7 Reasons Why Your Jet Ski Battery Keeps Dying [Stay Charged?]

Do you ever feel like you have to replace your jet ski battery every year?

It can be quite puzzling why the battery in your Sea-Doo, Yamaha, or even Kawasaki keeps dying and needs to be replaced often. Maybe your jet ski battery won’t stay charged even after charging it?

Let’s go over all the ways your jet ski battery keeps dying or won’t hold a charge.

1. Inactivity Of Jet Ski

The number one reason a jet ski battery dies or becomes weak is because it’s not being used enough.

People tend to only drive their jet ski during the warm months and then let it sit during the winter. When the jet ski battery sits for long enough, the internal plates start to sulfate, and it kills the battery.

If your jet ski will be sitting for months without being ridden, you need to keep the battery on a smart charger or a solar charger.

I use a solar battery charger that is under 5-watt and keep it plugged up when I’m done riding for the day. On my last battery, I got over 5 years out of it, which is quite a lot more than the 1-year others get. The solar battery charger is so affordable and easy to do that I’m surprised more people don’t know about this trick!

2. Battery Is Cold

A jet ski battery will die or become weak if left in the cold for too long.

When you winterize your jet ski, it’s best to take the battery out and keep it in your garage or some place where the wind and cold won’t get to it that much. You don’t need to cover the battery, it’s best you don’t, just don’t want it outside in the elements.

You can put the smart battery charger on it every so often to keep it topped up. Most importantly, charge the battery the night before you want to go for a ride at the start of the season and it will be fine.

3. Not Using The Correct Battery Charger – Overcharging

Using the incorrect battery charger will cause a battery to fail or not charge completely. A bad battery charger can also make it seem the battery is charged even when it’s not.

If you’re using a battery charger that plugs into the wall, you need to make sure it’s a smart battery charger like this one here*. This smart battery charger needs to be 12 volts and at 500ma or 2 amps of charging power.

You don’t want to rush a charge into a jet ski battery, they’re too small and anything over 2 amps is asking for trouble. Also, a smart batter charger will turn on and off when the battery needs it, which prevents overcharging. Don’t use the old-school trickle chargers, as they can overcharge a battery.

If you’re using a solar charger, you must make sure it’s 12 volts and under 5-watt. Too much wattage and you’ll cook the battery, but you can use a charge controller that will regulate this charge and protect the battery; a charger controller is more effort and not worth it if a lower wattage solar panel will do. For best results, I find a solar charger between 1 and 5 watts to be the best, here is one I suggest you buy*.

4. Battery Failure

Sometimes lead-acid batteries just fail, even new ones can have a manufacturer defect right out the box.

Jet ski batteries take a lot of abuse from the wave jumping to the heat and cold.

The internal plates are not always the strongest, they’re heavy, but can be brittle if they suffer enough abuse. The non-sealed ones also dry out and loose water, which they need to make power.

If charging the battery won’t bring it back to life, then it’s a dud and needs to be replaced. Even if it’s a new battery, I’ve seen them fail, and it’s just the luck of the draw, but they should have some warranty within a certain time frame.

I suggest when buying a sealed, ready to go battery, that you have the store do a load test on it before you leave. Any jet ski dealership or autoparts store can easily do this and should be doing it, as they know some new batteries can be dead.

5. Improper Battery Size

group of batteries

I’m surprised how common it is to see people bring in jet skis with entirely wrong size battery and complain of starting issues.

You must make sure you have the correct size battery for your jet ski. They’re all 12 volts, but they come in many different physical sizes, and that affects starting power.

I would see people bring in a jet ski with a battery half the size, with blocks of wood to make it fit. Sure, it might start the jet ski a few times, but it will fail as it can’t keep up with the jet ski needs.

Not only that, but the battery is loose fitting and bounces around, which destroys the battery. The battery must fit snug in its compartment or else the internal plates get destroyed and kill the battery.

6. Battery Hooked Up Wrong

I’ll be fair, the batteries on some jet skis are a pain to replace.

It’s because of the odd placement of batteries that many jet ski owners hook them up backwards; they put the positive on negative and negative on positive.

Hooking the battery up backwards is not a good thing, in the best case it blows a fuse and worst case it blows the computer.

The order you hook up the battery can also affect the battery. When you connect the battery you do positive first then negative, and when you disconnect the battery you do negative first and then positive.

For the non-sealed batteries, they have a vent hose that is supposed to connect to the jet ski that vents out. If you don’t hook that up right, the battery acid spills into the bilge and corrodes things. Also, hydrogen gas goes into your bilge, which is very bad too, so make sure to vent your battery! Not every jet ski battery has a vent, usually if you have screw caps on top of the battery it needs to be vented.

