Faulty Alternator? (Volvo D1-30/EH450 LA Exide Batteries)

[Ian_Rob]

I am experiencing a re-occurrence of a battery alarm problem that I was experiencing earlier in the season. With the engine running I only measure 14.1 volts at the battery terminals. Does this point to a faulty alternator?

 

[gregcope]

@Ian_Rob I think you should post allot more info. Other charging sources? Voltage when not being charged. Alarm frequency?

 

[jamie N]

The voltage should read a minimum of 13 volts. A good alternator should put out between 13.5-14.5 volts.

 

[Pete7]

Ian, could be but equally it could be corrosion on the connections. Before spending lots of dosh, spend a morning following both positive and negative battery cables and cleaning each connection. Then take a reading off the back of the alternator and compare with the reading on the battery. 14.1v isn't bad for an ordinary alternator and should work just fine charging batteries. What is the engine btw?

Pete

 

[Ian_Rob]

Sorry, the internet here is lousy, leaving my replies totally out of sequence. This was my reply to Greg.

Other than a two small (2 x 20W) solar panels the only charging source is the engine alternator.

Typically the panel alarms sounds shortly after switching off the engine with a barely audible half-beep that becomes a regular 1 beep every 3 seconds.

The speed at which the alarm first sounds depends on the loads that are running at the time. We timed it yesterday and with the fridge on, the first half-beep started 9 mins after we had stopped the engine (having run it for 30 mins) and became a regular beep within 30mins. The alarm mirrors the cycling of the fridge compressor.

When sailing during the week, without the engine running and with only the chart plotter and autopilot on, the first beep occurred approximately 1.5 hours after the engine was switched off. Dimming the chart plotter display was sufficient to stop the beeping though presumably it would have started again if I hadn‘t run the engine in idle.

I don’t know whether the problem is due to the battery, the alternator or both.

- We anti-fouled in early May and were out of the water for a week. For the whole of the time we were connected to shore power. Three hours before launching we disconnected and noticed the first beep shortly after the boat was back in the water. To my mind this suggests that it is battery problem but they were checked in April and were reportedly in good condition.

- With the engine running at 1800rpm the voltage measured at the battery terminals was 14.1 volts but isn’t that too low suggesting perhaps an alternator issue.

 

[Ian_Rob]

The voltage should read a minimum of 13 volts. A good alternator should put out between 13.5-14.5 volts.

So my 14.1v reading may be OK. I was thinking that it should be at rather higher. ThankyI.

 

[Oily Rag]

My alternator is rated at only 14 volts, so I'd be happy with that when running the engine.

You get the alarm when the engine is not running, so is it warning of low voltage on your battery? What is the voltage when the alarm starts to beep?

 

[Bilgediver]

I am experiencing a re-occurrence of a battery alarm problem that I was experiencing earlier in the season. With the engine running I only measure 14.1 volts at the battery terminals. Does this point to a faulty alternator?

The alternator could well be putting out 14.5 volts. Have you checked at the alternator and do you have a diode splitter in the circuit as this gives a volt drop and if fitted the voltage sensing wire should go to the battery terminals.

 

[Ian_Rob]

I am not sure if this is sufficient but some answers to the questions asked:

With the engine running the voltage at the alternator (measured across the positive alternator terminal and the engine ground) is 14.96v compared to 14.14v at the battery terminals.

The first half-beep is at 12.73 volts and the alarm becomes a constant repeating beep at 12.61 volts (measured at the battery terminals).

Thankyou.

 

[Boater Sam]

So it is the inverter that is beeping due to low voltage.

I think your batteries are toast through persistent undercharging, 40w at best of solar will give insufficient charge and running the engine for half an hour is nothing. You need to run the engine until the charging current is down to 2% of the battery rated capacity to ensure that they are fully charged.

 

[Oily Rag]

Ian, I'm trying to help, but a bit confused. The beeping starts when the engine isn't shut down. What is it that beeps? (Boater Sam mentions an inverter. Do you have one?)
Everything on my boat would be happy with 12.73 volts, but you start to get an alarm, so back to asking what it is that beeps.

I can imagine a device measuring voltage at, say, the fridge and sending an alarm, especially if there are some poor contacts causing a volt drop. What do you have to switch off to stop the beeping? Have you tried isolating circuits one at a time?
Good luck!

