Alternator issue

[Midnight]

The Beta 43 on Midnight has a retro fitted 110amp domestic alternator. Not the one that came with the engine so it's wired differently and the live is switched by a relay. All seems to work except when the batteries are fully charged the red ignition light comes on. If I switch on a light it goes out. Originally it was connected to an Adverc battery manager but it is now unplugged. I also have 2 solar panels. Any idea what would cause this,?

[Js north]

Where are you based?

 

[Tony Brooks]

11 minutes ago, Midnight said:

The Beta 43 on Midnight has a retro fitted 110amp domestic alternator. Not the one that came with the engine so it's wired differently and the live is switched by a relay. All seems to work except when the batteries are fully charged the red ignition light comes on. If I switch on a light it goes out. Originally it was connected to an Adverc battery manager but it is now unplugged. I also have 2 solar panels. Any idea what would cause this,?

 

Which alternator light, or do you only have one. If it is one light then it is a bodge and one failing alternator can bring it on. Also with well charged batteries if one alternator regulates at a higher voltage then the other one may virtually shut down again making the lamp glow.  I think this is well charged batteries because putting a load on the batteries (the lamp) would make the alternator start charging again.  However, more info and some tests are required for anything more definative.

[Midnight]

1 hour ago, Tony Brooks said:

 

Which alternator light, or do you only have one. If it is one light then it is a bodge and one failing alternator can bring it on. Also with well charged batteries if one alternator regulates at a higher voltage then the other one may virtually shut down again making the lamp glow.  I think this is well charged batteries because putting a load on the batteries (the lamp) would make the alternator start charging again.  However, more info and some tests are required for anything more definative.

It is non-standard wiring. There's a red ignition light and a green fault light both added when I followed a wiring diagram supplied by Adverc for a Prestolite alternator. I'm sorry I don't have a pdf version now and the printed version is on the boat. The Presolite died last year so I swapped it for a secondhand noname unit bought from an alternator specialist who said it was similar. The Prestolite was obsolete and spares were not available. The red light issue happened on both alternators and I think after the solar panels were fitted. The starter battery alternator is the original and on a separate wiring system.

[cheesegas]

Does it happen in the dark too? If your solar controller is set to a slightly higher voltage than the alternator's regulator, when the batteries are full the solar controller will be able to get the batteries to the higher voltage. This causes the alternator light to glow faintly (it's only a difference of less than a volt usually!) as the current flows from the solar controller to the alternator as there's a potential difference.

[nicknorman]

2 hours ago, Midnight said:

The Beta 43 on Midnight has a retro fitted 110amp domestic alternator. Not the one that came with the engine so it's wired differently and the live is switched by a relay. All seems to work except when the batteries are fully charged the red ignition light comes on. If I switch on a light it goes out. Originally it was connected to an Adverc battery manager but it is now unplugged. I also have 2 solar panels. Any idea what would cause this,?

 

Although this might be slighly annoying I don't think it is a big deal. With no load on the fully charged battery and possibly some slight input from the solar, the regulator has shut right down to the point that there is no field current and hence no (or not much) voltage on the D+ terminal - just the same situation as you have when you turn the ignition on before starting the engine. Hence the light comes on as it supplies a small current to the field windings. If it annoys you, leave a light on inside!

 

I suppose the only question is whether the alternator is otherwise charging correctly up to its full output when required. If so, I would consider this light annoyance a "feature of the model". If it is not, perhaps there is a blown field diode.

Edited January 16 by nicknorman

[Tony Brooks]

8 hours ago, Midnight said:

It is non-standard wiring. There's a red ignition light and a green fault light both added when I followed a wiring diagram supplied by Adverc for a Prestolite alternator. I'm sorry I don't have a pdf version now and the printed version is on the boat. The Presolite died last year so I swapped it for a secondhand noname unit bought from an alternator specialist who said it was similar. The Prestolite was obsolete and spares were not available. The red light issue happened on both alternators and I think after the solar panels were fitted. The starter battery alternator is the original and on a separate wiring system.

 

If this is happening on both alternators, it means the two banks are linked in some way. Does your solar controller have two outputs, one connected to each bank, or has something like a VSR been fitted so the solar can charge both banks. On the present info I am with Nick, probably nothing to worry about as long as the lamp goes out with a load on the bank and both batteries are being charged

[Midnight]

5 hours ago, Tony Brooks said:

 

If this is happening on both alternators, ........

Sorry if I confused you I meant on both domestic alternators i.e. the Prestolite that died and then the replacement.

 

14 hours ago, nicknorman said:

 

I suppose the only question is whether the alternator is otherwise charging correctly....

I think it is. Last Saturday after being on shore power the Mastervolt charger will have fully charged the batteries. I took the boat a short distance to the Club's pump-out jetty and noticed the light on all the way. After spending awhile sorting out the shhh-you-know-what, I checked the battery voltage at 12.96v. When I restarted the engine the voltage went up to around 14.6v (senior memory moment but near).

 

14 hours ago, cheesegas said:

Does it happen in the dark too? If your solar controller is set to a slightly higher voltage than the alternator's regulator, when the batteries are full the solar controller will be able to get the batteries to the higher voltage. This causes the alternator light to glow faintly (it's only a difference of less than a volt usually!) as the current flows from the solar controller to the alternator as there's a potential difference.

I've never cruised in the dark but I will check next time I'm aboard. I'll also check to see if the solar controller can be adjusted. It's one of these. How would I find out what to adjust it to, or if it can be adjusted should I just reduce it bit at a time?

UPDATE!
I spoke to Photonic Universe who said the easiest way to reduce the MPPT voltage is to change to the Gel Battery setting. 

Edited January 17 by Midnight

[nicknorman]

1 hour ago, Midnight said:

I think it is. Last Saturday after being on shore power the Mastervolt charger will have fully charged the batteries. I took the boat a short distance to the Club's pump-out jetty and noticed the light on all the way. After spending awhile sorting out the shhh-you-know-what, I checked the battery voltage at 12.96v. When I restarted the engine the voltage went up to around 14.6v (senior memory moment but near).

 

 

This shows that the alternator is slightly charging a nearly full battery, but not necessarily that it can charge a low battery to its fullest extent. Anyway it is just something to keep an eye on - if you have means to check the charge current, check it is giving plenty of amps when the batteries have been used without shore power. If not, just bear in mind that if it seems to take a long time to charge the batteries, it is possible that the alternator is only working at reduced output. I am not saying this is the case, just that it is a possibility.

[Midnight]

2 hours ago, nicknorman said:

 

This shows that the alternator is slightly charging a nearly full battery, but not necessarily that it can charge a low battery to its fullest extent. Anyway it is just something to keep an eye on - if you have means to check the charge current, check it is giving plenty of amps when the batteries have been used without shore power. If not, just bear in mind that if it seems to take a long time to charge the batteries, it is possible that the alternator is only working at reduced output. I am not saying this is the case, just that it is a possibility.

 

Usually when we were out summer cruising the charge amps in the morning after mooring overnight were around +50amps. When the batteries are showing 100% on the MICC the amps drop down to single numbers. I know 100% is a meaningless bean count figure, but the voltage is usually in the high 12s to low 13s, overnight it drops to the low 12s. The four batteries are cheapo unbranded things I bought from Streethay in 2021 after my old AGMs died at Tixhall Wide and they couldn't get the Numax 120s I wanted. I don't expect them to last much more than 3 years so will probably get replaced later this year. I also intend to replace the noname alternator with a 12v 150amp Prestolite (2605048).

 

 

 

Edited January 17 by Midnight