Reply
 
Thread Tools Search this Thread
 
Old 07 March 2004, 13:33   #21
Member
 
Country: Ireland
Town: Dublin
Boat name: wizzard
Make: REDBAY
Length: 7m +
Engine: 225 optimax
Join Date: Sep 2002
Posts: 835
Setup

Nice clean set up in the engine bay, what about the extra push if you are asking the alternator to deliver current to two flat batteries with the sw in both position, I have seen this only last week where a flat battery in a hard boat jumped from an adjacant battery which became flat also.When the motor was boost started from a pack, it couldnt idle until one of the dead batts was removed from the circuit, the alternator might not be able to deliver current to 2 flat batteries gavin
__________________

__________________
www.dublinsislands.com

WHEN THE CAT IS AWAY THE MICE GO TO REDBAY..............
gavin is offline   Reply With Quote
Old 07 March 2004, 14:10   #22
Member
 
Country: UK - England
Town: Cippenham
Boat name: Falcon1
Make: Falcon
Length: 6m +
Engine: 115hp Mariner Four S
MMSI: 235021077
Join Date: Jun 2003
Posts: 508
am i being thick or are both ends of the diode connected to the same terminal?
__________________

__________________
chrisallse is offline   Reply With Quote
Old 07 March 2004, 14:34   #23
Member
 
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,962
Yes, the blue wire carries the charging current unless/until the blue knob is turned to connect the main ground.
Chris, yep, you are. This terminal is normally open. The connecton is made by tightening the blue knob when the battery is required. Look at the circuit diagram.

A normal diode can be used but these have a voltage drop of about 0.6 - 0.7volts. This will ensure the battery is not fully charged. The schottky type has a drop of about 0.4v so the battery charge will be pretty well complete, depending on the voltage regulator output.
There was a time when schottky diodes with a high current capability were not available. I've used ordinary diodes with complete success.

Gav, the problem you describe is simply because the engine is not able to produce enough power to spin the alternator at tickover. A well designed modern engine should be able to cope with the extra load. I have seen a situation where a slightly slack alternator belt slips when charging a flat battery but is ok when the battery is charged. Also, this system is supposed to prevent you ever having 2 flat batteries!

Edit.. forgot to say. The thinner black wire is, indeed, the negative for the unswitched supply.
__________________
JW.
jwalker is offline   Reply With Quote
Old 07 March 2004, 15:03   #24
Member
 
Country: UK - England
Town: Cippenham
Boat name: Falcon1
Make: Falcon
Length: 6m +
Engine: 115hp Mariner Four S
MMSI: 235021077
Join Date: Jun 2003
Posts: 508
see what you mean now...didnt realise the blue knob isolates the neg.....what happens to the diode if you forget to close the isolator and switch to the backup batt?
__________________
chrisallse is offline   Reply With Quote
Old 07 March 2004, 15:19   #25
Member
 
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,962
Nothing.
__________________
JW.
jwalker is offline   Reply With Quote
Old 07 March 2004, 16:08   #26
Member
 
Country: UK - England
Town: Cippenham
Boat name: Falcon1
Make: Falcon
Length: 6m +
Engine: 115hp Mariner Four S
MMSI: 235021077
Join Date: Jun 2003
Posts: 508
Have you tried it? wouldnt the load current try and flow through the Diode?
__________________
chrisallse is offline   Reply With Quote
Old 07 March 2004, 17:42   #27
Member
 
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,962
Yes, of course it would. But diodes block current from the reverse direction. That's their job.
__________________
JW.
jwalker is offline   Reply With Quote
Old 08 March 2004, 12:15   #28
Member
 
gtflash's Avatar
 
Country: UK - England
Town: southampton
Boat name: TOP CAT 2
Make: Scorpion 8.1
Length: 8m +
Engine: 250hp HO
Join Date: Aug 2003
Posts: 1,318
what sort of current does the schotty handle rms?

If you use just a 1, 2, and both switch then disimilar batteries then surely a less than adequate battery could be over pushed and cook, batteries arent like resitors they dont always draw just what they need gradualy dop they?

What do the standard marine split chargers do?
__________________
gtflash is offline   Reply With Quote
Old 08 March 2004, 13:06   #29
Member
 
Pete7's Avatar
 
Country: UK - England
Town: Gosport
Boat name: April Lass
Make: Moody 31
Length: 9m +
Join Date: Aug 2001
Posts: 4,850
Err, forgive for saying but isn't this a bit OTT. The boat is a 6.5m rib with an outboard and its a Yamaha, so its bound to start even with the starting rope they all come with, which should satisfy the surveyor when she is coded.

Peter
__________________
Pete7 is offline   Reply With Quote
Old 08 March 2004, 14:28   #30
Member
 
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,962
Quote:
Originally posted by gtflash
what sort of current does the schotty handle rms?

If you use just a 1, 2, and both switch then disimilar batteries then surely a less than adequate battery could be over pushed and cook, batteries arent like resitors they dont always draw just what they need gradualy dop they?

What do the standard marine split chargers do?
The package I used contains two of, 15amp diodes.

As a battery charges, its voltage rises and this controls the amount of current which flows into it. Eg. if the battery is at 12v and the charger is at 14v then there is 2v pushing the charge current. When the battery has reached about 12.8v (max.), then there is only 1.2v pushing the current through it. So, the batteries look after themselves depending on their state of charge.

I've never used a marine split charger but I guess a relay connects the charge current when the ignition is switched on or, perhaps, clever ones sense the charge voltage and switch the relay when the voltage reaches a level which indicates the alternator is running.
I'm sure someone can tell us.
__________________

__________________
JW.
jwalker is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 08:26.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.