12 Symptoms of a Bad Jet Ski Battery

Jet skis are an absolute blast when they’re working correctly, but mechanical issues can be an all too common occurrence. It’s sometimes difficult to know exactly what’s wrong with your jet ski unless you know what to look for. It could be the battery or several other things.


Here are 12 tips to know if your jet ski has a bad battery:

  1. You notice broken terminals on the battery.
  2. There’s a bulge or swelling in the case.
  3. The plastic casing has cracked or ruptured plastic.
  4. The battery is leaking out acid or water.
  5. Your battery is discolored.
  6. Your battery is showing bad voltage reading.
  7. Your battery fails the load test.
  8. The engine fails to start.
  9. The engine is cranking slowly.
  10. Your battery is giving off a weird smell.
  11. Your battery is old.
  12. The lights and other electronics aren’t working properly.

Let’s take a deeper look at each of the above signs and symptoms of a bad jet ski battery.

1. You Notice Broken Terminals on the Battery

If you’re wondering if your jet ski battery has gone bad, a visual inspection should be the first thing you do. If you notice that the terminals on your battery are broken or covered in crud, this could be a sign of a bad jet ski battery.

2. There’s a Bulge or Swelling in the Case

A visual inspection will also reveal if the protective case around the battery has started to bulge or swell in any way. Bulging or swelling is usually the result of an overcharged battery. An overcharged battery becomes a hazard, so you should replace it immediately.

3. The Plastic Casing Has Cracked or Ruptured

While a crack or tear in the plastic casing around your battery doesn’t immediately mean that the battery is bad, cracks open the battery up to a world of possible hazards. It would be wise to preemptively change your battery before anything bad can happen.

4. The Battery Is Leaking Out Acid or Water

If a visual inspection reveals that your battery is leaking acid out, immediately replace the battery. Battery acid is extremely dangerous if touched by exposed skin and can lead to serious injury if left unattended.

If you have a wet-cell battery, then the battery will contain water, which must be properly maintained. Water leaking out can lead to sulfation on your battery, which is the number one cause for a battery dying prematurely. Leaking water may be a sign that your battery should be replaced.

5. Your Battery Is Discolored

Your battery may appear to be in otherwise good shape, but if any part of the cells has started to turn brown, you should replace the battery. Brown on your battery is caused by lead dioxide or grid corrosion, both of which are bad news and reason to replace your battery.

6. Your Battery Is Showing Bad Voltage Reading

In order to properly read the voltage on your battery, you’ll need access to a multimeter. You’ll also have to know how to properly read a multimeter in order to make an informed decision. You know your battery is bad needs replacing if your reading shows any of the following results:

  • The battery is fully charged, but the voltage reading is 12.4 or less.
  • You notice that the battery is constantly charging but can’t reach higher than 10.5 volts.
  • The battery gives off a reading of 0.

Follow the instructions about how to read your multimeter to ensure you don’t misread the results.

7. Your Battery Fails the Load Test

Your jet ski’s battery must have a voltage reading of between 12.0 and 12.5 to start up the jet ski.

If you perform a load test and the reading is less than this or can’t hold within this range, your battery is bad, and your jet ski won’t operate.

Keep in mind that to perform an accurate load test, you must charge your battery fully.

8. The Engine Fails To Start

If your jet ski engine fails to start, then there could be several issues, but a bad battery is certainly one of them. Just because your jet ski doesn’t start doesn’t mean you have a bad battery, but it should be the first thing you check.

Use the above method of fully charging your battery and perform a load test to determine if your battery is the culprit behind the engine not starting.

Additionally, if the battery is bad, the engine will make multiple clicking sounds indicating that it is trying to start. If you only hear a single click or no click at all, the battery is not the problem.

9. The Engine Is Cranking Slowly

If the engine turns over slowly when you try to start your jet-ski, the odds are that your battery is deteriorating.

Your jet ski may start 1 or 2 times after the initial slow cranking, but your battery will eventually die if the problem persists. It’s best to change it before you’re stranded in the middle of the lake.

10. Your Battery Is Giving Off a Weird Smell

A strange smell given off by your battery is never a good sign. A cracked or swollen case usually accompanies this, and both are signs of a bad battery in need of replacement. Upon noticing this, remove it from your jet ski and have it replaced.

11. Your Battery Is Old

If you’ve had your jet ski for several years and haven’t replaced the battery yet, then it could deteriorate at any time. A typical jet ski battery is designed to last for 3 to 5 years. Anything longer than this is a rarity and a gift.

12. The Lights and Other Electronics Aren’t Working Properly

If you try to turn your headlights on or if you notice strange lights igniting your dashboard, it could be a sign of a bad battery. There could be a loose wire or bad connection, but the battery is all too often the culprit behind lighting problems.

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