7. It’s Not Your Battery

Plenty of starting issues may seem to be related to your battery, but not all of them are your battery.

To be fair, the vast majority of problems I’ve seen with jet skis not starting relate to the battery needing a charge or replaced. Also, batteries lie, so don’t trust them, get a new or charge it even if you don’t think you need to.

Things like a bad starter relay can make it seem like it’s a bad battery, or even a blown fuse!

I go into great details on why your jet ski won’t start and what to do here.

Signs Of A Bad Battery

How you know you have a dead battery is when you put your key on and all your jet ski does is click multiple times. This is not to be confused with one click you get from a bad starter relay.

Also, a battery could be so bad that the watercraft doesn’t even turn over or barely does anything. Some watercraft will even say “12 volt low” to let you know the battery is weak.

Does The Jet Ski Have A Charging System?

I often get asked if riding around for a bit will charge your battery on your jet ski. This works for cars, but not for jet ski engines.

Your jet ski does have a charging system, but it uses a stator instead of an alternator as found in cars. A stator does not fully charge your battery, but instead maintains a charge.

So riding your jet ski will not fully charge it, it will put a slight charge back but when you leave the watercraft for a few hours, the battery will be dead again.

Can I Jump My Battery on My Jet Ski?

Do NOT jump your jet ski battery from your truck battery!

I know this can be a hotly debated topic, even with cars and jumping them with another car, but it’s best you don’t. Yes, it may work a few times, but you run the risk of destroying your computer in your car/PWC or the very rare, but real chance, of batteries exploding.

There are far better ways to jump start a jet ski that I cover in great detail here.

Why Does My Battery Go Dead?

You only have to replace your battery in your car every few years, so why can’t your jet ski battery last longer?

The reason why your car battery lasts longer is that you constantly drive it, and your jet ski is only ridden parts of the year.

When a battery sits, it goes bad by sulfating. Sulfating is when the plates on the battery build up and cause it to lose charge over time. The same thing would happen to your car if you only drove it a couple of times a year, but happens faster for a jet ski because it’s a smaller battery.

How Long Do Jet Ski Batteries Last?

A good jet ski battery can last 3 to 5 years as long as you keep it charged when you’re not using it and keep it away from freezing.

If you don’t keep your jet ski battery on charge when you’re not using it or go months without riding your jet ski, then you can expect it to last a year.

As mentioned earlier in the post, I suggest a solar charger that is under 5-watt to keep your jet ski battery ready to go. They’re so easy to use and affordable that it just makes sense. Most of these solar chargers have quick connection that makes it even easier.

What If I Can’t Charge My Battery?

You’ll need to charge your battery if it’s dead. You could also disconnect the negative cable to keep any excess power draw from happening, but this is merely a band-aid on the problem.

Also, the old saying about how you can’t put a battery on concrete is false. It’s best to keep the battery out of the elements and charge it the night before you need it.

Winter Battery Storage

It’s best to get your battery out or keep it on charge during the winter.

I’ve seen many people go out to their watercraft when the winter is over and try to get it ready for the summer. They try to start the PWC, but the engine won’t turn over because the battery is dead.

They’ll call up whoever winterized their jet ski and complain that they didn’t do it right and want the problem fixed.

If you do not keep your battery charged with a battery charger or solar charger, then there is a good chance your battery will be dead by the time warm weather comes around. The cold and the lack of being charged kills the battery quickly, and often it can’t come back to life from it.

Jet Ski Battery Won’t Stay Charged

If you find that your jet ski battery won’t stay charged, then it’s a good chance something is draining it or the stator has stopped charging.

To check to see if the stator is bad, you need to take the jet ski out of the water and turn it on for a few seconds and test the voltage of the battery.

The battery should be pushing close to 14 volts, if it’s at or below 12 volts, then something is wrong with the charging system.

Other things that will keep a battery from charging…

  • Bad Rectifier.
  • Bad Grounds.
  • Sulfated Battery Plates from sitting too long or improper charging.
  • Bad Computer.
  • Wrong size battery.
  • Damage or corroded battery cables.
  • Blow Fuse.
  • Broken Gauge.
  • Broken Key.
  • Leaving the key on when you’re not using it (happens often).
  • Broken battery charger or not using a smart battery charger.
  • Overcharging the battery. You want to stay under 2 amps when charging a jet ski battery and use a smart charger, so it doesn’t overcharge when the battery is full.

More is covered in the jet ski won’t start post here.

43 thoughts on “7 Reasons Why Your Jet Ski Battery Keeps Dying [Stay Charged?]”

