Bat Buss

[rwarre]

I am not planning on having a battery bus in my wiring plan. If I do not have any electrical items on without the engine running is this ok. I plan on using flashlights or the battery powered light that is on my headset at night before start up. My EFIS is connected to the master switch and comes on at the same time as everything else. The EFIS has a two hour rechargeable back up battery. Am I missing something? Thanks, I really appreciate suggestions.

[L.Adamson]

Just wondering how you're going to start the engine? The Pitt's M12 that I hangar with, uses a high pressure scuba tank for air starts. Of course that takes a system to send air to each cylinder in succession.

Other than that, if you have an alternator, then you need a battery to act as a reservoir.

L.Adamson --- RV6A

edit: Never mind, now that PCHunt has probably explained the correct situation...

[PCHunt]

Maybe "rwarre" meant he wasn't planning to have a HOT battery bus???? i.e.: everything goes off with the master switch off.

[L.Adamson]

Originally Posted by PCHunt

Maybe "rwarre" meant he wasn't planning to have a HOT battery bus???? i.e.: everything goes off with the master switch off.

Now that' it's morning.........I do believe you're correct!

L.Adamson

[rwarre]

Thanks for correcting my ignorance. You're right in that everything will go on and off with the master switch. Thanks

[Ironflight]

Technically speaking, you DO have a "Battery Buss" - it's just that short length of "hot" wire that goes from the battery to the Master Solenoid. If you ever need to have something in the "Always On" category, you just connect it there (through circuit protection, of course), and you can claim to have one of those fancy "Battery busses"....

Paul

[chaskuss]

Originally Posted by rwarre

I am not planning on having a battery bus in my wiring plan. If I do not have any electrical items on without the engine running is this ok. I plan on using flashlights or the battery powered light that is on my headset at night before start up. My EFIS is connected to the master switch and comes on at the same time as everything else. The EFIS has a two hour rechargeable back up battery. Am I missing something? Thanks, I really appreciate suggestions.

That depends. Do you have anything that needs a hot "memory" wire? If so, than just run that to the hot side of the main relay with an inline fuse for circuit protection, as Paul suggested. If you have an endurance bus, the supply wire for that will need circuit protection (breaker or fuse) I just checked my main wiring schematic. Both my MicroEncoder and MicroMonitor have memory wires. My battery bus only has 6 items on it.
I'll bet your EFIS needs a battery hot wire to keep it's internal battery charged.
Charlie Kuss

[chaskuss]

Originally Posted by rwarre

snipped Am I missing something? Thanks, I really appreciate suggestions.

What about your radios? Most modern radios use digital tuning and have a feature to allow you to program radio stations into memory. I'm sure they have a "battery hot" wire to retain that memory.
Charlie Kuss

[TX7A]

What type of local circuit protection would be used on the hot wire coming from the battery? This of course would be on the forward side of firewall.
As mentioned before, items on my batt buss list would be keep alive, cabin light, cig. lighter power port, etc.
Would these from B&C be robust enough?
http://www.bandc.biz/index.asp?PageA...WPROD&ProdID=9
http://www.bandc.biz/index.asp?PageA...PROD&ProdID=10

I would like to avoid the ANL type if possible.

Note:
I "may" also hook my Lightspeed EI power to the buss also so I don't have to go directly to the battery. Still trying to decide if that is wise or not.

Thanks for thoughts / experience on this.

[chaskuss]

Originally Posted by 7A_@ABI

What type of local circuit protection would be used on the hot wire coming from the battery? This of course would be on the forward side of firewall.
As mentioned before, items on my batt buss list would be keep alive, cabin light, cig. lighter power port, etc.
Would these from B&C be robust enough?
http://www.bandc.biz/index.asp?PageA...WPROD&ProdID=9
http://www.bandc.biz/index.asp?PageA...PROD&ProdID=10

I would like to avoid the ANL type if possible.

Note:
I "may" also hook my Lightspeed EI power to the buss also so I don't have to go directly to the battery. Still trying to decide if that is wise or not.

Thanks for thoughts / experience on this.

What size wire are you bringing through the firewall? That will determine your options for circuit protection. For smaller gauge wires (22AWG to 16AWG), your first link would work. The second like would also work, but has the downside of having molded in PVC insulated wire. Common, commercial grade PVC insulation does not have the abrasion resistance or resistance to heat that Tefzel insulation gives you.
If you plan to bring more than one small wire through the firewall, installing a 6 fuse, fuse block like the one shown in the link below might be a better idea. See

http://www.steinair.com/fuseblocks.htm

ANL fuses are a "fast acting" type. They are only for use on the charging system. The idea is for the fuse to blow quickly (in an over voltage event) to prevent damage to the avionics in the instrument panel. In all other situations, the fuse or circuit breaker protects the wire, not the appliance down circuit.
For the feed wire going from the battery to my main fuse blocks, (6AWG) I selected Littelfuse's MidiFuse series fuse holder and corresponding fuse. See

http://www.littelfuse.com/part/498900.html

This holder uses a slow acting fuse, so it won't easily be blown by transient voltage spikes. There are plenty of other methods to protect larger wires, including self resetting circuit breakers.

Charlie Kuss
PS I got my holder and fuse for free. LittelFuse has a place on their site to request free samples.