Assimilator Wiring Three Phase 850 MkIII

Lovel · Jun 3, 2023

Hi there, recently when carrying out a bit of town/heavy traffic riding I was finding my battery was not being charged enough at low revs and as normal/expected the assimilator light came on at low revs. Indicators were slow to respond unless upping the revs a bit. Got me thinking about going the three phase alternator route. The electrics on my bike are basically all original and seem to function well enough on the open road, but less so in heavy traffic hence I’m loathed to change out TBH as everything does indeed work. However if I changed to three phase which would give me bit more oomph at lower revs, just wondering how to wire the additional wire with regards to the assimilator? Looking at the wiring diagram below there are two alternator inputs for the assimilator and these seem to be connected up to same circuit and both with diode protection. If I added a third alternator wire from three phase could I fit it with an additional diode and just hook it up to the existing two pins that are already linked internally by the look of it?

Assimilator Wiring Three Phase 850 MkIII

L.A.B. · Jun 3, 2023

As far as I'm aware, there's no need to connect the third leg of the 3-phase to the assimilator, however, you'd be better off replacing the assimilator with a voltage monitor in my opinion because the assimilator doesn't give an indication of system voltage or whether the battery is actually being charged.

kommando · Jun 4, 2023

I went 3 phase when I used my 850 mk2a for a daily commute in city traffic with lights on. I went from a nightly top up charge to needing no charge at all. It's big advantage is the higher charge rate at low revs which fixed my issue. Today I would convert to LEDs on headlight and tail to reduce wattage which would have the same effect, cheaper too.

Lovel · Jun 4, 2023

kommando said:
I went 3 phase when I used my 850 mk2a for a daily commute in city traffic with lights on. I went from a nightly top up charge to needing no charge at all. It's big advantage is the higher charge rate at low revs which fixed my issue. Today I would convert to LEDs on headlight and tail to reduce wattage which would have the same effect, cheaper too.

I went LED route initially but felt was going down a rabbit hole when I was getting a strobe effect from the headlight and ended up changing a few more components such as solid state regulator etc. Now going whole hog to three phase and regulator etc , but tbh the original kit did work although not so well in town. Why did I start down this path, I should have left alone and learned to live with it? I’m going back to conventional bulbs as there is danger in overcharging too.

Lovel · Jun 4, 2023

L.A.B. said:
As far as I'm aware, there's no need to connect the third leg of the 3-phase to the assimilator, however, you'd be better off replacing the assimilator with a voltage monitor in my opinion because the assimilator doesn't give an indication of system voltage or whether the battery is actually being charged.

The assimilator appeared to have been working illuminating at idle, although perhaps not actually telling the truth of what was really going on with the charging. i just feel that although my system was ancient it was working to an extent and got me from A to B no problem. That why I was thinking to retain it with the 3rd alternator wire connected to the assimilator as well, with or without a diode.

marshg246 · Jun 4, 2023

Lovel said:
Hi there, recently when carrying out a bit of town/heavy traffic riding I was finding my battery was not being charged enough at low revs and as normal/expected the assimilator light came on at low revs. Indicators were slow to respond unless upping the revs a bit. Got me thinking about going the three phase alternator route. The electrics on my bike are basically all original and seem to function well enough on the open road, but less so in heavy traffic hence I’m loathed to change out TBH as everything does indeed work. However if I changed to three phase which would give me bit more oomph at lower revs, just wondering how to wire the additional wire with regards to the assimilator? Looking at the wiring diagram below there are two alternator inputs for the assimilator and these seem to be connected up to same circuit and both with diode protection. If I added a third alternator wire from three phase could I fit it with an additional diode and just hook it up to the existing two pins that are already linked internally by the look of it?

The two resistors bias the transistor "on" so the light lights. The diodes convert the AC to half-wave DC and each on in it's turn biases the transistor off. The capacitor holds the transistor off between pulses. To add a third AC leg would likely need the capacitor and maybe one of the resistors changed.

Assimilators do not tell you that the battery is charging. At best they tell you that the rotor is spinning in the stator and that there is some AC voltage available to be regulated and made into a charging current. Like LAB said, a voltage monitor is a much better solution as it tells you if you are actually charging,

Lovel · Jun 4, 2023

marshg246 said:
The two resistors bias the transistor "on" so the light lights. The diodes convert the AC to half-wave DC and each on in it's turn biases the transistor off. The capacitor holds the transistor off between pulses. To add a third AC leg would likely need the capacitor and maybe one of the resistors changed.

