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I would not be surprised if the alternator has a diode problem. I think even the 10/11 AC alternators were set at 13.8 with ACRs at 14 to 14.2. Then the A127s 14.2 to 14.4

 

The other reason for a low charging voltage is high charging current flows but after six hours that should not be the problem unless there are battery cells shorting.

 

We need to know which alternator is fitted or a photo

Edited by Tony Brooks
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9 hours ago, Mike the Boilerman said:

 

Yes I have an Inlander on the boat I'm on now. Curiously I just checked the current draw as it flattened my (apparently knackered) one year old 200ah battery bank overnight. It draws 5.7A when running. 

 

It is virtually identical inside and out to the 15-year-old Shoreline I have in my liveaboard, which is still working fine BTW. (Fingers crossed!) 

 

Oh forgot to say, my battery bank is being charged by a single 100W solar panel. My gut feeling is this is not big enough to power the fridge 24/7 even in summer as it only delivers 7A when the sun is overhead on a midsummer's day. The rest of the time it tends towards 2-3a. 

Insufficient battery charging.This pretty much says it all (& I've seen the same numbers for myself)

My 12V Shoreline fridge/freezer is on 90% of the time, it's old & tired (11 years old). Always keep it on 2. Draws about 5A.

I agree with MTBs solar figures too although I have 660W.

 

So under ideal conditions like we've had the last few days your solar panel can keep up with your fridge say 12 hours per day, then overnight it pulls 60Ah from your batteries.

Under ideal conditions your solar panel is also charging your batteries by just 2A max, putting in 24Ah back into your battery bank.

 

So you are short by 36Ah per day under optimal conditions & zero inefficiencies.

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55 minutes ago, Tony Brooks said:

I would not be surprised if the alternator has a diode problem. I think even the 10/11 AC alternators were set at 13.8 with ACRs at 14 to 14.2. Then the A127s 14.2 to 14.4

 

The other reason for a low charging voltage is high charging current flows but after six hours that should not be the problem unless there are battery cells shorting.

 

We need to know which alternator is fitted or a photo

Hi tony, according to calcutt paperwork it is a lucas A127M 55a fitted 1991, hopefully ive posted a picture, 

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22 hours ago, oats said:

Hi batteries never allowed to get below 12.2 this was first time, as just posted, think i got myself in a pickle with the solar etc, have two 113 amp batteries + 110 starter, only got 100w mono solar, not mppt controller, this has always been ok for us for past four years as we don't use much power, fridge, water pumps, a couple of led lights. Will be getting another solar panel and mppt controller later, all good helpful points.

We have a 100W "portable" solar set up, which has a PWM controller built in to the panel(s). The controller seems to be quite a common one, and when I read the manual, I found that once it gets to acceptance voltage, it gives a timed charge , before going into float. In our case, this gets the batteries to about 80% charged. Once it has gone into float, it is extremely reluctant to go back to acceptance and raise the battery volts from 13.6V or so to 14.2V. The result is that our set up will just about keep up with our discharge rate during the day, and there is a net discharge while the fridge is running. 

 

We are normally cruising, so the solar is a minor source of charge for the batteries. It certainly wouldn't allow us to sit for 7 days without some other source of power, even with our current weather.

 

If shore power is available, the battery charger similarly goes into float early, but comes out of float and jacks the voltage up for a few minutes if there is any demand for power. 

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23 minutes ago, oats said:

Hi tony, according to calcutt paperwork it is a lucas A127M 55a fitted 1991, hopefully ive posted a picture, 

Is this it http://news.prestolite.com/drupaldocs/A127MT Info & Specification.pdf it quotes the output at 13.5 volts but not the maximum voltage

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1 hour ago, oats said:

Hi tony, according to calcutt paperwork it is a lucas A127M 55a fitted 1991, hopefully ive posted a picture, 

 

In that case I would expect the regulated voltage to be a little above 14 volts unless for some reason it has a weird regulator so after six hours cruising I would expect the charging current to be low and the voltage to be much higher. Its not so either the current is still very high or the alternator has lost a phase.

 

This is over and above any fridge problem.

 

Try another six hours of running and see if the voltage comes up. If not towards the end feel the batteries. If any are hotter than the rest or smelly then you have shorted cell(s) and that would tend to ho;d the voltage down. If the voltage is still low and the batteries are the same temp then the alternator is  suspect but best check the drive belt and all charging connections

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1 minute ago, Tony Brooks said:

but best check the drive belt

 

An easy one to overlook in our tendency to over-technicalise in these threads. 

