6 Causes and Fixes for a Jet Ski Battery That Keeps Dying 

Jet skis are one of the best and most fun ways to enjoy a day on the water. Whether you live near a river, lake, or ocean, a jet ski allows you to cruise at high speeds, similar to a motorcycle on the highway. However, your fun in the sun can get cut short with a faulty jet ski battery that keeps dying. 

Jet ski batteries are finicky components to otherwise stout jet skis. Much like a car battery or a golf cart battery, they have limited life spans and can die prematurely for many reasons. Jet ski batteries can fail for many reasons, such as overcharging, cold weather, dead cells, or any other number of issues. 

In this article, we’ll look at the top 6 reasons that your jet ski battery keeps dying and what you can do about it. If you don’t want to have your day on the water cut short by a bad jet ski battery, continue reading to find out what you need to do. 

Why Does My Jet Ski Battery Keep Dying? 

If you’ve owned a jet ski for any amount of time, you have likely noticed that the batteries don’t last as long as other types of batteries. The main reason for this is that jet ski batteries are smaller than other batteries and don’t get used as frequently. Also, imagine the amount of banging around they do when you jump waves or even flip your jet ski. A common misconception about batteries is that they give out when you overuse them. 

While this is sometimes true, underusing them is just as big of a problem. Because jet ski batteries only get used for a small part of the year, they often sit for long periods of time without being used. Let’s take a deeper dive into these reasons, as well as several of the other main reasons that your jet ski battery keeps dying. 

Incorrectly Storing Your Jet Ski Battery 

One of the biggest issues that people run into with their jet ski batteries is that they don’t properly store them. This is especially common during the winter months for people who live in areas with freezing temperatures. 

Improperly storing your battery during winter can lead to corrosion on the terminals as well as dead cells within the battery. It’s imperative that you take extra time and measures to make sure that your jet ski and battery are stored the right way when it’s not being used. It’s important to note that you can’t just park your jet ski anywhere during the winter and expect everything to work like normal when you go to start it back up in the spring or summer. 

How to Fix It

Fixing the problem of improper storage is relatively easy as long as you follow a few simple steps. Here’s how to store your battery the right way. 

  1. Remove the battery from inside the jet ski. You’ll have to disconnect the terminals in order to remove it. Once you’ve done that, you can take the battery out of the jet ski. 
  2. Next, store the battery in a cool, dry place that’s anywhere from 55 to 65 degrees. This is best done in a conditioned garage, basement, or shop area where you can regulate the temperature. Never let your battery freeze. Also never store it directly on concrete.
  3. Rather than to simply let your battery sit for the entire winter, you should connect it to a trickle charger. A trickle charger will continue to keep your battery charged without overcharging it and causing a whole other set of problems. A good trickle charger will make it so that your battery is ready to go at a moment’s notice. Here is our favorite trickle charger and maintainer.

Here is the detail on the benefits of trickle charging your jet ski battery over the winter.

Overcharging Your Jet Ski Battery Can Cause a Short Life

Another common issue for jet ski batteries is that they’re often overcharged. Jet skis don’t need to be charged after every single use, but they do need to be charged fairly frequently. Overcharging can lead to overheating your battery or to melting components inside the battery itself. Overcharging can mean charging too long, or even at too high of amperage.

Regardless of why you’re battery is getting overcharged, the outcome is always that it fails to hold a charge. The more often you overcharge your battery, the quicker it will die when you disconnect the charger. Let’s take a look at how to prevent overcharging your battery which can lead to its premature demise. 

How to Fix It

The best way to prevent overcharging your battery is to purchase a smart charger that automatically turns off when the battery is fully charged like our favorite here. Most jet ski batteries should only be charged at about 1.5 amps, so this charger is perfect. Jet ski batteries are smaller than other batteries, but they still take several hours to charge completely. It’s difficult to know when exactly you should disconnect your charger without the use of a smart charger. 

If, however, you don’t want to buy a smart charger, another option is to read your jet ski’s owner manual and see if it lists a recommended battery charging time. If it does, you should charge the battery at a slow rate of one amp per hour for the recommended time. It won’t always be charging for the perfect amount of time, but it will at least get you close. 

Underusing the Jet Ski Battery Can Cause Failure

As previously mentioned, another big battery killer is underusing your jet ski. Jet ski batteries are smaller than other batteries and aren’t meant to sit idly by and hold their charge for long periods of time. Lead acid batteries can lose up to 1% of charge per day. If you leave your ski for a month, you may only have a 70% state of charge. Lead acid batteries should never be used under 50% state of charge or they will become permanently damaged. The battery actually charges itself while it’s being used on the jet ski, which means that the more you use it, the longer it will take to die. 

However, if you live in colder climates, you’re not going to use your jet ski during the winter months. The reason that inactivity kills a jet ski battery is that battery sulphation occurs within the battery which inhibits the movement of electrons. The slower that battery electrons move, the faster your jet ski battery will die. This is why it is important to leave it on the charger/ battery maintainer during the off season.

