Capacitor, keep or remove?

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Danno said:
The cap sends a charge into the windings of the stator to excite the coils and produce current, just as a good battery does. If your setup has an inline capacitor, the blue can is just excess weight.
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Hi Danny,
I don’t understand your thoughts.
I assumed that because our bikes had permanent magnets in the rotor, unlike car alternators that have windings energised through slip rings and brushes, that it didn’t require an exciter current to initiate charging. In other words I thought our puny alternators would charge from a flat battery.
My Commando with Boyer ignition will start with a very flat battety
All very interesting
al
 

2MC Capacitor & Lecky IGN

GDay Folks, Most Commando owners will be aware that out of the factory the bike (MKIII 850 in my case) was fitted with a Lucas 2MC capacitor, designed to get the bike going if you've been daft enough to flatten the battery. My question is simply how can this function be maintained when most of...
www.accessnorton.com www.accessnorton.com
 
L.A.B. said:

2MC Capacitor & Lecky IGN

GDay Folks, Most Commando owners will be aware that out of the factory the bike (MKIII 850 in my case) was fitted with a Lucas 2MC capacitor, designed to get the bike going if you've been daft enough to flatten the battery. My question is simply how can this function be maintained when most of...
www.accessnorton.com www.accessnorton.com
Click to expand...

That thread was hard to understand so will ask for the other electrically challenged folk (or I might be alone ?)

You have a Pazon (or something similar) ignition, more modern R/R and can keep the blue 2MC can wired into the loom ?.

You get a flat battery, then what ?
Disconnect the battery ? (I thought that was bad for the alternator with the engine running ?) then kick the bike over ?
What do you do when the engine starts off the 2MC regarding the battery ?
Or does the battery flatness come in to play.

I seem to remember one Triumph TR5T had a bad battery but just turned the ignition on and a few kicks later it fired up (same 2MC and charging system as a Commando)
It would be good to know the official procedure if a flat battery was encountered (in layman's terms)

Some of the posts seem to suggest the 2MC is doing other things when the engine is running.
 
The cap should start the bike if the battery doesn't have a short, or you run without a battery. If the cap is in good condition it may take a few kicks to get it charged up. Virtually all caps have a leak down rate; the better the cap the lower leak down rate. The batter acts as ballast and to some degree acts like a cap.

Having a properly speced battery and a cap is a good combination. The cap will make an output when it sees a change in system voltage such as when a directional is switched on or when you switch the headlight beam up or down or when the brake light is engaged. For those of you that have ammeters you will see the needle fluctuate much less when a cap is part of the harness; a good cap will mello, if not eliminate, flickers in the headlight at low RPM.

DynoDave can tell you a lot more the benefits or drawbacks. My vote is to have both.

Best.
 
Alan L said:
Hi Danny,
I don’t understand your thoughts.
I assumed that because our bikes had permanent magnets in the rotor, unlike car alternators that have windings energised through slip rings and brushes, that it didn’t require an exciter current to initiate charging. In other words I thought our puny alternators would charge from a flat battery.
My Commando with Boyer ignition will start with a very flat battety
All very interesting
al
Click to expand...
The stator needs a current to begin putting out it's own. Normally the battery supplies this, but in the event of a dead battery, the capacitor shoots just enough current into the system to excite the coils and get current output rolling.
 
Danno said:
The stator needs a current to begin putting out it's own. Normally the battery supplies this, but in the event of a dead battery, the capacitor shoots just enough current into the system to excite the coils and get current output rolling.
Click to expand...
No. A permanent magnet alternator does not need excitation current.
 
"It acts as a filter for noise spikes."

What do "noise spikes" do in this application? I removed the capacitor in '08 and have never seen any sort of issues - headlight flicker or any other indication of voltage variation other than the normal increase in charging system voltage as the RPM rises from idle.
 

Ripple (electrical) - Wikipedia

en.wikipedia.org en.wikipedia.org
"Ripple (specifically ripple voltage) in electronics is the residual periodic variation of the DC voltage within a power supply which has been derived from an alternating current (AC) source. This ripple is due to incomplete suppression of the alternating waveform after rectification. Ripple voltage originates as the output of a rectifier or from generation and commutation of DC power."

Capacitor, keep or remove?

"Ripple voltage from a full-wave rectifier, before and after the application of a smoothing capacitor"
 
Thanks LAB, I restore vintage tube (valve) gear and understand ripple voltage/capacitors in audio equipment and the adverse effect of ripple AC voltage in that application. But I don't understand what the adverse effect is in a vehicle charging system if there some AC (ripple) riding on the DC. IOW, what bad effect on the charging system does the Norton capacitor eliminate?

Since my charging system works fine with no capacitor since 2008, my conclusion is that the cap has no functional effect for good or ill. But I have made erroneous conclusions in the past...;)
 
Normally the battery does a good job of smoothing out the ripple. The problem with ripple or rather high frequency spikes is that it affects electronics and can give malfunctions. So if your bike has points or a well designed electronic ignition the MC2 is not needed except for flat battery starting.
I can't tell if a MC2 can diminish the RFI (Radio Frequency Interference). When I designed computers decades ago, I put small ceramic capacitors on each IC as they handle high frequencies better than an electrolytic capacitor (like the MC2).
 
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OK, makes sense - I'm familiar with RFI and how it can effect electronics but I don't associate it with having an effect on vintage systems like the Commando. However, in thinking about it, I recall some folks have mentioned having trouble reading Norton voltages with some digital multimeters and responses have suggested it's an RFI issue that can effect certain E-ignition systems. I haven't personally seen that but it has certainly come up on this site. I have always ASSumed that such RFI was due to a non-resistance secondary ignition path, not anything to do with AC ripple voltage from the charging system but maybe so...
 
maylar said:
No. A permanent magnet alternator does not need excitation current.
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I guess they hung the blue can on there for decoration. Take one off a stock Norton, pull the battery and try to kickstart it. If you are correct, it should fire right up. The rotor is a permanent magnet, The stator does nothing until it gets a tickle from the electrical system, either from the battery or the blue cap.
 
MexicoMike said:
"It acts as a filter for noise spikes."

What do "noise spikes" do in this application? I removed the capacitor in '08 and have never seen any sort of issues - headlight flicker or any other indication of voltage variation other than the normal increase in charging system voltage as the RPM rises from idle.
Click to expand...
That's because the 2MC is for starting with a dead battery.
 
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