A127 Alternator Internals

[BEngo]

Thinking about a home brew Li☆FePo battery install. Key issues are not overloading the alternator and switching it off when battery charged .  I believe the A127 regulator is powered from the internal wire that connects it to the output of 3 field diodes separate from the main 6 output rectification diodes.

Questions:

Is my belief correct?

If so can I effectively switch the alternator OFF  by open circuiting this wire?  Or will residual magnetism continue to produce an unregulated o/p?

If the internal wire is open circuited will this give the field diodes grief, resulting in damaged and loss of magic smoke?

 

 I don't want to change the alternator for anything fancier than an A127, because the whole shebang is Kelvin powered and is about on its practical limits now.  I also don't need more than about 60A on my LA set up.

Thank you for your thoughts.

N

[MoominPapa]

30 minutes ago, BEngo said:

Thinking about a home brew Li☆FePo battery install. Key issues are not overloading the alternator and switching it off when battery charged .  I believe the A127 regulator is powered from the internal wire that connects it to the output of 3 field diodes separate from the main 6 output rectification diodes.

Questions:

Is my belief correct?

If so can I effectively switch the alternator OFF  by open circuiting this wire?  Or will residual magnetism continue to produce an unregulated o/p?

If the internal wire is open circuited will this give the field diodes grief, resulting in damaged and loss of magic smoke?

 

 I don't want to change the alternator for anything fancier than an A127, because the whole shebang is Kelvin powered and is about on its practical limits now.  I also don't need more than about 60A on my LA set up.

Thank you for your thoughts.

N

Yes. The Gibbo-approved method:

 

1) Remove regulator and disconnect spade connector on wire from alternator internals.

2) Insulate or remove wire from alternator internals.

3) Run new wire from spade terminal on regulator to switch or relay contact.

4) Other switch or relay contact connects to D+ terminal (this is one side of the charge light, which is very handy if the switch is on the instrument panel next to the charge light,)

 

I do this with a switch every day to unload the alternator for cold engine start: no problems.

 

It's also worth noting that my A127 can run all day flat out charging LiFePO4 batteries without burning itself out. It's in a well ventilated place in a well ventilated engine room and the drive belt runs around the circumference of a 21" flywheel, so there are plenty of fan revs even at idle.

 

I highly recommend using an adjustable "tractor regulator" with LiFePO4 which allows you to tweak the charge curve to suit.

 

MP.

 

[Tony Brooks]

6 minutes ago, MoominPapa said:

Yes. The Gibbo-approved method:

 

1) Remove regulator and disconnect spade connector on wire from alternator internals.

2) Insulate or remove wire from alternator internals.

3) Run new wire from spade terminal on regulator to switch or relay contact.

4) Other switch or relay contact connects to D+ terminal (this is one side of the charge light, which is very handy if the switch is on the instrument panel next to the charge light,)

 

I do this with a switch every day to unload the alternator for cold engine start: no problems.

 

It's also worth noting that my A127 can run all day flat out charging LiFePO4 batteries without burning itself out. It's in a well ventilated place in a well ventilated engine room and the drive belt runs around the circumference of a 21" flywheel, so there are plenty of fan revs even at idle.

 

I highly recommend using an adjustable "tractor regulator" with LiFePO4 which allows you to tweak the charge curve to suit.

 

MP.

 

Something about this does not ring true. I think the waning lamp would be on all the time the switch is in the charge position because there is no "feed" from the field diodes to put it out and I don't see how connecting the regulator to the warning lamp would provide enough current for maximum output - that is what the field diodes do.

 

Maybe I am misunderstanding what you say.

 

I would start as you describe but at step 4 connect the second relay/switch terminal to the lead from the field diodes that you removed in step 2. This means you will have two wires coming out to the alternator, each connected to one of the relay/switch terminals.

[MoominPapa]

14 minutes ago, Tony Brooks said:

Something about this does not ring true. I think the waning lamp would be on all the time the switch is in the charge position because there is no "feed" from the field diodes to put it out and I don't see how connecting the regulator to the warning lamp would provide enough current for maximum output - that is what the field diodes do.

 

Maybe I am misunderstanding what you say.

