Alternator wiring diagram

[moggyjo]

Sorry Moggyjo, I can't help in any way but I think I know where to come for help when I need it. Those other guys are great.

Yes they have all been absolute stars :cheers:If I took the top off it would of I thought invalidate the guarantee, although I don't know where the reciept is, I can remember more or less exactly when I got them, it was a couple of weeks before Bloxham Steam Rally.I took the photo of the battery yesterday. I can't see a green light on it?

[Sir Nibble]

Yes they have all been absolute stars :cheers:If I took the top off it would of I thought invalidate the guarantee, although I don't know where the reciept is, I can remember more or less exactly when I got them, it was a couple of weeks before Bloxham Steam Rally.I took the photo of the battery yesterday. I can't see a green light on it?

The little round window on top should give a view of a little coloured ball which is a hydrometer itself. They are difficult to see but I am sure I am seeing patches of green reflected in the top. Take a look tourself with a torch, if I am wrong about the green we may hit paydirt.

[Dylan]

My previous batteries batteries looked very similar to the ones in the pic, but with a different sticker. I wasn't impressed I'm afraid, very lazy, didn't last long and I could never get the top off them. The little green window would glow green enthusiastically long after they were cream crackered. I assume this monitors one cell only, and the other five could be dead in theory?

[Sir Nibble]

The little green window would glow green enthusiastically long after they were cream crackered. I assume this monitors one cell only, and the other five could be dead in theory?

Yup, but it's the best we have to go on, and it would be unlikely for batteries to badly sulphate that unevenly.

[moggyjo]

Guy came round today to try and sort out the alternator, he said battery readings were 12.31, 12.31 and 12.72, the alternator was putting out 28amps at middling to low speed, the alternator wire to batteries were quite loose, so he re did them and also the wiring to the fridge was toooo small for the distance, he said it needs to be 10mm multi strand, he tested at the fridge end and it had lost just over 1volt in the distance which he thinks will be the reason the fridge is flashing low voltage uneccesarily. He did not know why the ignition light did not go out, so I still have that problem.

[Sir Nibble]

Guy came round today to try and sort out the alternator, he said battery readings were 12.31, 12.31 and 12.72, the alternator was putting out 28amps at middling to low speed, the alternator wire to batteries were quite loose, so he re did them and also the wiring to the fridge was toooo small for the distance, he said it needs to be 10mm multi strand, he tested at the fridge end and it had lost just over 1volt in the distance which he thinks will be the reason the fridge is flashing low voltage uneccesarily. He did not know why the ignition light did not go out, so I still have that problem.

That is most interesting, 28A but the light doesn't go out, hmmm. The underspec wiring certainly explains the fridge alarm but not why the battery voltage drops to 11ish after a short while. Less than 10A charge per battery is low if they are discharged, I still suspect them. Is the alternator new?

[Chris Pink]

He did not know why the ignition light did not go out, so I still have that problem.

 

Have you tried revving the engine up as high as it will go (briefly) to see if that makes the light go out?

[moggyjo]

Have you tried revving the engine up as high as it will go (briefly) to see if that makes the light go out?

yes

[Chris Pink]

battery readings were 12.31, 12.31 and 12.72

 

 

The battery readings are not that bad really, was that before or after charging? If there was loose cables it might explain difference between the batteries.

 

So did you understand where to measure them to compare those readings over a period of use?

[moggyjo]

The battery readings were taken lunch time when the batteries were flatish, had not run engine since Tuesday as was out yesterday. Just phoned place where we got alternator, he suggested to try a 5watt bulb instead of the usual 2watt, and thought possibly my engine does not run fast enough to make light go out (old Perkins 315) but to try the bulb first, so just going to go and take the pannel off to see what sort of fitting it is, thankyou for your patience

[Chris Pink]

The battery readings were taken lunch time when the batteries were flatish, had not run engine since Tuesday as was out yesterday. Just phoned place where we got alternator, he suggested to try a 5watt bulb instead of the usual 2watt, and thought possibly my engine does not run fast enough to make light go out (old Perkins 315) but to try the bulb first, so just going to go and take the pannel off to see what sort of fitting it is, thankyou for your patience

 

 

It seems to me that your problem may be practically resolved, the readings are not duff battery readings, although getting the alternator light to go out will result in a higher rate of charge.

 

If you get chance, look into the possibility of getting a larger engine pulley although as pointed out will make water pump go faster so take mechanical advice on this.

 

After charging and letting them rest an hour can you take another reading from the same place as the guy who looked at the alternator? - to see how far they come up after a charge.

 

Fridge - in the winter? Touching on one of my bête-noires there. especially as has been remarked fridges don't like running in cold rooms (!!!). Turn it off until April!

[chris w]

..................... although getting the alternator light to go out will result in a higher rate of charge.

 

If the alternator light doesn't go out you will be getting no charging from the alternator. It won't be due to engine speed but solely lack of sufficient excitation current. Put a 10W, 47 ohm resistor in parallel with the light; that should fix it.

 

Chris

Edited January 17, 2008 by chris w

[Bones]

If the alternator light doesn't go out you will be getting no charging from the alternator. It won't be due to engine speed but solely lack of sufficient excitation current. Put a 10W, 47 ohm resistor in parallel with the light; that should fix it.

