Backup Battery, not for Skyview, for EMS, Transponder, IFR, etc...

[ebackscheider]

What have or are folks doing for backup battery for EMS, Transponder, IFR Navigator, etc..? My HDX's have the battery. I was thinking of doing a dual diode connection to the other important things and connecting them to a smaller backup battery buss. Is this acceptable, the diode thing? I am also going to install a 2nd alternator, but still looking for a quick battery type backup for just a few items. Looking to learn what others have and are doing! Thanks!

 

[Raymo]

Here is an option that is commonly used. There are different amp/hr sizes available. I think the diode is built into the unit.

TCW Integrated Back Up Battery System - FAA Certified | Aircraft Spruce

TCW Integrated Back Up Battery System - FAA Certified The Integrated Back-up Battery System, IBBS, is an electronic system that combines a rechargeable battery pack, a charger and switching logic in one convenient package.

www.aircraftspruce.com

 

[RVDan]

Assuming that you are using the Dynon EMS, it will be powered by the HDX backup battery.

 

[maartenversteeg]

True for teh Dynon EMS, but the transponder and IFR navigator have their own supply from the main airplane bus, so these are not receiving power from the Dynon backup battery.

 

[Carl_Froehlich]

For IFR, consider a full system design for power reduancy, not just cobbling together multiple backup batteries. Here a thoughtful dual battery, single alternator design with no backup batteries offers significant advantage.

 

[GalinHdz]

Do you really want to press on in actual IMC with an electric failure or just land at the nearest airport and fix the problem? YMMV

 

[airguy]

Do you really want to press on in actual IMC with an electric failure or just land at the nearest airport and fix the problem?

Depends on the failure. Historically alternators are much more likely to fail in flight than a battery. A dead battery is found prior to flight - whereas alternators tend to die during flight. One or two batteries as your heart desires simply defines your ability to continue flight without an alternator - but a backup alternator allows you to continue flight to the destination rather than an immediate divert. Losing BOTH alternators, on a single flight, amounts to spectacularly bad luck (or bad maintenance) and then you are indeed relying on battery power for an immediate divert.

Personally, I run an EarthX 900 with dual alternators. A dead component (battery OR alternator) gets addressed prior to flight - a dead alternator in flight results in continued flight to the destination on the backup and replacement prior to further flight. In the highly unlikely event of losing both alternators in flight, I have nearly an hour reserve in the battery with full IFR operability for an immediate divert - and once that goes dead I still have 45 minutes on the Dynon EFIS with everything else dark. If all that goes dead and I haven't managed to put it on the ground yet - then Jesus loves me and I'm ok with that.

Backups and redundancy have practical limits, and these are mine. YMMV.

 

[Carl_Froehlich]

“One or two batteries as your heart desires simply defines your ability to continue flight without an alternator - but a backup alternator allows you to continue flight to the destination rather than an immediate divert.”

Not at all correct. Simple fixation on the alternator as the only point of failure is wrong. For that matter alternator failure, while more likely than other single point failures has the least impact - just land before your battery dies.

Review the NTSB reports of twin engine aircraft with dual alternators that suffered sudden and total power failure. The root cause is always the same, a common single point failure.

Look at all the other stuff (switches, connectors, relays, etc.) that can keep power from getting to the panel besides the alternator - if you cannot live without a specific piece of equipment then mitigate the risk. Having two identical ship batteries, with independent feeds to left/right side of your panel, with tested backup modes is what I do. And - no backup batteries required or desired.

Carl

 

[airguy]

“One or two batteries as your heart desires simply defines your ability to continue flight without an alternator - but a backup alternator allows you to continue flight to the destination rather than an immediate divert.”

Not at all correct. Simple fixation on the alternator as the only point of failure is wrong. For that matter alternator failure, while more likely than other single point failures has the least impact - just land before your battery dies.

Review the NTSB reports of twin engine aircraft with dual alternators that suffered sudden and total power failure. The root cause is always the same, a common single point failure.

Look at all the other stuff (switches, connectors, relays, etc.) that can keep power from getting to the panel besides the alternator - if you cannot live without a specific piece of equipment then mitigate the risk. Having two identical ship batteries, with independent feeds to left/right side of your panel, with tested backup modes is what I do. And - no backup batteries required or desired.

