Points vs EI electrical power question...

Which draws more power from the charging system in normal operation, points or EI? I searched all over the internet but can't find an answer to that question. I was hoping someone here might have done such a test...

My Wassell EI draws 2 A.

My Boyer Micro Power drew a a couple of amps at idling RPM, dropping to about 0.3 A at higher RPM. That’s from distant memory though- I’m prepared to be gainsaid on that.

From my old 4 wheeler street racing days, typical coil saturation current using points was 2 - 3 amps.
One would think an EI would require the same current to saturate its' associated coils. In effect, the EI uses transitor, or other semi-conductor wizardry, rather than points.

Slick

Whether points or EI, arn’t they just switches? The coils are what accumulate and hold the power, from what I know.

jamesp said:

Whether points or EI, arn’t they just switches? The coils are what accumulate and hold the power, from what I know.

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I think you explained it better than I did!

Slick

Not an answer to what you actually asked but an observation based on experience. A few years ago I was headed from PA to Tennessee with concours when my stator paced it in on the Blue Ridge Parkway. I have an Old Britts Power Arc ignition and he has a Boyer. We decided the best option was to swap batteries back and forth as needed since his charging system was still OK. I ran with no headlamp for the next 200 or so miles and we never had to switch batteries after the initial swap. I don't think I would have made it that far if I had conventional breaker points

Hmmm...yeah, in thinking about the point (NPI) that both are just switches - one mechanical, one electronic - the actual power draw of either "switch" is probably of no impact at all in the power draw.

I believe power draw of the ignition is foremost determined by the coil(s) resistance.
Less ohm = more amp.

MexicoMike said:

Which draws more power from the charging system in normal operation, points or EI? I searched all over the internet but can't find an answer to that question. I was hoping someone here might have done such a test...

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I'll get to your actual question in a minute. But first, consider and engine that is not running but the ignition is on. At least one set of points will be closed. So, there is a continuous current through at least one coil.

For the rest of this, forget capacitance and reluctance, too complicated to describe here so I'm going with simple resistance (yes, I absolutely know it's way more complicated). Also, it's easier to understand on bike without a ballast resistor and two 12-volt coils like most non-Norton British bikes.

With the EIs we use, there are two coils, but half of the resistance each so the load when the EI's output transistor (switch) is closed is the same as one set of points being closed plus a small current for the electronics of the EI.

Since much of the time with points, both sets are closed, the points will draw more overall.

Perfectly clean points themselves add no voltage drop and therefore no current draw to the circuit but the output transistor of the EI does add a tiny bit.

EIs with two 6-volt coils, nominally, Current =12/3.2 so 3.75 amps when the output transistor is "closed" and 0 when open - a meter will average out around 2 amps. Points with two 12-volt coils is 3.75 amps if only on set of points is closed but 7.5 amps when both are closed, a meter will average out around 4 amps. No, I have not measured the points average current, I have measured the EI current (Tri-Spark). Tri-Spark specifies 3amps max, and 2 amps typically (depends on the coils used).

In the Triumph world Lucas Rita is ‘well known’ to have a heavy draw compared to Tri Spark (and others).

Is this a fallacy ?

Not much difference when the engine runs, with the ignition on and the engine stationary one set of points will keep one coil energised and then eventually burn out, all the current EI's will turn off after a few seconds.

Fast Eddie said:

In the Triumph world Lucas Rita is ‘well known’ to have a heavy draw compared to Tri Spark (and others).

Is this a fallacy ?

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Depends on original or "Rex's Revival Circuit". It should have been somewhat like current EIs power wise but the electronics of the day hindered that. When you felt one, it was warm to hot which means wasted current. Not sure how the upgraded one compares - I', guessing that it should be closer to modern as far as current draw.

From here: https://www.rexs-speedshop.com/wp-content/uploads/2018/10/Rexs-Revival-Ignition-Fitting-Guide-Rev4.pd:

Rex’s “Revival” circuit uses significantly less power than the old AB5 unit. The new circuit board is mounted to the metal lid of the AB5 case and the huge power consuming resistor is removed. Fitting requires the lid to be drilled and great care is needed to avoid metal particles from the drilling from coming in to contact with the replacement electronics

With the points ignition I ran for the past 20+ years, I ran with no battery - just the built-in capacitor in the solid state MityMax rect/reg unit. One kick warm, maybe 2 kicks cold - lights off for starting. I am installing the Vape EI and a Motobatt 12V 7A battery; as all EI systems, there is a minimum voltage requirement for the black box to operate (>5V). Not sure which draws more power but the requirement for minimum voltage must relate to different power draw, from starting to road riding.

marshg246 said:

Depends on original or "Rex's Revival Circuit". It should have been somewhat like current EIs power wise but the electronics of the day hindered that. When you felt one, it was warm to hot which means wasted current. Not sure how the upgraded one compares - I', guessing that it should be closer to modern as far as current draw.

