Dual Battery or Alternators?

[jakej]

Spot on Walt!!
Post #3 also is more to the point for us down under - we don’t have FBO’s everywhere in ‘outback’ country so an Alternator or belt failure etc have real consequences when far from service centres. Not normal to carry spare Alt, belt & torque wrench just in case it’s needed.
Same applies when talking about fuel range, IF & when/where Avgas is available it can easily cost $14/us gal. That’s why I also talk about having extra fuel capacity (at least the plumbing in place) for many who wish to travel this wide brown land 😉

[jakej]

Spot on Walt!! Applies to VFR here as well.
Post #3 also is more to the point for us down under.
We don’t have FBO’s everywhere in ‘outback’ country so an Alternator or belt failure etc have real consequences when far from service centres. Not normal to carry spare Alt, belt & torque wrench just in case it’s needed.
Same applies when talking about fuel range, IF & when/where Avgas is available it can easily cost $14/us gal. That’s why I also talk about having extra fuel capacity (at least the plumbing in place) for many who wish to travel this wide brown land 😉

[rv8ch]

There are some great resources available here where this is discussed throughly.

http://www.aeroelectric.com

As others have said, batteries are very reliable, but keep in mind that issues affecting the battery can come from other places, like grounds, contactors, crimps, etc. These are discussed regularly and mitigations are suggested. As with many things in aviation, it comes down to good design, implementation, and maintenance. Electricity is magic, but keeping it flowing correctly in your RV is not!

[Bevan]

My vote is for a backup alternator before a backup battery (a reservoir).

The backup alternator can supply a lot more power (over time) to complete a long cross country flight, while the battery is held in reserve for high draw things like lights and transponder. A battery always has a somewhat of an unknown condition and therefore an unknown and finite capacity, good for staring the engine, but not as good for indefinite supply of electrons.

Bevan

[Tom Martin]

Keep in mind that likely 90% of us did our training in a bare bones Cessna 150. There are hundreds of champs and cubs that have NO electrical systems and use handheld radios when required. An iPad will give you nav capabilities that we could not have dreamed about a dozen years ago.
If your mission is as simple as you describe then save your money, WEIGHT and complexity and go with a simple system, one that can be repaired at any airport.
Carry a handheld radio and a basic tool kit and you will likely be able to solve most issues yourself.
If after flying for a while and you feel the need for more stuff it can be added. Make allowances in your panel for upgrades as required.

[lr172]

Originally Posted by amaris

I think I'm looking for the ability if something goes wrong to be able to fly 30 or 45 minutes to the next bigger airport where I have a chance to get something fixed or replaced instead of being forced into landing and the closest runway.
The idea of being able to fly on until I'm ready for a refuel is appealing or continue the mission, but I don't think I'd trade adding a lot more complexity and cost for that option if it doesn't make sense.

The smaller bu battery on the G5 and G3X would be an emergency all else has failed scenario and not relied on for anything other than to hopefully give me some guidance while I'm landing asap.

Given your VFR only mission, I would argue that it should be relatively easy to land your plane with little or no DC power if you have a G5 with a BU batt, assuming your skills are sharp and you understand how RPM affects the Pmags power generating ability. If you take care of and test your battery and properly shed load in the event of an alt failure (assumes you have a volt gauge to determine this), you should have no issues getting 30 minutes of use from that battery.

Larry

[RONSIM]

my choices -- I test the B/U alternator, periodically, by shutting down the primary (old original Suzuki?, external regulator). I carry a EarthX jump-pak (picked up at Sun n Fun) for the dead-battery issue. I have never had to use any of the backups on my plane, but the jump-pak has been used on several cars and other planes. Bought another jump-pak for the car -- wife has used it twice, on friends' cars.

Ron

[jdmrv7a]

I agree -- I test the B/U alternator, periodically, by shutting down the primary. I would rather replace the primary at home rather than traveling. I do have a G5 with it's small backup battery. The Garmin G3 system is also backed up by the TCW 6AH integrated backup IBBC. Main Battery is Earth-X 900.

Adding the a Earth-x Jump Start kit to the survival kit would be handy on remote trips with limited support.

[airguy]

I run a single oversized battery (EarthX 900 vented) with dual alternators here. I test the backup alternator on just about every flight, typically I'll cut off the primary and run on the secondary for at least half of every cross country, so they both get a fair bit of time.

An alternator is likely to fail in flight versus failing on the ground. A battery is likely to fail on the ground as versus in flight. I have had a few occasions where I turn on the master on an airplane and nothing happens - I have never yet had an occasion where I started the airplane and the alternator did not come online.

[amaris]

Well sure seems there are essentially 2 camps out there. Dual battery or dual alternators. All of your responses and logic make me think if I only read your response, you could convince me of going with your way.

Keep sending your thoughts, much appreciated!