Alternator wiring diagram

[moggyjo]

No, the bulb wattage will effect cut in speed but not output. I would expect that a voltage of 13.8V applied to a discharged 100Ah battery would push a current of around 20A, (Chris will be along in a moment to calculate it exactly for us). This is where I am having difficulty, If your battery is discharged, and the terminal voltage is reaching 13.8V, and this results in a charge of only 0.5A the only logical conclusion is really spectacularly knackered batteries. If this was correct, then the alternator should be driving up to it's regulated voltage which I cannot immediately quote with any certainty but should be significantly over 14V. This is where the problems arise, each reading gives the lie to the others, I really wish I had the time to come and look at this!!!

 

Go back to the meter, read the voltage at the alternator output, engine battery and domestic battery, let's see what difference, if any there is.

Sorry to be a pain Snibble but do I test them with engine running and ignition light off, if so I need to find a bit of wire to cross the B+ and D+ this scares me a bit to do this, it is quite safe to do that I hope!!!!!!

[Keeping Up]

Just a random thought, on the basis that if things don't seem to make sense, think laterally: picking up on the poiint that "Batteries as flat as pancakes and this was almost as soon as I turned the engine off" is there a possibility that the voltmeter and ammeter are correctly displaying the voltage and charging-current of the starter battery rather than the domestic battery, and that the real problem lies in the split-charge relay?

 

The voltage readings quoted in SNibble's last post should settle that point (though Snibble you didn't state whether the engine should be running or not)

[Sir Nibble]

Just a random thought, on the basis that if things don't seem to make sense, think laterally: picking up on the poiint that "Batteries as flat as pancakes and this was almost as soon as I turned the engine off" is there a possibility that the voltmeter and ammeter are correctly displaying the voltage and charging-current of the starter battery rather than the domestic battery, and that the real problem lies in the split-charge relay?

 

The voltage readings quoted in SNibble's last post should settle that point (though Snibble you didn't state whether the engine should be running or not)

Yes indeed, that is one possibility which these tests would highlight.

Sorry to be a pain Snibble but do I test them with engine running and ignition light off, if so I need to find a bit of wire to cross the B+ and D+ this scares me a bit to do this, it is quite safe to do that I hope!!!!!!

Yes, 'fraid so.

I'm sorry, I can't give a truly definative answer to that, but the tests I've been able to do at this end suggest that it is. It's been done once already so what's to loose? Make the contact as brief as you can.

[moggyjo]

just got up and tested the batteries they read 12.27.

All I had on yesterday was the tv for about 10 mins while putting it on wall to test speakers and lights for no more than a hour and my digital radio for about 5 mins this morning. I have not put the fridge on yet, I'll put it on now but suspect it will drain the batteries will test again in a hour.

[moggyjo]

just got up and tested the batteries they read 12.27.

All I had on yesterday was the tv for about 10 mins while putting it on wall to test speakers and lights for no more than a hour and my digital radio for about 5 mins this morning. I have not put the fridge on yet, I'll put it on now but suspect it will drain the batteries will test again in a hour.

fridge been on a hour, battery now reading 12.09

[moggyjo]

Results of testing battery every hour with Fridge, laptop and radio on.

 

 

9.30am 12.27

12.09

12.18

12.18

12.06

11.85

3.30pm 11.74

Fridge light has still not come on but will have to run engine and will still have to touch the B+ & D+ to get light to go out thats a hassle to do

[Sir Nibble]

OK, your alternator was not charging, now it is. The voltages you quoted me by pm for "on charge" are good, and really you cannot ask more from the alternator than that. If the current is low despite healthy voltages then that clearly speaks of high battery resistance or severe sulphation. The battery voltages you quote above say "Flat". I think it's time for a review of what we know. I am going to pm Chris W for an opinion.

[Sir Nibble]

B+ & D+ to get light to go out thats a hassle to do

You could do that by shorting across the warning light at the panel if it's easier.

[moggyjo]

Tested alternator when firing up engine and it says 14.51.

