Alternator troubles

[Guest]

After running my engine for a while this morning, I noticed that the battery monitor was showing a very slow recharge. Normally my battery level rarely goes below about 95% and I get it charged up fairly quickly via solar at the moment or plugging in to shore power. While I was in Castleford I was off grid, battery bank dropped. I'm pretty sure these batteries are on their way out but that's a different story. 

 

Anyway, back to Leeds this afternoon and I was pretty sure a 4 hour cruise would top the battery bank up to full. Didn't get above 95%. I was beginning to think that the battery bank had finally given up the ghost. When I got back to my mooring I plugged in and within an hour my Victron 50A charger had topped them up to full.

 

So I'm thinking the alternator is on the blink, although the starter battery was showing 14 point something volts while I was cruising and the domestics were only showing about 12.9 volts while cruising. Now it's actually the other way round, according to the battery monitor. 

 

 

although the sparky who fitted my battery charger I don't think hooked up the starter battery to it.

 

But still thinking the alternator is not running properly. Is there any way to test it and what would that be? I also wonder if it's not engaging properly as I saw it had come loose the other day so tightened it up but I think there is a little bit of slack on the belt.

 

Any advice would be much appreciated! Long message just to say my alternator is acting up, I realise. 

[nicknorman]

Does your engine have 1 or 2 alternators? Many modern engines have 2 alternators, a small one for the starter battery and a large one for the domestics.

 

If you have 2 alternators it would explain why the starter battery was charging happily whilst the domestics weren’t.

 

Yes first thing to check is that the belt is correctly tensioned. After that you should check the alternator output voltage with the engine running, using a multimeter (be careful of the moving belts!). If the domestic battery voltage is down around 12.something then try checking the voltage on the connections on the back of the alternator, put the meter between the fat wire on B+, and the case.

 

If you just have the one alternator there will be some kind of split charge device that connects the alternator to both sets of batteries when the engine is running, separates them when the engine is stopped. Normally it’s a relay. So this is a possible cause of the problem.

Edited June 18, 2020 by nicknorman

[ditchcrawler]

1 minute ago, nicknorman said:

Does your engine have 1 or 2 alternators? Many modern engines have 2 alternators, a small one for the starter battery and a large one for the domestics.

 

If you have 2 alternators it would explain why the starter battery was charging happily whilst the domestics weren’t.

 

Yes first thing to check is that the belt is correctly tensioned. After that you should check the alternator output voltage with the engine running, using a multimeter (be careful of the moving belts!). If the domestic battery voltage is down around 12.something then try checking the voltage on the connections on the back of the alternator, put the meter between the fat wire on B+, and the case.

If you have one its probably the split charge relay

[nicknorman]

You beat me to my edit!

[matty40s]

This happened to me a few weeks ago, an overnight out saw the batteries fall off a cliff late evening (with the music blaring....birthday you understand).

Only just managed to start the enjun next morning early on, the sun hadn't hit the solar panels yet. 

Investigated next day. I had connected the starter to the domestics over winter to keep it charged, and it was very warm, disconnected it, and it fell off a cliff, down to 9.5v within 10 minutes.....the rest of the bank stayed where it should have been. 

 

Not bad going for a battery purchased in 2003.

[Tony Brooks]

9 hours ago, NB Caelmiri said:

After running my engine for a while this morning, I noticed that the battery monitor was showing a very slow recharge. Normally my battery level rarely goes below about 95% and I get it charged up fairly quickly via solar at the moment or plugging in to shore power. While I was in Castleford I was off grid, battery bank dropped. I'm pretty sure these batteries are on their way out but that's a different story. 

 

Anyway, back to Leeds this afternoon and I was pretty sure a 4 hour cruise would top the battery bank up to full. Didn't get above 95%. I was beginning to think that the battery bank had finally given up the ghost. When I got back to my mooring I plugged in and within an hour my Victron 50A charger had topped them up to full.

 

So I'm thinking the alternator is on the blink, although the starter battery was showing 14 point something volts while I was cruising and the domestics were only showing about 12.9 volts while cruising. Now it's actually the other way round, according to the battery monitor. 

 

 

 

although the sparky who fitted my battery charger I don't think hooked up the starter battery to it.

 

But still thinking the alternator is not running properly. Is there any way to test it and what would that be? I also wonder if it's not engaging properly as I saw it had come loose the other day so tightened it up but I think there is a little bit of slack on the belt.

