Dead Battery Advice

skippy88

skippy88

New Member
Oct 22, 2022
9
Australia
Boat Info
Sea Ray 355 Sundancer 2007
Engines
Twin Mercruiser 350 MAGNUM MPI 300hp V8 petrol
Hi guys, need some newbie advice!

Sea Ray 320 2007

I stupidly left both my battery isolators + some light switches on overnight. I came over today and the 12V battery in the control panel shows dead.

However I did leave shore power + AC converter (battery charger) on the same night. Should the charger have worked while the battery iso was on?

I tried starting the engines. Stbd one turned on. Port one didn't. Then tried the bridge button and turn on the Port on, but no luck.

After a bit even the Stbd one didn't want to turn on anymore.

Now, I've the shore power on, battery iso off, and battery charger on. I came back after an hour and still 12V was dead. Now I've left it like that for the night and will check on it tomorrow.

So my question is, after a full night of charging, should I expect it to work tomorrow? Or should I book a electrician ASAP? Unfortunately the hatch lift seems to run on 12V and doesn't work at the moment, so getting access to jump them might not be so easy?

Thanks everyone! Definitely learnt my lesson to follow my own checklist next time and turn the iso off when I leave the boat!
 
A couple of things about the boat's electrical configuration -
The isolation switches do not disconnect the charger/converter from the batteries.
The switches also do not disconnect any of the critical or safety systems from the batteries (bilge pumps, etc)
The charger/converter is fused (fuses or circuit breakers) to the battery banks.
The charger/converter is designed to not only charge the batteries but also manage nominal house and helm loads.
If the battery bank has a bad cell there is nothing the charger/converter can do to support starting the engine on that bank. A shorted battery cell will also not allow the emergency start switch to crossover the other bank for engine starting - there is a dead short.... In fact there is a distinct possibility of blowing up the battery and making a real mess.
Lastly, a lead acid battery that is fully discharged is permanently damaged and will never be able to regain its capability.

So, you are down to really three things - A bonafide battery failure, a charger/converter failure, or a blown fuse/circuit breaker in the charger/converter...
As an edit the engine alternators need to be checked out also. A shorted rectifier bridge in the alternator will take out a battery.
 
Thanks all - firstly I don't know how old the batteries are as I have purchased the boat recently, but visually they looked pretty new.

To confirm, battery iso ON + shore power ON+ AC converter ON should be able to handle leaving a few lights on overnight without depleting the battery right? Which means I probably have an issue with the converter or fuse for the converter, so I'm not expecting to see the battery charged when I get there tomorrow.

Is the fuse for the AC converter in the engine bay? At the moment I have no way of getting in there as the bay door won't open with shore power. I have heard something about plugging a battery pack into a 12V port somewhere to get the hatch door open - does anyone know if this is possible on the Sundancer and where the port is etc?

Thanks again!
 
skippy88 said:
Thanks all - firstly I don't know how old the batteries are as I have purchased the boat recently, but visually they looked pretty new.

To confirm, battery iso ON + shore power ON+ AC converter ON should be able to handle leaving a few lights on overnight without depleting the battery right? Which means I probably have an issue with the converter or fuse for the converter, so I'm not expecting to see the battery charged when I get there tomorrow.

Is the fuse for the AC converter in the engine bay? At the moment I have no way of getting in there as the bay door won't open with shore power. I have heard something about plugging a battery pack into a 12V port somewhere to get the hatch door open - does anyone know if this is possible on the Sundancer and where the port is etc?

Thanks again!
Click to expand...
So if your hatch won't open on shore power, you likely have a breakdown between the battery charger and the battery. I know when I had my issues the hatch would open, although very strained. In my case the battery, being low on water, wasn't holding a charge at all. However, like you said, all the 12 volt stuff on the boat worked without issue when plugged into shore power. Not sure if there is a fuse for the charger, mine has a breaker/switch on the panel.

If you have a old fashioned cigarette lighter at the helm, you can back feed the system to open the hatch. Search the site for various instructions if none show up here.
 
one thing if the battery is completely drained it will have zero resistance for the battery to start charging. Charging system need some resistance to get the ball rolling. One way to trick is to pull the battery out hook a charger to it then use jumper cables to any other battery. Once you let it sit for a few minutes hooked up like this you will be back to normal.
 
While into straightening out your issues with the converter/battery system, if your converter isn't a "Smart Charger", now would be a good time to upgrade it.
 
