Amperes and headlights - am I imagining a problem?

This is a topic that I started about a year ago, but I want to raise again.

My question - does the reading on the ammeter in my headlight (1970 roadster) reflect the flow of amps in the circuit between alternator and battery as well as the circuit between the headlight and the battery, or just the circuit between headlight and battery?

The background is that I installed a sparx 3 phase alternator and sparx rectifier some time ago. My headlight ammeter still showed that amperage was way less than zero with the headlight on. I had the original ammeter and it waved around so much that I did not trust it; so I have replaced it. Now I am getting a rock solid reading; when I have the pilot light on the reading is -2 amps; headlight on dip is -5 amps and headlight on full beam is -10 amps (maybe -9).

I would have thought that because the rectifier is connected to the battery, and the lighting circuit (and ignition circuit) is connected to the battery there is really one circuit and that if the rectifier is doing its job the circuit should run at very close to 0 amps. I am concerned that the battery is not being recharged so that eventually if I run the headlight the bike will stall at low revs (Boyer ignition that needs 9 volts).

Today I gave the bike a good run; an hour with lights at dip ie -5 amps showing; when I got it home the battery measured 12.8 volts; and I put it on the charger; it initially charged at full charge, but within 30 minutes was on maintenance; so it was not too low (fully charged before I went). I was riding on the motorway at between 3500 and 4000 revs (home from the Classic races at Hampton Downs).

I am using a Motobatt 7ah battery; I have read posts suggesting with a sparx system it is desirable to have a 12 or 14 ah battery so that the rectifier does not have to work as hard, and can send power to the battery at close to the amperage that was being generated.

Does my ammeter indicate a problem somewhere or is it just two circuits that operate independently even though they are connected?

If the ammeter is wired as per original, all the electrical power - except the circuit to the horn - goes through it. This is one reason the world in general got rid of wired ammeters in vehicles - a failed meter means no elec power! Why the horn circuit doesn't go through it, I have no idea. But that's what the wiring diagram shows.

You should not have been showing a discharge at cruise with the headlight on low beam unless there is some sort of problem...but the problem could be an improperly reading ammeter as well as any number of other things from poor connections to a bad alternator. With the headlight on, you should show a discharge at idle, then it should go to the plus side as the RPM comes up and the battery charges then, after cruising for a bit the ammeter should show zero as the battery reaches/maintains full charged.

"Today I gave the bike a good run; an hour with lights at dip ie -5 amps showing; when I got it home the battery measured 12.8 volts"

She is charging. You need to measure the voltage across the battery. When you start the motor is should climb to around 14.2 at 3000 rpm.

12.8 after a long run is very good. I think yr ammeter is wired wrong or buggered.

Cheers

thanks for the input.

I will test the battery voltage under revs tomorrow; I have checked the alternator before with an auto electrician and it appeared to be charging properly- it should be given that it is brand new; given that the harness, alternator, rectifier and ammeter are all new the most obvious conclusion is a wiring issue - I did the wiring and I have no experience before doing it so I may well have stuffed up.

That said everything works fine and it is really simple; no indicators just front and rear lights and brake light; boyer ignition so simpler than stock; the only things I have different from stock are the ignition, the sparx alternator and I have wired in a connection for a battery charger; rather than have another connection to the battery I spliced the connection to the charger into the main loom immediately before the battery (LAB has said that he doesn't like multiple connections to the battery). Also I have followed Jean's advice and connected the positive earth from the alternator to the positive connector to the battery rather than an earth point on the frame.

I guess I could shift that to the frame and see if that makes any difference.

The only other possibilities that I could see are the connectors to the bulb in the head light - I recall that there are 4 spade connectors; I have used two and left two bare; maybe the other two might make a difference - but I don't really see how...

I have noticed that my ammeter pretty much indicates the state of charge of the battery if you know what to look for. For example. Starting up, the battery may not be fully charged, maybe 12.4V or so and at idle the Pazon is pulling maybe 2-3A and the meter shows discharge. When the rpms get above 3K, it shows charge, otherwise it shows discharge. After a while on the road cruising at 3.5-4K or so and the ammeter showing charging, the battery has finally taken a charge and has reached maybe 13.8V or so, and then the ammeter reading drops to near 0. Sometimes this happens pretty quickly if the battery is close to being charged, then the ammeter will flicker back and forth around 0 and finally settle down to around 0. Now if you have a bad battery or one that doesn't take a good charge, strange things will happen and it's hard to figure. Sometimes the flickering around is just vibration, it's hard to tell, but the zener will switch pretty quickly between charge and discharge.

Hope this helps, a volt meter may tell you more in conjunction with the ammeter. You have to think what state of charge the battery is in to get a real feeling for what the ammeter is showing. But with no power from the alternator, the ammeter will just show what current is going through it, mostly discharge unless the switch is off.

