Canadian HO Alternator

[Blackduck]

Battery sizre has very little to do with it apart from enough reserve to start the engine.
You could have a 1000 amp alternator and it will not hurt the battery "IF THE REGULATOR" is working correctly.
Look at cars, 30/40 years ago the biggest alternator was around 35 amps.
Now they are 90 plus and the batteries in a most cases are a lot smaller than then.
The battery is just a buffer when the engine is running, the alternator drives all electric requirements
Lead acid batteries can take a littler more charging voltage than gel cells, most auto alternators will have too much charging voltage for gel cells so you need to careful if fitting different types of batteries.
If fitting alternative alternators I would be checking the charge voltage after installation to make sure the voltage is within spec.

[MarkT]

Battery sizre has very little to do with it apart from enough reserve to start the engine.
You could have a 1000 amp alternator and it will not hurt the battery "IF THE REGULATOR" is working correctly.
Look at cars, 30/40 years ago the biggest alternator was around 35 amps.
Now they are 90 plus and the batteries in a most cases are a lot smaller than then.
The battery is just a buffer when the engine is running, the alternator drives all electric requirements
Lead acid batteries can take a littler more charging voltage than gel cells, most auto alternators will have too much charging voltage for gel cells so you need to careful if fitting different types of batteries.
If fitting alternative alternators I would be checking the charge voltage after installation to make sure the voltage is within spec.

Sorry - it's the other way round per my research and my own experience.  Reports are, AGM batteries can take more voltage that will boil off the liquid in a lead-acid battery.  google "compufire gold wing battery" and read what you find.

[Blackduck]

I did not mention AGM batteries but gel cells, they are different.
AGM's take the same charge voltage as lead acid, maximum of 14.7 preferably between 14.2 and 14.4 volts. There is also a warning not to leave them on charge for a long time as it can damage they.

[valky1500]

I did not mention AGM batteries but gel cells, they are different.
AGM's take the same charge voltage as lead acid, maximum of 14.7 preferably between 14.2 and 14.4 volts. There is also a warning not to leave them on charge for a long time as it can damage they.

You obviously don't believe that we are not talking about a charging voltage at the battery. 

We are talking about a current source passing threw the battery so to feed the circuits. 

[Blackduck]

The current does not pass through the battery to supply electrical requirements, the only current going into a battery is to charge it, current leaving the battery is usually for cranking or if the alternator is not charging.
The battery is as I said before basically a buffer when the engine is running. All electrical requirements in a normally operating system are taken care of by the alternator.

[valky1500]

The current does not pass through the battery to supply electrical requirements, the only current going into a battery is to charge it, current leaving the battery is usually for cranking or if the alternator is not charging.
The battery is as I said before basically a buffer when the engine is running. All electrical requirements in a normally operating system are taken care of by the alternator.

That is very true, as long as it was said before, that the battery is within limits and or matched to the alternator output...

or it's toast.   

[Blackduck]

The only matching of battery to alternator is voltage, IE 12 to 12 , 24 to 24.
Google High output altrnators or check http://www.aalcar.com/library/alternator_highoutput_alternator.htm
The only "matching" they refer to is an alternator with sufficient grunt to maintain charge in high power situations. Having a higher amp alternator causes no problems. The problems only come from bad connections or faulty regulator.
Nowhere will you find references when fitting a high output alternator to also fitting different batteries unless it is to do with the actual service being asked of the battery or batteries.

[MarkT]

The only matching of battery to alternator is voltage, IE 12 to 12 , 24 to 24.
Google High output altrnators or check http://www.aalcar.com/library/alternator_highoutput_alternator.htm
The only "matching" they refer to is an alternator with sufficient grunt to maintain charge in high power situations. Having a higher amp alternator causes no problems. The problems only come from bad connections or faulty regulator.
Nowhere will you find references when fitting a high output alternator to also fitting different batteries unless it is to do with the actual service being asked of the battery or batteries.

This is just wrong.  In fact Compufire sells the higher capacity battery with the hi-output alternator as a kit - and cautions if you don't upgrade the battery you will experience battery failure.  I didn't upgrade and ruined the existing battery and the new same-sized one I replaced it with.  This is with a NEW in-spec 90 amp alternartor that worked just fine charging the properly-sized battery once I bought it.

