Some clarity re: current loads and alt capacity

[John Courte]

Hi,

I'm drawing out my electrical system (based on Bob Nuckolls' Z11). I added up all the electrical loads and came up with 74 amps.

This is everything. Boost pump, efis, strobe pack, servos the whole works. As far as I know, a 74-80 amp alternator doesn't exist for our application, and if it does, it's probably heinously expensive. Granted, there aren't too many situations in which everything would be on at the same time, and even then, not for very long. What's the solution here?

Or am I thinking about this the wrong way?

thanks,
-John

 

[Mike S]

Or am I thinking about this the wrong way?

thanks,
-John

Yep, look at the load on normal cruise flight, add lighting if you plan on a lot of night flight.

This is the area you should target to determine your alt output.

I would add at least 25% above the level you get, for recovery of the battery after starting. 33% is probably better.

I suspect you will surprise yourself at how low the cruise current requirement is.

The battery will furnish power in addition to the alt, so for short term usage stuff like boost pump, it really does not effect the outcome much.

Sure others will chime in here, but a 60A unit will drive a lot of stuff when it comes down to it.

As a last resort, setting up a dual battery, dual alt system and splitting the load is another way to do things.

Good luck, Merry Christmas