Charging (or battery) issue?!

Yesterday evening I decided to visit a friend who is 120 miles away. So I packed my tankbag and set off with my 1971 Commando 750.
I knew that my battery whas not in good shape but I thought that since I would ride along the highway it would be charged eventually.
Despite my hopes, battery had other plans in mind. Soon as I turned on the lights I saw that I actually had no lights as they were bright as candles.
Again, I thought that it would get better along the way since I would be riding at constant revs.
After a while the engine started working intermittently. I had to turn off the lights and disconnect the rear brake light switch (as pressing the brake pedal it would stall the engine!) to keep going.
Eventually I managed to get nearby my home before the engine died.
I had a spare battery so I replaced it and everything went back to normal.
I didn't make a second attempt to leave though as I didn't know if the battery was actually being charged.

I have Boyer ignition, 12V 12amp dry type battery installed and standard spec alternator.
My warning light is working but was not on at any time to indicate possible alternator problem.

I know that Boyer ignitions are consuming a lot of power, but shouldn't the alternator be able to keep the engine and electrical system working despite the fact that my battery was dead?

If you have original charging system you have 110 watts maximum and that's at over 3k revs. It's barely enough to run the ignition and lights in standard form. The Boyer will make things very tight power wise. Add in the age of components and wiring, and you can appreciate the problem.

The standard warning light doesn't tell you that the battery is actually being charged. All it does is show that the alternator is putting out something.

There are several options to improve things and logical move would be bigger alternator and a power box of some sort. Personally I use a 3 phase alternator and Boyer power box which has been fine for years and simplifies wiring. It also ditches the rectifier and zener. Obviously you need a good battery too.

Ian

IMO,
1. Check your voltage output from generator !!!!!!!!! whilst running to any battery and it should be charging 13+ volts. If not the geni/alternator is a gonnner
2. If producing charge, check that the battery terminals are very tight.. And if generator is "charging " (from previous check) the battery is deemed wasted..
3. If its charging replace the battery with new or swap to a "known good" battery and try again...

Start at the beginning and eliminate one thing at a time before you buy a 961 or a BMW...

Boyer don't like low battery voltage and will spit the dummy and do all sorts of strange things and engine will stop.
Try starting with a low battery, you might be lucky and it will start and if you are unlucky it will launch you off your bike when it kicks back (timing advanced).
I know it happened to me on a triumph and all my mates thought it was extremely funny to see me hopping around swearing.

Also commandos have dynamo's not generators there is s subtle difference in their manner of operation.

You need all the power you can get and moving to a solid state regulator and having good wiring and earths will go a long way.
I run a LED battery voltage monitor and it changes colour when the voltage drops below a set point and I need to run above 3k to keep the battery charged when the lights are on.

Cheers
Peter R

Also commandos have dynamo's not generators there is s subtle difference in their manner of operation.


Commandos have alternator no a dynamo. The two have different type of power output the voltage rectifying components are not part of the same unit as they are on most modern cars but most motorcycles do it that way.
The standard set up charge warning light as already stated just tells you you have AC output from your alternator. Not the DC level being feed to the battery (or not).

Firstly you know your battery is on it's way out so change it before you do anything more. Then check out the systems output. Try rhe old test of rev it an see headlight getting brighter if you are out on road but volt meter is more accurate.

All the wiring upgrades listed are a good idea and all help towards better electric system but start with what is known to be at fault. Then work from there the only original bits of my electric system are the switches (for appearance) all rest is changed the alternator failed an it did 50 miles no problem even using Estart an old Boyer so sounds to me like your old battery or capacitor my be shorting if charge system is working.

What is a good battery for a MK3? Any suggestions? Ones to stay away from?

Peter R said,

Also commandos have dynamo's not generators there is s subtle difference in their manner of operation----------

I take it that's a mistake Peter R, i'm certain you know that's not the case!

Dynamo? Generator? Try alternator for Commandos

+1

thats what i love about forums, so many opinions based on so little facts! :mrgreen:

JimC said:

Dynamo? Generator? Try alternator for Commandos

Click to expand...

1. 'dry cell' battery? if AGM type be very suspicious of it, no matter its age.
2. Check charger connections to the reg/ref.
3. Can never trust boyah's factory trigger wires.
4. I've had tail light ground strap fraying suck the juice or short current so thought it was boyah and charger till learned better.

