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Alternator voltage?
- Thread starter mbaldock
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mbaldock
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Guys, I apologise if I seem to have wasted someones time, I did try to search for details but (as I said originally) what I did find was, to me at least, very confusing.
Kind regards
M
Kind regards
M
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mbaldock
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Thanks Wammers, always a bit intimidating to ask a question of you experts ... still at least the very helpful TSB pointed out by The Mad Hat man seems to suggest that my 14:08 is ok and I just need to sort out the voltage drop. Thanks again.
Best
M
Best
M
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Datatek
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Feck me Tony, how many more times? The D+ is an input to the alternator that provides the excitation current to start charging, once the alternator starts charging it provides it's own excitation current via 3 diodes and the fixed point regulator, this means that the charge lamp now has 12 volts on both sides of the filament so it goes out.
It does NOT sense battery voltage.
Datatek
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As I said, get rid of the volt drop and it will be OK.
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Yes and that is how the controller knows the state of the battery and how much field current to apply dependent on battery state and draw on the battery from systems to control the output. The controller HAS to know and HAS to monitor the battery state to vary the current output as needed. Just like the EAS has to have a pressure switch to sense pressure and turn the compressor on and off. Some alternators have a separate connection for this others don't. In this case D+ is the sensing terminal.
Datatek
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Sorry you are talking total nonsense. there is no current flow in either direction in the D+ line once the alternator has started charging. The regulator is a constant voltage variable current device. The current varies as the product of the load, as the load increases the voltage tries to drop below set point, this causes the regulator to pass more current to restore the voltage to the set point.
The wire to the D+ can be removed completely once the alternator is running and it will make absolutely no difference to the performance of the alternator.
I used to modify alternators for marine use with special regulators These had remote battery voltage sensing via a separate pair of wires and battery temperature sensing. They followed a microprocessor controlled variable charge cycle, when first stated they charged at 14.8 volts for a period which would be cut short if the temperature rise was too high. Then charging would be stopped and the battery voltage decay measured via sense wires, the charge cycle would then either repeat or switch to demand based float charge.
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op2:
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How does it know what the voltage is, is it telepathic? The voltage regulator has one function and one function only. That is to turn up or down the field coil voltage via the brushes within set parameters to vary the output of the alternator as needed. It has to sense or monitor the battery voltage to know when or when not to do that. The battery voltage has to be fed back to the controller or it wouldn't have a bloody clue what to do.
Datatek
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The alternator knows only when the voltage at the regulator tries to drop below the set point, it is an entirely internal function. There are no parameters, just the voltage set point. An increased load will cause the output voltage to drop, this drop will cause the regulator to increase the field current to compensate to maintain the set point until the current limit of the alternator is reached. It works without the D+ or battery connected once the alternator has started.
Tell me how you get a current flow in a line with alternator output on both ends of the circuit? Apart from drops in the wiring which are non existant with no current flow, one end of the D+ line has alternator output voltage from D+, the other end has alternator output voltage from the main output via the ignition switch, there is no potential difference. The fact that there is no current flow in the D+ line is proved by the fact that the lamp goes out. You cannot control anything with no current flow.
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Ok i give up, the controller does not have a bloody clue what the battery voltage is at any time it just guesses.
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From a lyman.....I design Aircraft Components, Ground Service Equipment and tooling....I am not to clued up on Automitive Electrical Generation....
But from the Image above the way I see it is the Alternator Warning Lamp 'L' and the Alternator Output to the Vehicle Services 'IG' which is connected to the Battery 'B' and Rectifier Signal 'S' should be at the same electrical potential and as such the warning lamp won't illuminate....
If the Alternator Output 'L' drops below the Battery Voltage which is connected through 'B', 'IG' or 'S' there is an electrical potential difference and the Lamp will illuminate in sympathy to such...
But from the Image above the way I see it is the Alternator Warning Lamp 'L' and the Alternator Output to the Vehicle Services 'IG' which is connected to the Battery 'B' and Rectifier Signal 'S' should be at the same electrical potential and as such the warning lamp won't illuminate....
If the Alternator Output 'L' drops below the Battery Voltage which is connected through 'B', 'IG' or 'S' there is an electrical potential difference and the Lamp will illuminate in sympathy to such...
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The regulator is the brain of the charging system.
It monitors both battery and stator voltages and depending on the measured voltages, the regulator will adjust the amount of rotor field current to control alternator output.
Regulators can be mounted both internal or external. Current technology uses an internal regulator.
It monitors both battery and stator voltages and depending on the measured voltages, the regulator will adjust the amount of rotor field current to control alternator output.
Regulators can be mounted both internal or external. Current technology uses an internal regulator.
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on your pic above, Saint then
Four wires connect the alternator to the rest of the charging system.
'B' is the alternator output wire that supplies current to the battery.
'IG' is the ignition input that turns on the alternator/regulator assembly.
'S' is used by the regulator to monitor charging voltage at the battery.
'L' is the wire the regulator uses to ground the charge warning lamp.
Four wires connect the alternator to the rest of the charging system.
'B' is the alternator output wire that supplies current to the battery.
'IG' is the ignition input that turns on the alternator/regulator assembly.
'S' is used by the regulator to monitor charging voltage at the battery.
'L' is the wire the regulator uses to ground the charge warning lamp.
StuckAgainSteve
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Ok i give up, the controller does not have a bloody clue what the battery voltage is at any time it just guesses.
Not wishing to upset anyone or take sides, datatek's explanation is exactly how I understood alternators to work.
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Not wishing to upset anyone or take sides, datatek's explanation is exactly how I understood alternators to work.
Don't worry nobody upset. How does the controller know when the battery is depleted and when it is full unless the battery voltage is being monitored? As the battery voltage falls by being drawn on the field voltage is turned up, as it gets full the field voltage is turned down. How does the controller know to do that? Does it have ESP?