 

Any advice would be much appreciated! Long message just to say my alternator is acting up, I realise. 

Not enough info as has already been said. How many alternators? If its a split charge system how is the charge split between banks? Alternator make/model/output rating?

 

Testing an alternator:

 

Test batteries in case one has developed a short circuit (difficult for boater to do with sealed batteries).

 

Check alternator belt is in good condition, fits the pulleys and is the correct tension.

 

Check all cable connections are clean, tight and in good condition

 

When the relevant battery is well discharged connect/use  a high current ammeter and start and rev engine to 1500 rpm plus  and expect the alternation's rated output for a few seconds. For domestic alternator that would probably be first thing in the morning. For the engine alternator it would be after several minutes of cranking. For a split charge system as per domestic alternator. If you can turn on a heavy electrical load when checking it help force the alternator to maximum output.

 

At the end of several hours (say 4 to 6) of alternator charging at 1000 to 1500 rpm check the charging voltage with no electrical loads turned on. It should be within a very few decimal points of the alternator's regulated voltage so say 14 to 14.4 volts. Keep charging until the voltage stops rising over half an hour or so.

 

Easiest way is to take it off and get it tested. The tested can then tell you its rated output and regulated voltage.

 

 

Four hours of cruising is nowhere near long enough to fully recharge a typical domestic ban to 100%, think more like 10 to 12.

 

Your meter is probably telling great big porkies in respect of percentage charged. Use tail current at the alternator's regulated volatge (say 1.4.V) to assess when the batteries are 100% charged. Keep charging on the alternator until the current has stopped falling for half an hour or so and the current is about 1 to 2% of nominal battery capacity. If the current stays a lot higher than  that you probably have a shorting battery cell. Check for hot spots on the batteries. That type of meter is a great friend of battery suppliers unless properly set up and correctly used - most boaters fail on both points.

Edited June 19, 2020 by Tony Brooks

[WotEver]

3 minutes ago, Tony Brooks said:

Keep charging until the voltage current stops dropping over half an hour or so.

You need to edit your post, Tony, a typo slipped in.

Edited June 19, 2020 by WotEver

[Tony Brooks]

1 minute ago, WotEver said:

You need to amend your post, Tony

Thanks, now ammeneded but not as you say. It should read the voltage stops rising. That's to try to ensure it is at the regulated voltage or close to it.

[WotEver]

Just now, Tony Brooks said:

Thanks, now ammeneded but not as you say. It should read the voltage stops rising. That's to try to ensure it is at the regulated voltage or close to it.

Ahh, okay, either one

[Alan de Enfield]

14 minutes ago, Tony Brooks said:

Easiest way is to take it off and get it tested. The tested can then tell you its rated output and regulated voltage.

 

To the OP

 

Not just taking it to your local garage to do a 'drop-test' for 10 seconds - that shows nothing but they will tell you it shows you need a new battery.

 

 

There are modern equivalents but it is surprising how many of these you still see hanging up in garage workshops.

 

If you can 'be bothered' you can do your own test by using a known load (such as a head-light bulb) of about 50 watts or more. This will give you a good approximation (good enough for 'Government work anyway) This will show you the condition (capacity) of the battery.

 

Charge the battery to 'full'.

 

Check the no-load voltage after standing for an hour.

Connect the load, and leave the load connected until the voltage goes down to ~ 12.1 volts.

Remove the load and leave the battery to stand for an hour, voltage should rise to ~12.2 volts

 

You have used 50% of the battery capacity.

As an example, say you used a 60 watt load, this is ~5 amps. If it took 10 hours to get down to 12.2 volts than 50Ah is 50% of the battery capacity, ergo the battery capacity is 100Ah

 

If it took 3 hours, then the battery capacity is 30Ah

 

[Tony Brooks]

Beware - drop testers such as Alan has shown need to be more or less matched to battery capacity  so using one designed for a 35Ah car battery (they are not sized in that way but it near enough for explanation) on a 110Ah battery will never give reliable results. It could easily show the 110 Ah battery as serviceable  when in fact it is faulty.

 

Also be aware that to prevent false faulty results the battery under test should be more or less fully charged.

[WotEver]

11 minutes ago, Tony Brooks said:

Also be aware that to prevent false faulty results the battery under test should be more or less fully charged.

I left the boot open on my car many years ago and flattened the battery.  At the time I had no easy way of starting the car and I wasn't in a rush so I called out the AA. Patrolman turned up, stuck his kit across the battery and said "You're battery is no good.  Want to buy a new one?"

