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StuieB
New User
Jun 22, 2011, 7:03 PM
Post #1 of 2
(1186 views)
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I received an email from a buddy who has left on a around the world single hand sailing voyage. His voltage regulator took a crap on him. He says:
my alternator will not charge my house bank anymore, it just overcharges my starting battery. Any ideas??... I never did buy a cheap regulator, oops. Just hope these panels can hold me over till i get there.
And I wrote back:
just disconnect the large red wire from the alternator when the battery is charged and hook it up
FOR A SHORT TIME when the battery is discharged below 12v. Watch the bat voltage with a
meter, Only hook and unhook the alternator wire when the motor is off otherwise a voltage spike
may damage the alternator internal diodes.
Remember that you have a diesel motor so the battery is only used to run the fuel pumps and starter
there isn't any coil or spark plugs to drain the dedicated motor battery. Also your fuel tanks are above
motor so you can probably run without the fuel pumps. meaning the only drain will be when you start the motor.
And you can start the motor numerous times without recharging. You can also run a wire from the
motor battery to the house battery switch thereby recharging the motor battery via your solar panels.
To Charge all batteries
Run a wire from the dedicated motor battery + to the output of the house battery switch. Put the battery
switch to the both setting. This way when the motor is running all batteries will be absorbing the
charging current. REMOVE this wire from the motor battery when the motor is off. In general you
want to maintain isolation for the motor battery. You may be tempted to run it through that extra
breaker and then to the battery switch so all you have to do is flick a switch - but this won't work for
long because the current flow will most likely be more than breakers rating. Use the heaviest gauge
wire you have.
You probably have a high output alternator that is capable of putting out more than 90 amps.
That's a lot of current you have to get rid of when the motor is running and the regulator is not
working or you will percolate the motor battery. So either disconnect the alternator wire or hook
the motor battery to the house batteries via the battery switch and turn on all lights, radio, plug in
the heat gun it can sink a lot of current and watch your gauge.
When you can get to a parts store buy a new regulator (duh) and a spare and a relay. Hook up the relay so it comes on
when the motor is on ie. ground to one side of the relay coil and a wire from the alternator output to the other side of
the relay coil. DO NOT USE THE LARGE RED WIRE GOING TO THE BATTERY because it is hot all of the
time. You want to use one of the small wires that go to the regulator that is +12v only when the motor is operating.
Then take a wire from the motor battery to the relays normally open contact (this will prolly be marked as NO) take the
other side of that contact to the house battery switch. This way when the motor is running it will charge whatever battery the
selected by the switch. When the motor is not running the relay will open effectively isolating the motor battery from the
others.
Is the advice that I gave him sound advice and is there any thing else that you can think of that would help
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 23, 2011, 5:24 AM
Post #2 of 2
(1170 views)
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Re: Got a hot one.
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Can't quite follow you and aghast that a diesel needs a battery for anything more than to start it. Especially for marine use. It will not trickle fuel and run - it needs high pressure and should be mechanical but who knows?
Leaving on this venture without both wind and solar chargers would be foolish in this day and age. Just use nothing but LED lighting and shut everything down till a NEW whole alternator can be installed.
No matter for the moment but I'd shut everything off till the next port. Better be good at paper charts and the compass as he may lose electrical navigation equipment. That and know prevailing currents which are known by date how fast and which direction. Been there done that with boating but not around the world but used currents to save fuel in a yacht (gas engines) but pigs big time. Like .5 MPG or best .75!
What kind of alternator?
At least he knows it's overcharging which can hurt 12v items or destroy them.
How big of a boat is this? If it needs power to steer it and can't be done manually he should know to set it straight ahead and figure out sea anchors to steer depending on size. Where is the next port?
T
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