Does it matter if the batteries in the amp metyer are a bit low, will it give a true reading?

[Sir Nibble]

Tested alternator when firing up engine and it says 14.51.

Does it matter if the batteries in the amp metyer are a bit low, will it give a true reading?

14.5 V is plenty, healthy discharged batteries with that sort of voltage shoved across them should be soaking up the current like a sponge. I would say that if the meter batteries are "a bit low" it should still read as accurately as ever, but your 15A max instrument is not the sort of kit to measure the output of a big alternator. Let it charge for as long as you reasonably can, you may find that the batteries wake up and begin to take more current.

[smileypete]

Tested alternator when firing up engine and it says 14.51.

Does it matter if the batteries in the amp metyer are a bit low, will it give a true reading?

 

Do the batteries under charge read a very similar voltage?

 

If not there's a poor connection somewhere. If you have a spit charge relay they're a prime supect for failing.

 

cheers,

Pete.

[moggyjo]

Do the batteries under charge read a very similar voltage?

 

If not there's a poor connection somewhere. If you have a spit charge relay they're a prime supect for failing.

 

cheers,

Pete.

Hi Pete,

The battery reeding after turning off the engine that was running for about 4 hours was 12.66 and yes there is a split charge relay.

[smileypete]

Hi Pete,

The battery reeding after turning off the engine that was running for about 4 hours was 12.66 and yes there is a split charge relay.

 

Hi,

 

What would be helpful to know is a reading of the voltage across the domestic battery +/- terminals not long after the engine is started but while the engine is running. Ideally this should be done when the domestic battery is partly flat and needs some charging.

 

Then at the same time take a reading of the voltage across the starting battery +/- terminals.

 

They should be pretty well identical, if not the split charge relay could be faulty or a connection to it could be poor.

 

cheers,

Pete.

Edited January 14, 2008 by smileypete

[moggyjo]

Hi,

 

What would be helpful to know is a reading of the voltage across the domestic battery +/- terminals not long after the engine is started but while the engine is running. Ideally this should be done when the domestic battery is partly flat and needs some charging.

 

Then at the same time take a reading of the voltage across the starting battery +/- terminals.

 

They should be pretty well identical, if not the split charge relay could be faulty or a connection to it could be poor.

 

cheers,

Pete.

Hi Pete, I did this test yesterday and the leisure and starter batteries both read around 14.60

[smileypete]

Hi Pete, I did this test yesterday and the leisure and starter batteries both read around 14.60

 

That sounds great.

 

It could well be the leisure batteries are kaput, as Snibble says.

 

If they have removable filler caps it might be worth checking the fluid level in them is above the 'plates' (wear eye protection and old clothes).

 

The voltage on the batteries shouldn't drop below roughly 12.2V before charging.

 

If properly charged new ones do this then it's likely the battery bank likely needs to be bigger or charged more often.

 

cheers,

Pete.

[Sir Nibble]

I have had an opinion from Chris, I am sure he won't mind me quoting it in full so I will.

I agree with you (with one proviso - see below). The leisure batteries are shot. The alternator is giving out a healthy voltage. One other thought, the leisure battery charger could be u/s. One test would be to charge the leisure batteries from the alternator for say 3 hours and see if that lifts their voltage. If not they're definitely cream-crackered. If they start to look better, I would suspect the mains charger is on the blink.

I would like to know how you are measuring the charge current.

In addition, why did you change the alternator in the first place? were your batteries spending lots of time flat?

[moggyjo]

I have had an opinion from Chris, I am sure he won't mind me quoting it in full so I will.

 

I would like to know how you are measuring the charge current.

In addition, why did you change the alternator in the first place? were your batteries spending lots of time flat?

The batteries are about a year old 3x1000ah since getting the new tv, I was finding that I was having to charge the batteries every day for at least 8 hours turning engine off at around 9 or 10 at night, TV off at around 11pm only to find in the morning batteries down to 11. something and every now and again the inverter would blow a fuse, either in it or at the 240 plug.