Notice if you have the original 68-70 harness, the only thing that is switched off with the ignition is the coil and rear lamp circuits. Everything else is still energized, but shouldn't be drawing current. That's why I pull the fuse when I quit riding.

I'm not convinced that you need a 14AH battery for the larger alternator. The battery will take what it needs, no more, if it's working right. You just won't have the reserve capacity.

Dave
69S

"
I'm not convinced that you need a 14AH battery for the larger alternator. The battery will take what it needs, no more, if it's working right. You just won't have the reserve capacity"

Yep, the larger battery is not needed unless you have a load like an electric starter that needs a lot of initial power. The only advantage a larger battery might provide is if you are out on a ride and the charging system fails. With an electronic ign system the larger batt can keep the bike running for a longer period of time - probably for at least an hour or more (lights off) which might get you home when the smaller battery wouldn't. But whether that's worth worrying about is another issue. Personally, I wouldn't install a larger batt for that purpose but others may feel differently.

Chris T said:

when I have the pilot light on the reading is -2 amps; headlight on dip is -5 amps and headlight on full beam is -10 amps (maybe -9).

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What wattage is the headlamp bulb (Dip/Main)?

Switching from dip to main beam ought to add around an extra 0.5A to the reading, not an extra 4A - 5A.

Pretty much every Lucas ammeter I ever watched as I rode was just like the compass in a Burmuda Triangle show. Then again, most of those bikes were neglected old lumps. :lol:

The ammeter on my '69 shows discharge with the pilot light on at idle, neutral with the light off. With the headlight on, I don't see positive charge on the ammeter unless I'm above 1800 RPM or so.

The red light on the '73 does the same thing - red light goes on at idle up to about 1600 RPM, then goes off.

I've just started up the bike and checked the battery charging with headlight off then on. At about 4000 rpm it was reading approx 14.5 volts; and it read the same 14.5 volts with the headlight on full beam at about 4000 rpm. So it seems like the rectifier is working properly; I think the most likely issue is the way that things are wired - which I will live with for the minute; as usual there are other issues that I can spend time on - like the backfiring from the right cylinder/exhaust which has just started...

The more I think about it the more I wonder if by connecting the positive from the alternator direct to the battery rather than to the earth point I have somehow created two circuits and that the ammeter is reading the circuit with the light on without taking the battery circuit into consideration. But that doesn't seem logical.

As I said in the post yesterday I recall that there are some choices of spade connectors to connect to and from in the headlight; maybe the different choices give different results; likewise there are 4 spade connectors on the ignition switch; you can connect the three wires to and from the switch with differing results (like bypassing the key); could these options have an impact?

LAB I cant remember what bulb I am using but it was a direct replacement for the last one and so far as I am aware "standard". Bought from Repco, an Antipodian auto parts supplier.

Thanks for everyone's input.

The trick was to trow ( wire in ) a three inch loop of Elc. Cable to the Ameter terminals ,
so when it fell to bits you didnt need to wire across the ameter terminals . :wink:

Best check is if the Headlamp brightens at around 15000 rpms , when its dark .

Chris T said:

The more I think about it the more I wonder if by connecting the positive from the alternator direct to the battery rather than to the earth point I have somehow created two circuits and that the ammeter is reading the circuit with the light on without taking the battery circuit into consideration. But that doesn't seem logical.

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Where is the Sparx reg/reg negative connected?

You haven't by any chance left the Zener diode connected?

Chris T said:

As I said in the post yesterday I recall that there are some choices of spade connectors to connect to and from in the headlight; maybe the different choices give different results;

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Either the headlamp is wired correctly or it isn't? Hopefully, it isn't wired so both beams are on together (see below)? More information required.

Chris T said:

likewise there are 4 spade connectors on the ignition switch; you can connect the three wires to and from the switch with differing results (like bypassing the key); could these options have an impact?

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Again we would need to know which wires and how you are connecting them to the switch. Is it the standard pre-71 two key position switch?

Chris T said:

LAB I cant remember what bulb I am using but it was a direct replacement for the last one and so far as I am aware "standard". Bought from Repco, an Antipodian auto parts supplier.

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Unless the gauge is not totally accurate, to go from -5 Amps to -9-10 Amps discharge when switching from dip to main beam would indicate that the main beam circuit is consuming an additional 48 - 60 watts. Either the main beam must be very bright (100+W) or perhaps the dip beam isn't going off when the main beam comes on?

Matt Spencer said:

Best check is if the Headlamp brightens at around 15000 rpms , when its dark .

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I reckon the headlamp would not be the only thing getting bright.

