7 Reasons Why The Batteries In Your Jet Skis Keep Dying

Ever find yourself scratching your head, wondering why it seems like you have to swap out the batteries in your jet skis every single year? It’s a common frustration – that feeling when the battery in your Sea-Doo, Yamaha, or Kawasaki jet ski just goes flat and needs constant replacement. Or perhaps you’ve faced the maddening scenario where no matter how much you charge it, the battery just won’t stay alive.

Well, fear not because I’m here to shed some light on this perplexing issue. We’ll dig into the reasons behind why the battery in your jet ski continues to die on you and explore what you can do to put an end to this never-ending jet ski saga. So, let’s get to the bottom of it and ensure you have more ride time and less trouble!

1. You’re Not Driving It Enough!

Jet ski batteries simply die because they’re not being used enough. People tend to only ride during the warm months and then let the jet ski sit during the winter. Your battery will die because it keeps sitting for too long and the internal plates start to sulfate. 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-watts and keep it plugged up when I’m done riding my jet ski 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 charger is so affordable and easy to do that I’m surprised more people don’t know about this trick!

2. The Cold Will Kill Your Jet Ski’s Battery

The cold will hurt your battery and affect starting power to the engine. When you winterize your jet ski, it’s best to take the batteries out and put them in your garage or some place where the wind and cold won’t get to it that much. You don’t need to cover it, it’s best you don’t, just don’t want it outside in the elements.

You can put the smart charger on the battery every so often to top up the jet ski’s charge. 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 thing is charged even when it’s not. I’ve had a few chargers lie to me, as they go off voltage to turn itself off, but you need amps to start a jet ski.

If you’re using a charger that plugs into the wall, I suggest you use a smart charger like this one here (Amazon Link Ad). This smart charger needs to be 12 volts and at 500ma or 2 amps of charging power.

You don’t want to rush a charge into the battery of a jet ski, 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 batteries need it, which prevents overcharging.

Don’t use the old-school trickle chargers, as they can overcharge!

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 thing, but you can use a charge controller that will regulate this charge and protect it; 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 (Amazon Link Ad).

What about a trickle charger or maintainer? Chargers go by many names, what’s important is that you have one that turns on and off as it’s needed. I call them smart chargers, because they’re smart enough to turn on and off. I’ve noticed more people use this term, especially on the internet, so it stuck.

4. Batteries fail – Happens Out Of The Blue!

Sometimes lead-acid batteries just suck, even new ones can have a manufacturer defect or be drained right out the box. Seeing the battery dying too quickly is not a surprise when you consider that it takes a lot of abuse from the wave jumping along with 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 jet ski battery won’t bring it back to life, then it’s a dud and needs to be replaced. Even if it’s new, 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 dealership or autoparts store can easily do this and should be doing it, as they know some new PWC batteries can be duds.

And the warranty? It doesn’t matter, I find warranties are a pain to use on batteries. I would invest in a smart charger, as it going flat from inactivity is the most common reason they fail.

5. You Have The Improper Size Jet Ski Battery

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 battery for their jet ski that was half the normal size, with blocks of wood to make it fit. Sure, the battery might start the engine a few times, but it will die as it can’t keep up with the jet ski’s needs. (Please, don’t use lawnmower batteries!) Not only that, but the battery is loose fitting and bounces around, which destroys it. It must fit snug in its compartment or else the internal plates get destroyed.

6. You’ve Hooked The Jet Ski’s Battery Up Wrong

I’ll be fair, the batteries on some jet skis are a pain to replace. (That’s an understatement if you ever messed with those rubber battery straps!) It’s because of the odd placement of batteries that many people hook them up backwards. When a battery is hooked up backwards, it can make you think it’s dead and stops the engine from starting.

Hooking the battery up backwards is not a good thing, in the best case it blows a fuse and worst case it blows the jet ski’s computer. The order you hook up the battery can also affect it. When you connect the terminals you do positive first then negative, and when you disconnect the terminals you do negative first and then positive.

For the non-sealed batteries, they have a vent hose that is supposed to connect to the hull that vents out. If you don’t hook that up right, the 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 one has a vent, usually if you have screw caps on top it needs to be vented.

7. It’s Something Else, Sometimes Batteries Lie

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

What Are The 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 dead that the jet ski doesn’t even turn over or barely does anything. Some jet skis will even say “12 volt low” to let you know the battery is weak.

Can You Keep A Battery Charger On The Battery All The Time?

As covered in this post, your batteries go dead from not being used. Keeping them active will extend their lives, but is it safe to keep the charger on all the time? You need to use a smart battery charger, they turn on and off as they’re needed. The instruction manual for your charger will let you know if they can be kept on the battery all the time. Ideally, you should not keep the charger on the battery. Over the winter, you should charge it once a month and then disconnect the battery.

For me personally, I keep the solar charger on all the time because it’s low power and has a charge controller. I get years out of my batteries, but the jet ski is also kept outside. That is important, as batteries charge they release hydrogen, which is explosive. It’s not a lot of hydrogen, but there are batteries that have exploded, so it’s a thing.

You’ll need to use your own common sense and what works for yourself. Honestly, most people can get away with just charging the jet ski the night before you want to ride. Many smart chargers will also desulfate to revive some dead batteries.

Wrap Up On Why Your Jet Ski’s Battery Keeps on dying On You

Jet ski batteries are prone to dying from inactivity. When not used frequently, the battery starts to sulfate. This buildup can eventually cause the battery to take longer to charge, become more prone to overheating, and ultimately fail. To avoid this, make sure to start your jet ski regularly to keep the battery active, or connect it to a smart charger when it’s not in use.



I started working at a power sports dealership in 2007, I worked in parts, service counter, and as a technician before moving to sales in 2013. I created in 2014 to answer common watercraft questions I would get from people. Now managing the site full-time, I continue to provide advice and web tools for my readers about watercraft. I've owned several watercraft, with a Sea-Doo Spark as my current main PWC.

43 thoughts on “7 Reasons Why The Batteries In Your Jet Skis Keep Dying”

  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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