Balmar 94LY Alternator and MC624 Regulator Weirdness

[steve.sharratt]

Hi All,

 

I recently installed the above in my narrowboat.  I removed the existing 12v Alternator that was charging the starter battery and replaced it with a 24v alternator to charge the house batteries.  I have just been running some tests and am seeing (possibly) weird results.  A couple of key points first.  I am running a vintage Lister JP3, so slow revs. The current setup is temporary and is using the existing infrastructure so am running off the smaller engine pulley. This results in lower revs at the alternator than is ideal but will get me through the season. The regulator gets its power from the start battery through the starter motor.  The starter battery is always off unless the engine is running so this effectively provides the ‘ignition’ element the regulator looks for. 

 

Here is the rub.  It seems as if the regulator is drawing about 4.5 amps (@24V) just to be on.  This seems very excessive. I.e. power consumption with inverter off is 0.21 amps, and with ignition on it jumps to 4.5 to 6 amps.  It isn’t stable either. It takes about 20 seconds to get to 4.5 and then slowly drops to around 4 but then jumps up to 6 amps. Test was done with inverter and solar off.  The irony is, as I have a slow revving engine, at idle, the net result is a loss of power.

 

I have checked the manuals but there is no mention of current draw at idle/engine off (which I assume means it is 0 or negligible).  I ran the standard tests as recommended by Balmar and everything is as it should be with the exception of the ignition-on test where Balmar state that the Field wire should be between 4 -22v and I am at 24.6v. I have emailed Balmar to confirm it is still ok (as they say ‘results should not differ greatly’).  No response as yet.

 

I have checked the voltage at the starter battery when on and off and it doesn’t move.

 

I will email Balmar but in the meantime, any thoughts are appreciated.

 

 

 

 

 

[BEngo]

As I understand it your alternator regulator is drawing about 5 amps when the engine is off or at low speed.

That is about par for the course and IIRC  compares fairly well with @nicknorman's numbers.

 

in operation the field is controlled  by the regulator to maintain an output voltage.  As the alternator slows, the regulator increases the field current until it hits the maximum, when it can do no more. With the alternator still the field will be at maximum. It will stay like that until the voltage the regulator sees is bigger than the set point value.  I dont know your particular regulator, but if its sense input is being fed off the start battery and the alternator does not charge the start battery then the regulator may not be seeing the domestic battery voltage.  It cannot then regulate as it is meant to. It would be a good idea to shift all the alternator connections to the domestic battery.

 

N

 

 

[steve.sharratt]

2 hours ago, BEngo said:

As I understand it your alternator regulator is drawing about 5 amps when the engine is off or at low speed.

That is about par for the course and IIRC  compares fairly well with @nicknorman's numbers.

 

in operation the field is controlled  by the regulator to maintain an output voltage.  As the alternator slows, the regulator increases the field current until it hits the maximum, when it can do no more. With the alternator still the field will be at maximum. It will stay like that until the voltage the regulator sees is bigger than the set point value.  I dont know your particular regulator, but if its sense input is being fed off the start battery and the alternator does not charge the start battery then the regulator may not be seeing the domestic battery voltage.  It cannot then regulate as it is meant to. It would be a good idea to shift all the alternator connections to the domestic battery.

 

N

 

 

That’s interesting, thanks BEngo.  Shifting to the domestic batteries would be problematic as I would need to include an additional switch otherwise the regulator would be permanently on.  Something else for me to forget!!  As I understand it, it is important that the regulator is initiated prior to starting the engine, hence wiring into the starter motor.  I do plan to install a DC-DC charger from the domestics to the starter. Do you think that a 20 amp charger would trick the regulator into thinking the output is higher?

[Tony Brooks]

If it is a six diode alternator, then the excitation current will be around 3 to 4 amps on a typical 12V alternator because there is no warning lamp in series to minimise the current (sorry no 24V experience, but it sounds about right). That is why the excitation connection is usually fed via the ignition switch or relay.

[ditchcrawler]

3 hours ago, steve.sharratt said:

That’s interesting, thanks BEngo.  Shifting to the domestic batteries would be problematic as I would need to include an additional switch otherwise the regulator would be permanently on.  Something else for me to forget!!  As I understand it, it is important that the regulator is initiated prior to starting the engine, hence wiring into the starter motor.  I do plan to install a DC-DC charger from the domestics to the starter. Do you think that a 20 amp charger would trick the regulator into thinking the output is higher?

The field to my 24 volt alternator is fed from the VE+ 24 volt terminal via a relay energised by the 12 volt field connection on the 12 volt alternator. thankfully one alternator is directly above the other

[adrianh]

Why not just add a small relay via the ignition switch (12 volt circuit?) to connect the 24 volt battery to its own charging alternator D terminal.

I have 2 x 12 volt circuits and 2 alternators working like this, you will however need a 2nd ignition lamp in the wire to the 24 volt alternator.

[nicknorman]

Yes the alternator regulator is just trying to maximise the output at low revs by stuffing the full battery voltage across the field/rotor. Around 4 to 5A is about right.

 

A well designed regulator such as the chip I use only puts in a small field current until it sense the alternator is spinning fast enough, then it ramps up the field current. No-one said a Balmar regulatorwas well designed! American - all brute force and no finesse!

 

I would strongly advise you to have all connections on one battery. Mixing between 2 batteries sounds like a really bad idea.

 

Anyway, surely the Balmar has an IGN input to turn it on and off - it’s designed to be permanently connected to the battery with the IGN input telling it when to turn on. I’ll have a look at the data sheet…

 

Edit

 

yes, you connect it permanently to the battery, and use the ignition connection to turn it on and off via a switch (very low current). Or you could use an oil pressure switch so it comes on automatically after the engine starts, avoiding the need for a manual switch (see page 4 of the manual).

Edited March 11, 2023 by nicknorman