Automatic alternator cut out/regen braking

[AXMonster]

John, its a kit from Jaycar in Australia that includes the switching system with hysteresis allowing switching the alternator off at 0% duty cycle and back on at 1%.

Its actuallu sold through Autospeed though as Jaycar no longer list it (but it comes from them.... Go figure?).

[AXMonster]

Right, Its all fitted and....... Its not working

After a lot of diagnosing, the circuits are both working as they should and are cutting off the field current to the alternator, however the alternator keeps producing voltage!

I finally worked out what's happening.

If the alternator is powered up then it stays powered up no matter what happens with the EXTERNAL field wire as it has an INTERNAL field feedback supply from a small 3 diode rectifier inside the alternator.

I'll have to pull the alternator apart and feed the internal field current to the pre-control relay side of the circuit to knock it out by the switching of the relays. It will then work.

I could just cut the link from the internal field supply, but this would then result in the battery (charge) light coming on whenever the alternator is working. I want to avoid this and have the system work as normally (transparent to the driver) as possible, and also have the warning light actually still work as a charge failure warning light!

Its good to hear the relays click in at 0% injector duty cycle and then back out again at >1%. I can actually hear the (potential) fuel savings LOL

One strange thing though, the duty cycle only reads up to 8% no matter what I do with the gas pedal. I think I may have peak hold injectors that need a small converter circuit to make the display work correctly. It'll have to wait though, as it works for switching the alternator so I'm not too bothered. Would be nice to see true duty cycle though.

Pictures to follow later

[AXMonster]

Hasn't gone so well today

First I removed the alternator to check which internal link was the self exciting system. I easily found the three small diodes that connect to the field input and also to the brushes through what must be the regulator???

Anyway, the wiring is shown as standard in the first picture below. The diode pack contains the 3 main rectifier diodes that handle the main current. The three field diodes shown connect to the field power bus bar, as does the field wire at the field power terminal post. This is the wire I tried to interrupt in the last 'experiment' but found it doesn't do much as once excited the alternator stays self exciting.

So, to prevent the alternator self exciting I needed to control the output of the field diodes and their power supply to the brush pack through the yellow wire.

I unsoldered connection X from the field connection post to the field power bus bar and connected the yellow wire to the field connection post. This is shown in the second 'modified' picture.
I then connected a new wire (green) to the bus car at X and ran it out of the alternator to the voltage/duty cycle dependant relays so it would only feed voltage to the field post when the control system required the alternator to be energised.

So far so good?? Well, in theory, yes.
In practice, no.

The engine ran and the alternator didn't energise until the voltage dropped below the threshold 12.4v. The alternator then energised and pumped the voltage up to a level way above the hysteresis value, switching the voltage switch off again.... and so it started cycling!! A quick turn of the hysteresis potentiometer soon had that sorted, and the engine ran with a falling voltage.
A number of times I set the low 'on' threshold and watched it switch on and then off, but for some reason in between controlled activations it would suddenly ramp the voltage up to around 16.5 volts!! My guess is that the voltage regulator wasn't working but somehow it was getting an excitation voltage

Anyhow, I tried to set a low voltage 'on' point that would correlate to 50% charge in the battery, but the draw on the battery must have been too great and the voltage collapsed too quickly to sub 10v. The switching circuit then stopped working, and there was no way of getting charge into the battery!! The engine kept running though, and the injector duty cycle meter actually showed 17% when I revved it a little (it hasn't ever showed higher than 8% even at WOT) Maybe it needs a lower supply voltage?? LOL

I gave up and put it back to standard.

More testing to be done on a rig I think, the vehicle testing isn't too clever

I need an alternator with an easily accessible regulator and field diodes so I can ensure that the regulator is working when I need it

[psmithrt]

Originally Posted by AXMonster

Hasn't gone so well today

First I removed the alternator to check which internal link was the self exciting system. I easily found the three small diodes that connect to the field input and also to the brushes through what must be the regulator???

Anyway, the wiring is shown as standard in the first picture below. The diode pack contains the 3 main rectifier diodes that handle the main current. The three field diodes shown connect to the field power bus bar, as does the field wire at the field power terminal post. This is the wire I tried to interrupt in the last 'experiment' but found it doesn't do much as once excited the alternator stays self exciting.

So, to prevent the alternator self exciting I needed to control the output of the field diodes and their power supply to the brush pack through the yellow wire.

I unsoldered connection X from the field connection post to the field power bus bar and connected the yellow wire to the field connection post. This is shown in the second 'modified' picture.
I then connected a new wire (green) to the bus car at X and ran it out of the alternator to the voltage/duty cycle dependant relays so it would only feed voltage to the field post when the control system required the alternator to be energised.

So far so good?? Well, in theory, yes.
In practice, no.

