Then, if your Digital Multimeter shows that you are using more than you are supposed to be, you may begin to check for the source of the issue.

  3. Remove possible sources of the drain. You can begin testing various electronic devices and other fuses on your boat to see which of them may cause the amp readout to lower. Once you have found a device that lowers this, you will know the source of the problem.

  4. Unplug the source of the drain and find an alternative powering method. Once you have identified the source of the problem, it is important to remove it and find another way to power it or to get rid of it altogether. 

6 Things That Drain Your Boat Battery [And What To Do About It]

Kern Campbell

Kern is a life long boater who finds great happiness sitting at the helm of a boat running on the open water. When he's not running the boat, he's likely anchored up along the beach with his wife, kids and good friends enjoying a great day at the coast.

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