 

Its surprising how tight a vee belt needs to be. I increased the tightness on mine today (despite considering it 'about right' in the first place) and squeezed an EXTRA 20A out of my alternator into a very flat battery. 30A became 50A.

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1 hour ago, Mike the Boilerman said:

 

An easy one to overlook in our tendency to over-technicalise in these threads. 

 

Its surprising how tight a vee belt needs to be. I increased the tightness on mine today (despite considering it 'about right' in the first place) and squeezed an EXTRA 20A out of my alternator into a very flat battery. 30A became 50A.

And the belt will now last longer. And the engine bay will be cleaner. 

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9 hours ago, Mike the Boilerman said:

 

An easy one to overlook in our tendency to over-technicalise in these threads. 

 

Its surprising how tight a vee belt needs to be. I increased the tightness on mine today (despite considering it 'about right' in the first place) and squeezed an EXTRA 20A out of my alternator into a very flat battery. 30A became 50A.

Whilst not wishing to detract from what you say after six hours running, even with a fairly significant charge reduction, the charging current should have fallen to a low level and that would have gone a long way to stopping any belt slip. After the batteries have recharged to a certain degree in the majority of cases belt slip will stop being an issue as the charging current falls.

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10 hours ago, Mike the Boilerman said:

 

An easy one to overlook in our tendency to over-technicalise in these threads. 

 

Its surprising how tight a vee belt needs to be. I increased the tightness on mine today (despite considering it 'about right' in the first place) and squeezed an EXTRA 20A out of my alternator into a very flat battery. 30A became 50A.

I've written here  before - but perhaps not dogmatically enough - in circumstances like these (or indeed in all circumstances) where more power is required from the main alternator fit a cogged belt rather than a straight V- belt. They're more flexible, wont load the bearings as much, only cost a little bit more and last and last and last.

It's not what the establishment says so I suspect I'll get shouted down....

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53 minutes ago, OldGoat said:

I've written here  before - but perhaps not dogmatically enough - in circumstances like these (or indeed in all circumstances) where more power is required from the main alternator fit a cogged belt rather than a straight V- belt. They're more flexible, wont load the bearings as much, only cost a little bit more and last and last and last.

It's not what the establishment says so I suspect I'll get shouted down....

 

I understand you point thanks. I might try it if I can find one long enough. My alternator pulley is 2.5" and the flywheel pulley is 30". I'll need a belt approx 3m long! A cogged belt is a good idea with small radius pulleys. 

 

I might even get yet a further 20a out of this alternator which states 70a on the data label. Most I'd ever seen it deliver was 30a until I modified the tensioning bracket yesterday, when it jumped to 50a. 

 

Edit to add:

 

Ah, just checked the belt label to see what length and I notice it is already a 'cogged' format belt. Duh. 

Edited by Mike the Boilerman
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15 minutes ago, Mike the Boilerman said:

 

I understand you point thanks. I might try it if I can find one long enough. My alternator pulley is 2.5" and the flywheel pulley is 30". I'll need a belt approx 3m long! A cogged belt is a good idea with small radius pulleys. 

 

I might even get yet a further 20a out of this alternator which states 70a on the data label. Most I'd ever seen it deliver was 30a until I modified the tensioning bracket yesterday, when it jumped to 50a. 

 

Edit to add:

 

Ah, just checked the belt label to see what length and I notice it is already a 'cogged' format belt. Duh. 

Happy to oblige - BB list one around 3.3m long!!

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On ‎30‎/‎06‎/‎2018 at 19:53, OldGoat said:

Holes in the floor is a good start, but if the fridge is 'boxed in' , eth you are not going to get much circulation/ heat exchange between the coil and the surrounding air. I have two computer fans running all the time that the compressor is running - and the coils are cool(ish). So that's one area to look at.

I ask again Is the coil / plate in the fridge  iced up??? If it is then you need to remove the ice and see if that improves matters.

It's hot, the fridge works hard, it's going to take more power - so look at that angle as well....  

Regardless of it being 12 or 230v (or make for that matter) good ventilation / air circulation  is essential. I've cut several 50mm holes in the floor behind the fridge and have a 100mm ?  12v computer fan extracting warm air. Mine is manually controlled (the fridge is 230v) and when I switch it on the air coming out of the grille is initially warm but cools down proving it's doing some good. So far as I can determine the fan uses about .2 of an amp when running, less than 5 amps a day were it to run 24/7  

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1 hour ago, OldGoat said:

I've written here  before - but perhaps not dogmatically enough - in circumstances like these (or indeed in all circumstances) where more power is required from the main alternator fit a cogged belt rather than a straight V- belt. They're more flexible, wont load the bearings as much, only cost a little bit more and last and last and last.

