Battery issue advice?

[the1andonlycmo]

Just a disclaimer:

Number one I know this is an old boat and I have only had her for one full season (last year) so I'm just getting to really know her....:huh:

Some things work intermittently (tachometer), some never work (clock, trim gauge), and some things always work (all the important things like the motor, the bilge, trim tabs, oil pressure gauge, temp gauge etc...) However, one thing that really has me worried is the battery gauge.

Number two is I'm brand new when it comes to anything other than jetskis so any advice is needed. I made the jump from a jetski to this beast! I will really need the help of this forum to get this girl back in tip top shape!

I have two batteries in this boat and they are both labeled, "Starting Marine Service Battery" on the sides and just "Premium" on the top. There are no dates punched on the batteries so I have no clue how old they are.... Just thought I throw that in there. I did pull them out for winter and keep them on tinder. I meant to get them tested over the winter but was much to busy with work.

Anyways at idle my volt gauge normally reads somewhere at or below 12. The only time it goes above 12 is when I am under cruising power. If I'm only in gear and slowly moving and have certain things (blowers, fridge,) on the power can get below 12 and even below 11 at times. This is obviously worrisome as we routinely are in the boat for two nights at a time. I primarily boat in a lake so we normally just cruise to a cove and cut it off and "camp" for the weekend so the batteries do not always get a charge every day when we are using them. My worst nightmare is going to start them up with a boat full of people ready to go home and not even being able to start! Also, just for full disclosure I do keep this boat off the water with no power hookups. The only time the batteries get a charge is when the boat is under way.

I am trying to determine whether the gauge is wrong, the batteries are bad, or the alternator is bad before I end up stuck out in the middle of a big lake with no one around. On one hand the problem is confusing because if the gauge is true then the boat should not have even started at times. I have turned the key on and seen the gauge read below 10 volts and the boat has started right up...

So I said all that to say my plan is to use a volt meter and test the batteries first while the motors are off. From what I have read they should be somewhere around 12 volts. If this checks out I will then test the batteries under load. This will be "fun" as I will have to keep the engine hatch up while cruising down the lake. Best I can tell this should around 13.5. If these readings are correct then my only idea is that the gauge is wrong? If these reading are bad I'm guessing I should just pull the batteries and have them properly tested.

I only have about 1 day a week to really work on this thing so I want to know what the best way to go about this before the big trips start in May. Thanks guys!

 

[Wylie_Tunes]

A battery thats still good but used, at rest, should be above 12.5. A fully charged battery should 12.8, but as they age, they dont recover to what they were new and fresh. 12V would nearly depleted. This could be a result of a failing battery or poor charge.

You are on the right path to get to a volt meter and start testing. Check the voltage at the batteries, check again at the output of the main battery switch and then again at the back of the gauge. With engine running, check right at the alternator charge lead and then again at the switch and batteries.

given the age of the boat, poor and corroded cable ends is very common. this can lead to low voltage at the end of the line, like the helm and voltage gauge. A voltage drop test will help isolate a poor cable.

 

[paulswagelock]

Regarding checking voltages, check at idle and anything over 1600 rpm. You can do it at the dock with the boat in neutral rather than bouncing across the lake. Be safe. Voltage should be 12.5-13 or so at idle, and greater than 14 at higher rpm. No need to check it at 3000 rpm, etc.

If the batteries have not left you stranded yet, I am guessing the gauge/gauge wiring is faulty. Also, if they are more than a few years old, replace them with high quality lead acid batteries from Deka, interstate, etc. that way you know the baseline, condition, and history.

 

[thegotoguyr]

Do you have a battery selector switch, that allows you to only draw from one whie parked? That way you save one charged for starting, they are not difficult to install if you don't. That is when the deep cycle and cranking batteries are to be used although there is debate on that issue.
Agreed, a fully charged battery, according to the interstate store I got mine from 2 weeks ago should be 12.7 volts, and above below 12.4 would be considered discharged. I would check all wiring connections around your alternator for signs of corrosion or just loose contact.

 

[the1andonlycmo]

Thanks a lot! I had read a lot about older corroded wires dropping current the farther away they go. This boat is definitely going to be an adventure. I freaked out when I found the OEM wiring schematics a couple of days ago from searching around on the forum.

 

[the1andonlycmo]

Thanks for giving me the numbers to check at. I was wondering if it was an exponential type gain from the alternator. This is super helpful.

Please disregard the fact that I thought I was going to have to be underway haha!:smt101 I was writing that post very very early this morning. I certainly would have thought of that once I got to the boat. I know I should more then likely replace them, but the admiral and I are fixing to start another round of education to move up in our jobs so money will be little tight. From what I have seen the good high quality batteries are not cheap.

 

[the1andonlycmo]

I do have a selector switch for 1,2, and all. Because I did not install it I'm not sure exactly how its wired/works, but I do understand the basics of them. There is so much to learn on this thing! I will need to become an amateur electrician to get all of this worked out.

The way I understand I need to have it switched to all while running to make sure both batteries are charging. Also, when we are on the hook I do normally switch it to one of the batteries to run the stereo, the fresh water system, etc... The interesting thing is the stereo works whether the battery switch is set to 1,2 or ALL which makes me think its hardwired to the batteries with an inline fuse.

Sometimes I think of how nice it would be to have everything OEM so that I didn't have to go back and try to figure out/fix what other people have done. But hey where would the fun in that be?:thumbsup:

 

[paulswagelock]

Think of the switches this way- all of your loads like stereos, lights etc. and the engine starter are all tied together. The switch simply chooses which battery(s) supply power to that load. So, choose 1, battery 1 supplies power to everything. Also, the position determines which battery gets charged while the engine is running.

So, 'both' is really for emergencies when neither battery has enough power to start the engine, but together they both do. Also, never move the switch while the engine is running since you do not know if it is a make before break switch. Lastly, really shouldn't run on 'both' because the alternator can't really charge both batteries efficiently and a bad battery can prevent the good one from charging.

since you store the boat without access to power, is it outside? An inexpensive solar charger can keep the batteries topped off.

And two really good batteries can be had for $230 total or so.

 

[the1andonlycmo]

Ok! that makes a lot more sense. Thank you for your input.

Hrm... running on both is what I always do so maybe that could be a reason why the meter is low? I could have one good battery and one bad battery. This does make sense though.

I'm guessing I should use #1 battery to start it, and run it to the other side of the lake on that one battery to charge it. And then use #2 to start it and charge it on the way back. Alternating it this way makes more sense if the alternator doesn't have enough to charge both.

I do keep the boat covered and outside. I'm thinking a rollout swim platform panel or two would be my best bet to minimize the loss of power back to the batteries due to the length of cable I would need if I mounted them on the bow. I have looked in to solar charging and talked to a very knowledge service guy at West Marine about it. Ultimately I decided I wanted to figure out if I had a battery/alternator/wiring problem before spending the money on solar chargers.

Wow I must be looking in the wrong place! :smt100 Most of the batteries I see are more expensive than that for only one. I was thinking somewhere in the 600-1000$ range.

 

[the1andonlycmo]

Here are pics of my batteries. They both look the same. I'm assuming they are group 27?

I'm assuming if I replace them I should do one deep cycle for the house and one starting battery?