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03-13-2019, 10:29 AM
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Join Date: May 2005
Location: Rescue, CA. KROB
Posts: 352
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If you used a IBBS, then why not just two Earthx?s
So as Ive be looking at others panels and electrical architecture I’ve noticed many builders with IFR panels are utilizing a TCW IBBS backup battery. I assume these are used for a combination of brownout prevention for the PFD/engine data/AHARS and backup power for the same items. All good. However TCW makes two models of 12v a 3 amp/hr and a 6 amp/hr priced at $230\$395 respectively. These must be located aft of the firewall and replaced (i believe i read every 4-5 years). Also they weight 18 ounces (not clear if the 6amp/hr is the same as the 3?).
Heres my question, why wouldn’t a builder just have two Earthx etx 680’s instead? The earthx is $379 but provides 12.4 amp/hrs. It does weight 2.75 more lbs but will allow starting off of an additional power source. It can be incorporated into a single alt / dual battery design like the z-19 or with a backup alt into a dual alt/ dual batt z-14. Also, it can be mounted on the firewall with the primary battery.
Thoughts?
__________________
Rob Lasater
Rv-14 flying baby, yeah.
Paid Dec 2019
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03-13-2019, 10:47 AM
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Join Date: Mar 2018
Location: Ocean City, MD
Posts: 82
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That's my plan at least. Two batteries either both mounted on the firewall or one back one forward, both EarthX.
I'll grab a G5 with the backup battery if I absolutely must have something dedicated to the EFIS.
__________________
RV-10 - Empennage 95%
QB Fuse - Working
QB Wings - Delivered
San Diego, CA
www.wheelswelded.com
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03-13-2019, 11:11 AM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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Quote:
Originally Posted by echozulu
That's my plan at least. Two batteries either both mounted on the firewall or one back one forward, both EarthX.
I'll grab a G5 with the backup battery if I absolutely must have something dedicated to the EFIS.
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Seems the consensus is you will want that weight aft of the baggage bulkhead if you are going with the standard 540 and metal Hartzell prop.
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03-13-2019, 11:14 AM
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Join Date: Mar 2018
Location: Ocean City, MD
Posts: 82
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Quote:
Originally Posted by Brantel
Seems the consensus is you will want that weight aft of the baggage bulkhead if you are going with the standard 540 and metal Hartzell prop.
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Yeah I need to do some more W&B scenarios before I put the battery down. But my back of the napkin calcs make putting it forward more appealing I think. If it's just myself I can always put ballast in the baggage compartment to get the CG in range, but when I need to carry four people and full bags I won't run out of CG before I do weight.
__________________
RV-10 - Empennage 95%
QB Fuse - Working
QB Wings - Delivered
San Diego, CA
www.wheelswelded.com
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03-13-2019, 11:28 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
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Quote:
Originally Posted by echozulu
Yeah I need to do some more W&B scenarios before I put the battery down. But my back of the napkin calcs make putting it forward more appealing I think. If it's just myself I can always put ballast in the baggage compartment to get the CG in range, but when I need to carry four people and full bags I won't run out of CG before I do weight.
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Recommend you sharpen your pencil and run the W&B numbers again.
With a standard IO-540 and Hartzell CS BA prop, my two PC-625 batteries mounted in the standard position behind the baggage bulkhead provide for a very good W&B across the aircraft loading range. I?ve flown with a comfortable CG with four people, baggage, full fuel all the way to gross weight.
Carl
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03-13-2019, 12:07 PM
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Join Date: Jun 2006
Location: Delaware, OH (KDLZ)
Posts: 4,196
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Quote:
Originally Posted by Av8rRob
So as Ive be looking at others panels and electrical architecture I?ve noticed many builders with IFR panels are utilizing a TCW IBBS backup battery. I assume these are used for a combination of brownout prevention for the PFD/engine data/AHARS and backup power for the same items. All good. However TCW makes two models of 12v a 3 amp/hr and a 6 amp/hr priced at $230\$395 respectively. These must be located aft of the firewall and replaced (i believe i read every 4-5 years). Also they weight 18 ounces (not clear if the 6amp/hr is the same as the 3?).
Heres my question, why wouldn?t a builder just have two Earthx etx 680?s instead? The earthx is $379 but provides 12.4 amp/hrs. It does weight 2.75 more lbs but will allow starting off of an additional power source. It can be incorporated into a single alt / dual battery design like the z-19 or with a backup alt into a dual alt/ dual batt z-14. Also, it can be mounted on the firewall with the primary battery.
Thoughts?
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I originally had a pair of Odyssey 680s, then upgraded to an Earthx 680 and a Earthx 2400. I've had them in for over a year and am happy with them.
I can run the 680 as an independent ebus or I can put it in parallel with the main bus if required on those frigid mornings. I also have dual alternators. I have a VPX Pro. I borrowed some of the concepts from Z-14.
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03-13-2019, 12:21 PM
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Join Date: Nov 2009
Location: Cambridge, UK
Posts: 83
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I'm with you Rob but, to answer your question, the IBBS is convenient. You can achieve a good level of resilience without needing to think too hard about the electrical system architecture.
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03-13-2019, 02:10 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by Raiz
I'm with you Rob but, to answer your question, the IBBS is convenient. You can achieve a good level of resilience without needing to think too hard about the electrical system architecture.
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+1 - well engineered for it's purpose. Still . . . it might be nice to have a separate battery (16Ah) and managed with the TCW technology
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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03-14-2019, 05:35 AM
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Join Date: May 2005
Location: Rescue, CA. KROB
Posts: 352
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Quote:
Originally Posted by Raiz
I'm with you Rob but, to answer your question, the IBBS is convenient. You can achieve a good level of resilience without needing to think too hard about the electrical system architecture.
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Fair enough reason. Convenience is a real motivation. Any others?
__________________
Rob Lasater
Rv-14 flying baby, yeah.
Paid Dec 2019
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03-14-2019, 06:02 AM
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Join Date: Oct 2011
Location: Kennesaw, Ga
Posts: 825
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2 batteries ++
Some already had 2 batteries (like myself) and use Odyssey 680s and also a the IBBS battery and a backup batt for the G5. The IBBS is solely for the G3X system. It's small, compact and designed for avionics. I wouldn't put an EarthEx batt in my plane if you gave it to me, especially not inside the cockpit. You can certainly have 2 difference sources to start your plane, and have backup batteries that are designed for avionics. Does that weigh an extra 3 to 5 pounds, I guess, so I'll lose another 5 lbs off the gut and call it even 
__________________
Amir
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RV-7
RV-10 - Sold
Supporting VAF since the first visit
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