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CANBUS-controlled alternator not supplying charge current - can anyone help?

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Invicta

New Member
Hi all...

I'm hoping someone can help... I'm at my wits' end here.

I'm streetfightering a BMW K1200S motorcycle. To make a long, boring story short, the bike's standard CANBUS electronics were replaced by a system incorporating conventional fuses and relays (the CANBUS ECU was fried when I bought the bike, and the replacement cost is truly terrifying).
Only one problem - the alternator no longer charges the battery when the engine's running!

Can anyone help in the quest for charge current? The alternator is a Denso / Nippondenso part, # EXK09S. Aside from the main output terminal, the alternator has a four-pin multi-plug on it's body. Two of the pins aren't used - one unused pin is labelled 'FR'. The pin leading to the engine ECU is labelled 'IG' and the pin which previously led to the CANBUS ECU is labelled 'L'.

I'm told that there is a simple mod one can perform to the alternator or wiring, getting it to charge the battery without the need for a CANBUS ECU.

One thing's for sure: if I have to listen to another auto-electrician sucking air between his teeth while saying: "Ooooooo... you can't do that", I'll do something amazing.

I've done enough engineering in my life to know that "It can't be done" really means "I'm not interested in doing it".
There's no such thing as an insoluble problem - there are only time-consuming ones.

Thanks, all. :)
 

MikeMl

Well-Known Member
Most Helpful Member
I have helped airplane homebuilders install Denso Alternators in aircraft. These have an internal voltage regulator. There is one pin which is basically an "enable" signal to turn on the alternator to make it charge. The enable signal is disabled during cranking so the mechanical drag of the alternator is minimized during cranking.

There is an output terminal which goes to the battery/bus.

Go to "aeroelectric.com" and read the stuff there about adapting automotive alternators to homebuilt aircraft.
 

Invicta

New Member
Hi Mike! Good to know you.

I'll check out those threads you mentioned. I'm currently reading info which indicates that some or all alternators used in CANBUS applications have the voltage-regulation function taken over by the CANBUS ECU to create a 'Smart charge' effect.

Do you have any idea which of the four terminals would provide the 'activation' signal? And if so, would that activation signal be battery voltage (12V)?
 

MikeMl

Well-Known Member
Most Helpful Member
I'll check out those threads you mentioned. I'm currently reading info which indicates that some or all alternators used in CANBUS applications have the voltage-regulation function taken over by the CANBUS ECU to create a 'Smart charge' effect.

Do you have any idea which of the four terminals would provide the 'activation' signal? And if so, would that activation signal be battery voltage (12V)?
I have never encountered an alternator that was controlled by canbus. I have, however, built several alternator controllers (voltage regulators) which PWM the alternator field current, so if you need to build your own, write back and I will post my circuit.

Usually, the built-in VR senses the battery voltage to control the alternator. Some alternators use "remote-sensing", so one of the pins might be for that. The control signal is usually provided by the key switch (or ECU). It simply defers the alternator from coming on-line until after the engine is running.
 
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fernando_g

New Member
CANBUS has two lines; CAN_H and CAN_L; both are required for the bus to function, since it is a differential bus.
Like MikeMi says, I also doubt that the alternator itself is controlled by the CANBUS...rather the CANBUS ECU via an analog signal of some sort controls the generator's field to adjust the energy produced.

I suspect that the pin labeled IG means Ignition, which is another way of saying, enable the generator when the engine has actually started. And the other pin "L" could be the field control.

Time for some reverse engineering....
If you still have the original CANBUS ECU, dissasemble it and try to follow the path of the "L" pin. Does it go to a transistor's collector? If so, is it a NPN or PNP? That way, you will see whether the field works by sinking sourcing current.

Once that you have determined that, it will be time to design your own alternator field controller. STMicro makes several field controller ICs, you can start from there.
 

tytower

Banned
These posts by Mike and Fernando are above me and I know nothing about Canbus.

When I put alternators on my Tractors I select one with the regulator box in the rear.
I connect the main terminal (which is probably IG) to the battery line anywhere.
Then there is always a diode in the alternator which attaches to the warning lamp on the dash . In all the cases I have seen positive is connected to the warning lamp which must draw better than 10mA or something like that to excite the field initially. Then the other side of the lamp is fed to the diode on the alternator where it then is grounded via the field coil ( all internal just find the diode connector) .

Turn on ignition and the lamp lights ,run the motor the lamp goes out. Well , works on Tractors ! L for Lamp ?
 
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picbits

Well-Known Member
These posts by Mike and Fernando are above me and I know nothing about Canbus.

When I put alternators on my Tractors I select one with the regulator box in the rear.
I connect the main terminal (which is probably IG) to the battery line anywhere.
Then there is always a diode in the alternator which attaches to the warning lamp on the dash . In all the cases I have seen positive is connected to the warning lamp which must draw better than 10mA or something like that to excite the field initially. Then the other side of the lamp is fed to the diode on the alternator where it then is grounded via the field coil ( all internal just find the diode connector) .

Turn on ignition and the lamp lights ,run the motor the lamp goes out. Well , works on Tractors ! L for Lamp ?
As above - I work on vehicle electronics and its saved me typing it all out.

Have some reputation for saving my fingers.
 
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