 

That battery lasted me another 3 years, and was still in the car when I sold it.

[Tony Brooks]

9 minutes ago, WotEver said:

I left the boot open on my car many years ago and flattened the battery.  At the time I had no easy way of starting the car and I wasn't in a rush so I called out the AA. Patrolman turned up, stuck his kit across the battery and said "You're battery is no good.  Want to buy a new one?"

 

That battery lasted me another 3 years, and was still in the car when I sold it.

Yes, one of the tricks of the trade that would get you or your mate a usable battery.

[bizzard]

I saved a chaps eyesight once using a drop tester on a Morris Minor 1000.  Thet were useful for finding a dead or shorting cell,  the first to boil.  An inch thick steel bar across the terminals is just as good.

[Tony Brooks]

4 minutes ago, bizzard said:

I saved a chaps eyesight once using a drop tester on a Morris Minor 1000.  Thet were useful for finding a dead or shorting cell,  the first to boil.  An inch thick steel bar across the terminals is just as good.

absolutely but not much good on these newfangled sealed batteries?

[bizzard]

12 minutes ago, Tony Brooks said:

absolutely but not much good on these newfangled sealed batteries?

For sealed batteries you need a stethescope to complement the drop tester. Someone to hold the drop tester on the terminals while you quickly run along the top of of the six or three cells listening for boiling with the stethescope, just like a doctor.

[ditchcrawler]

3 hours ago, Alan de Enfield said:

 

To the OP

 

Not just taking it to your local garage to do a 'drop-test' for 10 seconds - that shows nothing but they will tell you it shows you need a new battery.

 

 

There are modern equivalents but it is surprising how many of these you still see hanging up in garage workshops.

 

If you can 'be bothered' you can do your own test by using a known load (such as a head-light bulb) of about 50 watts or more. This will give you a good approximation (good enough for 'Government work anyway) This will show you the condition (capacity) of the battery.

 

Charge the battery to 'full'.

 

Check the no-load voltage after standing for an hour.

Connect the load, and leave the load connected until the voltage goes down to ~ 12.1 volts.

Remove the load and leave the battery to stand for an hour, voltage should rise to ~12.2 volts

 

You have used 50% of the battery capacity.

As an example, say you used a 60 watt load, this is ~5 amps. If it took 10 hours to get down to 12.2 volts than 50Ah is 50% of the battery capacity, ergo the battery capacity is 100Ah

 

If it took 3 hours, then the battery capacity is 30Ah

 

That is the only way I know of doing it.

[Tony Brooks]

4 hours ago, Alan de Enfield said:

 

 

If you can 'be bothered' you can do your own test by using a known load (such as a head-light bulb) of about 50 watts or more. This will give you a good approximation (good enough for 'Government work anyway) This will show you the condition (capacity) of the battery.

 

Charge the battery to 'full'.

 

Check the no-load voltage after standing for an hour.

Connect the load, and leave the load connected until the voltage goes down to ~ 12.1 volts.

Remove the load and leave the battery to stand for an hour, voltage should rise to ~12.2 volts

 

You have used 50% of the battery capacity.

As an example, say you used a 60 watt load, this is ~5 amps. If it took 10 hours to get down to 12.2 volts than 50Ah is 50% of the battery capacity, ergo the battery capacity is 100Ah

 

If it took 3 hours, then the battery capacity is 30Ah

 

 

That is a true full, not 100% on that meter and not when some charger drops into float. Its when the current has stopped falling over about an hour.

[Guest]

11 hours ago, Tony Brooks said:

Not enough info as has already been said. How many alternators? If its a split charge system how is the charge split between banks? Alternator make/model/output rating?

 

Testing an alternator:

 

Test batteries in case one has developed a short circuit (difficult for boater to do with sealed batteries).

 

Check alternator belt is in good condition, fits the pulleys and is the correct tension.

 

Check all cable connections are clean, tight and in good condition

 

When the relevant battery is well discharged connect/use  a high current ammeter and start and rev engine to 1500 rpm plus  and expect the alternation's rated output for a few seconds. For domestic alternator that would probably be first thing in the morning. For the engine alternator it would be after several minutes of cranking. For a split charge system as per domestic alternator. If you can turn on a heavy electrical load when checking it help force the alternator to maximum output.

