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TCW IBBS or IPS with G-900X

Plummit

Well Known Member
I want to be able to run my panel during engine start but the builder didn't provide for that. Stein built the panel and they made no provisions for running the avionics during engine start. The problem is that the battery (Odyssey 925) just isn't strong enough to keep the voltage above the minimum threshold to maintain the panel. Yes I've replaced the battery with a new one.

TCW makes 2 options: the IBBS and the IPS. The IBBS will provide a back-up battery that runs the avionics, even if there is an electrical failure. The IPS is supposed to maintain the voltage during engine start only. There is no "back-up" provision.
What have others done, short of adding a second battery?

-Marc
 
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Still in the build stage…

I installed a IBBS for IFR backup as well as voltage support during starts.

Do you have the Garmin GAD 27? That’s easily configured for voltage support during starts.
 
I just installed the 6Ah IBBS battery in my 9. My Dynon radio used to shut off during engine starts. I just added a G5 and GPS175 to my panel and the IBBS keeps everything powered up with no brownouts.
 
I just added an IBBS 3A system, I use it to boot up my GRT before engine start. I also have my Garmin G5 hooked up to it. I'm very happy with it.
 
Thanks guys, looks like the IBBS is the ticket, and I'll get the big battery (6ah) to give the most back-up time available.

-Marc
 
IPS

I installed a IPS to maintain 12v primary to my 12v-28v converter. I put startup avionics on the 28v bus. Solved any brownouts on startup.
It also added another feature to keep the 28v bus alive all the way down the 8.5v in case of emergency I could feed straight off battery to essential bus.
 
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Or, take a total system approach.

I have two PC-625 batteries. Each one runs half of the panel. I do engine start with both batteries in parallel and power to one SkyView EFIS, and some associated avionics like Comm #2 (Dynon radio). The other SkyView EFIS and the power hungry GTN-650 remain off for engine start (I do not have full faith with the GTN-650 riding the engine start voltage drop).

Result - with no backup batteries the one SkyView EFIS remains on - so full EMS indication is there during the start sequence.

The other benefit it this setup eliminates all need for any backup batteries for all practical single fault casualties - maintaining full IFR flight for ~1.2 hours (if only one battery available after the fault) or up to 3 hours if both batteries are available after the fault.

Carl
 
Or, take a total system approach.

I have two PC-625 batteries. Each one runs half of the panel. I do engine start with both batteries in parallel and power to one SkyView EFIS, and some associated avionics like Comm #2 (Dynon radio). The other SkyView EFIS and the power hungry GTN-650 remain off for engine start (I do not have full faith with the GTN-650 riding the engine start voltage drop).

Result - with no backup batteries the one SkyView EFIS remains on - so full EMS indication is there during the start sequence.

The other benefit it this setup eliminates all need for any backup batteries for all practical single fault casualties - maintaining full IFR flight for ~1.2 hours (if only one battery available after the fault) or up to 3 hours if both batteries are available after the fault.

Carl
So in the event of smoke in the cockpit, the usual procedure is to turn off the master (not sure what controls both batteries in your case),
what happens to your panel now?
 
Yep - POH immediate action on any electrical failure is to open both Master Solenoids (there is one on each battery). This isolates the “fat” wires in the plane from power, including the alternator. After this immediate action the pilot has has up to three hours of IFR battery capacity available to land and figure out what happened on the ground.

The panel is not powered from Master Solenoids. Each batter provides power to half the panel, and each battery can be cross connected to either side of the panel in the event of the fault being on a battery (or associated wiring).

In other words, the worst case scenario is you are left with half a panel (EFIS #1, Comm #1, etc.) after the fault but that side can be restore by moving that side toggle switch to the “alternate” position.

Carl
 
Yep - POH immediate action on any electrical failure is to open both Master Solenoids (there is one on each battery). This isolates the “fat” wires in the plane from power, including the alternator. After this immediate action the pilot has has up to three hours of IFR battery capacity available to land and figure out what happened on the ground.

The panel is not powered from Master Solenoids. Each batter provides power to half the panel, and each battery can be cross connected to either side of the panel in the event of the fault being on a battery (or associated wiring).

In other words, the worst case scenario is you are left with half a panel (EFIS #1, Comm #1, etc.) after the fault but that side can be restore by moving that side toggle switch to the “alternate” position.