  1. My Jet Ski is telling me I have low voltage, I took the battery out and did a load test and it seemed fine, charged it, ran good for one ride, next time I got a low voltage. I put a meter on it while running and the voltage slowly went down. Put the battery in my other jet ski and the voltage went up and held at 13.5 volts. It sounds like my charging system is not working, checked the fuses.

  2. My Seadoo starts and runs good then when I come in shut down and go to start it again it chirps with the key, but won’t start just clicks. The next day it starts and the same thing happens, it’s happened that way three times so far. The voltage meter says Battery is at 11.9. Assuming it’s not the battery since it starts the next day-any help on this?

    • 11.9 volts is at the point that I would consider the battery bad. It starting the next day could be from it resting and then having enough energy to start the jet ski but not enough for another start until it rests some more. I would replace the battery to see if it helps. You can be sure it’s the battery by taking the battery to an auto parts store or your local dealer and letting them do a load test on it. Voltage doesn’t matter as much as amps and only a load tester can determine that.

  3. I know Yamaha doesn’t use AGM batteries and I wanted to check to see if you knew why?

    Seems like that would be the best route to take.

    Do the dealers supply the battery? If you purchase a new ski from a dealer could you ask them to put in a AGM battery?

    • The manufacturers ship out the cheapest batteries they can from the factory. It’s to keep costs down and to keep it simple for prepping the unit for delivery. Sometimes the battery comes with the unit in the crate and sometimes it shipped separately and the dealer needs to pay for it which is why you get charged a prep fee when buying new. Most dealers will give you a better battery if you pay extra for it, I’ve done this a few times.

  4. I have a brand new, 2018 Yamaha VX Limited with only 16 hours on it. Took it out this weekend, ran it for about 25 minutes, then shut it off to do lunch on beach. Went to start it up, got “Lo Bat” message. Finally started after 3-4 attempts, but then got warning light and engine symbol and power was limited (4000 rpm/6 mph). Took over an hour to get back to marina. Without looking at it, servicer said try new spark plugs. I don’t know, but seems like a battery thing. Thoughts?

    • Seems like a battery issue, but more importantly it’s a brand now 2018 so its best to get it back to the dealership because something is not right. The battery should not be bad this quick unless they gave you a bad battery or a dud. The warranties are the strongest in the first year of a watercraft and something like this is not normal.

  5. Your unit might have a bad magneto (like a car alternator). Seadoos should be completely dead when your key is not plugged in. So if you have something using power it might be the bilge syphon pickups.

  6. I have a seadoo and just replaced the battery about a week ago. I went out for a few rides earlier in the week and it ran well. I just went out and tried again, but nothing turned on. It seems like this would be a battery issue, but do you have any ideas what it might be or what to try to rule things out? Any help would be appreciated!

    • You might have something draining your battery, a bad key or a bad DESS post. It could also be a loose connection or a bad fuse, many possibilities.

  7. I have a 2003 SeaDoo RXDI. My batteries have always been stored in a non climate controlled garage (New York) from November to May. In May I put the battery on a trickle charge for 24hrs or until the charger reads “charged”. During the season the battery sits for sometimes 3 weeks without use. I have used both AGM and fillable batteries and have had no difference in performance. I change the battery every 4 years and have not had one fail.

  8. So it could be the rectifier or the stator. I had the same problem with my 2005 GTX and having changed the rectifier the Seadoo centre were saying it was a huge job to get the stator out and would cost hundreds. I did a lot of research and found that another problem can be the fuse for the charging system. Cost me pennies for a couple of standard spike fuses which you can buy anywhere and fixed the problem. Its worth trying anyway and is theasiest job but if you check the ones in there already they’ll be slightly black on the spikes if theyve gone. Saved me hundreds!!!

  9. I was recently given a 1989 seadoo and the charging system needs isn’t keeping the battering charged. If you charge the battery it will start up but the battery doesn’t last and dies. Once is starts the thing runs great until the battery dies. Just wondering if it would be the flywheel magneto stator or something else like the ignition coil. What else should I be looking for and is it going to be pricy to fix?

    • It’s best practice to have the battery disconnected when charging. But if you’re charging with an under 5-watt solar charger then I usually keep the battery connected. But for wall chargers that are under 2 amps, I disconnect the negative cable from the battery. Don’t go over 2-amps when charging a jet ski battery.

  10. Thanks so much Steven I just ordered two genius lithuim battery chargers to trickle charge my skis this winter! And won’t miss scraping my arms up trying to reconnect batteries next spring!