 

At the end of several hours (say 4 to 6) of alternator charging at 1000 to 1500 rpm check the charging voltage with no electrical loads turned on. It should be within a very few decimal points of the alternator's regulated voltage so say 14 to 14.4 volts. Keep charging until the voltage stops rising over half an hour or so.

 

Easiest way is to take it off and get it tested. The tested can then tell you its rated output and regulated voltage.

 

 

Four hours of cruising is nowhere near long enough to fully recharge a typical domestic ban to 100%, think more like 10 to 12.

 

Your meter is probably telling great big porkies in respect of percentage charged. Use tail current at the alternator's regulated volatge (say 1.4.V) to assess when the batteries are 100% charged. Keep charging on the alternator until the current has stopped falling for half an hour or so and the current is about 1 to 2% of nominal battery capacity. If the current stays a lot higher than  that you probably have a shorting battery cell. Check for hot spots on the batteries. That type of meter is a great friend of battery suppliers unless properly set up and correctly used - most boaters fail on both points.

Thanks Tony! This is all very useful information. I shall book mark this for later needs.

 

Thankfully I've found the cause of the weird goings on with my electricity and so no longer need to replace a battery bank! (yet). It turned out that my rather dodgy battery isolation switch was set somewhere between 1+2 and 2. Even though the battery monitor was showing that it is fully charged,  all kinds of strange things were occurring - lights dimming, starter battery showing less than 10v. So set the battery isolation switch to 2 as it usually is and all seems to be well again.

 

To be honest, I could probably do with some kind of electrical system audit because I'm sure it's a bit all over the place and I don't really know what is what. I suspect my batteries are probably getting long in the tooth as I've had them running for 3 years and the previous owner had them for 2 years before me so who knows how old they are and what their capacity is now. But for some reason, like my pair of gas cyclinders which should easily be empty by now, seem to keep persisting.

 

Thanks all for the advice! Panic over. Battery isolation switch was set wrong. I must have knocked it.

Edited June 19, 2020 by NB Caelmiri

[Tony Brooks]

Personally I would ditch that switch and fit a proper battery isolator and a voltage sensitive relay for the charge splitting. That would almost certainly reduce the main charging cable length that is always a good thing.

 

As that switch seems not to have an off position I suspect you have one or two master switches to the right of it.

 

As I warned your battery monitor is almost certainly telling an enormous lie. Please do not use it to see when the batteries are fully charged. use tail current as I explained above. Once you are sure the batteries really are fully charged you can recalibrate the meter and then  will tell more or less the truth for a short while and the gradually tell larger and larger lies.

[Guest]

1 minute ago, Tony Brooks said:

Personally I would ditch that switch and fit a proper battery isolator and a voltage sensitive relay for the charge splitting. That would almost certainly reduce the main charging cable length that is always a good thing.

 

As that switch seems not to have an off position I suspect you have one or two master switches to the right of it.

 

As I warned your battery monitor is almost certainly telling an enormous lie. Please do not use it to see when the batteries are fully charged. use tail current as I explained above. Once you are sure the batteries really are fully charged you can recalibrate the meter and then  will tell more or less the truth for a short while and the gradually tell larger and larger lies.

Will do Tony! I will have to find a local boat sparky that knows a bit about this kind of thing and get something fitted. Definitely not my area of expertise. Thanks again!

[Tony Brooks]

It might pay you to study the electrical notes on my website and use them to work out exactly how your charging system is wired.

[TheBiscuits]

On 19/06/2020 at 19:27, NB Caelmiri said:

To be honest, I could probably do with some kind of electrical system audit because I'm sure it's a bit all over the place and I don't really know what is what.

 

Ask @Duck-n-Dive. He'll probably be able to sort out your stalling issue for you while he's there too.

On 19/06/2020 at 19:40, NB Caelmiri said:

I will have to find a local boat sparky that knows a bit about this kind of thing and get something fitted.

At Chorley with a bust driveplate at the moment so not far from Burscough, but to be honest he's worth getting from the other side of the country.

[Duck-n-Dive]

I am indeed stuck in Chorley with no driveplate, but I can have a look if you want. 

I will be nearer to Leeds when

a) I have a boat that works

b) CRT open the locks

 

I think a) will be sooner

[TheBiscuits]

10 minutes ago, Duck-n-Dive said:

I am indeed stuck in Chorley with no driveplate, but I can have a look if you want. 

I will be nearer to Leeds when

a) I have a boat that works

b) CRT open the locks

 

I think a) will be sooner

 

I'm mixing up the one at Burscough with the one at Leeds I think.