Sterling alternator controller

T

Tarka1

Well-Known Member
Joined
24 Nov 2004
Messages
203
Location
Me Whittington (Staffs); Boat Porthmadog
iris-security-surveys.web.officelive.com
Wondering whether anybody can shed some light on a charging problem. Bukh 20 with a 50amp alternator has been fitted with a sterling contoller but struggles to get 2 110amp batteries up to 14 volts (dropping down to 13.4 when the fridge is switched on). The contoller shows all of the lights suggesting high charge rate followed by float charge and has been checked by sterling and given the OK. All checks, as suggested by sterling, have been carried out (including momentarily earthing the field wire - this gave 16 volts) and no problems discovered. Is it possible that the alternator has lost the ability to deliver the full 50 amps? Any other ideas of what to look for would be appreciated.
 
Any diode splitters? What is the voltage drop between the alternator+ and the battery+ ?
 
It would be worthwhile checking each battery individually as one may be dud.
Other wise put a multimeter with pos lead on the alternator out terminal then check the voltage with -ve lead at the fridge +ve wire (with fridge and engine running) The volltage you read is actual volt drop.

If it is more than about .5 volt then move the -ve lead back through the wiring to measure drop at fuse and switch. it should be apparent that excess voltage is lost in the switches or wiring.

If all else seems OK it is possible the alternator is not giving full output from perhaps a dud diode. The output voltage may appear OK but will sag with a load like a fridge. Or it could be that the alternator is simply not driven fast enough to produce full output. You may need to remove alternator for testing on a test bench.

You can however check things like the condition of the slip rings and brushes and the continuity of the diodes. 6 or 9 of them. good luck olewill
 
I have exactly the same set up (engine, alternator, batteries, sterling, fridge, but I do have a split charge diode). Are you sure it isn't working??
You should find the batteries are being charged at circa 14/ 14.8v, but after charging stops they won't read 14v.
Having stopped charging but with fridge and maybe instruments on mine reads somewhere in the 12.2 to 12.5 range -- in other wordss no-where near 14v. After everything is switched off for an hour or so the voltage is circa 12.7-12.8 and a week later is 12.7 --- in my (limited) experience this is fine
 
Find someone that has a clamp on DC ammeter? You need to know the current out of the Alternator.

If there are no undue voltage drops or sense wires the wrong side of diodes then either the Alternator is producing too little or your batteries are taking too much current. Testing the diodes individually normally is difficult unless the diodes can be separated from the stator coils.

So I suggest asking around for anyone with a current clamp.
 
Where is the alternator controller sense wire connected and where in the circuit is your voltage reading coming from?

If your batteries are fully charged do you still see the voltage drop when a load comes on? Is it only the fridge or does putting some similar load (i.e. 3 cabin lights) also result in a voltage drop?

Final question, what gauge, type and condition is the high current wiring on the boat (including the -ve's)?. This includes the wiring from alternator to batteries and batteries to main switch as well as engine to battery -ve?
 
I've got say the ampclamp is the way to go to test the output as best you can, but remember to put the battery system under load up to the point you start getting a volt drop. A duff battery if in parallel with the rest will drag the whole lot down as it can have less resistance and act almost like a short in charging mode.

Another horrible one I looked at recently was the dicky alternator - as it got warm under load, the windings in the stator expand (not by very much, but they do) and there was slight damage to the "ceramic" insulation on the wire - just enough to short alot of one of the windings out and drop the current output. Horrid, horrid morning finding that one.

I'd check the easy thing first - the output from the alternator with your ampclamp and work your way back through the system measuring the voltage drop across the cabling as you go, always whilst under load. Sounds silly, but remember to write down what you get because depending on how complex your system is (terminations, fuses, joints, switches) it can all get rather messy...

But I would make an effort to get the batteries tested individually. Here's one that might give you a rough idea and it's cheap - http://www.conrad-direct.co.uk/electronic/lead_acid_battery.sap
Unfortunately I can't find the website for mine - it reads the exact amp hour the battery is capable of up to 250 amphour but it was 270 quid... If I find it I'll post it.


Hope this helps.

Tony.
 
You must log in or register to reply here.

Share this page

Top