14.8volts

[PabloPicasso]

This spring I've noticed that the battery voltage when I first start the engine is higher at 14.8v. (Previously the highest I'd seen was 14.6v). Is this normal or an indicator of impending problems?

I have one 85ah lead acid car type battery only.

I have plans to get a second battery with a larger capacity if I can find space for it.

 

[krbp32]

I would not expect to see more than 14.4v. imho you are close to overcharging You could take it to be bench tested or monitor it closely.

 

[sarabande]

what's the rated alternator output ?

14.8 sounds high, but not excessively so.

I'd look first for verification of the figure: is the voltmeter calibrated ? Have you checked it with a good megger ?

 

[VicS]

what's the rated alternator output ?

14.8 sounds high, but not excessively so.

I'd look first for verification of the figure: is the voltmeter calibrated ? Have you checked it with a good megger ?

I agree ........ check the reading ..... if its with an inexpensive multimeter the indication may be high because its battery is failing.

14.8 is too high for some types of battery but I believe that modern calcium types can ( should ??) be charged at 14.8.

 

[halcyon]

I agree ........ check the reading ..... if its with an inexpensive multimeter the indication may be high because its battery is failing.

14.8 is too high for some types of battery but I believe that modern calcium types can ( should ??) be charged at 14.8.

Back in the late 80's / early 90's AC Delco bought out the Freedom battery, which I think was the first Calcium battery, but we had to make Westerly a special mains charger for them, charging to 15.4 volt, floating at 14.6 volt.

So some batteries different, some car alternators regulate above 15.0 volt to suit the headlights, but 14.8 is high for extended running and is in a high gassing area, so you may not destroy the battery, you will be using lots of water.

Also check for bad connections if it.s machine sensed, check voltage at the terminals on the back of the alternator, if 14.2 / 14.4 volt check for bad connections.

Brian

 

[PabloPicasso]

The voltage is indicated on my Garmin plotter at the helm. Would this be accurate enough. All the readings are from this unit. I have a meter so I can check at the battery.

If there is an overcharging problem is the issue likely to be with the battery, the rectifier, or where?

 

[rivonia]

On the garmin increase the backlight to its brightest. leave it on for a while and check the voltage again. I know it is a very simplified test BUT it should show a drop.

 

[halcyon]

The voltage is indicated on my Garmin plotter at the helm. Would this be accurate enough. All the readings are from this unit. I have a meter so I can check at the battery.

If there is an overcharging problem is the issue likely to be with the battery, the rectifier, or where?

If the voltage is high at the battery terminals, check at alternator terminals, if that reading is he same get the alternator checked, if the alternator is reading right, i.e 14.2/14.4 volt check fior a bad connection on negative circuit.

Brian

 

[Richard10002]

The voltage is indicated on my Garmin plotter at the helm. Would this be accurate enough. All the readings are from this unit. I have a meter so I can check at the battery.

If there is an overcharging problem is the issue likely to be with the battery, the rectifier, or where?

First thing to do is to find out if there is actually an issue.

If the reading on the Garmin is worrying you, it could be wrong. you need to buy a multimeter and check the voltage across the battery to see what is really going on.

 

[VicS]

The voltage is indicated on my Garmin plotter at the helm. Would this be accurate enough. All the readings are from this unit. I have a meter so I can check at the battery.

If there is an overcharging problem is the issue likely to be with the battery, the rectifier, or where?

I'd definitely check the voltage then with a decent multimeter.


If the volts are genuinely too high then as Brian suggests check any battery sensing connection if it is battery sensed or internal connections if machine sensed. Then suspect the regulator..

 

[richardabeattie]

We are talking about fractions of a volt. 14.8 as opposed to 14.2. Are the ordinary £10 multimeters most of us have really that accurate? How can the accuracy be tested?

 

[Richard10002]

We are talking about fractions of a volt. 14.8 as opposed to 14.2. Are the ordinary £10 multimeters most of us have really that accurate? How can the accuracy be tested?

I hope they are accurate to a tenth of a volt or so - otherwise, what's the point?

 

[VicS]

I hope they are accurate to a tenth of a volt or so - otherwise, what's the point?

If I am reading the spec for my Maplin cheapy correctly it should be within ± 0.09 volt at 14 volts on the 20 volt scale. However calibration is only guaranteed for 1 year

 

[PabloPicasso]

First thing to do is to find out if there is actually an issue.

If the reading on the Garmin is worrying you, it could be wrong. you need to buy a multimeter and check the voltage across the battery to see what is really going on.

Ok I have a meter somewhere. I'll dig it out and check at the batt terminals and at the alternator.

 

[PabloPicasso]

I'd definitely check the voltage then with a decent multimeter.


If the volts are genuinely too high then as Brian suggests check any battery sensing connection if it is battery sensed or internal connections if machine sensed. Then suspect the regulator..

If it is the regulator, how expensive would that be to get repaired?

 

[halcyon]

If it is the regulator, how expensive would that be to get repaired?

Depends on alternator make and model.

Brian

 

[charles_reed]

I think many replies on this may be missing the point of the question.

Immediately after start-up one would expect to see a very high voltage (mine hits 15.1v on either external or internal regulator) within 30" this is down to 14.8 and continues to fall as the batteries recharge.
With an NMEA 2000 bus I can also read the system volts - this never goes above 14.1 and is usually @ 13.6v.

Before pontificating on the OP's query, there are two points that I suspect need to be answered.
1. What are the Garmin-reported volts after say 10' running and
2. Is the feed from the Garmin taken off the battery or just from the charging circuit?

I would agree that before panicking I'd check the readings with a digital multimeter, rather than rely on the accuracy of the Garmin.

I certainly wouldn't rush the alternator to the electrical repair shop on such insubstantial evidence (especially as a failed regulator has the opposite symptom, not reaching charging voltage).

 

[VicS]

I certainly wouldn't rush the alternator to the electrical repair shop on such insubstantial evidence (especially as a failed regulator has the opposite symptom, not reaching charging voltage).

Not necessarily. I have had a regulator fail with the volts going high, ...at least the ammeter went full scale. Luckily only intermittently. There was no voltmeter on the system but there was an ammeter

 

[halcyon]

I
Immediately after start-up one would expect to see a very high voltage (mine hits 15.1v on either external or internal regulator) within 30" this is down to 14.8 and continues to fall as the batteries recharge.

I would look for under sized cable or bad connection, no way should the alternator or battery voltage show those voltages at that state of charge.

Brian

 

[ianj99]

I think many replies on this may be missing the point of the question.

Immediately after start-up one would expect to see a very high voltage (mine hits 15.1v on either external or internal regulator) within 30" this is down to 14.8 and continues to fall as the batteries recharge.

I don't agree. Although the alternator regulator will initially turn the alternator output up, the fact that the battery will have been discharged during starting means its voltage will not be high. If this were not the case, the alternator regulator would sense the high voltage and interpret it as a fully charged battery and then switch to float voltage. (depending on how sophisticated the regulator is)

So 14.8v shortly after starting means that the battery is probably fully charged already and the voltage should then drop to around 13.6-14 fairly quickly.
If the battery seems to charge up very quickly compared to what it used to, then it implies that its capacity is much less. You would expect to see this on an old / sulphated battery. So maybe you should think about the battery and whether its on its way out?