How to Fix It 

In order to fix the problem of inactivity, you simply need to ride your jet ski more often, at least during the warmer months of the year. However, this isn’t always possible when it’s cold outside. Fortunately, as long as you follow the steps listed above that explain how to store your battery while not using your jet ski, your battery will be saved from underusing it. 

Cold Weather Can Kill Jet Ski Batteries 

Cold weather is perhaps the biggest battery killer out there, jet ski batteries included. In order for your battery to work properly, there are a series of chemical reactions going on inside of it. In the same way that you’ve likely noticed that you move slower when it’s cold outside, the electrons inside your battery also move slower when it’s cold out. 

If your battery is exposed to the cold for too long, those electrons slow down and never regain their full capabilities. That means that when temperatures warm up and you want to use your jet ski, your battery will be unable to hold a charge and will die faster than normal. It’s likely that your battery will be completely dead and your jet ski won’t start up at all. 

Never let your jet ski battery freeze or you will find yourself buying a new one next season.

How to Fix It

Once again, the problem of keeping cold weather from ruining your battery can be fixed by properly storing it during the winter months. By removing the battery from within the jet ski and storing it in a cool, dry place with a regulated temperature of between 55 and 65 degrees, cold weather won’t kill your battery. 

Problems With the Charger or Charging System on the Jet Ski

Another common culprit for a seemingly faulty battery is that it might not be the battery at all. If you hook your battery up to a faulty charger or charging system, then your battery will fail to charge. That doesn’t mean that your battery isn’t holding a charge properly, it means that it wasn’t charged to begin with. 

The stator is like an alternator on your jet ski. (learn more about a stator here) If your stator goes out on your jet ski, it can fail to charge your jet ski when riding. If your battery goes below 50% state of charge, you can do permanent damage.

How to Fix It 

Fixing this problem is as simple as purchasing a new charger. Trickle chargers are great for keeping your battery charged during winter or storage months. If you decide to replace your current charger with a duplicate, make sure that you buy one that’s compatible with the type of battery that you own. 

You Have a Defective Battery

Finally, it’s possible that your jet ski battery keeps dying simply because your battery has gone bad. Unfortunately, not all batteries are built the same and there are manufacturing errors that occur while the battery is being made. As a general rule of thumb, if your battery is showing problems and it’s older than three years, your best bet is to replace the battery. 

Whether your battery is defective because you simply got a rotten deal or because it’s suffered from cold weather, improper storage, or any other number of issues, defective batteries are unfortunately common in jet skis. 

How to Fix It 

The only way to fix a defective battery is to buy a new one. While it’s possible to replace the cells within the battery, it’s expensive, and it’s cheaper and easier to purchase a new battery. 

Best Replacement Batteries for Jet Skis

We have been using these batteries over the years and usually, they last us about 5+ years on our Superjet. They have never let us down on the water, and we highly recommend them. On our Honda Ski, it even lasted 12 years which is huge for a jet ski battery. We have had other batteries in the past from big box stores, but they just won’t last more than 2-3 seasons. They may be a bit cheaper upfront, but not worth it in the end.

Things to Check Outside of the Battery 

Outside of the battery and the charging system, there could be a variety of other reasons that your jet ski isn’t working properly. There are components on the battery itself as well as other parts inside the jet ski that can affect its operation. Here is a list of things that can cause problems with your jet ski that resemble a dead battery. 

  • Wrong or faulty rectifiers 
  • Bad grounds or a loose electrical connection 
  • A blown fuse somewhere in the jet ski 
  • A broken computer or key that helps the jet ski to operate 
  • Accidentally leaving the key in the on position while the jet ski isn’t in use. This will kill the battery but isn’t an indicator of a faulty battery. 
  • Your starter relay might be defective, which won’t allow your jet ski to start up. 
  • You might have one or more faulty spark plugs, which will also impede your jet ski’s ability to start. 

How Long Should a Jet Ski Battery Last? 

A healthy jet ski battery should last anywhere from three to five years. However, this timeline is subject to change depending on how often you use your battery and how well you take care of it. Properly storing your battery during the winter months and when you’re not using it for prolonged periods of time will greatly increase your battery’s lifespan. 

If you don’t care for your battery, it can give out in as little as one to two years. 

How to Make My Jet Ski Battery Last Longer? 

Everyone wants to get the most out of their jet ski and to have it operating at its best. However, in order to get the most out of your battery, you’re going to have to put some work into it. Here are some tips and tricks to make your jet ski battery last at least three to five years, if not longer. 

  • Proper winter storage. The biggest way to make your battery lasts as long as possible is to properly store it during the winter months or during periods of prolonged inactivity. By hooking it up to a smart charger or trickle charger, you can keep your battery healthy and greatly increase its lifespan. 
  • Keep the battery terminals clean and corrosion-free. It might be necessary from time to time to disconnect the terminals from the battery itself and clean them. You should apply grease to the terminals before storing it for winter, and you should use a mixture of baking soda and water to clean the terminals from time to time. Soak the terminals and use a soft brush to remove any corrosion. 
  • Only use a stationary charger to jump-start a dead jet ski battery. Using a car or other piece of equipment to jump-start a dead battery could possibly overcharge the jet ski battery and damage it. You should only use a freestanding battery of the same size or an approved battery charger.