  11. I just put Battery tender lithium batteries in my jet skis can I leave them on a Battery Tender lithium JR 750 mA automatic trickel Charger in the Skis for the winter I’m in WI. and there in the Garage but its not heated garage. Thanks so much for any advice, I hate to take them out if I can avoid it its a hassle on these things with the brain box on top and the bungie cord tie downs

    • A covered garage is great for storing jet skis in, it helps to keep the cold wind off of them. If the garage gets below freezing for 24 hours straight I would recommend getting them winterized. You don’t have to take the batteries out if you don’t want to. You could charge them the night before you take them out if that is easier, but every month I would go in and check the batteries to make sure they’re not dying during the winter. If the batteries seem like they’re getting weak then charge them overnight and repeat. Since you have the lithium batteries make sure you get the correct battery charger to go with them.

  12. We have a Kowasaki and replaced the battery in May. We ride it every weekend but the last several weeks have had to jump it or put it on a charger for a few hours because it was totally dead, even after leaving a solar charger on it during the week. Something is draining the battery but we don’t know what. We make sure the key is turned off when we are done with each ride. Any suggestions? Thanks in advance!

    • There could be many reasons why your battery is draining and it is best to let a repair shop look at it to see what is doing it. I’ve seen ECM go bad and drain the battery to even corrosion on the connections to drain a battery. I know Kawasaki have a type of battery switch in the glove box that is orange that you should flip to off when done riding. Also, make sure the solar charger gets sunlight throughout the day and is not somewhere dark. Make sure the solar charger is also connected right with positive going positive and negative going to negative (I’ve done this before). If the solar charger is installed backward it will drain the battery. One more thing is that even though the battery seems new and you just bought it, this doesn’t mean it hasn’t gone bad. I would get the battery checked out to make sure it hasn’t failed internally and if you’re still under warranty get it replaced. Jet ski batteries take a lot of abuse with jumping waves and it’s important to get good sealed batteries made for such abuse.

    • Hi,

      I ad a similar problem and it was a pain.

      Mines a Seadoo but turned out to be the 30amp fuse for the charhing system. Changed that fixed it but then the fuse kept blowing so changed the regulator, put another new fuse and job done.

      Hopefully this is helpful for you.

  13. I use my yamaha jetski to fish from do a lot stop and starting also have a gps/fishfinder on all the time my question is can I install a larger deep cycle marine battery (40-50 ah) or go with two smaller jetski batteries.

    • This is a very interesting question that I have not gotten before. I personally won’t go with a bigger battery but maybe 2 little jet ski batteries and the second have an on/off switch on it. A simpler way might be carrying a small jump pack?

  14. I replaced my battery in my 2011 Seadoo GTI 130 last Memorial Day. I forgot to unhook the battery over the winter and today was the first time I tried to run it. The computer came on and stated it was in limp mode but would not start. I went and bought a trickle charger and it is now hooked up and says it is charging. That is all I need to do right?? I am VERY glad I found your site, I almost jumped it with the car. One other question, I have found mixed reports about using a jump pack?? Any concerns there??

    • Charging the battery with a battery charger is a good first step. If the battery is too far gone it might not charge even if the battery charger says it’s charged. You’ll know it’s fully charged if the ski starts up fine with no alarms going off or you take the battery to an auto parts store to let them load test it. If the battery is bad that model uses something like a 4-stroke battery (ETX30L). I have a video on YouTube about changing that style battery, just search YouTube for how to change a Sea-Doo Battery. You NEVER want to jump a jet ski with a car, that can fry the electronics of the jet ski. Small jump packs are fine, but something that is not needed. The best thing to do is keep a smart battery charger on the battery if you’re not going to be using it for more than a month.

    • Any solar panel over 5 watts should have a charge controller. Try to stick to 1.5w to 2.5w solar chargers for jet ski batteries.

  15. Just got my waverunners back from the shop and batteries checked out good. Do I need to keep them on a trickle charge or disconnect them to avoid having them drain if I use them every 2-3 weeks? Batteries are Power Source WP16CL-BS 12v21ah. I can hear them cycling or doing something every 10 mins or so.

    • It would be best to keep a battery charger or a solar charger like we talk about on the jet ski when not using it. But if you’re hearing clicking every 10 minutes then that is not normal. I’ve seen ECMs go bad and get confused and flip relay’s constantly and it drains the battery. It would be best to have the shop look at what is causing the clicking.

  16. We have 2 jet skies. Will the 2.5 solar panel supply enough power to charge both skies or do we need a panel for each jet ski ? Thanks.

    • You need a solar panel for each jet ski to maintain the charge. If the batteries are completely dead then they need to be charged with a battery charger or replaced. The solar panels could charge the batteries, but it would take a long time and they work better to maintain the charge so that the jet ski is ready to when you want to ride it.

  17. I was wondering if there is a preferred amp for battery chargers. I was looking to get a 7.2 amp smart charger for using on my sea doo batteries along with other bigger batteries. Will this be too high of an amp for the sea doo battery?


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