Charging system weak...

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MexicoMike

MexicoMike

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Just discovered today that my charging system - Alton 150W/Podtronics single phase - is not putting out much charging voltage. Needs to get to nearly 3k RPM to hit 13V and if I turn on the headlight it will never get to 13.

When I installed the Alton it was putting out 13+v at 1500 RPM and around 15 at 3k and was able to charge the batt with the headlight on with no problem above 2kRPM. That was through a Lucas rectifier/Zeners. I'm sure I checked the voltage when I converted to the Podtronics a few years ago but I don't remember any figures. If the voltage numbers had been like the figures I'm seeing today I would not have installed it.

Anyway, today I checked the alternator and it was putting out over 20VAC at 2k RPM, increasing as RPM went up, so I'm looking at the Pod. Seems logical to me that if the alternator has plenty of suds but there isn't much going to the batt, that the Pod is the problem.

I guess I could reinstall the old Lucas Rectifier and see how that works but I hate to drill a hole in the CNW rearset to accommodate the zener!

Any thoughts? Would the Zener be OK just hanging out in the air for long enough to see if the voltage improves with the Lucas?
 
MexicoMike said:
Just discovered today that my charging system - Alton 150W/Podtronics single phase - is not putting out much charging voltage. Needs to get to nearly 3k RPM to hit 13V and if I turn on the headlight it will never get to 13.

When I installed the Alton it was putting out 13+v at 1500 RPM and around 15 at 3k and was able to charge the batt with the headlight on with no problem above 2kRPM. That was through a Lucas rectifier/Zeners. I'm sure I checked the voltage when I converted to the Podtronics a few years ago but I don't remember any figures. If the voltage numbers had been like the figures I'm seeing today I would not have installed it.

Anyway, today I checked the alternator and it was putting out over 20VAC at 2k RPM, increasing as RPM went up, so I'm looking at the Pod. Seems logical to me that if the alternator has plenty of suds but there isn't much going to the batt, that the Pod is the problem.

I guess I could reinstall the old Lucas Rectifier and see how that works but I hate to drill a hole in the CNW rearset to accommodate the zener!

Any thoughts? Would the Zener be OK just hanging out in the air for long enough to see if the voltage improves with the Lucas?
Click to expand...

I don't remember where I got it but I've attached a file. How you read the voltage makes a big difference. An analog AC meter will probably read differently than a digital, and loaded or open makes a difference, and the only way to actually know the peak voltages is an oscilloscope. At any rate, the output of your stator seems quite low if you're checking with it disconnected.

Yes, the Zener can take a few minutes without the heatsink - just make sure it doesn't get to hot too touch.
 

Attachments

My digital meters won't work properly with the engine running. They give very erratic readings.
It seems there is too much RF interference.
The analog meter appears to work properly. It gives voltage readings similar to the installed Sparkbright voltage monitor.

Glen
 
worntorn said:
My digital meters won't work properly with the engine running. They give very erratic readings.
It seems there is too much RF interference.
The analog meter appears to work properly. It gives voltage readings similar to the installed Sparkbright voltage monitor.

Glen
Click to expand...

I rarely use digital meters for anything automotive. Even without noise problems, to get a alternator output reading stable enough to read you would need to keep the engine RPM very stable. At least with an analog meter you can see it jumping around a point and average it in your head. Even measuring the output from the rectifier or PODtronics often is hard with a digital meter, again because it doesn't stay stable long enough for the meter to sample.
 
Thanks for the data - interesting stuff! Since I'm using a Fluke DMM as opposed to an analog meter, I think I'll go ahead and substitute the Lucas rectifier/Zener and take another voltage reading at the battery. If there's no improvement, I'll look more into the stator though I did check it for continuity/shorts and it checks OK. I have an old VTVM that I use for working on vintage ('60s and earlier) tube (valve) equipment. Unfortunately, it's in the US and the Norton and I are in Mexico.
 
No, I removed the Cap some years back...

One question...My Lucas rectifier is for the 180W three phase Lucas alternator that was in the bike pre-Alton. So it has three input connecting points for the alternator while my Alton single phase alternator has two outputs. If I connect the alton to two of the inputs on the rectifier, will the rectifier function? This is another of those "I can't remember what I did" things. I BELIEVE I had the Alton running with that rectifier before I purchased the Pod but maybe I'm mis-remembering. Heck it was eight years ago! ;)

Also, I never thought about an AC voltage component being present in the output of a regulator/rectifier. I've always assumed there shouldn't be any. Is there some amount that is normal/acceptable?
 
MexicoMike said:
No, I removed the Cap some years back...

One question...My Lucas rectifier is for the 180W three phase Lucas alternator that was in the bike pre-Alton. So it has three input connecting points for the alternator while my Alton single phase alternator has two outputs. If I connect the alton to two of the inputs on the rectifier, will the rectifier function? This is another of those "I can't remember what I did" things. I BELIEVE I had the Alton running with that rectifier before I purchased the Pod but maybe I'm mis-remembering. Heck it was eight years ago! ;)

Also, I never thought about an AC voltage component being present in the output of a regulator/rectifier. I've always assumed there shouldn't be any. Is there some amount that is normal/acceptable?
Click to expand...

I can't find a schematic of the Lucas 3-phase rectifier so I'm not sure on your first question. I'm guessing that you can use two of the three input terminals and if there is no output, move one stator wire to the other input terminal.

A bridge rectifier does not actually convert AC to smooth DC, it turns the negative component of the signal positive. Then the regulator (Zener) lops off any part higher than the desired charging voltage (red line). So, the voltage is still going from 0 to the charging voltage at twice the AC frequency (for single-phase). Finally the capacitor and/or battery smooths it out.