 

Chris

 

my alternator light only goes out if i rev the engine..... does revving the engine not result in excitation current? It will stay out if I reduce the engine speed once revving it.

 

Yours, confused of dimitshire

Bones.

[Chris Pink]

If the alternator light doesn't go out you will be getting no charging from the alternator. It won't be due to engine speed but solely lack of sufficient excitation current. Put a 10W, 47 ohm resistor in parallel with the light; that should fix it.

 

Chris

 

Jo stated a charging current of 28A a while back, I had an alternator that would self-excite initially but would put out more when the light went out.

 

Can you safely short circuit the light? I didn't have a light for a long time, simply a switch.

[chris w]

my alternator light only goes out if i rev the engine..... does revving the engine not result in excitation current? It will stay out if I reduce the engine speed once revving it.Yours, confused of dimitshireBones.

 

Revving the engine high will usually produce some excitation current due to there being some residual magnetism in the rotor. Once excited, the light will stay out because the alternator produces its own rotor current once it's been excited. However, you shouldn't need to rev up. It means the lamp is not allowing enough excitation current to flow initially.

 

If you wire a 47 ohm (7 watt) resistor across the lamp it will cure the problem and the lamp will go out immediately the engine starts at idle revs. (from Maplin: 37p part no. L47R) here

 

Chris

 

Jo stated a charging current of 28A a while back, I had an alternator that would self-excite initially but would put out more when the light went out. Can you safely short circuit the light? I didn't have a light for a long time, simply a switch.

 

If you short circuit the lamp, you will create an excitation current that is only limited by the rotor's static resistance. Rotor resistance is typically about 3 ohms so at least 4 amps will flow. Actual excitation current needed is only about 200mA.

 

The issue with shorting it out is that a) you have no indication that charging is taking place and if you inadvertently leave the ignition on, you will be placing a permanent 4A load on your starter battery.

 

Chris

Edited January 17, 2008 by chris w

[Sir Nibble]

Something occurred to me, yesterday someone measured 28A of charge from this alternator into domestic batteries with light on, so how is the split charge relay pulling in then?

Sob, snivell my brain hurts.

[Chris Pink]

Chris

If you short circuit the lamp, you will create an excitation current that is only limited by the rotor's static resistance. Rotor resistance is typically about 3 ohms so at least 4 amps will flow. Actual excitation current needed is only about 200mA.

 

The issue with shorting it out is that a) you have no indication that charging is taking place and if you inadvertently leave the ignition on, you will be placing a permanent 4A load on your starter battery.

 

Chris

 

The reason i asked is that i have a switch on my alternator because the engine is hand start and it takes the alternator load off while i start the engine.

 

I can see from your reply that it would be better to have both switch and light in series.

 

And yes i did leave it on once and flatten the battery.

[moggyjo]

Something occurred to me, yesterday someone measured 28A of charge from this alternator into domestic batteries with light on, so how is the split charge relay pulling in then?

Sob, snivell my brain hurts.

I'm pretty sure the light was out when he got the 28A reading.

Should I go for the 5watt bulb or do what Chris has suggested?

[chris w]

Should I go for the 5watt bulb or do what Chris has suggested?

 

Either method will work perfectly. Take your pick.

 

Chris

[moggyjo]

Either method will work perfectly. Take your pick.

 

Chris

Thanks Chris.

[moggyjo]

Well after nearly a week of connection being tightened up etc, I have to say I don't seem to be getting much more power from the 100ah alternator than I was from the 55ah one and £200 down. Nick went to get a 5watt bulb for ignition lastnight, he said they have a different fitting so didnt get it, would a higher wattage bulb make any difference to power coming out of alternator.

Is it worth getting a drop test done on the batteries?

[chris w]

Well after nearly a week of connection being tightened up etc, I have to say I don't seem to be getting much more power from the 100ah alternator than I was from the 55ah one and £200 down. Nick went to get a 5watt bulb for ignition lastnight, he said they have a different fitting so didnt get it, would a higher wattage bulb make any difference to power coming out of alternator.

Is it worth getting a drop test done on the batteries?

 

A higher wattage bulb will make no difference at all to the power out of the alternator.

 

Once the ignition light is extinguished, the current you get out of the alternator is only dependent on rpm up to the altermator's rated output. Typically at NB revs, you will get a maximum of 60-70% of the alternator's nominal current output. So a nominal 100A alternator will deliver typically about 60-70 amps max at around 1200rpm engine speed (2400rpm alternator speed).

 

Chris

[moggyjo]

A higher wattage bulb will make no difference at all to the power out of the alternator.

 

Once the ignition light is extinguished, the current you get out of the alternator is only dependent on rpm up to the altermator's rated output. Typically at NB revs, you will get a maximum of 60-70% of the alternator's nominal current output. So a nominal 100A alternator will deliver typically about 60-70 amps max at around 1200rpm engine speed (2400rpm alternator speed).

 

Chris

Mine is only putting out just under 30amps, can you think why this is please, Wendy

[Chris Pink]

Mine is only putting out just under 30amps, can you think why this is please, Wendy

 

More a question for Chris than you really but has it been established that there isn't a diode in the charging line?

 

Forgive (ignore) me if I'm going back over old ground but this topic has got too long to completely review!

[chris w]

Mine is only putting out just under 30amps, can you think why this is please, Wendy

 

 

How are you measuring the current (eg: built-in meter or external multimeter)?

 

Chris