Dead battery questions from yesterday

Allen · Aug 15, 2016

Ok, so I went out on the river to tool around with all the recreational crowd in my boat, and maybe do a little fishing.

The boat was plugged in so the batteries should have been freshly topped off. After a couple hours of pulling cranks I noticed my older Lowrance LMS 480 was going in and out, and finally shutting itself down. I started to just think that well, it is 12 years old after all and is finally just in its death throes. Next thing I know the boat motor (115 Yamaha 4-S) just ups and dies. I hit the key and nothing, battery is dead. I hooked it up to my 24 volt bank with jumper cables and made it back to the ramp without a hitch.

The battery is maybe a year old Interstate starting battery and I go through cleaning of the terminals each spring just to avoid this crap.

The batteries are currently being charged as I write this and I am planning on pulling the starting battery to have it tested tonight.

So here are my questions in case the battery itself is fine (which I now doubt as we only trolled for a couple hours and the livewell was the biggest electrical draw).

1. Is it likely my alternator went out, and how do I as a home mechanic even test an alternator? Or do I just punt and get it an appointment at a shop?

2. How often do Guest onboard chargers go bad. The starting battery is hooked up to an 8-9 year old Guest that has never before been a problem, is it possible the charger fried the battery? I'd have thought if that were the case the battery would have been dead at the ramp though.

3. Any other thoughts other than going through the wiring from stem to stern and cleaning contacts?

Captain Ahab · Aug 15, 2016

I had a Cabelas on-board go bad on me. Thought it was my batteries at first. Test the charger first and then test battery and alternator.

espringers · Aug 15, 2016

Your lms must not have a voltage sensor/overlay option? That would let you know if the alternator is putting out voltage when the motor is running. Or just use a voltmeter at the terminals with it running. Or borrow someone else's newer sonar with a built in voltage indicator.

DirtyMike · Aug 15, 2016

Either way, you'd think with the big motor running, you'd have charged your battery. sounds like alternator.

Allen · Aug 15, 2016

espringers said:
Your lms must not have a voltage sensor/overlay option? That would let you know if the alternator is putting out voltage when the motor is running. Or just use a voltmeter at the terminals with it running. Or borrow someone else's newer sonar with a built in voltage indicator.

Oddly enough it does, I think I turned it off several years ago though as it seemed to read too low. I often had readings of 10.6-11.5 volts even with the motor running. Hah, maybe my alternator has been weak for years.

- - - Updated - - -

DirtyMike said:
Either way, you'd think with the big motor running, you'd have charged your battery. sounds like alternator.

My thoughts exactly. The big motor died about 5 minutes into idling after having just run from Expressway bridge up to Heskitt.

Davey Crockett · Aug 15, 2016

All sorts of good advice. If need be, You might also be able to test your alternator by hooking up muffs and a battery charger and start motor, if the Alt is working the charger draw should drop when the motor is running. Works better if your battery is drained down it should show how many amps your charger is putting out. I like my Stanley charger with digital readout , It has a built in alt. tester and a battery reconditioning function. It brought an old tractor battery back to life and that made me smile. I wouldn't chance an old boat battery but for vehicles that I hardly use it has already saved me the price of the charger .

NJL · Aug 15, 2016

Its pretty easy to check your systems if you have a voltmeter handy.

To check your battery, first throw the charger on it over night. Then when your ready to test it, attach the voltmeter (set to DC volts) leads across the terminals and crank the engine. On a good battery the voltage level shouldn't drop below 10 VDC. If it does, that means your battery isn't holding a charge like it should.

To check your alternator, apply the voltmeter across the battery terminals while the engine is running. The reading should be 13-15 VDC. If the voltage reads less than this, it means your alternator output isn't enough to charge the battery. If it's above this, then the voltage regulator in the alternator is bad and your overcharging and damaging the battery.

To check your charging system unhook the leads from the battery and attach the volt meter to them. Turn on the charger, the reading should be 13-15 VDC. If its less than that, it's not charging the battery. If it's more than that, it's damaging & reducing the life expectancy of the battery.

Up Y'oars · Aug 15, 2016

I had a similar issue a few years ago and I then found out that my on-board charger was not charging the batteries. We found this out by running a voltmeter on the charger to see if it was pushing any amps thru the terminals. Nope. I pulled the charger out of the boat (six yrs old) and replaced it with a Minnkota 320 digital charger system.

Allen · Aug 16, 2016

Thus far, battery when charged tests good. Pulled it and had it on my shop charger over night and Interstate tested it for me this morning by putting a load on it.

8(?) year old Guest onboard charger = bad. No lights on, measures around 0.5 volts when plugged in.

Regulator/Rectifier will be tested tonight. There's still a reason it wasn't getting a charge from the main motor.