I'm measuring the charge current on that setting I showed you 20v, across the batteries when I turned engine off last night after 4 hours was 12.66,

Wendy

[Sir Nibble]

You are measuring the battery voltage, earlier on you stated that the alternator was making only half an amp, how did you measure that. The duty cycle you describe for your batteries, especiall the down to 11V bit looks like a recipe for sulphation, which would explain what we are seeing now.

[smileypete]

Another way to find out what's going on with the batteries would be to check them with a hydrometer after a good charge.

 

cheers,

Pete.

[moggyjo]

You are measuring the battery voltage, earlier on you stated that the alternator was making only half an amp, how did you measure that. The duty cycle you describe for your batteries, especiall the down to 11V bit looks like a recipe for sulphation, which would explain what we are seeing now.

my friend used a amp meter, (the type off of the dashboard with 2 wires onto the split charge relay nuts.

What is sulphation, is it furring up of the plates?

[Sir Nibble]

my friend used a amp meter, (the type off of the dashboard with 2 wires onto the split charge relay nuts.

What is sulphation, is it furring up of the plates?

my friend used a amp meter, (the type off of the dashboard with 2 wires onto the split charge relay nuts.

With the relay disconnected? If he did this with the relay closed then you have measured the losses rather than the charge.

What is sulphation, is it furring up of the plates?

Yes, it is where the sulphur in the sulphuric acid electrolyte combines with the lead in the plates to form a coating of lead sulphate which "masks" the sulphated area from the electro chemical action and thereby the battery looses capacity.

Edited to agree with Pete, if you are able, a hydrometer test of the batteries would be very useful, just after charge for preference.

Edited January 15, 2008 by snibble

[smileypete]

Some info on how to use a hydrometer here:

 

http://www.canalworld.net/forums/index.php...p;hl=hydrometer

 

Edited to say:

 

If the batteries are right under the deck it may be impractical to use a hydrometer, as they're usually about a foot long so that much space is needed.

 

Edit 2:

 

A hydrometer can usually be had quite cheaply from a car accessories/parts place, it looks like a giant pipette with a float in it.

 

cheers,

Pete.

Edited January 15, 2008 by smileypete

[moggyjo]

just been told the split charge relay resistance was less than one tenth omes when closedits just been sugested to charge the batterys for a hour, then disconnect all the positives and then straight away test them with the meter then leave them for a hour and then re test to see if they all read the same, then connect my telly to one battery take reading then the other etc to see if they still read the same, if not they are nackered, is this right?

[smileypete]

just been told the split charge relay resistance was less than one tenth omes when closed

 

Doesn't really tell us much as zero ohms would be great and one tenth of an ohm far too much.

 

I would do the test I outlined in post #63, exactly as stated.

 

If a half flat battery goes straight to 14.6v while being charged from an engine at idle, it tends to suggests the battery is kaput,

 

A good way to confirm this is by checking it with a hydrometer.

 

cheers,

Pete.

[Sir Nibble]

just been told the split charge relay resistance was less than one tenth omes when closedits just been sugested to charge the batterys for a hour, then disconnect all the positives and then straight away test them with the meter then leave them for a hour and then re test to see if they all read the same, then connect my telly to one battery take reading then the other etc to see if they still read the same, if not they are nackered, is this right?

This suggestion is an attempt to apply a sort of flint axe discharge test to the batteries individually to see if any of them are still ok. One reading lower than the rest would point a finger at that battery, but since they have spent their lives connected they are unlikely to differ by much. All reading the same means they are all equal, and that could be equally knackered as well as equally good.

 

If a half flat battery goes straight to 14.6v while being charged from an engine at idle, it tends to suggests the battery is kaput,

 

A good way to confirm this is by checking it with a hydrometer.

I would be careful with this, the undefinable extra input to any test of experience is absent here, and I for one would not like to make too much of this without an alternator output graph and knowledge of the alternator shaft speed during test. I really suspect BIG TIME that the batteries are an ex parrot. Any chance of borrowing some to test? Even one would do.

Edited January 15, 2008 by snibble