Question about the backup battery.

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Rich
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Re: Question about the backup battery.

Post by Rich »

Wiring diagrams and the POH show the emergency power drives the the AI and floodlight only. These are both a subset of components on the essential bus. The manual says it'd power both for up to 1-1/2 hours. This sounds credible given the mAh rating of the emergency batteries. Even more so if only one of the two are being used.

I don't know that it'd be such a great idea to remove the floodlight altogether. I routinely use it at night to illuminate the panel beyond what instrument lights do, such as switches. For those who still use paper for one thing or another (charts, checklists, route changes, etc.) or trying to find that pen you dropped, it's a great thing to have. And the aircraft manufacturer can not assume things like EFBs are available for use in an emergency.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: Question about the backup battery.

Post by Steve »

Rich:

The Emergency battery drives the AI and Pilot's map light only. The Floodlight is the EL panel mounted below the glareshield, which is powered from an inverter on the Essential Bus. The Emergency battery cannot power this (at least on our vintage DA 40s). The Emergency power switch is a DPDT toggle, with one side selecting the power source for the AI (either Ess Bus or Emergency battery), and the other selecting the power source for the Pilot's map light (either Ess Bus or Emergency battery).

Maybe semantics, but this is how the components are designated on the schematics, and I don't want a new pilot thinking that the Emergency battery is supposed to power the electroluminescent panel (Floodlight) below the glareshield (which it doesn't).

Steve
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Re: Question about the backup battery.

Post by Rich »

Steve wrote: Sat Aug 22, 2020 3:53 pm Rich:

The Emergency battery drives the AI and Pilot's map light only. The Floodlight is the EL panel mounted below the glareshield, which is powered from an inverter on the Essential Bus. The Emergency battery cannot power this (at least on our vintage DA 40s). The Emergency power switch is a DPDT toggle, with one side selecting the power source for the AI (either Ess Bus or Emergency battery), and the other selecting the power source for the Pilot's map light (either Ess Bus or Emergency battery).

Maybe semantics, but this is how the components are designated on the schematics, and I don't want a new pilot thinking that the Emergency battery is supposed to power the electroluminescent panel (Floodlight) below the glareshield (which it doesn't).

Steve
This might be true for yours, but wiring diagrams 9225-60-01 and 9233-10-03 dated dec.01 and dec 2000, respectively, and page 3-34 of the POH hard copy as delivered with my plane show it feeding the flood light dimmer.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Rick
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Re: Question about the backup battery.

Post by Rick »

Rich wrote: Sat Aug 22, 2020 4:07 pm
Steve wrote: Sat Aug 22, 2020 3:53 pmRich:

The Emergency battery drives the AI and Pilot's map light only. The Floodlight is the EL panel mounted below the glareshield, which is powered from an inverter on the Essential Bus. The Emergency battery cannot power this (at least on our vintage DA 40s). The Emergency power switch is a DPDT toggle, with one side selecting the power source for the AI (either Ess Bus or Emergency battery), and the other selecting the power source for the Pilot's map light (either Ess Bus or Emergency battery).

Maybe semantics, but this is how the components are designated on the schematics, and I don't want a new pilot thinking that the Emergency battery is supposed to power the electroluminescent panel (Floodlight) below the glareshield (which it doesn't).

Steve
This might be true for yours, but wiring diagrams 9225-60-01 and 9233-10-03 dated dec.01 and dec 2000, respectively, and page 3-34 of the POH hard copy as delivered with my plane show it feeding the flood light dimmer.
Mine is the same as Rich's. Actually, all 3 DA40's I've had were that way. I have never heard of the pilot map light being fed off the emergency switch - in my other DA40's the pilot map light was fed directly from the battery. As in, if you left it on, it would drain the battery, even with the master switch off! Are you sure your map light doesn't work unless the master is on? Maybe Diamond finally fixed this annoying behavior!
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Re: Question about the backup battery.

Post by Steve »

I went back and studied the wiring diagrams better. You guys are correct. I guess that proves that I have never used it! And I do remember folks having the issue with the Pilot's map light draining the battery. Sorry for the confusion....
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Re: Question about the backup battery.

Post by Rich »

This thread made me think back to the one time I had an electrical system failure - night VFR over NE AZ. This was a generator failure in a Tri Pacer that went undetected long enough that all electrons quit flowing and the flashlight lasted like 4 minutes.

This required use of the instrument emergency lighting (AKA radium-painted dials :D ), as long as it lasted. Which wasn't long.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: Question about the backup battery.

Post by CFIDave »

Rather than a Garmin GI-275, the Mid-Continent Instr & Avionics MD-302 SAM (standby attitude module) is already a certified option on new DA42s and DA40s, and standard on the DA62. https://www.flysam.com

It's not cheap (more than $8K + installation) but eliminates the need to replace battery packs every 2 years.
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Rich
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Re: Question about the backup battery.

Post by Rich »

The open-circuit voltage on my emergency pack came in this year at about 44.6 volts. I have in mind to replace my AI with one of the electronic alternatives, such as an RC Allen 2610. I don't know what voltage will be presented by the battery pack when under the pretty light load of the 2610. So I sent off an inquiry to Kelly Mfg. to see if this higher voltage would cause the smoke to leak out of the unit.

Has anyone asked this question previously or, better yet, tested it? :D
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: Question about the backup battery.

Post by Rich »

Rich wrote: Sat Aug 22, 2020 8:56 pm The open-circuit voltage on my emergency pack came in this year at about 44.6 volts. I have in mind to replace my AI with one of the electronic alternatives, such as an RC Allen 2610. I don't know what voltage will be presented by the battery pack when under the pretty light load of the 2610. So I sent off an inquiry to Kelly Mfg. to see if this higher voltage would cause the smoke to leak out of the unit.

Has anyone asked this question previously or, better yet, tested it? :D
Response from Kelly Mfg.:

The max voltage recommended for the RCA2610-3 28 volts, the unit can tolerate up to 32 volts for a short time, any voltage above that can and will damage the instrument.

The internal battery on the RCA2610-3 will power the instrument at 100% brightness for 1 hour, if you dim the brightness to 80% it will power the instrument for 2 hours, at 60% brightness you will receive the maximum battery span of 3 hours. Our internal battery offers hands free operation, as long as the aircraft is moving, should you lose power to the instrument the battery will automatically start powering the instrument. You can turn battery power off by pressing and holding both DIM buttons simultaneously until the 10 second count down starts.


So it would seem that if one installs one of these it would be highly recommended to get it with its backup battery and disconnect the lead at the emergency backup switch that would feed the AI.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: Question about the backup battery.

Post by Rich »

Digging into the implications of converting the AI - especially our old steam-gauge edition of the DA40 - to an electronic model produced some interesting data. Changing out the OEM unit for anything else requires including considering how the existing backup battery setup is or is not affected. For the RC Allen 2610 the 42+ volt AA battery stack is a no-go. For the newer battery pack it might be OK, as it has a lower nominal voltage that might be acceptable. For my case, the built-in battery backup for the 2610 looks like it's necessary. But the Continued Airworthiness section for this device states that the battery pack should (is required to?) be replaced every 3 years. As an option, the additional cost of the battery pack is $176, so I'm guessing the replacement pack (looks easy to replace) is likely to run about the same price, whereas the AA-pack approach is effectively free. An additional ~$60/year isn't a big deal for me, but something to know about beforehand. There is also the regulatory question of whether disconnecting the AI circuit from the AA-pack feed is a minor modification :scratch:

I haven't dug into the same issue for various alternatives, such as the AV-30 - not enough information to be found on the website. But it behooves one to understand this complication.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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