Carl

Your illustration of the twin with sudden and total power failure is a red herring Carl, and I suspect you know that. The crew had a dead battery, jump started it and took off - AGAINST the operating procedure for that aircraft. Both alternators may have been operating at takeoff, but the gear and flaps retraction after liftoff drew more power than the alternators and depleted battery (combined) could provide - and the bus voltage dropped below what the engine computers needed to keep alive - putting them in the dirt. The POH specifically called that out, prohibited it, and the crew ignored it.
Now, if you want to include the second part of my statement, which you conveniently dropped in order to make your point, it will eliminate that problem - "A dead component (battery OR alternator) gets addressed prior to flight" - that does not mean "jump start it and roll". Jump starting an aircraft and departing immediately is NEVER a good idea, as you've effectively got no reserve against an alternator failure. It needs to be fully charged or replaced if it won't hold a charge.

In any case - we've gotten off the original question of backup batteries for individual components. Arguing about proper electrical system design deserves it's own thread.

 

[Carl_Froehlich]

Fully agree - jump starting is forbidden in my POH. A jumped battery has been abused and you can no longer rely on whatever reserve capacity you designed for.

But - you picked the one example of pilot error. Look at the others where a high resitance contact got hot during flight and failed. Unfortuanly it tends to be common buss connection (designed in single point failure risk).

A battery, assuming it has not been abused, is very reliable. The connections to that battery (grounds, master solenoids, other switches) are not. For IFR I do not rely on any single component, other than the engine, to not fail. How many people are flying with a single Avionics Master?? A second alternator just mitigates the one risk of loosing the primary alternator - a failure that is not at the top of the list of bad things to happen.

I stand by my statement. There are better ways to ensure power to the panel for IFR than cobbling together a bunch of backup batteries. For VFR get the Dynon backup battery and a hand held and be done.

 

[airguy]

There are better ways to ensure power to the panel for IFR than cobbling together a bunch of backup batteries. For VFR get the Dynon backup battery and a hand held and be done.

And on this point, we agree - there are better ways for that. Your statement was worded to indicate an overbroad application however, in my opinion.

For my own purposes, my aircraft is electrically dependent for continued engine power as well as nav - so I have a redundant power generating source as well as a large reserve. Certainly I'm in the minority of small aircraft owners/builders that have chosen this path.

Going down the path of trying to eliminate single-point failures is a non-starter in the small aircraft we fly - we only have one propeller, one crankshaft, one wing, etc etc - there are practical limits to trying to impose "ultimate safety" on a small GA single no matter how good your intentions are. If a person is unable to accept ANY risk for single-component failure, then they need to stay on the ground. "Best practices" are certainly a goal to adhere to, but there are limits.

 

[ebackscheider]

Assuming that you are using the Dynon EMS, it will be powered by the HDX backup battery.

Are you sure the EMS is powered by the HDX Batt? It has it's own power line. Just trying to verify, as I just hooked up the EMS power to it's own breaker last night. Or, at least something labeled EMS

 

[ebackscheider]

Didn't mean to open a can here. I'm going dual Alternators, but want my IFR stuff backed up to battery as well. If I'm on an approach and it all dies, I don't want to die. No, I would not press on knowing there was an issue, but I want to get out if I find myself there.

 

[maartenversteeg]

Are you sure the EMS is powered by the HDX Batt? It has it's own power line. Just trying to verify, as I just hooked up the EMS power to it's own breaker last night. Or, at least something labeled EMS

I am confused, I can't find any power connection on either the 37 or 25 pin connector on the EMS. Where are you connecting power to the EMS, which pin/connector. I am pretty sure that the EMS gets it's power via the Dynon network connections, my EMS works and does not have any additional power lines. Except for the bus voltage measurements that are wired to the pins 1 and 2 of the 37-pin connector on the EMS.

 

[RV8JD]

Are you sure the EMS is powered by the HDX Batt? It has it's own power line. Just trying to verify, as I just hooked up the EMS power to it's own breaker last night. Or, at least something labeled EMS

From the HDX Pilot's User Guide, units powered and not powered by the HDX display/SV-BAT-320 backup battery:

 

[airguy]

The EMS does have a power connection (red wire, pin 1) - but it's for monitoring voltage on the bus, not for powering the EMS. EMS operating power comes from the HDX, whether on ships power or backup battery power.