It's not what the establishment says so I suspect I'll get shouted down....

Not by me you wont, I say its vital.

 

Inland boats tend to have the smallest alternator pulley the supplier can get and cogged/toothed belts will drive well on far smaller diameters than plain belts. its just common sense.

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Just re checked everything I think, belt is notched tightened it up a bit didn't need much, if any, checked connections all clean & tight. Did find wire from alternator to diode has been spured off for rev counter but someone has connected the thin wire to the alternator & spured off the thicker wire. Could that create the problem, I am going to replace the thick wire then spur off the thin rev counter wire, if all that makes sense, out shopping now will try sending pic when I get back. Cheers

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51 minutes ago, oats said:

Just re checked everything I think, belt is notched tightened it up a bit didn't need much, if any, checked connections all clean & tight. Did find wire from alternator to diode has been spured off for rev counter but someone has connected the thin wire to the alternator & spured off the thicker wire. Could that create the problem, I am going to replace the thick wire then spur off the thin rev counter wire, if all that makes sense, out shopping now will try sending pic when I get back. Cheers

 

So you have a slit charge diode. If its a simple passive one than you automatically loose around half a volt or so of charging voltage. That needs addressing. I would suggest by fitting a Voltage Sensitive Relay but you will need to rewire the alternator output to the domestic bank and connect the  sense side of the VSR to the same bank.

 

However 13 volts plus half a volt or so does not get you to 14V +

 

I don't understand the bit about the rev counter. The revcounter is normally fed  from the ignition switch for the 12V+ supply and the W terminal on the alternator (phase tap) for the pulses. It has nothing to do with the  main B+ terminal.

 

Could your supposed rev counter feed be for a split charge relay?

 

If you ave a split charge diode then a thick wire should run from the alternator B+ terminal to one diode terminal and nothing else.

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20 minutes ago, Tony Brooks said:

 

So you have a slit charge diode. If its a simple passive one than you automatically loose around half a volt or so of charging voltage. That needs addressing. I would suggest by fitting a Voltage Sensitive Relay but you will need to rewire the alternator output to the domestic bank and connect the  sense side of the VSR to the same bank.

 

However 13 volts plus half a volt or so does not get you to 14V +

 

I don't understand the bit about the rev counter. The revcounter is normally fed  from the ignition switch for the 12V+ supply and the W terminal on the alternator (phase tap) for the pulses. It has nothing to do with the  main B+ terminal.

 

Could your supposed rev counter feed be for a split charge relay?

 

If you ave a split charge diode then a thick wire should run from the alternator B+ terminal to one diode terminal and nothing else.

Ah I'm really confused the very old grey matter not working. I assumed the thin wire going into a loom was rev counter oops. Hopefully I'll send a picture. Don't understand electrical, OK with mechanical. Cheers

1530535182640795127741.jpg

23 minutes ago, Tony Brooks said:

 

So you have a slit charge diode. If its a simple passive one than you automatically loose around half a volt or so of charging voltage. That needs addressing. I would suggest by fitting a Voltage Sensitive Relay but you will need to rewire the alternator output to the domestic bank and connect the  sense side of the VSR to the same bank.

 

However 13 volts plus half a volt or so does not get you to 14V +

 

I don't understand the bit about the rev counter. The revcounter is normally fed  from the ignition switch for the 12V+ supply and the W terminal on the alternator (phase tap) for the pulses. It has nothing to do with the  main B+ terminal.

 

Could your supposed rev counter feed be for a split charge relay?

 

If you ave a split charge diode then a thick wire should run from the alternator B+ terminal to one diode terminal and nothing else.

Ah I'm really confused the very old grey matter not working. I assumed the thin wire going into a loom was rev counter oops. Hopefully I'll send a picture. Don't understand electrical, OK with mechanical. Cheers

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OK so it is a split charge relay 9te black box) and the tap feeds the split charge relay. Nothing much wrong there so we are back to why the low voltage after six hours running.

 

No sign of a revcounter connection on the photo because not enough of the back of the alternator is shown.

 

The little blck box on the end of the alterntor is a radio suppressor.

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3 minutes ago, Robbo said:

That’s a relay.

Thanks I said I'm useless at electrics, I was told it was, so what's a diode look like n where would I find it? Cheers

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