Alternators not charging batteries at tick-over?

[alt]

Another question on behalf of a friend....
2 x KAD 43's.

Normally when engines started, it was evident that batteries were being charged by the alternators, even on tickover... the voltage gauges were showing anywhere between 13 - 14v.

Lately, when the engines started, gauges only showing 12v, until engines reach about 1600 RPM (superchargers kicking in), the gauges show 12v... and then they shoot up to charging levels.

Anyone got any bright ideas? I remember people telling me on older boats that the alternator wouldn't charge the batteries until it reached a certain rpm, but these aren't ancient engines (2003).

The batteries are in good condition (start engines no prob and charged via shore power regularly).

 

[omega2]

Belts ok?

 

[Cruless]

I would test your batteries with a proper load battery tester. Shore power battery chargers are very good at hiding the fact that a battery is weak.

 

[Talulah]

Corrosion on wire terminals.
Wire fallen off back of alternators.
Worn out bushes.

 

[Momac]

I would agree, from experience with kad32 engines , the alternators should be charging the engines even at tickover. kad43's should be no different.

Is this affecting both engine alternators at the same time ? Seems odd that both are equally affected at the same time so what has happened recently to cause it ?
Have the isolator switches been turned off with the engines running - which can damage the alternator?

 

[lpdsn]

Saily boat, but my alternator never kicks in at tick over. Give a few revs for a second or so and it does and will happily charge at tick over. Just needs enough voltage to initially activate the field coils I suspect.

 

[alt]

Think I found the issue... the connector on D+ on one of the alternators had sheared off, hopefully get it sorted tomorrow.

 

[alt]

OK so it appears that the broken connection has solved the issue. Now when the port engine is started, there is a charge. BUT, there is no charge output from the starboard. So, it's alternator out and send to the local fixers.

Question is... with the port alternator removed, can the boat be used? All wires will be taped up, but will the KAD's alarms go mad, or can it cause damage?

 

[blampied]

I'm not an expert, so maybe I'm talking bollocks, but had a similar intermittent problem, always after having been hooked up to shore power or solar panels.

If you have a split charge diode make sue the alternator sensing wire (yellow) is to the engine start batteries lug not the auxillery house battery or bow thruster battery lugs. It shouldn't make much difference and most of the time won't

However If you have been connected to shore power and your super doper 4 stage battery charger has topped off all the batteries until they are all super full, they require no charge.

When you start up you take a belt out of the starter battery which feeds back as a voltage drop through the sensing wire to tell the alternator to charge. If your sensing wire has been mistakenly put onto one of the other lugs on the split charge diode, it's split from the start battery so the alternator isreceiving the voltage from the fully charged batterie. which has full voltage.

 

[alt]

I'm not an expert, so maybe I'm talking bollocks, but had a similar intermittent problem, always after having been hooked up to shore power or solar panels.

If you have a split charge diode make sue the alternator sensing wire (yellow) is to the engine start batteries lug not the auxillery house battery or bow thruster battery lugs. It shouldn't make much difference and most of the time won't

However If you have been connected to shore power and your super doper 4 stage battery charger has topped off all the batteries until they are all super full, they require no charge.

When you start up you take a belt out of the starter battery which feeds back as a voltage drop through the sensing wire to tell the alternator to charge. If your sensing wire has been mistakenly put onto one of the other lugs on the split charge diode, it's split from the start battery so the alternator isreceiving the voltage from the fully charged batterie. which has full voltage.

Thanks for the tip. I'll have a look this weekend

 

[Otter]

OK so it appears that the broken connection has solved the issue. Now when the port engine is started, there is a charge. BUT, there is no charge output from the starboard. So, it's alternator out and send to the local fixers.

Question is... with the port alternator removed, can the boat be used? All wires will be taped up, but will the KAD's alarms go mad, or can it cause damage?

What else is driven by the belt that goes on the missing alternator? On mine it's the water pump!

 

[alt]

What else is driven by the belt that goes on the missing alternator? On mine it's the water pump!

On the KAD engines the alternator has its own belt, so... nothing