From here: https://www.rexs-speedshop.com/wp-content/uploads/2018/10/Rexs-Revival-Ignition-Fitting-Guide-Rev4.pd:

Rex’s “Revival” circuit uses significantly less power than the old AB5 unit. The new circuit board is mounted to the metal lid of the AB5 case and the huge power consuming resistor is removed. Fitting requires the lid to be drilled and great care is needed to avoid metal particles from the drilling from coming in to contact with the replacement electronics

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I have tried a Rex's speedshop revival ignition unit
And the draw is same as my original Lucas Rita
I have spoken with them about the claim that their new unit draws less
And they told me yes it draws less
But couldn't tell me how much less or how much their unit draws !

baz said:

I have tried a Rex's speedshop revival ignition unit
And the draw is same as my original Lucas Rita
I have spoken with them about the claim that their new unit draws less
And they told me yes it draws less
But couldn't tell me how much less or how much their unit draws !

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As I alluded to, it's a quite complicated question. To actually answer you would need the parameters such as RPM; circuit resistance, reluctance, and capacitance; and, the schematics of the old and new circuits; or, you would have test going by the average draw (recording ammeter). In either case, any answer they gave you would only be at that specific speed, coil set, and testing method or it would be an average; so, it's bad business to state it.

If you're saying you checked with an analog ammeter at a certain RPM, on the same day and the same bike and the meter read the same with the old and circuits, then they lied. If you're saying under the same conditions the case temperature was the same, then they lied. Almost anything else you did is the "seat of your pants" and not nice to say they lied since you don't know.

marshg246 said:

As I alluded to, it's a quite complicated question. To actually answer you would need the parameters such as RPM; circuit resistance, reluctance, and capacitance; and, the schematics of the old and new circuits; or, you would have test going by the average draw (recording ammeter). In either case, any answer they gave you would only be at that specific speed, coil set, and testing method or it would be an average; so, it's bad business to state it.

If you're saying you checked with an analog ammeter at a certain RPM, on the same day and the same bike and the meter read the same with the old and circuits, then they lied. If you're saying under the same conditions the case temperature was the same, then they lied. Almost anything else you did is the "seat of your pants" and not nice to say they lied since you don't know.

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Yep it was on the same day within minutes
I unplugged the original and plugged in the new
I was not happy with with the output of my Alton alternator between idle and 2000 rpm
I was expecting the new unit being made from modern components to draw less than the old unit
That's when I contacted them
They could not answer
The unit is now on the shelf!

an article that I downloaded (from here...) suggests that the original RITA AB5 ignition amplifier drew a lot of current, but the power consumption of the later AB11 unit was comparable with a points set up.

daveforty said:

an article that I downloaded (from here...) suggests that the original RITA AB5 ignition amplifier drew a lot of current, but the power consumption of the later AB11 unit was comparable with a points set up.

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According to this article, the AB5 and AB11 are interchangeable except that the AB5 uses twice the power of the AB11 and the AB11 uses about the same power as points. The AB5 has a big power resistor that the AB11 and Rex's do not have.

http://www.aoservices.co.uk/info/RITA.pdf

baz said:

Yep it was on the same day within minutes
I unplugged the original and plugged in the new
I was not happy with with the output of my Alton alternator between idle and 2000 rpm
I was expecting the new unit being made from modern components to draw less than the old unit
That's when I contacted them
They could not answer
The unit is now on the shelf!

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Were you comparing an AB11 against the Rex? They should be about the same. An AB5 against the Rex is most definitely not the same.

I'm no RITA expert and in fact got rid of the only one I ever had installed, an AB11, because I knew it was inefficient when I felt the heat it produced. I've worked on bikes with a AB5 and they get very hot!

Hot = Power Loss!

I've never worked on one with a Rex unit.

marshg246 said:

Were you comparing an AB11 against the Rex? They should be about the same. An AB5 against the Rex is most definitely not the same.

I'm no RITA expert and in fact got rid of the only one I ever had installed, an AB11, because I knew it was inefficient when I felt the heat it produced. I've worked on bikes with a AB5 and they get very hot!

Hot = Power Loss!

I've never worked on one with a Rex unit.

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Yes an AB11 unit
The sole reason I bought it was because it was advertised as needing less power