Charging system doesn't work anymore....help!

Saskatoon2005

Master Chief Petty Officer
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Apr 27, 2005
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Hello all,

I also have a posting about a fuel starving engine, but that is not the only problem....

I have a 1975 Johnson 70HP outboard. I recently noticed that the outboard no longer charges the battery, or at least it is slowing getting drawn out. I checked the battery tonight and it was at 9.0 volts DC. So i have it hooked up to a charger and it is charging...I also have a portable battery booster that I have to recharge as I used it to get my outboard going as well.

There is no melting of the potting on the stator, so i assume it is all right as well.

I need to know where to go from here to get it running nicely again. What could have damaged the charging circuit? It has a new battery and the connections are all mint. Please advise!
 

Barnacle_Bill

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Re: Charging system doesn't work anymore....help!

Check your rectifier/regulator. If you ever hooked up the batteries backwards, even for a split second, that could blow it. Or it could have just ied of old age. While you have it out check your stator according to your manual.
 

jtexas

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Re: Charging system doesn't work anymore....help!

also, running the engine without a battery connected will smoke the rectifier, which is the same as not getting your lugs on tight enough. if you have wingnuts on the battery posts, use pliers.

It doesn't look good for that battery - once they get down below about 10.5V, they're usually pretty much toast.

In fact, you might have a bad battery and not a bad alternator at all. Could have been old stock off the shelf, maybe?

Check the engine FAQ section of iboats for the rectifier testing thread.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

Yeah, I was curious as to what may have happened to the battery....but I will check the rectifier/regulator as well. Thank-you for your help and I will let you know how it turns out.

Patrick
 

F_R

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Re: Charging system doesn't work anymore....help!

I had the same thought. Once you get the battery charged up again, have it load tested. Unless it is completely discharged, 9 volts is way low. Like a dead cell.
 

Vic.S

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Re: Charging system doesn't work anymore....help!

also, running the engine without a battery connected will smoke the rectifier
Not true! What blows diodes is disconnecting the battery while the battery is running! That causes a big surge in the voltage and that blows the diodes.

A battery that has been discharged as low as 9 volts has had it. Charging it might restore a little bit of life but it is never going to recover fully. No battery should ever be left in even a partially discharged state and even a deep cycle battery should not be fully discharged.

When testing rectifiers (see the post in the engine FAQs) use the diode test range of digital multi-meters, not one of the ohms ranges. Meters vary some will do it on the ohms ranges , some will do it on some of the ranges, some won't do it at all.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

I just checked the battery and it is 12.04 volts DC. I am going to take it Canadian Tire to have a load put on it and check it out. This is after charging it for over 12 hours at a 10 amp charge....should it be better?

Thanks for replies..

Patrick
 

ezeke

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Re: Charging system doesn't work anymore....help!

My big deep cycle batteries can take several days to recharge on a trickle charger when they are down low. Check the rectifier the way Mr. Joe Reeves describes in the Engine FAQ forum on this site, but always disconnect it before testing.

BTW, It is nearly impossible for the rectifier to charge a battery that is connected with bad battery cables.
 

Vic.S

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Re: Charging system doesn't work anymore....help!

10 amps is a pretty high current unless you have a big battery. Normally with a basic non regulated charger charge until the volts have been at around 14.4 for an hour or so. Let is rest for 12hours then check the volts. 12.7 or 12.8 is good and fully charged 12.2 is only about half charged around 11.7 is effectively flat. If it is less than 12.7 try charging for a bit longer, let it rest and check again. If you get it up to 12.7 - 12.8 or more it should take a couple of weeks or more to fall below 12.6 if it is good. It falls quickly at first but then more slowly.

If you can test the acid in the individual cells with a hydrometer.

I reckon yours is no good.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

Yeah, the battery fluctuates, and doesn't stay at 12 volts....I think it is bad....but I will have it check ed at canadian tire, after I check the rectifier. Unfortuenately, I can't get a new rectifier until after the long weekend, and we are taking the boat up to the lake....anything i can do to make the battery last..if I buy a new one? They usually come with a warranty...can I just use it for the weekend and then exchange it for a new one?
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

Yeah, I checked the rectifier, and it is shot! So is there any quick fix for the rectifier so I can get back on the water a.s.a.p? Everything is closed today, so I can't pick up one.

