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Emergency or Second Battery

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Lee Schaumberg

Well-Known Member
Joined
Aug 28, 2003
Messages
215
Location
Northern Wisconsin
Hello

The internal mounted battery will keep an EFI alive for up to 2 hours but everything else goes black. Wanting to communicate, have tranponder output, and lights require more power. If the battery cable falls off or the alternator fails your lost!

A spill and leakproff motorcycle battery may do the job. People use a second alternator or starting battery as spares but they are heavy and take up alot of room. A new motorcycle battery would work. You can get them cheap and rated for any power you want.

Some EFIs give a prompt and time to go to stand by power. Engines with out mags require power to stay running.

So what are the thinkers doing?

By the way it's now 29 deg far with a high expected in the upper 40s but wind is 0 mph and I'm looking at that tacker sign that says we drink coffee so we can do stupid things faster!
 
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rpellicciotti

Active Member
Joined
Feb 10, 2005
Messages
43
Location
Memphis, TN
I think this is one of those areas where you can really over-think it if you are not careful. I have friends that have dual alternators, dual batteries, GPS units with built-in backup battery, etc. This is way overkill in my opinion.

I have been flying for 30+ years and I have never had a battery fail in flight. I know people that have had batteries go flat or won't take a charge after using them for some time but never catastrophically fail. I have seen alternators and generators fail. So, I have decided to run a single battery, single alternator system on my airplane. My airplane is equipped with two EFIS screens, two radios, a transponder, a single electronic ignition (and one mag) and night lights.

If my alternator fails in flight, I will get a low voltage indication and annunciation. When I get it, I can reduce load by switching off everything except my PFD screen and one nav/com. By doing this, my electrical load is reduced to about 4 amps. My 17 amp hour battery would then last almost 4 hours. I only have 3 hours of fuel (with reserve) in my airplane. Therefore, I can certainly divert to the nearest airport without any problem.

Ok then, what about battery failure? The battery I use costs $80.00. So, I replace it every two years whether it needs it or not (cheap insurance). I put the old battery in my lawn tractor and dispose of it's (now 4 year old) battery. Never had a battery failure doing it that way (in the airplane or the lawn tractor). If I were to have a sudden, catastrophic battery failure in flight, I could pull the master breaker and continue to navigate on my portable GPS and communicate on my handheld radio (which I always carry with me).
 

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Waiter

Well-Known Member
Joined
Mar 17, 2005
Messages
156
Location
Northwestern Ohio
I have dual electronic ignition. Normally, both ignitions run off the main electrical system.

In the event of failure of the main electrical system, a Cross tie relay drops out and one of the EIs runs on a small battery.

The EFIS also has an internal battery. This battery can run the EFIS for about two hours.

You can review my electrical diagrams (for my LongEZ) on my web site. Goto:

www.iflyez.com

Go down the left side and click on UPGRADES > ELECTRICAL

Waiter
 

Lee Schaumberg

Well-Known Member
Joined
Aug 28, 2003
Messages
215
Location
Northern Wisconsin
Hello and thanks to rpellicciotti and waiter

It seems waiter has an aux battery in there. By the way I have an original set of LongEz plans that I bought in time. I used to fly new Cessnas back and visit with that one guy that worked for BD.

Rpelliccitti - Never did I have a battery or gen-alt failure. Knock on wood! I too have a hand held that allows me to communicate and navigate if I have to. I'm just looking for my cake and want to eat it too.
Lee
 

Lee Schaumberg

Well-Known Member
Joined
Aug 28, 2003
Messages
215
Location
Northern Wisconsin
Hello

After more reading and thinking (sorry r+12) I came up with the following -
!. One Alternator with an external regulator OV & UV protection is provided
2. One main battery about 17ah
3. Small second battery about 7 ah sealed and drip proof to mount in cockpit
4. Carefully designed main and alternator bus
5. Dual Electronic Ignition
6. A head mounted lite (headlite) so I don't have to hold a flashlite
7. A piece of wood to beat on if I need to

After the skematic is designed I will post it.

Lee
 

addaon

Well-Known Member
Joined
Feb 24, 2008
Messages
1,686
Location
San Jose, CA
If you're thinking of always wearing the headlight, I promise that at least once (hot night, you have a headache) you won't... and isn't that when you have the problem? If you're planning on having it somewhere always accessible, how are you going to make sure the battery stays fresh? If it's part of your pre-flight, are you really going to scrub a flight for that reason? You're adding a huge human factor to avoid a minor equipment factor. Sure, have a flashlight with a long-shelf-life lithium battery somewhere; but you're much better off with cabin lights you can trust. If you don't trust your electrical system, put a small ELT battery (6 year shelf life) hidden behind a diode for the cabin lights, and replace it when you replace your ELT battery.
 

addaon

Well-Known Member
Joined
Feb 24, 2008
Messages
1,686
Location
San Jose, CA
I have one. They're not bright enough (at least, the model I got about three years ago aren't) to be comfortable to use for map-reading and such. They're also pretty big.
 
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