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New introduction and alternator question

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waynemil

Member
Hello everyone,
I just wanted to introduce myself. My name is Wayne and I purchased a rv7 Slider this July and it is in the shop in Chino CA getting the panel redone. I will post some pictures when it is complete and put some items in the classified section. I will be keeping it in Van Nuys when it is finished(which should be by Thanksgiving--Hopefully 2013:)). I sold my Bonanza because my wife and son were not that interested in flying so I decided to get a 7 after a friend gave me a ride in his 6, as well as another member giving me a ride in his 10. Thanks for getting me hooked!

My question is on backup alternators. I purchased the plane power FS-14 that goes in the accessory mount. Unfortunately my shop said the tach drive is in the way. I was wondering if anyone has run into this problem and has a fix. My engine is the Mattituck TMX 0-360. An alternative would be the B&C, which states it fits around the tach drive, but is only 20 amps and you have to get a regulator. Finally, I could just scrap the backup alternator and get a TCW Technologies backup battery.

Thanks for any ideas- I'll be going to the shop tomorrow to talk with a mechanic but wanted to get a head start.


Wayne
 
Welcome to VAF and the land of decisions (experimental).

You have the option to choose now (cost effective too). Many have backup alternators and have assessed the risks that that is what they have decided. Many others have batteries, and there are different battery chemistries and reasons for them. Many paths to risk mitigation.

I chose the TCW backup battery for my system. There is not a long well thought out set of reasons, just lower weight, cost, and the time it provides for alternator out seems to be good. Mostly, it was recommended by the Stein crew to keep low starting voltage from triggering a G3X reset after route programming.

My logic in general is this; Is the back up (alternator) more reliable than the main? Why? What fails and why? Where is the worst place you could be when it goes out? What do you want to do, complete the mission or stop. How long will it take before the backup fails? Then what? How long will that take, what do you want to draw power in that time? Remember you still have the main battery too.

My Dynon is a backup instrument and it has a self contained backup battery, the G3X will use the TCW. Not claiming it is best case, but it is what I have.

Others will give their experiences and configurations to help you decide. Many ways to reduce your risk of a single point failure here.

Oh, will you really need that tach drive with your new panel?

Happy flying.
 
The B&C is rated for 20 amps on a 28-volt system, but will actually put out 34 amps on a 14-volt system. I have one on my 9A.
 
Replace one magneto with a P-mag and use that to provide your tach signal. Simple, you make it easier to start your plane and reduce your fuel consumption.

And welcome to VAF!
 
If it's the backup alt why not use the SD8, cheaper and lighter? I believe most EFIS running with dual electronic ignition together will use about 3-4 amps leaving 5 amps for other emergency bus items. With dual EI and an EFIS on my EBUS I wanted more capacity than the 4 amp/hr TCW had. Also future maintenance of the battery and knowing it would give me rated capacity in an emergency situation changed my mind. Cost was close to the sd8, and I don't have to do capacity checks and buy new batteries. Downside is my G3X restarts with the voltage drop at engine start, but I feel it's a good compromise. On the other hand the TCW can be used to power on the avionics before start to test it and keep the avionics running.
 
If you have a cable driven tach or a tach drive generator...then the easy solution is to get rid of either of those. If you're getting a panel upgrade, I'm guessing you're getting some sort of new EFIS / EMS? If so, there is likely no need for that old technology....there are typically much better & easier ways to get an RPM reading than those old tach drives or generators. Both the PP and the B&C are fine units, but as Bill mentioned depending on your equipment, it also would be wise to look at some sort of backup battery to keep a potential EFIS/EMS from rebooting on startup. Not necessarily for protection, but more for convenience of being able to keep things even keel on the EFIS during start (and see all the EMS readings immediately).

I'm afraid at this point we just don't know enough about the rest of your configuration to give you an educated direction to go.....

Cheers,
Stein
 
alternator

Thanks everyone for you very helpful responses. Believe it or not, the culprit seems to be-- the "and20000" pad is missing from the back of the engine. It just has a plate covering the shaft. It is possible the previous owner took it off and did not reinstall it when he removed the vacuum system. It is almost $1,000 in parts for the pad and shaft adaptor so if he does not have it, I will probably go with the backup battery. Thanks also for the information on the sd8 alternator. That looks nice too, but installs on the pad which I am missing.


Thanks again,

Wayne
 
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