It’s official, I’m an idiot… help!

[lbdavis]

Here’s how I proved it:

The electrical system on my boat is rather simple. I have one wet cell house battery and one dedicated wet cell start battery. My only means of charging them are with my alternator (I’m on a mooring.) I have no Link20 or the like; I use my digital voltmeter to take readings in different places in the system and I also read the voltage with my chartplotter.

When charging, I use my make-then-break battery selector switch to change the charging from the starting battery to the house battery to adequately charge both.

Well, today (here comes the idiot part), I accidentally switched the battery selector to switch to (you guessed it) off. It was on “off” for about .25 seconds before I switched it back to “1”. I screamed many words not suitable for this board and scrambled up to the chartplotter to see if I had indeed fried my alternator…. “12.3V”, says the chartplotter. More bad words from me are followed by bad smells from the engine compartment.

I shut down the engine and feel the alternator. It’s REALLY hot. I calm down and enjoy a wonderful day of sailing on Casco Bay before I fire the engine back up hours later. Each battery was at 12.2V when I started the engine. My typical voltage reading from my alternator would be 14.6V, now it is 13.6V. Apparently I didn’t totally fry it, but it certainly isn’t charging at full strength.

How could this be? Is it possible to partially fry an alternator? Is this alternator doomed?

I think I'll be getting a new one anyway as I really should have two onboard. Can I keep this one as my backup?

[Stillraining]

Ibdavis:

Most all modern day alternators are internally regulated...so no you did not fry it but your reg..took a hit of possibly a 100V spike depending on your RPM at the time...13.6 however will still charge your batteries just not quite as efficiently...Sail/run it like it is for awhile you might have gotten lucky..

But it's definitely an easy rebuild if needed...40.00 bucks at an auto electric shop..

Iv done worse and I ain't tellin...

FWIW....14.6 is a little high...13.5 to 14.2 is normal

[sailingdog]

14.6 might be normal for bulk charging phase with fairly low batteries.

Originally Posted by Stillraining

Ibdavis:

Most all modern day alternators are internally regulated...so no you did not fry it but your reg..took a hit of possibly a 100V spike depending on your RPM at the time...13.6 however will still charge your batteries just not quite as efficiently...Sail/run it like it is for awhile you might have gotten lucky..

But it's definitely an easy rebuild if needed...40.00 bucks at an auto electric shop..

Iv done worse and I ain't tellin...

FWIW....14.6 is a little high...13.5 to 14.2 is normal

[trantor12020]

Will a Zap-Stopper prevents this problem of high voltage spike? I understand Zap-Stopper is a zener diode. So I make myself one using 3-4 pcs of 24V 5W zener in parallel and connects it to the alternator output. I imagine a 100V spike would be shunted by the zener when the voltage raises to pass 24V and should there be any reverse voltage from say an induced lightning, that will also be shunted (forward bias) immediately. I haven't any proof this works but in theory.

ps: ibdavis, welcome to "I'm an idiot Club". I'm member too. Recently I drove my boat over a submerged breakwater and broke the rudder mount. I thought I saw the rocks, but somehow the grey matters the holds that piece of info decides to quit at that very moment !

[brak]

I am sure more of us are members of this club. We should start a formal membership list, dues, badges and all.

I started my engine with a closed raw water intake seacock and ran it that way for at least a 2-3 minutes. Since it's fresh-water (coolant rather) cooled, it did not overheat (yet) but the exhaust elbow was pretty darn warm to touch and I was afraid that I killed the impeller (though once i opened the seacock and restarted the engine, I got the water flowing so impeller should be fine - I didn't really open it to check, this may be dumb thing number 2 in the making).

I did more dumb stuff, this is just the most recent example.

[BarryL]

Hello,

When my alternator stopped charging I took it off the boat (took about 10 minutes) and brought it to an automotive electrical repair place. They diagnosed a bad voltage regulator and installed a new one for $40.

I do have a question for you, why don't you just place the switch on 'both' before you start the engine? Then you never need to touch the switch while the engine is running.

Barry

[Maine Sail]

There is a really "crafty" alternator guy down behind Paul G. White Tile & Flooring off Allen Avenue. Go down the drive way to the right of Paul G. White and he will be on the right in an old garage. He can fix it!!


P.S. Get one of these and you'll never need to worry about doing that again!!
Battery Link Automatic Charging Relay
It would have already paid for its self!!



Kaza Auto Electric
64 Allen Ave
Portland, ME 04103

(207) 797-6658

[therapy23]

Originally Posted by BarryL

Hello,



I do have a question for you, why don't you just place the switch on 'both' before you start the engine? Then you never need to touch the switch while the engine is running.

Barry

If this is done without a regulator splitting (controlling) the charge to each, one battery will be overcharged while the other is undercharged.
Common mistake with simple two battery setups with one start and one house. Different discharge states requiring different charge parameters.

[Omatako]

Originally Posted by therapy23

If this is done without a regulator splitting (controlling) the charge to each, one battery will be overcharged while the other is undercharged.
Common mistake with simple two battery setups with one start and one house. Different discharge states requiring different charge parameters.

In my experience it's more a case of the voltage regulator seeing the voltage of a fuller battery and then backing off the charge rate so that the flatter battery never gets the chance to charge.

I'm not sure that any battery would over-charge while the other is under-charged.

Andre

[artbyjody]

Originally Posted by Omatako

In my experience it's more a case of the voltage regulator seeing the voltage of a fuller battery and then backing off the charge rate so that the flatter battery never gets the chance to charge.

I'm not sure that any battery would over-charge while the other is under-charged.

Andre

I'll second having a newer battery selector switch. I have revamped my entire electrical system on the Barberis, with new panels as well as the new BlueSea Battery Automatic switching system:



I am very pleased with this over the Perko / Guest standard Off/ 1 / 2 / both switch. Although, I will state that when first installed for some reason it didn't register the actual battery charge of 13.5 for either of the two banks of batteries until after the engine had been run. Not sure why but - its working now.

What I like about it - is its on / off and automatically switches to house batteries if starter battery is low. No interaction is required and it automatically switches charging current to least charged. What this means if you still wire it using a charger where you have one lead to on and another to the other, if one is already to level - the other lead gets diverted to other battery - decreasing battery re-charge times. Or you can go with a single lead from a charger and it saves you from having to buy a more complicated charger.

Thats been my experience with the BlueSea item I provided pic for... and so far - its working as advertised.

related link: Add a Battery - Blue Sea Systems