You asked a basic question, and I am not sure anybody answered it for you:

"Does the reading on the ammeter in my headlight (1970 roadster) reflect the flow of amps in the circuit between alternator and battery as well as the circuit between the headlight and the battery, or just the circuit between headlight and battery?

Answer: the ammeter should read the net charge or discharge into or out of the battery, taking all the loads and charge into account.

Is it possible that the ammeter is wired backwards?

Stephen Hill

Not intended as a thread highjack but have been following this thread with interest as after a loose alternator wire connection resulted in a flat battery causing a failure to proceed, roadside fix and away again with ammeter showing 6A with lights off and then surprised to see only 2A with lights on. Just starting to check my system, best of luck with yours Chris.
Iain

"Does the reading on the ammeter in my headlight (1970 roadster) reflect the flow of amps in the circuit between alternator and battery as well as the circuit between the headlight and the battery, or just the circuit between headlight and battery?

Answer: the ammeter should read the net charge or discharge into or out of the battery, taking all the loads and charge into account

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.

So am I right in concluding that if all is operating properly the ammeter should show a reading of close to 0? While the light and the ignition take power (amps?), the rectifier should be reading that and sending the same quantity of amps back into the battery?

DogT; my old ammeter combined with my old ammeter acted much as yours is - without the light on; it fluctuated wildly anyway, but it was always in negative when I started up; at between 3000 and 4000 rpm it would fluctuate into positve; then if I turned the light on it would go back to negative.

Having read the recent posts I would be grateful for confirmation (or otherwise) of one conclusion that I have made. When I tested the battery under power yesterday I got readings of about 14.5 volts at 3000 - 4000 rpm, with light off and then again with light on full beam. Based on that I concluded that the alternator and rectifier were working as they should and charging the battery. Is that a proper conclusion? Or could it be that because the bike wants enough power to run the ignition and lights the battery will just send out 14.5 volts for so long as it can; so that my reading is what the battery is sending out; rather than what power is being sent into it from the alternator; in which case my testing has not confirmed that the alternator/rectifier is working properly.

Chris T said:

So am I right in concluding that if all is operating properly the ammeter should show a reading of close to 0? While the light and the ignition take power (amps?), the rectifier should be reading that and sending the same quantity of amps back into the battery?

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With a Sparx three phase alternator fitted and functioning correctly, I would expect the ammeter to show a 0 to positive reading most of the time, regardless of whether the lights were on or not, except when running at low RPM, the Sparx alternator should be capable of producing more power than the bike's electrical system can use.

Unfortunately various questions that were asked still remain unanswered, so it makes it difficult to continue.

Where is the Sparx reg/reg negative connected

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?

LAB - I'm away from the bike at the moment so can't check, but my recollection is that I connected that direct to the negative terminal on the battery as per the Sparx instructions; I know that I did everything as per Sparx instructions other than to connect the positive to the battery terminal as recommended by Jean, rather than to the earth point on the frame.

You haven't by any chance left the Zener diode connected

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.

No I took that off; but I did not do anything with the wire that lead to the zener diode other than to tape it over and isolate it so that it is a dead end; is that correct; I thought that if I did not isolate it I could get a major short.

Chris T said:

Where is the Sparx reg/reg negative connected

Click to expand...

?

LAB - I'm away from the bike at the moment so can't check, but my recollection is that I connected that direct to the negative terminal on the battery as per the Sparx instructions; I know that I did everything as per Sparx instructions other than to connect the positive to the battery terminal as recommended by Jean, rather than to the earth point on the frame.

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With the original pre-71 charging system, the regulator (Zener) and rectifier output (-) would normally be connected to the other side of the ammeter.
Theory: If both poles of the reg/rec unit are connected to the battery, then the ammeter may only be reading the current that is passing through the electrical system from the battery and perhaps why it is always a negative value, however, this is just a guess.

Now you've got me confused too. I just went out and without starting the bike, I don't have headights without turning on the ignition. Go figure. When I do turn on the ignition and switch on the headlamp, I get more discharge amps on the meter in low beam than high beam????

I know, I'm not helping, I may need to check out my wiring and it's too cold out to mess around very long but I'll get back on it.

As far as your battery and charging system, as long as the rectifier/regulator is putting out more voltage than the battery, you will read more volts than the battery. The battery will take amps as long as there is more voltage from the regulator than the battery voltage until the battery voltage reaches the regulator voltage, but you can't read the 'battery voltage' in that case, but your ammeter will read charge. When your battery is charged, the ammeter should read 0. Mine charges up pretty soon after I start riding, only a few minutes to 5 minutes. Depending on the condition of your battery, it may discharge quickly using the headlamp and other things, but if the battery is in good shape it should charge up pretty quickly with enough rpm. With the high output alternator, your battery should stay in a good state of charge during riding, it will probably always show discharge at idle.

Dave
69S