Ok Ok I hear you guys, I had a bad day yesterday.
Yes you are correct it is not a Dynamo.
I was thinking of the actual coil itself and yes it is an alternator or at least it produces alternating current.
It is not an alternator as in a vehicle alternator as in it does not have a field winding for regulation.
It is not a generator as it does not have brushes and field regulation.
It does have a current limited coil that puts out voltage proportional to the speed of a spinning magnet.
It has a sweet spot where the maximum power is.
The zener is basically a shunt regulator and the coils will be outputting maximum (but self limited) current all the time and either the zener consumes all this current on no or small loads or as the load increases the current through the zener decreases and as the load increases the current will limit and the voltage will drop.
Theoretically the coils can be shorted and due to self current limiting and ohms law power=volts x current power =zero.
I call this a dynamo coil but it is not exactly a dynamo in the strictest sense.
Try shorting your car alternator or generator and see what happens.

This should set the cat amongst the chickens, but I'm happy to be wrong again, or if it's my wife wrong still.

Cheers

Technically Its a Lucas permanent magnet rotor, single [or later 3 phase] radial coil laminated magnic flux path alternator, ask any DIY windmill power head.

Yes, but it still has a fixed magnetic flux (permanent magnet) and has no flux regulation as in alternators via field windings etc
IE by any other name it is a basic dynamo coil, flux density determines how much power can be generated.
Try to exceed the max power available and down goes the voltage and thus the resultant output power until the volts =0 and output power = 0.

Bluemax and Hobot we seem to be wondering off topic again. Regardless of the exact manor of the way in which it generates electric its makers Lucas and several motorcycle manufacturers including Norton called it an Alternator. So lets leave it at that an maybe help the poor owner with posts on how to get his machine working again :wink:

Yep point taken I started off with on subject comment but alas drifted, I will goto the naughty corner.

Plenty of thoughts here!
OK, as I wrote, soon as I replaced the battery with a good one, problem was solved.
I rode the bike for some miles at daytime and there was absolutely nothing wrong.
I am very insecure of taking it for a long ride during night time though. Is the alternator going to produce enough to sustain bright lights, charge the battery and keep the engine running smoothly...?
Rectifier and Zener Diode were replaced by a Single Phase powerbox a few years ago.

At the risk of being castigated that is the exact regulator unit I use. I have a standard single phase alternator and standard wattage headlight and tail light.
I find as other have said that you need the revs up to keep the charging up. I was also concerned with a possible battery going flat while driving at night as you are.
As my assimilator was stuffed I installed a simple bi coloured LED driven by a voltage sensing circuit that was red when the battery was below 12.4 volts (selectable) and green when above. When the headlight was on and riding around town it mostly was orange (just holding) but once above 3k it was green.
It actually told me my alternator windings were failing (rotor polling due incorrect clearance) on one of my road trips by slowly going from green to red.
So I found it very useful and it gave me confidence in the state of charge of the battery.
I also just run standard points so not sure what the difference in current drawn for Boyer compared to points, others may be able to comment on this and if it is an issue.
But I do know older Boyer unit do not like low battery voltages.

There are other variant of this type of battery monitoring and I seem to remember it being discussed somewhere in this group.

I hope this post is helpful and not too off topic.
I assume you removed the wiring to the zener when you installed the new regulator, I'm sure you did.

Peter R

I replaced the stock warning light system with one of these:

http://sparkbright.co.uk/sparkright-ecl ... onitor.php

As already stated, the stock warning light gives very little useful information, just that there's an AC output. You could have a bad rectifier or zener(s), or regulator and not know it.

Headlight on, with a 3 phase alternator and solid state regulator, I find that the light stays green or >13.2 VDC at anything over 2100 +/- RPM. The ignition is a Pazon Altair, I don't know how power hungry it is compared to a Boyer.

Battery is a DURAGM-15L-US Duracell Ultra AGM; $85 from Batteries+Bulbs store. That, coupled with a Dyno Dave starter and aircraft battery cables and it spins like a top.

Stopped at a traffic light the warning light will go from steady green to amber to slow flashing red then reverse itself as you accelerate away. It's all very reassuring.

olChris said:

IMO,
1. Check your voltage output from generator !!!!!!!!! whilst running to any battery and it should be charging 13+ volts. If not the geni/alternator is a gonnner
2. If producing charge, check that the battery terminals are very tight.. And if generator is "charging " (from previous check) the battery is deemed wasted..
3. If its charging replace the battery with new or swap to a "known good" battery and try again...

Start at the beginning and eliminate one thing at a time before you buy a 961 or a BMW...

Click to expand...

Have you done any of these... ?....

To add to the list you could lose the blue can capacitor. If old it has been known to become a slow short !