Alternator charging battery

[RC]

So how much (if any) should the alternator be maintaining the charge in a boat's battery. I charge my battery after each time I go out. I just got back from a 3 day trip and towards the end of the 3rd day my battery was getting weak. (and we were only on the boat a couple of hours each day) Put it on the charger this morning and it's still going. A friend of mine has a '99 Bayliner. He has had his battery for over a year and never has charged it. (uses the boat a lot) He thought it was getting weak once, put it on the charger and it was fully charged in about 10 minutes. Sounds like his alternator is doing the job. My boat is an '86, does that have anything to do with it? Thanks

 

[calwldlif]

Re: Alternator charging battery

OK?
What do you do on the boat?
Radio
Elec trolling motor
Microwave
Refrigerator
Air conditioner

If all you do is run the engine and no
accessories then yes your charging system needs
attention.

 

[RC]

Re: Alternator charging battery

Just the radio and not very much of that. Where do you suggest I start?

 

[calwldlif]

Re: Alternator charging battery

I know what boat your friend has
What about you?
There are basically 2 types of
alternators
one with volt reg internal
one with volt regulator external



(if you don't have an old boat with generator)

Quick test is put volt meter on battery poles
when running engine.
more than 12 less than 16
idle will be on the low side ,1500rpm average side

 

[bjcsc]

Re: Alternator charging battery

How old is your current battery? They don't last forever...

 

[Silvertip]

Re: Alternator charging battery

Yup, it sure helps to know if we are talking about an outboard or I/O, engine manufacturer, horsepower, battery type (deep cycle, combo, starting, etc), age, and any other details about your boating activity.

 

[RC]

Re: Alternator charging battery

Boat is an 86 Four Winns 190 Horizon I/O 4.3L OMC. Battery is just over a year old and is a starting battery. When I bought the boat it was originally set up with two batteries one a starter one deep cycle. Since I don't have a need for a deep cycle I now use just the one. It is also set up with the battery switch for two batteries and I always turn the switch to off when not using the boat or its docked for the night. The only accesory I ever run is the radio and it's not used that much.

 

[jastacey]

Re: Alternator charging battery

Check the fan belt, if you can turn the alternator fan blades with your hand, the alternator is not charging to it's full potential, tighten the belt, and if the battery water level is low, use distilled water, it just takes 1 oz. od regular tap water to ruin a battery.

 

[calwldlif]

Re: Alternator charging battery

I am going to give
a wild asss guess
If the battery switch is
trying to charge the deep cell that isn't
there it will starve the one that is.
I am not an expert with dual bats
and selector switches.
remove selector switch and put proper
cables to the bat you have.
Most likely this is your trouble

 

[Texasmark]

Re: Alternator charging battery

Get a voltmeter and check the voltage at the battery terminals (not the clamps attached to them) with the engine running at 2000 rpm's.

You should measure real close to 14.5 volts on any charging system. Variance (primarily) can be attributed to how much current the system is having to supply when you make the measurement.

24 hours after you last charged your battery (and didn't use anything electrical) the battery post voltage should read 12.75 or more for a full charge.

I/O engines use high output alternators so you should be able to recharge a low battery quickly.

Most dual battery setups send current to both batteries and the internal resistance of the battery determines which one gets more or less current. The voltage is fed in parallel so they get the same voltage. This is bad because the bad battery (usually sulphated up) has the highest resistance and therefore gets the least current......but it's the one needing the most current.

If a battery is missing, like your original setup, it should make no difference whatsoever, unless you have a switch that selects either start or troll, have the troll batt removed, and the sw in the troll position. Then you get nothing except maybe a damaged alternator from excessive voltage.

HTH

Mark

 

[studlymandingo]

Re: Alternator charging battery

Sounds like you do have a battery or charging system issue.

 

[RC]

Re: Alternator charging battery

I could turn the fan blades on the alternator fairly easily, I tightened the belt and now can barely move them. That should help. I don't think the missing battery is an issue because when in use the battery selector switch is always set to "1" for the starter battery. I assume this isolates that battery and ignores the one not attached. I'll get a voltmeter like you suggest Mark and see where that gets me. Thanks

 

[bjcsc]

Re: Alternator charging battery

Most dual battery setups send current to both batteries...

This is true if they have an isolator installed. This is likely as most mixed battery setups (1 starting, 1 deep cycle(house)) use isolators. I'm pretty sure you have to use one if you use mixed batteries. Basic dual battery setups ( non-isolator) only charge the battery selected. You need to figure out what you've got. Trace down the charging wire from your alternator. It will either go to an isolator or to the switch...

 

[Texasmark]

Re: Alternator charging battery

If you could spin the pulley on your alt you just hit upon your problem. You should not be able to spin the alt pulley with your hand if the belt is correctly set.

The more power the alt has to put out to charge a discharged battery, the more power it requires from the engine. This power is delivered via the fan belt-pulley.

If the pulley slips, when the alt needs power it aint-a-gonna get it.

Mark

 

[hiflyer]

Re: Alternator charging battery

be carefull on the belt tighting. pulley should not slip. but belt shoud have some deflection about 1/2 " on the long side. to much will burn the front alt. bearing out. thats pricey. Buy a hydrometer not the bent type check the acid level. 2. check battery voltage before start . then again 5 min after. with eng running, like above 14.2-14.6 is right shut off after 10 min,and see after 10 min more how far it, voltage fell, should be about the same. if not! you, prob have an alt. problem. weak diode ect internal. I am assuming all wires cleaned and retightened. some corrision does not show but will cause a bad connection.

 

[RC]

Re: Alternator charging battery

The belt is now tight so I can't spin the fan. My manual says the deflection should be 1/4", hiflyer you say 1/2" but I can clearly move that belt about a full inch and there is no more room to adjust the alternator. Could the belt be the wrong size?

 

[hiflyer]

Re: Alternator charging battery

A hard to believe its the original but may well be.
B they tend to stretch over time. adj should leave some room on bracket never at the end .
C Take it off have it measured any auto
supply store. IF doubt it, but if you they can read original size on it They can tell you weather it has stretched to far. If its a newer belt and has not stretched someone Might have put on a longer belt by mistake
Go down a 1/2 on length. Split the difference on adj. deflection 3/8 its an old bearing. be prepared to readj. after a few hours as the new belt will seat itself to the pulleys.

 

[Texasmark]

Re: Alternator charging battery

Yes they stretch and yes you hit upon your problem. If your manual says 1/4" so be it. Part of the number depends on the length of the run. The longer the run the more it will deflect with the same tension.

Do as your book says. If your setup is OEM then a new belt of the same length should work correctly. But that's not to say that a 1/2" shorter belt wouldn't work either. Most belts have a mfgr's part number on them, part of which is the length.

When installing, don't stretch the belt over the pulley with a screwdriver type thing and don't prise too hard on the aluminum shell of the alt with a sharp object. They have been known to crack.

And on wearing out the front bearing......hear you but to get 100k miles on your boat brudday you are going to have to do some boating. :/

My 2c,

Mark

 

[Texasmark]

Re: Alternator charging battery

So, where are we on this?

Bumping it up.

Another dead end? Hopefully not.

Mark

 

[b00tstrap]

Re: Alternator charging battery

Take the battery to an auto parts store, my local store will do some tests and tell if the battery is still good. This rules out shorted cells, etc..

If you had a dual battery switch, then not having the second battery will not cause a drain.

Check for 14.5vdc at the battery terminal as previously suggested. If the voltage is low (or too high) then the battery will suffer.