Charging system weak...


BTW, none of this is perfect like the picture. There are all kinds of eddy currents, spikes, delay times, voltage overshoots, etc. so if you were looking at an o-scope output it would look quite a bit more messy. ​
 
MexicoMike said:
No, I removed the Cap some years back...

One question...My Lucas rectifier is for the 180W three phase Lucas alternator that was in the bike pre-Alton. So it has three input connecting points for the alternator while my Alton single phase alternator has two outputs. If I connect the alton to two of the inputs on the rectifier, will the rectifier function? This is another of those "I can't remember what I did" things. I BELIEVE I had the Alton running with that rectifier before I purchased the Pod but maybe I'm mis-remembering. Heck it was eight years ago! ;)

Also, I never thought about an AC voltage component being present in the output of a regulator/rectifier. I've always assumed there shouldn't be any. Is there some amount that is normal/acceptable?
Click to expand...

A legit lucas 3 phase rectifier has 6 diodes and using only 4 for a two lead input will work. You still need a zener to control max voltage to 14.3v. A capacitor would be very beneficial as an efficiency booster while charging up to the max allowed by the zener.
The MKIII system with a 2 diode rectifier and 2 zeners acting as regulator AND rectifier is OK as well.
I have used a podtronics and find it not so good unless a capacitor is used.

If the magnets of the alton rotor have decreased, the power output will go downward also.
The wave shapes shown above are for "no load" output and is not what is really seen in the system, especially if you added a cap.
 
I hooked up the Lucas rectifier and the output voltage to the batt was a couple tenths of a volt higher but not anywhere close to what I had measured years ago when I installed the Alton.

BUT at that time I had the Trispark whereas this time I had the OEM ignition, which I had just reinstalled a few days ago for "curiosity purposes." I wondered if that was the difference. So I decided to UNINSTALL the OEM ignition and put the TriSpark back in. What do you know, charge voltage to the batt jumped dramatically, back up to 13+ at idle with either the Pod or the Lucas. So that ended my temporary experiment with the OEM ignition. ;)
 
you still have a week charging system. it is just masked with the trispark. think about it, the stock system was only rated at 120 watt and your alton is supposed to be 150 but the stock system did work on an all stock bike.
 
I suppose the charging system could be weak but I can't see where that "weakness" is. The alternator hasn't changed and it checks OK. The Podtronics checks OK and substituting the Lucas Rectifier/Zener doesn't make a noticeable difference. I opened/cleaned/remade all wiring connections related to the charging/ignition system and there was no change in output. I'm continuing to investigate...
 
The alternator output is entirely based on RPM. 0 to 120 watt @ "X" rpm. It has a variable source impedance.
If at 3000 rpm there is "NO LOAD" it will make lots of voltage since the "current draw" is ZERO.
It is capable of "Y" watts and based upon any load (average resistance) lights or ignition, the current (times) voltage is the watts.
I would fully expect a points/coil with an average higher current draw to pull down the voltage compared to the average lower current draw of the TS yielding a higher residual voltage.
At 3000 rpm the watts potential from the alternator is constant. The battery (and light bulbs) do not like high voltage and thus we add a zener and waste the excess wattage starting @ 14.3 volts.
http://atlanticgreen.com/images/zener.gif
 
MexicoMike said:
I suppose the charging system could be weak but I can't see where that "weakness" is. The alternator hasn't changed and it checks OK. The Podtronics checks OK and substituting the Lucas Rectifier/Zener doesn't make a noticeable difference. I opened/cleaned/remade all wiring connections related to the charging/ignition system and there was no change in output. I'm continuing to investigate...
Click to expand...
Did you come to any conclusion with this?
 
marshg246 said:
I rarely use digital meters for anything automotive. Even without noise problems, to get a alternator output reading stable enough to read you would need to keep the engine RPM very stable. At least with an analog meter you can see it jumping around a point and average it in your head. Even measuring the output from the rectifier or PODtronics often is hard with a digital meter, again because it doesn't stay stable long enough for the meter to sample.
Click to expand...
Re; "to get a alternator output reading stable enough to read you would need to keep the engine RPM very stable."
that is the only way to read the output of an alternator IMO. the REG/REC balances the out put to the load according to the engine revs, revving the engine up and down doesn't give you a stable reading at any time!!!!

Also clean the earth wire to the frame-it can make a difference if you have any corrosion.
 
baz said:
Did you come to any conclusion with this?
Click to expand...

Only that the standard ignition uses more power than an electronic so there is less power available for charging. But when you consider that these charging systems were known to have limited power at the time - think of all the riding at night Lucas jokes - frankly, I think the performance is normal and it's why Lucas came out with a 180W three phase alternator in the late 70's. If I decided to run the OEM ignition permanently, then the Shorai battery definitely would not be compatible because there is definitely not enough power available to run the stock ignition and keep a Shorai at a minimum acceptable charge level.
 
Re;"these charging systems were known to have limited power at the time - think of all the riding at night Lucas jokes - frankly, I think the performance is normal and it's why Lucas came out with a 180W three phase alternator in the late 70's"

This may be true but most Brit bikes when the Lucas Alternator came out had a magneto for ignition, so needed no charge from the battery at all.
 
I think the ballast resistor is the big power draw with the OEM ignition. On my Norton, with the resistor in the circuit, the charge voltage basically drops by one volt throughout the rev range. IOW, a decent charge rate of, say 13.4 at 1500 RPM without the resistor becomes 12.4 with it, which is discharging the battery.
 
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