Also, what causes the rectifier to go bad? Does it drain the battery when the motor is running? Or is the battery just used to start the motor if the rectifier is blown?

If I replace the rectifier, what should I be careful of to not have it blow again? What precautions should I take?
 

F_R

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Re: Charging system doesn't work anymore....help!

Rectifiers are usually blown by loose or correoded battery, cable connections. or connecting the cables backwards (you can't get it disconnected fast enough to prevent rectifier damage), or sometimes by using jumper cables.

The battery is used only for starting and accessories, so you can run quite a bit before discharging it too far.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

What gauge can I install to monitor the activity of the rectifier?
 

Vic.S

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Re: Charging system doesn't work anymore....help!

The most likely thing to have blown the rectifier is connecting the battery the wrong way round. Instant death I'm afraid.

The battery supplies the power for the starter, the rectifier converts AC produced by the engine's coils into DC to recharge the battery.

Unless you know what you are doing it is not possible to improvise.

It might be a sensible idea to check the coils. If you have yellow, yellow/blue and yellow/grey wires you should get a low but measurable resistance between any two and twice the resistance between the yellow and the yellow/blue as you do between the yellow/grey and either of the other two.

With the engine running you should get somewhat more than 12volts AC between yellow/grey and either of the other two. (I don't know what you'll get between yellow and yellow/blue)
 

Vic.S

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Re: Charging system doesn't work anymore....help!

What gauge can I install to monitor the activity of the rectifier?

Either an ammeter in series with the rectifier output (red wire) that wiil show the current flowing from the rectifier OR simpler probably a voltmeter across the battery connections. You'll see 12.7 ish as previously said if the battery is charged. It will fall to maybe 10volts while it is cranking the engine but when running it should rise again as the battery charges and once it gets up to 14ish you know the battery is getting well charged. If you connect a voltmeter across the battery though, for safety, fit a fuse close to the battery connection.
 

ezeke

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Re: Charging system doesn't work anymore....help!

"So is there any quick fix for the rectifier so I can get back on the water a.s.a.p? Everything is closed today, so I can't pick up one."


You don't have to have a rectifier on the motor; it is there to charge the battery and for the tachometer. Just map the wiring and take it off until you get the replacement. As long as you have enough battery to start the motor you should be fine.

A good voltmeter gauge and a tach should keep you fairly up to date on what is going on with your rectifier.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

Thanks for the replies guys.....onemore thing.....

My battery was somehow damaged during all of this.....either because i didn't know that it was not being charged, but i have used it twice....once for 5 hours trolling, and then again intermittantly, while using the radio to listen to music. It is a small stereo, and no amp or subwoofer.

Is it possible that the tilt motor could be draining the battery? I checked over the whole starting circuit and everything was perfect. I will disable the stereo until I am able to fix the rectifier. I remember having the radio on, and when I would operate the power tilt and trim, the radio would cut out, the motor was not running, would this have any negative results to the rectifier, or motor?

Thanks again.
 

ezeke

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Re: Charging system doesn't work anymore....help!

Your rectifier is unregulated, which means that there is no cap on the voltage level. For that reason, most no maintenance car batteries can't be used. The best choice if you want to run a few small accessories is the biggest dual purpose deep cycle marine battery that you can fit on board. That type of battery can stand many times more discharge/recharge cycles and also acts as a regulator itself.

You can add a regulator, but they cost more than the battery.
 

Saskatoon2005

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Re: Charging system doesn't work anymore....help!

I just figured that there was something you could throw together from Radioshack or The Source!
 

Vic.S

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Re: Charging system doesn't work anymore....help!

was something you could throw together from Radioshack

I have just remembered that I had the circuit for the rectifier on P'bucket You'll have to choose 6 suitably rated diodes. They have got to take the maximum current output from the engines coils and have an adequate reverse voltage rating.

4fd8c66a.jpg
 
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