 

[pvb]

With the engine running the voltage at the alternator (measured across the positive alternator terminal and the engine ground) is 14.96v compared to 14.14v at the battery terminals.

The standard alternator on the D1-30 has battery sensing (usually a yellow wire) to compensate for any voltage drop due to cabling, diodes, etc. Your voltage drop is quite large - if it's the result of a diode splitter, you might consider replacing it with a low-loss splitter (Victron ArgoFET, etc).

You've posted about this problem before - Ongoing Battery Issue Did you do the basic voltage checks suggested by Paul Rainbow in that thread?

 

[PaulRainbow]

So it is the inverter that is beeping due to low voltage.

I think your batteries are toast through persistent undercharging, 40w at best of solar will give insufficient charge and running the engine for half an hour is nothing. You need to run the engine until the charging current is down to 2% of the battery rated capacity to ensure that they are fully charged.

Who said anything about an inverter ?

40W of solar is more than enough to keep batteries charged on a mooring.

 

[Ian_Rob]

Ian, I'm trying to help, but a bit confused. The beeping starts when the engine isn't shut down. What is it that beeps? (Boater Sam mentions an inverter. Do you have one?)
Everything on my boat would be happy with 12.73 volts, but you start to get an alarm, so back to asking what it is that beeps.

I can imagine a device measuring voltage at, say, the fridge and sending an alarm, especially if there are some poor contacts causing a volt drop. What do you have to switch off to stop the beeping? Have you tried isolating circuits one at a time?
Good luck!

Thanks Oily.

The beeping is a low voltage alarm from the electrical panel. It only happens when the engine isn't running. I haven’t got an inverter.



The boat is kept on a swinging mooring and is normally use at three weekly intervals or less during the season. When not in use the domestic batteries are trickle charged from 2 x 20w solar panels. The engine battery is left to fend for itself. The original domestic batteries were replaced in 2019 (after 11 years) and the engine battery in 2021 (after 13 years) so until now, the regime hasn’t been too bad.

 

[PaulRainbow]

I am not sure if this is sufficient but some answers to the questions asked:

With the engine running the voltage at the alternator (measured across the positive alternator terminal and the engine ground) is 14.96v compared to 14.14v at the battery terminals.

The first half-beep is at 12.73 volts and the alarm becomes a constant repeating beep at 12.61 volts (measured at the battery terminals).

Thankyou.

The alarm thresholds seen very low to me. 12.73V is a fully charged battery, 12.6V is 90% charged, should be no alarms at all at those voltages.

 

[pvb]

The alarm thresholds seen very low to me. 12.73V is a fully charged battery, 12.6V is 90% charged, should be no alarms at all at those voltages.

You gave good advice in the OP's previous thread about his battery issues, yet it seems he hasn't followed it.

 

[Ian_Rob]

The standard alternator on the D1-30 has battery sensing (usually a yellow wire) to compensate for any voltage drop due to cabling, diodes, etc. Your voltage drop is quite large - if it's the result of a diode splitter, you might consider replacing it with a low-loss splitter (Victron ArgoFET, etc).

There is an yellow cable at the back of the alternator terminated in a plastic female connector but without any reciprocal connector as well as a smaller diameter red cable, cable tied to the positive red cable. I suspect that this smaller cable is the sensing cable as it is labelled ALT/REFR?.

You've posted about this problem before - Ongoing Battery Issue Did you do the basic voltage checks suggested by Paul Rainbow in that thread?

It was a bit inconclusive. I initially found a 0.3 volt difference between the voltage measured at the dash meter and the battery terminals but when I checked again 30min later they were almost exactly the same.

 

[pvb]

It was a bit inconclusive. I initially found a 0.3 volt difference between the voltage measured at the dash meter and the battery terminal but when I checked again 30min later they were almost exactly the same.

You don't seem to be getting anywhere. Wouldn't it be worth paying a marine electrician for an hour or so to sort it out?

 

[Ian_Rob]

You don't seem to be getting anywhere. Wouldn't it be worth paying a marine electrician for an hour or so to sort it out?

I think you are right pvb….. Thanks for your and everybody else’s help.