[Blackduck]

Indeed with Compufire that appears to be the case, they say their alternators charge at a higher voltage which could damage a standard battery.
The only other references I could find use an approximate sizing of 4:1, IE for 90 amps full load they say use a 360 AH battery. As a battery should never see the full output of the alternator in normal use this would appear to be  a safety  margin if the regulator fails and the alternator charges at maximum rating plus way higher voltage.
When that happens it gets expensive, things like radios, sound systems and electronics just fry.
Had it happen on my boat, $1000 for  a new sounder plus a radio
Still say a high output alternator with a good, correctly functioning regulator will not destroy a battery
Each to their own opinions, facts are better but sometimes hard to get a clear answer from a lot of sources.

[valky1500]

Indeed with Compufire that appears to be the case, they say their alternators charge at a higher voltage which could damage a standard battery.
The only other references I could find use an approximate sizing of 4:1, IE for 90 amps full load they say use a 360 AH battery. As a battery should never see the full output of the alternator in normal use this would appear to be  a safety  margin if the regulator fails and the alternator charges at maximum rating plus way higher voltage.
When that happens it gets expensive, things like radios, sound systems and electronics just fry.
Had it happen on my boat, $1000 for  a new sounder plus a radio
Still say a high output alternator with a good, correctly functioning regulator will not destroy a battery
Each to their own opinions, facts are better but sometimes hard to get a clear answer from a lot of sources.

That's a half decent answer and that's what we are talking about here.

I look at it more in this way:
Given the alternator is connected to the battery for the purpose of starting, lights and ignition (SLI). That means we use an SLI battery but no matter what it's made of the power level decreases while the engine is running. Add to that the accessories like lights, and anything else that's turned on as the engine idles. At under 1500RPM there is no charge to the battery (that is controlled by the regulator or the ECU?).

When the RPM's increase above the idle level, the already depleted and weakened battery gets a charge from anywhere between 20 to 40 amps. Every time that happens the insides of this battery such as plates or walls, etc. become weaker and with each time to the point of it frying the battery. It can and very well might fry everything else that's connected to and running off the battery at that time as it draws power. Even the 55AMP fuze won't stop that from happening because that isn't the purpose of the fuze. The weak link here is the battery. 

Yes given the OEM alternator of the Valkyrie is a 40AMP output and so the battery would be in that range. A double power alternator would put that battery in the range of the GW batteries so the easiest remedy is doing just that. 

[Gryphon Rider]

Blackduck & valky1500:

Both of you have a partial understanding of the charging system and how it interacts with the rest of the Valkyrie's circuits.  I am not going to try to quote the misconceptions that each of you present as incontrovertible fact, but I will present my understanding of these systems in as much detail as I think is required to make my points.

1. A high current alternator will damage an under-sized battery, even when the voltage regulator is working properly.

This is how the regulator functions:  The regulator wire is connected to a circuit that is live when the engine is running.  This is not to provide power to the circuit, but to read the voltage.  If the voltage is found to be lower than a certain threshold, current is allowed to flow to the field windings of the alternator, and power is supplied to the battery and circuits connected to the battery.  The regulator only regulates voltage, NOT CURRENT.

If a discharged battery is supplied with voltage higher than the voltage of the battery at that moment, it will use ALL of the power it is supplied to either charge itself, or if electrical energy supplied at a rate higher than than the rate the battery can convert to chemical energy, it will allow the extra current to flow through the battery and out the negative cable into the chassis ground.  What restricts this extra flow is the internal resistance of the battery.  All else being equal, what determines the batteries ability to accept charging energy is the surface area of the plates, i.e. the amount of chemical interaction allowed between the lead and the battery acid.  A larger battery has a larger plate surface area and thus can accept a larger charging current.

So lets say you haven't ridden your Valk for a few weeks and your battery just barely has enough power to start your bike.  If your bike usually requires 100W just to run the ignition and lights (I haven't done the calculation), that leaves 320W to charge the battery, and given the low voltage of the battery, your alternator is running at its full 546W capacity.  Lets say that given its discharged state, your battery is capable of absorbing energy at a rate of 280W.  That leaves 166W of power remaining, which is absorbed by the internal resistance of the battery, which heats the battery.  As the battery charges, however, the voltage quickly increases, and the regulator reduces the output of the alternator accordingly.

