comfortcat

comfortcat

Well Known Member
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Although I'm starting with an O-320 with standard Mag/Carb installation on my RV-9A, I'm planning the electrical for the future. I want to add a backup battery (small? 7AH) and I'm wondering where folks put it?

Anyone on the firewall? If so, do you have pictures of the mount?

advTHANKSance

Dkb
 
If you're only planning for the future, why not just wait until then? Battery technology is poised for another big leap, in 5 years who knows what will be available.

Another thing to consider, instead of having a backup battery how about a back up alternator? Assuming you're going all EFIS, an 8 amp vacuum driven back up is perfect and affordable.
 
Sig600 said:
If you're only planning for the future, why not just wait until then? Battery technology is poised for another big leap, in 5 years who knows what will be available.

Another thing to consider, instead of having a backup battery how about a back up alternator? Assuming you're going all EFIS, an 8 amp vacuum driven back up is perfect and affordable.
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I'm with Sig. I know it's a bit of a drift from the OP question. But I really don't understand why we would want a second battery. Use a bigger battery (if more capacity is what you're after) but batteries are so limited anyway and are of a constant diminishing capability. I use the 8 amp backup alternator as it makes such sense (to me). It could run all my essentials for the full duration of fuel on board should the main alternator fail.

Bevan
 
Lots of folks use a 2nd battery to keep avionics up while starting the engine. Another way to do this is with a power stabilizer.

Options:
  1. TCW IBBS-12v-3ah, Backup Battery, 1.1lbs, $230
  2. EarthX ETX6A, Backup Battery, under 1lb, $150 (w/diode & resister sourced elsewhere)
  3. TCW IPS-12v-4a, Maintain EFIS voltage during start, 0.5lbs, $295
  4. Plane Power FS1-14, Backup Alternator, 6lbs, $695

I like the idea of an hour or two backup of critical instruments without the weight penalty of a backup alternator.

I'm leaning towards option 2.
 
grayforge said:
Hmmm.... twice the capacity, same size and only .4lbs and $40 more.
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....and if you don't want to spend all the money right now, you can get a simple sealed cell alarm system battery that weighs more but only costs $20. I put them under the seat on a 6/7, behind the panel on the tandems. Put in the fancy lightweght later, or now if you can afford it - same locations.

Oh - primary purpose for me is that starter motor voltage sag.
 
But where...

It's the "behind the panel somewhere" part that I'm looking for.
A backup battery just makes sense to me. Shorai is the target (and from Batterymart.com for a good price)

I have two fuse blocks, one for master and one for essential bus. I'll have the master batter hooked to the master bus (through the master switch) and the backup battery to the Essential bus through a switch. When flying, both master switches will be on.

Ah, but where does the backup battery go???

Pictures?

Dkb



grayforge said:
I'm thinking of installing one of these behind the panel somewhere:

LiFePo (Lithium) weighing under a pound.
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David,

Have you compared the EarthX batteries to the Shorai?

Pros for EarthX:
  1. They have a presence on this board and Kathy from EarthX is up here answering questions.
  2. They actually approve of using their batteries on aircraft and have a section of their site covering Experimental aircraft.
  3. The EarthX batteries have internal circuitry to balance charging of the cells and limit the discharge point to avoid damaging the battery.

Regards,
Russ
 
Im not sure how big the battery is that you're looking to mount, but I'm holding off on cutting the lightening holes in my -7's center rudder pedal bracket in case it will be useful for mounting something.
 
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FIN
9A
 
Thanx!

OK Guys!

Thanx for the info. I bit the bullet and got the small lightweight battery now, so I can get the size correct. Since they do not off-gas or leak acid, I figure under the seat in my 9A would be OK.

Pictures help me a lot.

CC
 
Why?

My question is why do you want and/or need a backup battery?

I have a SkyView (D100 before that) that has its own backup battery, my handheld GPS (Garmin 496) has its own battery backup, my Dynon D1 Pocket Panel has its own backup battery, I keep a charged handheld with headset adapters in the plane, and my ignition can run independent of ship's power.

With all that redundancy built into the plane, I can navigate and keep the plane upright long enough to get on the ground.

There are procedures for dealing with a radio failure in IMC so I really don’t see or feel the need for adding the complexity and weight of yet another battery.

What am I missing here?

Rumor has it that airplanes fly perfectly well without radios, transponders, and a lot of other stuff people tend to add to their eBus, which I don’t have and don’t feel is required.
 
In my case, none of my avionics have backup batteries. Plus, a single beefy backup battery may be more cost effective than multiple backup batteries from your avionics vendors.
 
I said that half-jokingly, but I may rig up a DC 12-volt motor, prop and ammeter, stick it out the car window and see what happens at 70 mph.
 
grayforge said:
Excellent idea!

Click to expand...

You laugh but that was exactly how the electrical system was powered on my first airplane (BC-12/65). It was the best of both worlds because you didn't need a transponder because the C65 did not have an "engine driven electrical system".
 
MY VP-X says that the EFIS and associated equipment draw about 2.5 amps at 10 volts (running off a small battery temporarily). So probably fewer amps at 14 volts.

This is for:
1. G3X Touch
2. AHRS
3. Engine Interface
4. GDL 39R
5. GMC 305
 
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