[MSFT-1]

I have a flying RV-8 (that I didn't build) with the O-360 engine and 35 amp alternator. With the engine running, my ammeter always reads approximately zero (+/- 2 amps) which I think means that the alternator is charging the battery in response to the various loads on the system. Here's my question:

How can I determine how much load I have and more importantly how much capacity I have left? I am considering adding a heated pitot tube that draws 3 or 4 amps, but before I do I would like to know that I am not running up against my limit.

Here is what I have in my system so far:

position lights
instrument lights
cabin lights
landing and taxi light
GNS 430 radio/nav
Garmin 327 transponder
Trutrak Digiflight autopilot
electric fuel pump (usually not on)
PS Engineering intercom
standard guages including an electric T&B
electric flaps

thanks for any insights.

bruce
N297NW

 

[wingtime]

Almost there...

You have a list of items in your electrical system so you?re halfway there. Now you just need to find out how much each one of those accessories draws while turned on. Make a list of the items you are likely to have on at one time. (Your not going to have on cabin lights while flying) Then add it up and compare the total possible draw to your alternator capacity. Ideally you'd like to have a higher output then draw.

Of course this doesn't take into account the peak surge when you turn an accessory. Also items like your radio are going to draw much more current when you transmit verses standing by.

BTW if your amp meter is reading positive your drawing juice from the alternator. If it is negative your drawing from the battery.

 

[jcoloccia]

Also, I don't know exactly but if I had to guess I'd say your battery contactor probably eats up about 1 amp.