Location for current sensors in dual alternator system

[walkman]

I will have a dual alternator single battery electrical system.

I will have two hall effect current sensing devices connected to the EIS 4000 and thence to the EFIS. Trying to finalize their location.

My plan was to put one on the battery + lead and the other on the standby alternator B lead.

The first tells me whether or not I am overloaded, the second tells me if the standby alternator is loaded (e.g. primary has failed) and if so what its generating.

The combination of the two should tell me 1) whether or not I have a primary alternator issue 2) whether or not the standby alternator has also failed, and 3) whether or not I need to do additional load shedding

Comments or suggestions for alternate configuration?

[rzbill]

I never considered the arrangement you propose.

Both mine are on the B leads so interpretation is identical.
Mixing the measurement style may lead to confusion at inconvenient time (at night in the soup)

It's your plane so your choice of course.

[Captain Avgas]

Originally Posted by walkman

My plan was to put one on the battery + lead and the other on the standby alternator B lead.

The first tells me whether or not I am overloaded, the second tells me if the standby alternator is loaded (e.g. primary has failed) and if so what its generating.

I'd put the primary ampmeter on the primary alternator B lead....that's where the juice is coming from. I don't think you need to waste a port with a second ampmeter. Of course you could always put the second ampmeter on the back-up alternator B lead but that alternator will never be on so that's a bit of a waste.

If you have an ampmeter on the primary alternator you will always know what it is producing and specifically when that device fails. Your voltmeter will tell you when the back-up alternator also fails (bus voltage will drop immediately from approx 14 to 12.5 and you will land asap).

But apart from the clear advantage of monitoring the primary alternator B lead current I don't think there's any other hard and fast rules to the game.

[JonJay]

The Aeroelectric schematic for a certified system shows a shunt on both alternators. They also run an idiot light triggered through the controller with a Hall effect sensor off of the back up to show overload.
Personally I don't have much use for a load meter unless my alternator goes south. So, I guess your approach makes sense but if the EFIS can only display one ammeter/load meter, that could be confusing as mentioned.

[RVG8tor]

Make sure you system will support dual Ammeters, the classic Dynon would not. What I did was put the ammeter shunt off my main alternator B-lead. I tied the standby alternator B-lead to the up steam side of the same shunt.

My logic was I wanted to know the load my system was pulling it did not matter what was supplying the power, Main or Standby alternator. If I don't notice the voltage alarm I will notice the "Stby Alt" on light, this comes on when the standby is producing power which only happens when the main bus voltage drops to the set point of the standby regulator, (13.5 volts if I remember).

This saves the weight of another shunt and or hall effect sensor, I really did not do the hall effect due to the extra cost, it is actually not very heavy. but I did not have a way with my EFIS to read separate ammeter. It works fine, if I kill the main alternator field the standby picks up the load and I can read the amps on the EFIS.

Cheers

[JonJay]

Originally Posted by RVG8tor

My logic was I wanted to know the load my system was pulling it did not matter what was supplying the power, Main or Standby alternator.
Cheers

Mike - curious why you want to know? If you set up your shunt as a charge/discharge and you lose your alt. it will then show load and you can manage it. Until then why does load matter? What does it tell you?

[rzbill]

Originally Posted by JonJay

if the EFIS can only display one ammeter/load meter,

OP noted EIS 4000. It will accept multiple hall effect connections and the display (while somewhat crude) will show the data. A paired GRT display will show any EIS data any way you want it.

[walkman]

Originally Posted by rzbill

I never considered the arrangement you propose.

Both mine are on the B leads so interpretation is identical.
Mixing the measurement style may lead to confusion at inconvenient time (at night in the soup)

It's your plane so your choice of course.

I don't think I'm mixing measurements.

the first tells me the charge/discharge state of the system regardless of the source of the charging current. I just assume that, unless the second ammeter shows current flowing, that the source is the primary.

In normal ops I would see a positive charge rate and 0 on the standby alternator.

In the condition of a degraded primary I might see a negative charge rate (discharge) and 0 on the standby. I think this situation is unlikely.

In the condition of a failed primary I would see either a positive or negative charge rate on the 1st sensor, and current being generated on the second sensor.

The value in my mind is this tells me two things 1) buss voltage has dropped to 13.8 to turn on standby alternator so most likely scenario is a failed primary alternator or regulator, 2) depending on the charge/discharge rate it allows me to manage my load.

I don't see any way to manage load without a sensor on the batter lead. Given that, I couldn't figure out any where else to put the 2nd sensor that added value.

[RVG8tor]

Originally Posted by walkman

.

The value in my mind is this tells me two things 1) buss voltage has dropped to 13.8 to turn on standby alternator so most likely scenario is a failed primary alternator or regulator, 2) depending on the charge/discharge rate it allows me to manage my load.

If you have the BNC standby regulator you can fly with the Standby Field switched to on. As long as the main keeps the buss voltage above the the standby regulator set point of 13.8 then it does not out put power. It will automatically assume the load if the main drops off, not need to wait to notice a voltage drop.

Turning on the Standby when needed is not wrong I just wanted to point out you can fly with it on with no worries that I have heard of. I test mine periodically just before shut down, I turn off the main and watch the standby pick up the load.

[RVG8tor]

Originally Posted by JonJay

Mike - curious why you want to know? If you set up your shunt as a charge/discharge and you lose your alt. it will then show load and you can manage it. Until then why does load matter? What does it tell you?

My location was really based on where I had room for the shunt. To be honest the only thing the ammeter shows me is that I might have something on I forgot to turn off like the boost pump, my idiot light can get washed out in bright sunshine. Other then telling me something is drawing excessive power the ammeter only tells me the alternator is providing power weather that is the main or the standby.

In battery only operations when I need to know discharge I have only the systems I want on powered and I will land as soon as possible.

The reason for the back up alternator is to make battery only operations a very remote possibility.