 

I would start as you describe but at step 4 connect the second relay/switch terminal to the lead from the field diodes that you removed in step 2. This means you will have two wires coming out to the alternator, each connected to one of the relay/switch terminals.

D+ terminal is connected to the field diodes and the flying lead, so what you suggest is electrically exactly the same as my method.

 

MP.

 

[Sir Nibble]

1 minute ago, MoominPapa said:

D+ terminal is connected to the field diodes and the flying lead, so what you suggest is electrically exactly the same as my method.

 

MP.

 

Yup.

[Tony Brooks]

Except

"4) Other switch or relay contact connects to D+ terminal (this is one side of the charge light, which is very handy if the switch is on the instrument panel next to the charge light,)" which suggested to me that you were talking about the terminal on the alternator side of the warning lamp with the cable it disconnected at the alternator.

 

Agree all fine.

 

[BEngo]

Thank you all.

MP:  My alternator cooling is OK position wise, but as it is on the biggest pulley  I could get on the engine/in the lathe (about 12 in dia vs 2 in on the alt) and there is .no reasonable way to run a belt on the flywheel rim it doesn't spin all that fast so airflow rate is not ideal. Hence I want to be able to turn the wick down if it gets too hot.

 

  I already have the tractor reg mod, but would you suggest using it in the hard wired original form, to adjust the charge voltage once and for all or would  there be mileage  in using the arduino to imitate a pot in the extra wirep according to temperature/state of charge/the price of fish in Grimsby?  What are the usable limits of variation using the tractor reg anyway?   Would it be better to take the job of regulation away from the regulator and use the micro for that as well?

 

I think that what with cell voltages, current measurement and limiting, over voltage shut down, battery and alternator temperature measurement, some sort of display to see what is going on etc, etc. I am going  to run out of IO pins on a single Arduino, even a Leonardo.  As a bit of a beginner, I am not sure I want to try to get my head round using two interconnected micro controllers! 

 

Nor, if it gets complicated, am I sure that I can spot and deal with all the failure cases.

All thoughts welcome.

N

 

[MoominPapa]

24 minutes ago, BEngo said:

 I already have the tractor reg mod, but would you suggest using it in the hard wired original form, to adjust the charge voltage once and for all or would  there be mileage  in using the arduino to imitate a pot in the extra wirep according to temperature/state of charge/the price of fish in Grimsby?  What are the usable limits of variation using the tractor reg anyway?   Would it be better to take the job of regulation away from the regulator and use the micro for that as well?

My system includes an Arduino, but it doesn't have control over the alternator regulator voltage, it's just controlled using a multi-turn pot. This was a deliberate decision to reduce complexity and possible failure modes. The tractor regulators have a fairly soft regulation characteristic: instead if dramatically reducing the output current as the voltage reaches the limit, they start to reduce the output at about 0.6v below the final voltage and reduce it more as the voltage approaches the limit. In my case the current starts to fall from about 75% charged. In some ways this is a disdavantage - LiFePO4 can charge faster if you keep the current up almost to 100%. It does have advantages though - the control loop is stable and doesn't oscillate, which I have seen with some A127 regulators. That would be bad, as the instantaneous cell voltage matters with LiFePO4 cells. It also makes detecting charge termination via voltage and current limits rather more stable. I have considered revising the system to give the Arduino control, but on balance I thing it's best the way it is. For a first iteration I'd certainly do it without Arduino control apart from on/off to handle charge termination and alternator overheat.

 

24 minutes ago, BEngo said:

I think that what with cell voltages, current measurement and limiting, over voltage shut down, battery and alternator temperature measurement, some sort of display to see what is going on etc, etc. I am going  to run out of IO pins on a single Arduino, even a Leonardo.  As a bit of a beginner, I am not sure I want to try to get my head round using two interconnected micro controllers! 

My system uses a Leonardo and has five single-ended analog channels of voltage measurement, four for temperature and a differential pair for current.  That's close to the limit for analog. Digital IO pins are easy to add using an i2c extender or 74HC595 shift register. Use a an OLED display on i2c for minimal pin count on that.

 

MP.