Now lets put in a 90A x 14.2V = 1278W alternator, which sees the same discharged battery voltage and supplies its maximum output as the battery charges at the maximum rate it can absorb, which didn't change when the alternator was upgraded.  Now there is 898W of power being absorbed by the battery as thermal energy, but the battery voltage can't increase any faster than with the smaller alternator because its maximum charging rate is no greater.

So the bigger alternator puts out 2.25 times as much power, but requires the battery to generate 5.4 times as much heat, given the same level of initial battery charge.  THIS is what damages batteries.  I pulled most of my numbers out of thin air, but I think I've sufficiently illustrated the concept.  An electrical engineer with charging system experience can correct me if needed.

2.  ALL of the circuits in the Valkyrie chassis are powered by the battery when the alternator is not able to supply enough power (e.g. engine off or below 1500 RPM, failed alternator, or more than 546W of power being used.  That is, there is no special circuit that is ONLY powered by the alternator.

If you understand wiring schematics, take a look at the one for the Interstate. (http://www.rattlebars.com/valkfaq/ISschem.jpg)  When the 55A fuse (labeled MAIN FUSE B) is intact, ANY point on the white wire between the alternator and the battery positive terminal is electrically the same point.  Thus EITHER the battery OR the (running) alternator can and does supply power to ALL the remaining circuits on the motorcycle, INCLUDING starting, lights, and ignition.  Note that the alternator's regulator wire (black/light green) APPEARS to be powering the ignition system and other circuits in the fuse block, but in fact it is not supplying power, but simply reading the voltage of these circuits.

There is a notable difference between the Standard/Tourer and the Interstate in that the Interstate's headlights and meters are not are powered through the ignition switch as they are on the Standard/Tourer, but are SWITCHED by circuits powered by the ignition switch.  This allows for two things: 1. the IS dual headlights are not fed through the 30A main fuse on the starter relay, and 2. the dash receives continuous power to keep the clock powered.  These two circuits DO bypass the 55A fuse when the alternator is supplying power, but are both protected by smaller fuses regardless.

3.  The battery is NOT being supplied ANY power by the alternator that bypasses the 55A fuse.  I don't know how to make it plainer than the wiring schematics.

[valky1500]

Blackduck & valky1500:

Both of you have a partial understanding of the charging system and how it interacts with the rest of the Valkyrie's circuits.  I am not going to try to quote the misconceptions that each of you present as incontrovertible fact, but I will present my understanding of these systems in as much detail as I think is required to make my points.

1. A high current alternator will damage an under-sized battery, even when the voltage regulator is working properly.

This is how the regulator functions:  The regulator wire is connected to a circuit that is live when the engine is running.  This is not to provide power to the circuit, but to read the voltage.  If the voltage is found to be lower than a certain threshold, current is allowed to flow to the field windings of the alternator, and power is supplied to the battery and circuits connected to the battery.  The regulator only regulates voltage, NOT CURRENT.

If a discharged battery is supplied with voltage higher than the voltage of the battery at that moment, it will use ALL of the power it is supplied to either charge itself, or if electrical energy supplied at a rate higher than than the rate the battery can convert to chemical energy, it will allow the extra current to flow through the battery and out the negative cable into the chassis ground.  What restricts this extra flow is the internal resistance of the battery.  All else being equal, what determines the batteries ability to accept charging energy is the surface area of the plates, i.e. the amount of chemical interaction allowed between the lead and the battery acid.  A larger battery has a larger plate surface area and thus can accept a larger charging current.

So lets say you haven't ridden your Valk for a few weeks and your battery just barely has enough power to start your bike.  If your bike usually requires 100W just to run the ignition and lights (I haven't done the calculation), that leaves 320W to charge the battery, and given the low voltage of the battery, your alternator is running at its full 546W capacity.  Lets say that given its discharged state, your battery is capable of absorbing energy at a rate of 280W.  That leaves 166W of power remaining, which is absorbed by the internal resistance of the battery, which heats the battery.  As the battery charges, however, the voltage quickly increases, and the regulator reduces the output of the alternator accordingly.