It’s not complex, based on your comment don’t know how old the batts are.
1 get all new batts
2 get a modern smart charger Promariner.
OR…
Get good tow insurance.
It’s not complicated.
 
I would take the batterys out of the boat and put a portable battery charger on the batterys until they are fully charged then I would load test the batterys to see if they are good, if no good get new batterys.
Now with batterys that you no are good then you can start to perform all the test that people mentioned above.

With the boat in the water and bad or removed batterys you have no working bilge pumps so I would be real careful with this.
 
Thanks for the comments guys. I had an electrician look at it today and after getting access to the engine bay looks like the AC converter wasn't connected to 2 of the batteries properly. Probably wasn't connected all along and I was just charging by running the engines up to now. So I think it's unlikely the batteries are at fault. Leaving them charging currently and seeing if they're at 13-14V tomorrow.
 
skippy88 said:
Thanks for the comments guys. I had an electrician look at it today and after getting access to the engine bay looks like the AC converter wasn't connected to 2 of the batteries properly. Probably wasn't connected all along and I was just charging by running the engines up to now. So I think it's unlikely the batteries are at fault. Leaving them charging currently and seeing if they're at 13-14V tomorrow.
Click to expand...
And the verdict today is?
 
I checked on it yesterday and the 12V panel showed 12.5V and going up. Everything works except STBD engine won't turn on. Only works while I bridge it with the Port Engine battery, the moment I let go of bridge, the STBD engine dies immediately. So looks like somewhere in this process the STBD engine battery 'broke' or it became so discharged that it's not getting charged. An electrician promised to take a look and replace the battery this Friday so fingers crossed I can go boating over the xmas / New Year period, which is really popular for boating here in Australia.
 
If you own a boat with 12v batteries, which is almost all of us, I recommend that you get a battery load tester to test the condition of your batteries. A volt meter will tell you what the voltage level of the battery is, but it won't tell you whether the battery can hold a charge.

12v batteries have a limited life span, and we all spend time wondering whether our batteries are good, and just replacing them because we aren't sure. Just spend $50 or whatever and buy a good tester so you know the condition of your batteries and you don't have to guess. The alternative is to pull them out of the boat and lug them to west marine or an auto parts store and have them tested, but that is a pain.

A tester will last you for years, and if you own boats you will use it over and over. I have 8 batteries across 4 watercraft, and I test the batteries each spring as part of my commissioning. It saves a lot of guesswork and headaches.
 
yobub said:
If you own a boat with 12v batteries, which is almost all of us, I recommend that you get a battery load tester to test the condition of your batteries. A volt meter will tell you what the voltage level of the battery is, but it won't tell you whether the battery can hold a charge.

12v batteries have a limited life span, and we all spend time wondering whether our batteries are good, and just replacing them because we aren't sure. Just spend $50 or whatever and buy a good tester so you know the condition of your batteries and you don't have to guess. The alternative is to pull them out of the boat and lug them to west marine or an auto parts store and have them tested, but that is a pain.

A tester will last you for years, and if you own boats you will use it over and over. I have 8 batteries across 4 watercraft, and I test the batteries each spring as part of my commissioning. It saves a lot of guesswork and headaches.
Click to expand...
Agreed, well said. @skippy88 you don't need a fancy one with all kinds of knobs and such, just a basic one. This one should do the trick, and it's 5% off :) Note I said "you", others may want something more advanced. Great way to test if a wire is live, or not, as well.

https://www.amazon.com/AstroAI-Digital-Multimeter-Voltage-Tester/dp/B01ISAMUA6/ref=sr_1_1_sspa?crid=3A1C983KBLEWT&keywords=volt+meter&qid=1671644617&s=industrial&sprefix=volt+meter,industrial,84&sr=1-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExUE5GUVFKTVpFSEZaJmVuY3J5cHRlZElkPUEwMTA2NDUyNjNVOVhLUzVHNlRHJmVuY3J5cHRlZEFkSWQ9QTA2NjU4MzAyNzJKNUlBODIxUlkmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
 
yobub said:
The alternative is to pull them out of the boat and lug them to west marine or an auto parts store and have them tested, but that is a pain.
Click to expand...
I agree, because by that time, I am not coming back with the same batteries. Hauling back brand new. Then I don’t have to repeat for 3 years.
I trust a battery like I trust marrying a crack whore hooker to be faithful.
 
 
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