Death of an Alternator

I

Interlude

Well-Known Member
Joined
10 Oct 2007
Messages
85
Location
Sydney
Visit site
Has any forumite experienced a blown alternator regulator or diodes due to a battery disconnect when the engine was NOT running?

I am well aware of the warnings re disconnecting batteries when the engine is running, said to destroy electronics, presumably due to over voltage or "back EMF" transients.

The setup is separate start and house batteries, VSR isolated etc. Sterling pro digital charger permanently connected to both battery banks by separate terminals on charger (as supplied by boat builder). When topping up the house batteries last week, I found a loose cable on the house bank - which was connected to load (and solar charger) at the time. When reconnecting the loose connection, I accidently left the connection to the Sterling pro digital charger off, as the cable fell down beside battery. (Note to self - must turn in electricians licence - shouldn't be issued to idiots!). Next time out, with this cable still disconnected, the alternator had failed. As the warning lamp does not trigger the audible alarm, we noticed only after several hours on engine when I checked the battery voltages.

I never liked having the charger permanently connected to the battery banks, and have disconnected it before fitting a new alternator, having verified at the local auto electrician that the old one was US. Now all working as intended, but I would like to know why the old alternator failed under these conditions - it is a little too causal to be coincidence.

Any thoughts?
 
Interlude said:
Has any forumite experienced a blown alternator regulator or diodes due to a battery disconnect when the engine was NOT running?

I am well aware of the warnings re disconnecting batteries when the engine is running, said to destroy electronics, presumably due to over voltage or "back EMF" transients.

The setup is separate start and house batteries, VSR isolated etc. Sterling pro digital charger permanently connected to both battery banks by separate terminals on charger (as supplied by boat builder). When topping up the house batteries last week, I found a loose cable on the house bank - which was connected to load (and solar charger) at the time. When reconnecting the loose connection, I accidently left the connection to the Sterling pro digital charger off, as the cable fell down beside battery. (Note to self - must turn in electricians licence - shouldn't be issued to idiots!). Next time out, with this cable still disconnected, the alternator had failed. As the warning lamp does not trigger the audible alarm, we noticed only after several hours on engine when I checked the battery voltages.

I never liked having the charger permanently connected to the battery banks, and have disconnected it before fitting a new alternator, having verified at the local auto electrician that the old one was US. Now all working as intended, but I would like to know why the old alternator failed under these conditions - it is a little too causal to be coincidence.

Any thoughts?
Click to expand...

The loose connection was the trouble and the damage to the alternator had already occurred ????????

The alternator had not really failed ... it just needed new brushes

A decent auto electrician should have been able to repair it anyway. Brushes, rectifier, regulator, slip rings are all bits I have replaced DIY


You say "pro digital charger". Do you mean ProDigital Advanced Regulator or ProCharge battery charger. :confused:
 
Last edited:
The loose connection was the trouble and the damage to the alternator had already occurred ????????
- Maybe, but the loose connection was on the house bank, and the positive terminal of the failed alternator showed the same voltage as the starter bank (12.5) not the house bank (14 on solar charge)

The alternator had not really failed ... it just needed new brushes
- The charge lamp did not illuminate with engine switch on - indicating regulator failure?

A decent auto electrician should have been able to repair it anyway. Brushes, rectifier, regulator, slip rings are all bits I have replaced DIY
- I have not been bale to find a source of diode bridge or internal N type regulator for the Hitachi LR160-741 alternator (55Amp) fitted to my YM3-20 engine - if you know of a source I can buy from on-line please advise.


You say "pro digital charger". Do you mean ProDigital Advanced Regulator or ProCharge battery charger.
- The shore power charger is a Serling pro digital 1230 12 volt 30 amp 4 step switch mode unit. I have no issues with the charger, seldom used as I am on a swing mooring with lots of solar for the house bank. I do have issues with the way the boat builder supplied a sealed starter bank and flooded house battery - connected to the single charger which can be set to either but not a mix - so if used will over-charge the sealed or under-charge the flooded batteries, but that belongs to another rant. I am going to take it apart to see how the three outputs are connected - just out of curiosity as it is now off the boat and if going back on will be connected to house batteries only, not both.

Any further thoughts are welcome, I would like to repair the original alternator to keep as a spare.
 
I had a problem with mine last year, stopped in Wales, Caernarfen (probably spelt wrong) but a fantastic auto electrician there, fixed and tested no charge, also did me a new selonoid for my starter less than half price!
The Harbour master will even give you a lift there and back, brilliant service best I have ever had, if it wasn't so wet there I'd have spent the winter as the marina was also so cheap.
 
As far as I can recall, High voltage, that being in excess of the diode rating, or a monentary reverse conection (Polartity) are the only way to damage or "Blow" diodes, I stand to be corrected.
Gordon
 
pampas said:
As far as I can recall, High voltage, that being in excess of the diode rating, or a monentary reverse conection (Polartity) are the only way to damage or "Blow" diodes, I stand to be corrected.
Gordon
Click to expand...
High forward current as well I would imagine. However it is high voltage surges resulting from disconnecting the load ( battery) while the engine is running that are usually blamed for blowing alternator diodes.

there is aspecified max reverse voltage that diodes will withstand... they are subjected to reverse voltage when used as rectifiers.
 
But the op stated that the engine was not running so I simplyfied my answer and in no way did I mean to belittle you reply,
 
You must log in or register to reply here.

Other threads that may be of interest

W
Battery suicide
Replies
17
Views
617
Refueler
Refueler

Share this page

Top