Now lets put in a 90A x 14.2V = 1278W alternator, which sees the same discharged battery voltage and supplies its maximum output as the battery charges at the maximum rate it can absorb, which didn't change when the alternator was upgraded.  Now there is 898W of power being absorbed by the battery as thermal energy, but the battery voltage can't increase any faster than with the smaller alternator because its maximum charging rate is no greater.

So the bigger alternator puts out 2.25 times as much power, but requires the battery to generate 5.4 times as much heat, given the same level of initial battery charge.  THIS is what damages batteries.  I pulled most of my numbers out of thin air, but I think I've sufficiently illustrated the concept.  An electrical engineer with charging system experience can correct me if needed.

2.  ALL of the circuits in the Valkyrie chassis are powered by the battery when the alternator is not able to supply enough power (e.g. engine off or below 1500 RPM, failed alternator, or more than 546W of power being used.  That is, there is no special circuit that is ONLY powered by the alternator.

If you understand wiring schematics, take a look at the one for the Interstate. (http://www.rattlebars.com/valkfaq/ISschem.jpg)  When the 55A fuse (labeled MAIN FUSE B) is intact, ANY point on the white wire between the alternator and the battery positive terminal is electrically the same point.  Thus EITHER the battery OR the (running) alternator can and does supply power to ALL the remaining circuits on the motorcycle, INCLUDING starting, lights, and ignition.  Note that the alternator's regulator wire (black/light green) APPEARS to be powering the ignition system and other circuits in the fuse block, but in fact it is not supplying power, but simply reading the voltage of these circuits.

There is a notable difference between the Standard/Tourer and the Interstate in that the Interstate's headlights and meters are not are powered through the ignition switch as they are on the Standard/Tourer, but are SWITCHED by circuits powered by the ignition switch.  This allows for two things: 1. the IS dual headlights are not fed through the 30A main fuse on the starter relay, and 2. the dash receives continuous power to keep the clock powered.  These two circuits DO bypass the 55A fuse when the alternator is supplying power, but are both protected by smaller fuses regardless.

3.  The battery is NOT being supplied ANY power by the alternator that bypasses the 55A fuse.  I don't know how to make it plainer than the wiring schematics.

<----- Electrical Engineer.

You have used the most words of anyone in trying to explain our topic. It's a rather good assessment too on several points. What was it again?

Oh yes, the ability of a high output alternator to wreak havoc every place else including frying the battery along with the circuits and anything connected to them.

The one point that has yet to be mentioned is the ground. It's just a reference point for the DC circuit. There are 2 grounds involved here. One is the alternator at the engine block, and the other is the battery and circuits at the frame. The benefits of being separated is that one ground is loaded with interference and noise while the other is filtered. Yet they are tied together and this is what we call a common ground.

It can be said, as most do and many assume, they are separate so they are not connected to each other but in fact they are tied together. That makes all of the circuits that are connected to the battery a part of the alternator as well and that's through the ground. This is also the reason why it can be so difficult to locate a grounding problem when it occurs prior to what can be caused by direct shorting.

My intentions here is not to get into the lengthily technicals but it's very easy to make the mistake of grounding it to the wrong source and I will give you one example here. If your alternator is not properly grounded it will not charge your battery.

...And it goes from there. 

[Gental Gaint]

old thread... I know... but, how do you tell the difference between the 40amp and the 90amp unit... I need to know, there is a seller on CL that has a 2000 gl unit that needs rebuilding for 15.00...

[gordonv]

No one has mentioned about the GW alternator not requiring any modifications. What do you call a modification?

Taking the 3 long bolts out, turning the section over to another bolt hole, and refastening it back together. I call that a modification, a simple one, but one non-the-less.

[The emperor has no clothes]

old thread... I know... but, how do you tell the difference between the 40amp and the 90amp unit... I need to know, there is a seller on CL that has a 2000 gl unit that needs rebuilding for 15.00...

I can't tell the difference from looking. I would suspect there are more windings on the 90 amp unit.

[indybobm]

I would think that it has a part/model # on it. Do an internet search and see what comes up.