The engine ran and the alternator didn't energise until the voltage dropped below the threshold 12.4v. The alternator then energised and pumped the voltage up to a level way above the hysteresis value, switching the voltage switch off again.... and so it started cycling!! A quick turn of the hysteresis potentiometer soon had that sorted, and the engine ran with a falling voltage.
A number of times I set the low 'on' threshold and watched it switch on and then off, but for some reason in between controlled activations it would suddenly ramp the voltage up to around 16.5 volts!! My guess is that the voltage regulator wasn't working but somehow it was getting an excitation voltage

Anyhow, I tried to set a low voltage 'on' point that would correlate to 50% charge in the battery, but the draw on the battery must have been too great and the voltage collapsed too quickly to sub 10v. The switching circuit then stopped working, and there was no way of getting charge into the battery!! The engine kept running though, and the injector duty cycle meter actually showed 17% when I revved it a little (it hasn't ever showed higher than 8% even at WOT) Maybe it needs a lower supply voltage?? LOL

I gave up and put it back to standard.

More testing to be done on a rig I think, the vehicle testing isn't too clever

I need an alternator with an easily accessible regulator and field diodes so I can ensure that the regulator is working when I need it

Axmonster,

Sorry to hear this is turning into such a project. I gave up on this mod for my Mazda when I found out it was self exciting.
Looking at your diagram ( and I could be wrong) it appears as though you would want to interrupt the whole self excitation at the input to the diode pack, not after. Might this be done at the point you call connection X. Is there any way to tell if this is where the diode pack is getting is internal energy from. It makes sense to me as this is where the red wire (pre self excitation) feeds into the diode pack does it not. Leave the yellow wire intact and figure where the diode pack gets its energy and interupt that. Again possibly connection X. You may have to run a wire out to your relay then back in. Does this even make sense? The diode pack must be getting its energy from somewhere within, right. I believe the yellow wire is post regulation which has a varying current to control your voltage output.
Just an idea. Again you have the alternator in front of you so maybe I'm wrong from just looking at the diagram.

[AXMonster]

I think I know what I need to do now

Ideally the feed to the regulator should be 0v whan I want the alternator ro be producing no output.

I think it may be gatting some excitition from elsewhere i.e. picking up RF and then this voltage/current acts as the power to get the coils energised.

I need to ground the input to the regulator when not in use i.e. ground the yellow wire.

I think a relay that is grounded on the NC side and then fed the field voltage/idiot light voltage when activated should do the trick. So when not in use the alternator field windings are not fed any voltage and cannot 'pick up' any voltage!!

[diesel_john]

An easy way to test your car to see if it has internal alternator energizing.
I connected a volt meter to my lighter outlet. (battery)
While driving along in high gear I shut off the key.
The voltage stayed at 14 volts. So a second source is present.

I would like to set mine up to charge only when the accelerator is at zero or low battery.

[ami8i]

Hello,
since I heard from the controlled BMW alternator I 'beared' some DIY ideas:

» I guess it would make sense to find a stronger alternator which is able to prive more current (Ampere) because charging times are shorter.

»The lowest cost solution would be some switches which are connetced in that way that alternators field is turned off when vacuum is high (less pressure in manifold) or even cheaper an idle switch. If voltage is beneath a certain value the altornator is feeded as usually.

» A more elgant (but cheap) way would be to modify the field voltage. If field voltage is low than the alternator is producing much current, if field voltage is high, less current.
What's about of a 2 levels of field voltage?
- 7-10V if injector PW = 0 and TPS = idle (engine 'brake') --> maximum current This could be done by a simple fixed voltage regulator like LM7807...

- ~14.5 during cruising so that a minimum of charging is done. I don't know if it's possible to design a fixed voltage booster. I read about voltage boosters which can rise voltage for e.g. 2.0V. I guess field current is small --> no problem with simple ICs. But I don't know if there exist ICs which provide a special amount of voltage independend of incoming voltage. The opposite function of LM78xx.

Plus some componentes (Z diode...) and the 'controlled' alternator should be ready....


I guess we have not to be afraid in voltage peaks. Older alternators were 'controlled' mechanically by contacts.




Hello AXMonster,
if you tried the circuit in AX then I remember that the battery alarm light on dashboard does not show each alternator failure (as I found it on the hard way). Maybe this is the same reason you reported with the diodes.


I don't know if your 'new' injectors are P&H type. I know the older BOSCH Mono jetronic SPI with a low Z injector. BOSCH added a resistor (5 Ohm or 10Ohm??) to lower current. If you want I can ask a well educated AX/106 guy with MA3.0 ECU.



If it's possible it's better to pick up the signal before the driver because there is is nearly a square wave.

»Horst

[Abner]

[YOUTUBE]

[AXMonster]

Originally Posted by ami8i

I don't know if your 'new' injectors are P&H type. I know the older BOSCH Mono jetronic SPI with a low Z injector. BOSCH added a resistor (5 Ohm or 10Ohm??) to lower current. If you want I can ask a well educated AX/106 guy with MA3.0 ECU.



If it's possible it's better to pick up the signal before the driver because there is is nearly a square wave.

»Horst

Horst,

Thanks for that info. If you could ask the person who knows about the MA Ecu I'd be most grateful

[ami8i]

Hello AXMonster,
sorry, forgot to post the 'general' reply earlier:

Pick up the square wave straight out of ECU. You should find the driver easily looking back(wards) the track beginning from injector pin of the big ECU plug. This transistor is a good point to pick up the signal.

Hope this helps. I guess we have to look at the compionents datasheet or running back the track to sort out which leg of the IC shows the injection signal
»Horst