Battery Dead

"I have a 5.0mpi 2007 on with

"I have a 5.0mpi 2007 on with 50 hours.

I am based in Cape Town, South Africa.

I have a 22 foot boat and recently fitted a sansui amplifier for the stereo.

As far as I am aware the stereo f the only "non standard apparatus that runs off the battery"

A week ago I arrived at the boat, having not used it in 5 days and the battery was dead.

I jumped it and used it for 30 mins.

It started perfectly thereafter and was last started but not run for any length of time on Thursday.

Today Sat I arrived at the boat and it was dead as a door nail!

The steroe man says it can;t be the amp as when the boat if off no power can be drawn.

Any advice?

Could a 6 month old battery go dud?"

"Hi Alon,

Yup a battery

"Hi Alon,

Yup a battery can go dead in 6 months. I had a Sears Diehard that went that route. It's not likely though. I'm suspecting the diode trio in the alternator. If bad the alternator will charge the battery when the engine is running but with the engine off it will drain the battery. Have the alternator checked. Is a bilge pump stuck on, radio, depth finder, gps, etc? Check."

"There are a couple of possibi

"There are a couple of possibilities here...
1) The previous post mentioned bad diodes in the alternator. This is certainly a possibility especially if the battery is permanently wired to the engine without a shut off switch.
2) The other possiblity relates to your use of the boat. Lets say you drive around and then anchor and play the stereo for awhile and then restart and run home. This will cause the battery to "deep cycle". This will cause an early failure of the battery. "Start" duty batteries are designed for just that. Start the engine, get recharged, sit awhile unused, and then start the engine again. Start/deep cycle batteries will tolerate having a drain on them for some time and then get start the boat (assuming they haven't been too deeply discharged) and then get recharged."

"Just reading along here...

"Just reading along here...

So are you suggesting that I rewire my stereo onto the trolling motor battery in my boat? I was thinking of doing this anyway, just to make sure there is a full charge in the start battery when I want to start the boat after listening to the stereo for a couple of hours while anchored.

Alon... a few more things..

1)If only using the alt to recharge the batt, you won't get a complete charge into the batt. You must use a batt charger to get a good deep charge.
2) It's pretty rough on that alt to charge a batt up from dead. That alt is going to get very hot working so hard all the time and it will cause an internal failure in the alt at some point.
3) Batts come with warranties for a reason. They can go bad right from the beginning.
4) After shutting the boat off, and just before you head home for the week, take off one of the batt cables. Use a 12 volt test light and probe between that empty batt post and the cable end you just took off. The light should not light up. If the light comes on, you have a drain on the batt (from somewhere) and it needs to be corrected. If the test light stays off, you may be looking at a bad batt.

Is this the same boat that you had electronic MPI problems with a couple of months ago? If so, could this be a related problem? (I can't remember what the other problem was)


Wrench"

"If there is a 120 v ac outlet

"If there is a 120 v ac outlet where you dock your boat, a Battery Float Charger is a good investment. Harbor Freight has them for <$10. I keep one on my Mercruiser and it is always hot to go. Good luck. JW in Dixie"