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If you used a IBBS, then why not just two Earthx?s

Av8rRob

Well Known Member
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?
 
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.
 
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.

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.
 
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.
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.
 
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.

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
 
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?

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.
 
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.
 
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.

+1 - well engineered for it's purpose. Still . . . it might be nice to have a separate battery (16Ah) and managed with the TCW technology
 
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.

Fair enough reason. Convenience is a real motivation. Any others?
 
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 :D
 
It was adding up the # of backup batteries I needed for my dual electronic ignition glass panel airplane that pushed me in this direction. I just went with two EarthX batteries on the firewall and skipped the tcw backups. I also have two alternators. My goal was system level redundancy, not just a few points. That was a net one lb gain from a single pc680 and alternator, basically because of the three contacts to manage my system. I switched to a Whirlwind prop to keep CG in check.
 
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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.

That was sort of my take on it.

For me my sole intent with backups is to get me out of the soup if something goes wrong. If it's an alternator issue, I have a backup. If something between the battery and through the VPX dies, I have the IBBS... if that all fails I have the G5 with it's backup battery.
 
Advanced Flight

I went with Advanced Flight EFIS devices. The IBBS is wired directly to the AFS EFIS for control and the EFIS manages switching the power source from the main system power to the IBBS in the event of a power failure. That was less complicated than installing a two battery electrical system.
 
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