I love electrical problems. Even better, as I contorted myself to pull the onboard charger out of the battery compartment, I especially enjoyed hearing the sounds of a titty sprinkling mouse scrambling for cover under the floor. If he doesn't get lured in by the peanut butter to his demise today, he best exit the damn boat before it hits the water again or I'm going to pull the plug and fill it with water to above the floor!

Fricking hate mice!

Tommyboy · Aug 16, 2016

NJL said:
Its pretty easy to check your systems if you have a voltmeter handy.

To check your battery, first throw the charger on it over night. Then when your ready to test it, attach the voltmeter (set to DC volts) leads across the terminals and crank the engine. On a good battery the voltage level shouldn't drop below 10 VDC. If it does, that means your battery isn't holding a charge like it should.

To check your alternator, apply the voltmeter across the battery terminals while the engine is running. The reading should be 13-15 VDC. If the voltage reads less than this, it means your alternator output isn't enough to charge the battery. If it's above this, then the voltage regulator in the alternator is bad and your overcharging and damaging the battery.

To check your charging system unhook the leads from the battery and attach the volt meter to them. Turn on the charger, the reading should be 13-15 VDC. If its less than that, it's not charging the battery. If it's more than that, it's damaging & reducing the life expectancy of the battery.

This is some great info for anybody to have on hand. I took a picture with my phone for future reference!

Allen · Aug 16, 2016

Tommyboy said:
This is some great info for anybody to have on hand. I took a picture with my phone for future reference!

Yep, it provided me with my path to eventual victory.

Davey Crockett · Aug 16, 2016

Allen said:
Even better, as I contorted myself to pull the onboard charger out of the battery compartment, I especially enjoyed hearing the sounds of a titty sprinkling mouse scrambling for cover under the floor. If he doesn't get lured in by the peanut butter to his demise today, he best exit the damn boat before it hits the water again or I'm going to pull the plug and fill it with water to above the floor!

Fricking hate mice!

Urgent, Worthy of putting the plug in and grabbing the water hose. My Lund was in storage when I bought it and I saw mouse turds in a storage compartment so I checked wires , seats and everything else that I could see and it all looked ok. Boat cleaned up nice and ran good but had a leak . After spending an evening of looking for lose rivets and holes I finally resorted to putting the plug in and putting water in the boat overnight and the next day no wet spot but boat still leaked when it was in the water. I finally figured out it was the plastic fill hose for the live well that leaked even when I wasn't using the well. It looked like drain tile, Mice love them

Allen · Aug 16, 2016

Yep, that would be about my darn luck at this point. I've had the most expensive boating season in this boat since the year I first bought it!

I'd actually do the fill the boat thing to make the little bassturd show himself, but to fill it above the floor boards would put so much weight on the trailer that I'm afraid I'd be back to the boat trailer shop next.

SDMF · Aug 16, 2016

Allen said:
Yep, that would be about my darn luck at this point. I've had the most expensive boating season in this boat since the year I first bought it!

I'd actually do the fill the boat thing to make the little bassturd show himself, but to fill it above the floor boards would put so much weight on the trailer that I'm afraid I'd be back to the boat trailer shop next.

Jackstands. Axle and tongue.

Allen · Aug 16, 2016

Ha ha ha. Maybe after the kids go to bed tonight I can go full Carl Spackler on him. If the peanut butter doesn't kill him.

Sub_Elect · Aug 17, 2016

Its the alternator. 100%!

Macnet36 · Aug 17, 2016

Anh em ủng hộ dịch vụ mình nhé

Captain Ahab · Aug 17, 2016

Macnet36 said:
Anh em á»§ng há»™ dá»‹ch vá»¥ mÃ¬nh nhÃ©

https://m.youtube.com/watch?v=6934-r6kgJo

Allen · Aug 17, 2016

Sub_Elect said:
Its the alternator. 100%!

Just to help squash any confusion over my poor choice in terminology, a Yamaha boat motor doesn't have an "alternator" as we think of when we look under the hood of our cars. Rather it has a stator, set of magnets, and a voltage rectifier (converts current to DC from AC) and a voltage regulator. In my example the rectifier and regulator are a combined unit.

Checked the stator last night and got 0.8 ohms on it across the board, so that should be good even though it's right at the upper limit of tolerances. Whew, that bad boy is roughly $400 on the interweb, and I'd have to imagine there's a small premium for it being available locally.

BTW, the mouse in no more.

Davey Crockett · Aug 17, 2016

Allen, Sounds like your having about the same luck as me this summer , No idea about Yamaha but I was able to find new CDI ignition parts for about 1/2 price on ebay . I replaced my stator ,trigger and switchbox for what a switchbox would have cost from online stores. Hope your luck is better than mine, according to specs mine were just on the edge but they all failed one at a time.
Glad your trapping went well , Did you get the momma the poppa or one of the babies ?

Dead battery questions from yesterday

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