Alternator question

[Johny London]

I noticed that my alternator voltage was creeping up a little the other day. Normally always 14.45 but saw as much as 14.7! It so happens that after that I came into a marina so not had cause to run the engine since. But, maybe I should be using it's down time to investigate? Not sure where to start, or if this could be an aberration or to do with batteries or something. Not had the opportunity to see if it persists either. Sorry for little information but it's been in my mind the last couple days. Batteries are 4x110 la (rather sulphated effective capacity about 25% of original). The alternator is a 175a on a Canaline 42hp.

thanks

[OldGoat]

2 minutes ago, Johny London said:

I noticed that my alternator voltage was creeping up a little the other day. Normally always 14.45 but saw as much as 14.7! It so happens that after that I came into a marina so not had cause to run the engine since. But, maybe I should be using it's down time to investigate? Not sure where to start, or if this could be an aberration or to do with batteries or something. Not had the opportunity to see if it persists either. Sorry for little information but it's been in my mind the last couple days. Batteries are 4x110 la (rather sulphated effective capacity about 25% of original). The alternator is a 175a on a Canaline 42hp.

thanks

Methinks you've cracked the problem yourself; batteries are all gunged up (technical term) and the poor alternator is trying to put some charge into a heap of sulphates.

You've got a reasonable (?) sized battery bank - so how have you managed to foul them up??

 

Go to the naughty step - stopping only to buy some new batteries, couple with the will to treat them better in future.

[BEngo]

Has the Alternator got a temperature compensated regulator?

Is it battery or machine sensed?

Is the wiring in good order with no corroded or loose  connections,?

Where is 14.7 V being measured? Battery or alternator connections or somewhere else?

N

[dor]

Have you had the batteries on a charger?

If my batteries have had a good charge from the solar, then the voltage can get up to about 14.7 as the batteries are fully charged.

Alternator has an uprated regulator in it which will regulate the charge to between 14.2V & 14.7V depending on the state of charge.

[Johny London]

Hi and thanks for the quick and informative replies. I know I should replace the batteries but the l/a's last me six weeks then they are like 25% capacity for a year. I'm trying to figure out lithiums and go for those before the la's completely fail.

Obviously - if I go for lithiums I'll be double concerned about a high alternator voltage. But from the above it looks as though what I saw might merely be a symptom of everything else then.

I'm afraid I don't know if it is temperature compensated (I would assume not) or machine sensed (?). Just it's a new thing I'd not seen happen before.

Also - no, batteries have not been on a charger (they are now though!) I can't remember the exact situation but I was coming to the end of a cruise and was probably at something like 75% charged.

The measurement was on the sg which has its own connections to the batteries.

[cuthound]

First check to see if your charger has a battery temperature sensor connected (A very thin wire going from the charger to somewhere in the battery box). If it has it is probably doing its job and increasing the charge voltage to compensate for the lower winter battery temperatures.

 

If it does not have a battery temperature sensor, then check for loose connections.

 

If none found then report back here.

Edited January 7, 2019 by cuthound

[Sea Dog]

46 minutes ago, Johny London said:

I know I should replace the batteries but the l/a's last me six weeks then they are like 25% capacity for a year.

Johny, this shows that your battery charging regime is woefully inadequate. This is the issue you need to address before you replace them with the same, with lithiums or with anything else.  

[Johny London]

Was, not is! I'm a good boy now  Well mostly... the truth is the la's don't really suit my needs.

Cuthound - I don't have a temperature sensor, but I'll check the wiring - where should I be looking? I would have thought a loose connection would have given rise to a lower voltage. Is it the alternator side of things or the metering side of things where I need to be looking? Everything was new when I got the boat 2 1/2 years ago. Was

thanks.

[Detling]

Don't get lithium batteries before it is sorted 14.7 volts = dead battery no ifs, no buts.

[Tony Brooks]

9 hours ago, Johny London said:

Was, not is! I'm a good boy now  Well mostly... the truth is the la's don't really suit my needs.

Cuthound - I don't have a temperature sensor, but I'll check the wiring - where should I be looking? I would have thought a loose connection would have given rise to a lower voltage. Is it the alternator side of things or the metering side of things where I need to be looking? Everything was new when I got the boat 2 1/2 years ago. Was

thanks.

 

Unless your alternator has had a remote controller/regulator fitted I simply do not understand what you mean by the metering side of things. I did not respond when I first read the question because the important questions had been asked by others and so far no substantive answers. You know your boat we did not although some may remember details from other threads but it is not fair to rely on that.

 

Make and approx age of engine? This will help us decode what type of alternator you PROBABLY have (not be certain because people change them).  From that we  can make an informed guess about it being machine or battery sensed.

 

Any other charging sources in use or very recently been in use when this occurred? (it could be solar deciding to do an equalisation charge or if the batteries went very flat or were disconnected from any solar controller the controller just might have set itself to 24 volts).

 

Any external alternator controllers like the Adverc, Kestrel, Sterling devices?

 

Beta did fit some 14.8 volt machine sensed alternators and if you have one of these it just means the batteries are pretty much fully charged with a low current flow. They also fitted an external controller as standard so do you have one? If the boat is just 2.5 years old this paragraph probably doe not apply. I think you will find the Smartguage (if that is what you mean by "sg" advice is that batteries with less than 50% capacity left are need replacing and the % readings are no longer reliable.

 

Does the warning lamp glow at various revs when you cup your hand around it? What is the voltage with a meter connected between the B+ (main pos output terminal) and + (warning lamp terminal) with the engine revving? This will indicate if a field diode has failed and that will give an excess charging voltage.

 

If all the main charging leads are thick enough, the terminals clean and tight, including the battery terminals then there is a possibility  the alternator's regulator has failed but we are far from that diagnosis now, especially as you have admitted you have exceptionally unserviceable batteries.

[Sea Dog]

16 hours ago, Johny London said:

I noticed that my alternator voltage was creeping up a little the other day. Normally always 14.45 but saw as much as 14.7!

I wonder if this could also be because you don't normally charge long enough to see the voltage rise that far? 14.7v is not an atypical figure for charging voltage to reach when the tail current is tending towards its lowest value.  This is alternator dependent but as Tony says above, some Beta fits are 14.8v.  If you are stopping the charge short of 100% on a regular basis, this would explain why your battery capacity falls away so quickly.

[WotEver]

54 minutes ago, Sea Dog said:

If you are stopping the charge short of 100% on a regular basis, this would explain why your battery capacity falls away so quickly.

This