Carl
So in your case opening the master(s) does not disconnect power from the busses? So I assume we now we have more switches to disconnect power?

Cockpit is still filling with smoke and you don't have time to read time POH, now what? In a few seconds you may not be able to see the panel.

(not sure you've ever seen a cockpit filling with smoke but I have (on the ground thankfully), it gets very exciting very quickly)
PS: small wires can emit large quantities of smoke as they melt, not just fat ones.
 
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So in your case opening the master(s) does not disconnect power from the busses? So I assume we now we have more switches to disconnect power?

Cockpit is still filling with smoke and you don't have time to read time POH, now what? In a few seconds you may not be able to see the panel.

(not sure you've ever seen a cockpit filling with smoke but I have (on the ground thankfully), it gets very exciting very quickly)
PS: small wires can emit large quantities of smoke as they melt, not just fat ones.

This scenario is why switches are grouped like this. Smoke in the cockpit, these switches to off.

This is also why my iPad will have Foreflight ready with the attitude feature available immediately if in IMC...although if this happens in IMC, things are not going to end well.
 

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So in your case opening the master(s) does not disconnect power from the busses? So I assume we now we have more switches to disconnect power?

Cockpit is still filling with smoke and you don't have time to read time POH, now what? In a few seconds you may not be able to see the panel.

(not sure you've ever seen a cockpit filling with smoke but I have (on the ground thankfully), it gets very exciting very quickly)
PS: small wires can emit large quantities of smoke as they melt, not just fat ones.

Walt - not how the design works.

Now consider my experience with RVs having absolutely dead or less than full capacity backup batteries, then overlay the risk of a pilot having an electrically dependent engine that finds himself with a stopped fan because the 60 minute backup power only lasted 15 minutes. Do builders actually test fly the plane on backup power alone to verify design targets are met?

I also suggest that a low probability but far more dangerous electrical system single fault casualty is a lithium type backup battery (or something connected to it) going nuclear. How does the pilot isolate that fire? My design mitigates this risk as multiple failures need to occur for me not to be able to isolate an electrical fault and still maintain at least half the panel.

Sorry for the thread drift but I had to comment on the trend of people just adding backup batteries while not carefully considering:
- What do I have left and how long will I have it (and does this support my IFR risk profile? I suggest that no less than a full hour of IFR flight is required, I have much more than that).
- How do I test that the various back batteries work as advertised?
- Do I have confidence that the backup batteries are properly charging - and how do I verify this?
- How often do these batteries need to be replaced to have some confidence they will meet minimum capacity requirements.

I say again, step back and overlay the requirements for what you want your plane to do, then look at a total system approach to meet those requirements as well as mitigate risk for any plausible single point failure. This includes any component (battery, alternator, solenoid, switch, etc.) as well as any connection or connecting wire.

If nothing else I’m hopeful IFR builders will see the value of not having all power going through a single Master Solenoid or the use of a single Avionics Master switch. If you want this function have two, one for each half of the panel (assumes two EFIS, two GPS sources, two radios, etc.). I can also state this is not at all hard to achieve.

Enough - stepping off my soapbox.

Carl
 
Carl,
We obviously have different philosophy's, I'm a big fan of keeping things really really simple, I don't want folks to have to take a special course to teach them about their electrical system when I'm done. So single battery, single or dual alternator, usually a TCW BU battery to keep a couple of important things going both during start and in an emergency, then another BU battery in the Stby G5 just in case.

Turn off the master and power is killed to everything except for those items running on the BU batteries, those are the 'keep me alive' items.

Battery voltage is always monitored on all BU batteries, so pretty easy to see that those items are always fully charged. Average run time on all BU batteries for what they power is about an hour, plenty of time to get down.

I think most folks in a airplane with a overly complex electrical system would not be able to remember what or how to isolate an electrical fault under pressure, even if you built it. Personally I think I'd rather have the engine quit than have to deal with an electrical fire/smoke in the CP hence my one switch and everything goes off mentality.

And as far as Lithium back ups, well I've not heard of a single case of a TCW or G5 battery causing any Nuclear meltdowns.

As for an electrically dependent engine, won't go there, to much complexity/risk with minimal gain IMO.

PS: the G900 does indeed have power input #2 to support backup power input.
and if anyone is interested this is the the master contactor I prefer to use:

https://www.gigavac.com/sites/default/files/catalog/spec_sheet/mx11.pdf
 
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