electrical questions

skidmk · #1 03-28-2007, 09:48 AM

Hi all,,, I've been studying the aeroelectric book and I had a question.

Planning an io360 in an rv8... battery in back. why is it (or why not) good or bad, to have the starter contactor and the master contacter in the back with the battery?

thanks

Mike

Mike S · #2 03-28-2007, 09:58 AM

Put the master close to the battery.

Put the starter contactor close to the starter, on the firewall.

If you put the starter contactor in the rear, you will need to run another hot lead (#8 or so) forward to the buss/charging circuit etc.

Mike

Paul Eastham · #3 03-28-2007, 10:00 AM

I don't have an aft battery so I haven't studied the issues, but...If it were me, I don't think I'd want an always-hot, unfused, heavy-gauge line (or two?) running all the way through the airplane with no way to shut it off.

Mike S · #4 03-28-2007, 10:10 AM

Quote:

Originally Posted by Paul Eastham

I don't have an aft battery so I haven't studied the issues, but...If it were me, I don't think I'd want an always-hot, unfused, heavy-gauge line (or two?) running all the way through the airplane with no way to shut it off.

That is what the master solenoid/contactor is for.

The hot line forward is run through the master. You are right about it being unfused, though.

If there was no hot line from the battery, there would be no way to charge the battery, and the "flywheel" effect on the system voltage would not be there.

Also, in the event of a failure of the alternator, or regulator, you would have a dead system.

When the battery is in the back, you must have a line forward that stays hot as long as the master is on.

Mike

dan · #5 03-28-2007, 10:22 AM

Or just put an Odyssey battery on the firewall like in the RV-7, and solve all sorts of issues. Do you REALLY NEED the battery in the BACK?

Paul Eastham · #6 03-28-2007, 10:30 AM

Quote:

Originally Posted by Mike S

That is what the master solenoid/contactor is for.

The hot line forward is run through the master. You are right about it being unfused, though.

Mike

He was asking about putting the contactors up front. If you put the contactors in the back with the battery, then you don't always have an always-hot line running all the way through. That's the point I was trying to make, but I didn't do it very clearly...sorry.

Mike S · #7 03-28-2007, 10:37 AM

Paul, you are correct about rear batt, front contactor--------sorry if I mis-understood what you were getting at.

Mike

f1rocket · #8 03-28-2007, 11:12 AM

With the battery in the back, you should place your master solenoid and battey buss (if you have one) as close as possible to the battery. The starter solenoid should be placed up front somewhere. I like it behind the firewall so that I don't have a hot wire running through the firewall.

In this situation, the only unprotected wire is the one running from your battery to the master soleniod and battery buss. I oversized these wires to handle the loads. They are less than a foot long.

You can power your master buss from the hot side of the starter solenoid. In any event, the master solenoid is used to power off this fat wire running to the starter solenoid should a problem occur.

The only problem a rear battery creates is the weight of running heavy 2AWG wires from the back of the airplane to the front. Other than that, the electrical protection is identical to a forward mounted battery installation.

skidmk · #9 03-29-2007, 08:30 AM

thanks guys,,, was pouring over Aeroelectic again,, I think I get it now. Randy do you mind if I pull some info from your diagrams?

M

f1rocket · #10 03-29-2007, 08:51 AM

That's what they are there for!