12v and 24v systems

Frogs97

Frogs97

Pre-takeoff checklist
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Frogs97
My wife has been on me for Christmas and birthday gift ideas. Apparently my repeated response of "A plane", hasn't been the kind of thing she's looking for. So I've been working on some ideas. One of the ideas was a BKool for summer flying. The rental planes I've been flying are all 12v, and I remember from another thread that many of the later model Cessnas are 28v. But, how prevalent is 24v in various planes?

I'm thinking that I could choose the 12v now, and if I end up with a 24v plane, I could just put my own 12v battery in the back with it. Just would rather not have to worry about keeping it charged, or carry the extra weight if I don't have to.
 
Seemed like the best answer since you didn't mention which models you were looking at. They introduced 24 volts in various years depending on model. Some never did get 24 volts.
 
Make it yourself, instead of buying it will save you some money.
 
Actually there is no such thing as a 28 volt system. you get 2.2 volts per cell in a lead acid battery. 3 cell battery is a 6.6 volts, a 6 cell battery is a 13.2 volt battery, a 12 cell battery is a 26.4 battery.

so you really have a 6 VDC, a 12 VDC, and a 24VDC systems.
 
Many of the appliances are dual voltage, check to see what your appliance really needs before you get wrapped around buying some thing you really don't need.
 
Tom-D said:
Actually there is no such thing as a 28 volt system. you get 2.2 volts per cell in a lead acid battery. 3 cell battery is a 6.6 volts, a 6 cell battery is a 13.2 volt battery, a 12 cell battery is a 26.4 battery.

so you really have a 6 VDC, a 12 VDC, and a 24VDC systems.
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I thought the 28 volt system described in later model Cessnas (out of the POH) refers to a nominal buss voltage of the system not the battery itself.

I know in my own aircraft with a 12 volt AGM battery the fully charged battery voltage is 12.6 and the buss voltage is usually around 14volts otherwise the battery wouldn't charge in a reasonable amount of time., hence the 14 volt nomenclature.
 
tsts4 said:
I thought the 28 volt system described in later model Cessnas (out of the POH) refers to a nominal buss voltage of the system not the battery itself.

I know in my own aircraft with a 12 volt AGM battery the fully charged battery voltage is 12.6 and the buss voltage is usually around 14volts otherwise the battery wouldn't charge in a reasonable amount of time., hence the 14 volt nomenclature.
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check voltage with a known good volt meter, with the engine off, see what you get. Charging voltage is always higher
 
Tom-D said:
check voltage with a known good volt meter, with the engine off, see what you get. Charging voltage is always higher
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To what end? It will read the battery voltage which for my own aircraft is around 12.6 when fully charged. However, the operating voltage of the buss is higher. This is why Cessna describes the electrical system as 28 volts vs 24 or 26, because that more accurately describes the buss voltage during normal operations.
 
All the electrical components in the aircraft are designed to run on 14 or 28 volts, as applicable, (except maybe the starter) because that's what the alternator is keeping the bus at. The batteries are 12 or 24 volts (nominal), but unless the bus voltage is higher they won't recharge and stay charged.

Charging voltages are actually a bit higher than 14 or 28, depending on temperature.
 
tsts4 said:
To what end? It will read the battery voltage which for my own aircraft is around 12.6 when fully charged. However, the operating voltage of the buss is higher. This is why Cessna describes the electrical system as 28 volts vs 24 or 26, because that more accurately describes the buss voltage during normal operations.
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Show me your reference.
 
Tom-D said:
Show me your reference.
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Cessna 172S and 182S Pilot Information Manuals.

Plus iif you go to an alternator supplier's website such as B&C or PlanePower, they describe their alternators and external voltage regulators in terms of 14 or 28 volts.
 
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Tom-D said:
Actually there is no such thing as a 28 volt system. you get 2.2 volts per cell in a lead acid battery. 3 cell battery is a 6.6 volts, a 6 cell battery is a 13.2 volt battery, a 12 cell battery is a 26.4 battery.

so you really have a 6 VDC, a 12 VDC, and a 24VDC systems.
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Actually, that's more likely the charge current. The open circuit voltage on a fully charged lead acid cell is only about 2.1V.

And guys the word is "BUS" not "BUSS" unless you're talking about kissing.
 
The misspelling is probably because we all saw Buss fuses all our lives. Simple mistake. Nobody cares. Well, almost nobody. :)

BTW, re: 12v or 14v? If my volt meter reads less than 14.3 something's wrong. 14.4 is typical.
 
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tsts4 said:
Cessna 172S and 182S Pilot Information Manuals.
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And all maintenance manuals. And the Cessna charging system manual, which has detailed charts showing what charging voltages shoud be at various ambient temperatures around the regulator. One needs a calibrated voltmeter and a thermometer to do it right.
 
Frogs97 said:
My wife has been on me for Christmas and birthday gift ideas. Apparently my repeated response of "A plane", hasn't been the kind of thing she's looking for.
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Obviously you haven't worked on this problem enough. ;)

Tell her to buy herself some shoes or diamonds instead. Once the collection amassed is large enough, the capital expenditure for the aircraft will look small.
 
One day not long after I bought my first airplane I came home and my wife had a nice ring with two crossing rows of rectangular channel set diamonds. I asked where that came from. She held it up, wiggled her finger, and said this was her airplane. That was 25 years ago and I still have no idea what that ring cost. I've never asked! True story.
 
Stewartb said:
One day not long after I bought my first airplane I came home and my wife had a nice ring with two crossing rows of rectangular channel set diamonds. I asked where that came from. She held it up, wiggled her finger, and said this was her airplane. That was 25 years ago and I still have no idea what that ring cost. I've never asked! True story.
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Was the ring 12 or 24 volt?
 
Stewartb said:
One day not long after I bought my first airplane I came home and my wife had a nice ring with two crossing rows of rectangular channel set diamonds. I asked where that came from. She held it up, wiggled her finger, and said this was her airplane. That was 25 years ago and I still have no idea what that ring cost. I've never asked! True story.
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Best never to ask. Win/win. :)
 
denverpilot said:
Obviously you haven't worked on this problem enough. ;)

Tell her to buy herself some shoes or diamonds instead. Once the collection amassed is large enough, the capital expenditure for the aircraft will look small.
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HA! Unfortunately, it's the OPEX that has her worried. I could go buy the plane right now without issue. But, every month the hangar and insurance bills were do I'd be getting an earful. Not to mention any MX.

Still trying to figure out how to make all this her idea!:wink2:
 
Tom-D said:
Many of the appliances are dual voltage, check to see what your appliance really needs before you get wrapped around buying some thing you really don't need.
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That's what I've found. Or stated another way, they work within a range of voltages, inclusive of 12-28v.
 
Frogs97 said:
Still trying to figure out how to make all this her idea!:wink2:
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Take her to an air show. Whatever she likes, buy that. Even if it's got a radial on the front. Hahaha.

(My wife is gaga over warbirds. No way in hell I'd buy one. Not even a T-6. I enjoy eating too much. YMMV.)
 
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