Assimilators do not tell you that the battery is charging. At best they tell you that the rotor is spinning in the stator and that there is some AC voltage available to be regulated and made into a charging current. Like LAB said, a voltage monitor is a much better solution as it tells you if you are actually charging,

Understood on the charging side about the false reading from the assimilator, but just wanted to explore if you could technically add the third wire into the circuit? Could splitting the 3rd wire and connecting to each of the stator output wires balance it?

L.A.B. · Jun 4, 2023

Lovel said:
The assimilator appeared to have been working illuminating at idle, although perhaps not actually telling the truth of what was really going on with the charging.

The assimilator is nothing more than a light switch, triggered by the stator AC output to switch off the charge warning light.

It doesn't give any indication that the DC system is charging nor does it control charging in any way, therefore, attempting to add the third wire which I believe is completely unnecessary won't change anything.

kommando · Jun 4, 2023

Lovel said:
I was getting a strobe effect from the headlight

I solved that issue on my B44 by fitting a larger capacitor instead of the 2MC but it is used with a battery, used a different LED on the Norton and did not get strobing. The LED development is so fast its hard to keep up with, the first ones I fitted had really bad beam focus in my Cibie unit, last ones work really well.

marshg246 · Jun 4, 2023

Lovel said:
Understood on the charging side about the false reading from the assimilator, but just wanted to explore if you could technically add the third wire into the circuit? Could splitting the 3rd wire and connecting to each of the stator output wires balance it?

No! If you really want to connect all three then you must add a diode in the same way the two that are there now. They are not "protection". They "throw away" half of the AC cycle to make half-wave DC. Connecting two stator wires together from a 3-phase stator is a bad idea - connect any two and you short out two coils in the stator. Splitting the 3rd wire and connecting to the other two shorts out the entire stator.

To fully understand, you would need to draw the entire circuit that included the rest of the charging circuit. Those two stator wires are not interacting with each other, they are interacting with ground via the bridge on a pre-MK3 and with the half-wave regulator on a MK3 or via the solid-state regulator if so equiped.

MichaelB · Jun 4, 2023

Lovel said:
I went LED route initially but felt was going down a rabbit hole when I was getting a strobe effect from the headlight and ended up changing a few more components such as solid state regulator etc. Now going whole hog to three phase and regulator etc , but tbh the original kit did work although not so well in town. Why did I start down this path, I should have left alone and learned to live with it? I’m going back to conventional bulbs as there is danger in overcharging too.

There are two Lucas 3 phases available. 10.5a/120w and 14a./180w. If you go 10.5/120w on a kick start, less issues with overcharging. Probably also stay with LED's..

Torontonian · Jun 5, 2023

Mk 111 . Check and clean all connectors first .

Lovel · Jun 10, 2023

My 3 phase stator after some 300 miles shown in the photos. Despite setting it up and easily achieving.008” clear around the rotor this happened today after a spirited run, reduced charging was the outcome. I guess it would be hard to claim a replacement as it could be down to how I installed it. I was quite happy with the install and double checked clearance after rotating the engine to different positions. PS i have removed and fitted my old stator numerous time in the past issue, so must have some degree of competency IMO.

marshg246 · Jun 10, 2023

Lovel said:
My 3 phase stator after some 300 miles shown in the photos. Despite setting it up and easily achieving.008” clear around the rotor this happened today after a spirited run, reduced charging was the outcome. I guess it would be hard to claim a replacement as it could be down to how I installed it. I was quite happy with the install and double checked clearance after rotating the engine to different positions. PS i have removed and fitted my old stator numerous time in the past issue, so must have some degree of competency IMO.

Did you happen to check the gap (as best you could) before removing. It's possible it was a shorted or otherwise overheated stator - not a rotor rub.

Lovel · Jun 10, 2023

marshg246 said:
Did you happen to check the gap (as best you could) before removing. It's possible it was a shorted or otherwise overheated stator - not a rotor rub.

I didn’t check, i didn’t think it was possible tbh.
Funny you mention about a short as the stator I received when new looked like this with two wires slightly protruding however I thought that they were flush with the stator encapsulation and the fact that the feeler gauge was also inserted I thought would be ok.

Lovel · Jun 10, 2023

Hmm the investigation continues. Note the score marks on the rotor, looks like I had some contact with perhaps that protruding wire which I thought had a gap. Appears to coincide with the stator wire. The issue seemed to occur when I was giving the motor some stick, maybe it touched at some point and shorted?

Assimilator Wiring Three Phase 850 MkIII

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