 

[nicknorman]

As a quick and dirty means of avoiding alternator over temperature, how about restricting the maximum field (rotor) current by means of a resistor between the regulator and the brush? It would perhaps be 2 ohms, but would have to be high wattage, say a 50w wirewound for safety. By limiting the maximum field current, you limit the maximum output current at lower rpm when the cooling is poor, whilst still allowing plenty of output at higher rpm when the cooling is better. I think this would cause some regulation droop in the output voltage but perhaps that is not a bad thing for LiFePO4 batteries.

 

This is the technique I am employing with my smart regulator project, the chip can be sent a parameter which is the maximum field current limit, (which will be set depending on alternator temperature) so the regulator would behave normally until the max field current limit is reached, then the voltage will droop as the maximum output current for the rpm and field current combination is reached. I think this is a better technique to deal with over temperature, rather than reducing the regulation voltage set point, as it takes into account alternator speed and hence cooling fan speed.

[Sir Nibble]

If you want to de-rate an A127 you could just drop a lower output stator in. They come in 45, 55, 65 and 70A.

[AndrewIC]

This video shows a tear down of an A127: 

 

[MoominPapa]

2 hours ago, Sir Nibble said:

If you want to de-rate an A127 you could just drop a lower output stator in. They come in 45, 55, 65 and 70A.

Is there a way to tell, by inspection, what stator is fitted?

 

MP.

[Sir Nibble]

7 minutes ago, MoominPapa said:

Is there a way to tell, by inspection, what stator is fitted?

 

MP.

Bung 12V across any two phases and measure the current. In the old days Lucas used different colour varnish but I wouldn't give that any credence now.

[MoominPapa]

4 minutes ago, Sir Nibble said:

Bung 12V across any two phases and measure the current. In the old days Lucas used different colour varnish but I wouldn't give that any credence now.

At room temp? The maximum output I see drops as the alternator heats up, which I've assumed is increased resistance in the stator and/or field. I guess the same effect would affect this measurement?

 

MP.

[Sir Nibble]

14 minutes ago, MoominPapa said:

At room temp? The maximum output I see drops as the alternator heats up, which I've assumed is increased resistance in the stator and/or field. I guess the same effect would affect this measurement?

 

MP.

It only takes a moment and is not going to be bang on. It's an indication that's all. 

[WotEver]

1 hour ago, AndrewIC said:

This video shows a tear down of an A127: 

 

I note that Paddy didn’t address the buggered front bearing...

[MtB]

Just now, WotEver said:

I note that Paddy didn’t address the buggered front bearing...

 

I was particularly impressed with his train wreck of a soldering iron!

 

 

[Tony Brooks]

 I agree if you are referring to the build up of oxide and gross lack of tip cleaning but if you are referring to size then I tend to disagree. I have found more damage is done by people using tiddly little irons that hold very small amounts of heat (note heat not temperature) that using a great big iron. from choice I would use a 1 lb or larger iron with a long fine tip. This heats the solder pad almost instantly so its off before the heat has melted insulation or travelled down into the diode although I suspect this was more of a problem on the ACRs and those with "electronic" style field diodes.

[WotEver]

12 minutes ago, Mike the Boilerman said:

 

I was particularly impressed with his train wreck of a soldering iron!

 

 

Agreed. 
 

 

2 minutes ago, Tony Brooks said:

I agree if you are referring to the build up of oxide and gross lack of tip cleaning

I certainly am. 
 

 

2 minutes ago, Tony Brooks said:

I have found more damage is done by people using tiddly little irons that hold very small amounts of heat

Yup, you need good thermal mass. I still have my dad’s ‘small’ soldering iron that he used to heat up on the gas hob. 

[MtB]

5 minutes ago, Tony Brooks said:

I agree if you are referring to the build up of oxide and gross lack of tip cleaning

 

Yep. 

 

And yes an appropriately sized iron always makes soldering a pleasure. 

 

 

[Sir Nibble]

1 hour ago, WotEver said:

I note that Paddy didn’t address the buggered front bearing...

They're crimped in. They can be pressed out and I have seen loads of replacements not held in place by loctite or with a retaining plate screwed on allowing enough axial movement for the shoulder on the slip ring to collide with the brush holder. I press the replacement in then machine the surrounding metal away to bring it flush with the outer race then secure it with 5mm screws.