28V conversion?

[chrixxer]

As I ponder upgrades, including swapping an alternator for the generator and possibly some rewiring to take advantage of the 70 amp current availability, I've been prompted to consider a 28 V conversion.

Is such a thing even doable? Wouldn't there have to be an STC/PMA alternator, battery, etc.? (337?) Wouldn't everything 12V have to be replaced or a transformer installed ahead of it? (Autopilot, existing avionics (that aren't 14-28V already), lights, etc.?

[gsxrpilot]

It'd be a lot cheaper to sell and go buy a 28v bird.

[chrixxer]

5 minutes ago, gsxrpilot said:

It'd be a lot cheaper to sell and go buy a 28v bird.

Kinda what I figured. But just for my intellectual curiousity, what would be required? Why would it be so expensive / impractical?

[gsengle]

Because you'd have to likely replace every wire in your airplane and every electric piece of avionics, and every light and and and


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[gsxrpilot]

...and likely some STC's involved.

[N6758N]

Plus the 12v system is listed on the type certificate ( I believe) so that right there makes it nearly impossible. There is really no reason to need 28v in a small airplane, the advantages of a 28v system don't really show up until you get into a larger aircraft. Plus, all modern avionics are made to work from 11-33 volts. If you want to take advantage of a 70 amp alternator, then just make sure the existing wires going to your main bus are appropriately rated in size for that load (there is a good chance you will not have to do anything). 70 amps is really overkill in a short body too, I don't think you would ever need that much, especially considering new electronics draw a lot less. I would say the best way to reduce amp draw cheaply and easily is to install an LED landing light, that should shed about 7-8 amps.

[gsxrpilot]

It's an admirable effort, but there are much cheaper/easier ways to achieve the same outcome. As @N6758N says, start with LED landing lights. I'd also to the Generator to Alternator conversion ASAP. It's a pretty common upgrade.

Then move on to replacing all your lights with LED's. And finally every time you upgrade a radio, nav, instrument, etc, you'll likely also be reducing the amp draw as well. And those upgrades will pay much better dividends. Better to upgrade the antiques in your panel rather than upgrade the electrical system to support the antiques.

[chrixxer]

Nod. It was just a thought; "hey, if I'm installing the alternator anyway, does it make sense to halve the amp load by doubling the voltage?"

We apparently did manage to exceed 50A as is though, in daylight, with the intercom, audio panel, two COM radios, two NAV radios, autopilot, transponder, and 2x 2A iPads charging (and just the beacon light on).

[gsxrpilot]

You could start by replacing the coffee grinder that is your beacon. It's a power hog and for $500 you can replace it with a blindingly bright, (don't look at it directly without a welding mask on), LED version that just sips the power.

[Marauder]

As I ponder upgrades, including swapping an alternator for the generator and possibly some rewiring to take advantage of the 70 amp current availability, I've been prompted to consider a 28 V conversion.
Is such a thing even doable? Wouldn't there have to be an STC/PMA alternator, battery, etc.? (337?) Wouldn't everything 12V have to be replaced or a transformer installed ahead of it? (Autopilot, existing avionics (that aren't 14-28V already), lights, etc.?

Since I have converted my plane to an all electric plane, I have been paying close attention to the power draw of the various hardware installed. I created a load plan in case I did lose the alternator and have marked my breakers accordingly.

The risk isn't whether your system is a 12V or 24V system, it is how much available reserve power you have in case you lose the alternator.

Converting everything, if even possible, would be expensive and as others pointed out, a stack of paperwork.


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[Andy95W]

2 hours ago, chrixxer said:

We apparently did manage to exceed 50A as is though, in daylight, with the intercom, audio panel, two COM radios, two NAV radios, autopilot, transponder, and 2x 2A iPads charging (and just the beacon light on).

You can't really just add up all the amperages on the circuit breakers.  Those are nominal numbers above the actual current draw of the equipment.  Additionally, the COM radio draws significant power only when it's transmitting- something you generally won't do with both radios simultaneously. 

None of us really have an issue with our 12-volt airplanes- and there are some that are really decked out with Avionics.

[Marauder]

You can't really just add up all the amperages on the circuit breakers.  Those are nominal numbers above the actual current draw of the equipment.  Additionally, the COM radio draws significant power only when it's transmitting- something you generally won't do with both radios simultaneously. 
None of us really have an issue with our 12-volt airplanes- and there are some that are really decked out with Avionics.

I'm in the process of updating my amp loading spreadsheet to reflect the new equipment added. I do know that I had some gains when some instruments were removed in favor the Aspen. Once I get everything recalculated, I will post the pre and post amp load data. An example of some changes would be the removal of the factory gauges. In total they drew over an amp while the JPI 900 that replaced them draws considerably less.


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[carusoam]

The sole advantage is in using lighter wire.

When building a new plane, or rebuilding an old plane, this could make sense...

If spending gobs of money on a new alternator, throw in a few more bucks for...

• an updated voltage regulator
• a JPI to display current and voltage
• a new Concorde battery with battery minder
• buy a new shunt, somebody has lost one before...

That's essentially the basis for electrical power generation and storage. Everything else is on the use side.

Typical PP ideas, not a mechanic.

Best regards,

-a-

[Yetti]

batteries, bulbs, alternator, radios, circuit breakers and some hassle from the FAA