Alternator display on engine management page

[Sam Staton]

I have two alternators - the main is a PlanePower 70amp, and the standby is a B&C gear driven 40amp. When I look at the PlanePower, I see total amps as a negative number. When I look at the B&C, I see total amps as a positive number. Which is correct, and how do I change the wrong one?

 

[Marc_J._Zeitlin]

I have two alternators - the main is a PlanePower 70amp, and the standby is a B&C gear driven 40amp. When I look at the PlanePower, I see total amps as a negative number. When I look at the B&C, I see total amps as a positive number. Which is correct, and how do I change the wrong one?

You don't say which alternator is on a shunt and which is on an induction coil, or which way you WANT the current reading to read, or what the ammeter is measuring. There are three possible measurements:

1. Alternator output
2. Bus Load
3. Battery current in/out

Personally, I like (3) as I find it the most useful if the electrical system is well designed, but most folks are (1). Generally (1), (2) and (3)-in will be positive current, and only (3)-out will be negative current (battery feeding current to the system).

If the PP alternator is using a shunt, then all you have to do is swap the shunt signal wires and the polarity will reverse.

But you have provided nowhere near enough information to give you a canonical answer.

 

[Sam Staton]

Sorry for not providing enough info. I am also using the VPX Pro. Both alternators field connections are powered from the VPX. The outputs of both are connected to the Vertical Power PPS. Which alternator is providing power is controlled by the individual field power switch. Any shunt would be internal to the VPX or the PPS.

 

[Marc_J._Zeitlin]

Sorry for not providing enough info. I am also using the VPX Pro. Both alternators field connections are powered from the VPX. The outputs of both are connected to the Vertical Power PPS. Which alternator is providing power is controlled by the individual field power switch. Any shunt would be internal to the VPX or the PPS.

Yeah, see, that would have been really useful information to have up front that would have saved me a lot of typing.

Assuming that both alternators are hooked up to the PPS correctly, and that they're hooked up to the VPX per pages 30/31 of the install manual, and if they're configured per page 57 of the install manual, then you'll need to change some setting in your EFIS (which you don't say which one you've got, so...) wrt to the current sensing.

 

[Sam Staton]

Dynon classic