Alternator questions

[lumphammer]

The engine is a Sole Mini-18 with an unknown manufacturer's alternator which has a separate regulator. I have just fitted a NASA battery monitor and found that the charging voltage is around 14.8-14.9 at about 3.0A. The Sterling instructions say that above 14.5 the regulator is faulty.

Is that probable? If so, will continuing to use engine charging damage the battery?

If I have to change the regulator I am thinking of fitting a new alternator instead of the existing.
Is there a formula that relates alternator size to battery capacity?

The output from the alternator on the cable to the regulator is marked A, F, N and E, and there is a separate B terminal to the battery. F, I assume is the field, E is earth.

Which cables should I connect the regulator to?

How can I tell if the alternator is N-type or P-type?

 

[pvb]

[ QUOTE ]
The engine is a Sole Mini-18 with an unknown manufacturer's alternator which has a separate regulator. I have just fitted a NASA battery monitor and found that the charging voltage is around 14.8-14.9 at about 3.0A. The Sterling instructions say that above 14.5 the regulator is faulty. Is that probable? If so, will continuing to use engine charging damage the battery?

[/ QUOTE ]Guess this hasn't just started happening, more likely you've just discovered it. So engine charging shouldn't damage your battery, although it might need topping up more often. You mention "Sterling instructions", does this mean the external regulator is a Sterling regulator?

[ QUOTE ]
If I have to change the regulator I am thinking of fitting a new alternator instead of the existing. Is there a formula that relates alternator size to battery capacity?


[/ QUOTE ] An often-quoted rule of thumb is to divide the battery capacity in Ah by 3 or 4 to arrive at the rough power of the alternator (in amps output). In practice, there's a lot of latitude - I charge over 600Ah with a 90A alternator without problems. When sizing a new alternator, you might allow for future expansion of your battery capacity.

[ QUOTE ]
Which cables should I connect the regulator to?


[/ QUOTE ] If you're buying a new "smart" regulator, it'll come with full fitting instructions.

[ QUOTE ]
How can I tell if the alternator is N-type or P-type?

[/ QUOTE ] If you're buying a new alternator, you just ask. If you're talking about your old alternator, and if you really can't find out what make/model it is, you could find out by following the instructions here in the Sterling installation guide.

 

[johnalison]

Just a thought; how are you measuring voltage? My Raymarine repeaters read voltage to 0.1 volts but are up to 0.3 wrong.

 

[SvenglishTommy]

I find my Sterling regulator seems a little too keen with the voltage too.

 

[lumphammer]

[ QUOTE ]
[ QUOTE ]
The engine is a Sole Mini-18 with an unknown manufacturer's alternator which has a separate regulator. I have just fitted a NASA battery monitor and found that the charging voltage is around 14.8-14.9 at about 3.0A. The Sterling instructions say that above 14.5 the regulator is faulty. Is that probable? If so, will continuing to use engine charging damage the battery?

[/ QUOTE ]Guess this hasn't just started happening, more likely you've just discovered it. So engine charging shouldn't damage your battery, although it might need topping up more often. You mention "Sterling instructions", does this mean the external regulator is a Sterling regulator?

[/ QUOTE ]

No, I'm trying to fit a Sterling regulator. I inherited the one already fitted with the engine/alternator setup when I bought the boat.

 

[William_H]

The size of the alternator Ireckon is more a question of what will fit and what you are prepared to pay for. Thhe current rating of an alternator is the max it can genrate while holding up a decent voltage. A bigger alternator will charge very flat batteries quicker especially if you have a smart charger but mostly an alternator is under utilised in battery charging unless you have a really big flat battery bank.
So I recomend stick with what you have.

Regarding the battery voltage on charge ie regulated voltage you need to check with a decnt multimeter (or even several) to get accuracy before you panic. As tated the sure sign of overvoltage charging is high charging current and batteries that need fluid topped up often. (I hope you can check fluid level.)

Smart chargers get more current into the battery by increasing the charge voltage however this voltage should fall to around or less than 14 volts when charge cycle is competed. ie trickle charge phase. So maybe that is what is happening. good luck olewill