12V/24V?

aerhed · #1 01-01-2009, 09:26 PM

Hi, is everyone using 12V systems in the RV10, or are some using 24V? Also, will a Piper mopar alternator fit in the 10 cowl with a narrow deck?

w1curtis · #2 01-01-2009, 10:13 PM

While from a "technical" perspective 24/28 volts is superior, from a practical perspective 12/14 volts is MUCH better. At 12/14 volts your accessories (batteries, starter, light bulb, etc) will be much less expensive and any weight savings you will achieve by using thinner wires will be eroded by the 24 to 12 volt converters you will have to carry around to be able to use standard 12 volt devices. Most current avionics will operate happliy on 10-32 volts but for what you are likely to put in the RV-10, the options are greater for 12/14 volts.

For larger aircraft with miles of wiring, the thinner wires that can be used with a 24 volts system can add up to significant weight savings. For aircraft the size of the RV-10 however, any savings will never outweigh the convenience of a 12 volt system. I knew of only one builder that was going with a 24 volt system but he subsequently sold his kit so I don't know of any anymore.

As for the alternator, I don't know about the Piper Mopar alternator but the Vans FWF kit now includes the superior Plane Power alternator rather than the crappy Nippondenso alternator provided in previous kits.

PJSeipel · #3 01-02-2009, 07:10 AM

I initially wanted to go 24V. From a technical perspective it's got a lot of advantages. Practically, however, I ended up where I would have been unable to do it without either a 12V bus or several 12V converters. I found that many accessories that I wanted were either not available in 24V configuration or were were much more expensive.

PJ Seipel
RV-10 #40032

Geico266 · #4 01-02-2009, 07:15 AM

Try getting a jump if you leave the master on.

N395V · #5 01-02-2009, 02:27 PM

For all the intuitive reasons of 28V is better I built my plane with a 28 V system.

For all the reason Mr. Curtiss mentions it was a big mistake and I wish I had gone with 14V.

aerhed · #6 01-02-2009, 06:26 PM

Ok, thanks. I've been in A/C maint. forever so I don't really need to know the why's, just the if'st. The Piper alt. is the old mopar pancake that was around forever. It's kinda big diameter but awful easy/cheap to rebuild/repair. A pretty good looking one came with the E4B5 I just bought.

David Clifford · #7 01-03-2009, 11:04 PM

I'm doing the same thing on my 10 as I did on the Cozy MKIV using two Odyssey batteries connected in-line with a busbar. A lead from the connecting busbar goes to the 12V master solenoid and the + terminal at the second battery goes to the 24V master solenoid. It works great on the Cozy. 24 volt handles the starter, fuel pump, landing gear, and the IP EFIS systems, radios, ect. The 12 volt side handles the interior lighting, power plug adapters for entertainment, and the 'el-cheapo automotive salvaged HID landing and taxi lights and some other 12 volt misc.. Used a standard Cessna style 3 pin aux power receptical wired to the 24V side for charging and emergency jump starting. It was a little weight penalty having the additional 12V heavy leads, extra solenoid, and an additional 16# battery, but there are absolutely no problems cranking over the engine due to a weak battery. On the 10, I flattened out the side lips of the supplied battery tray and rivited on 3/4" aluminum angle to form a boxed tray.. The solenoids are bolted to the angle and the dual batteries now fit perfectly side by side in the modified tray.

mkmuch · #8 01-03-2009, 11:08 PM

Quote:

Originally Posted by David Clifford

I'm doing the same thing on my 10 as I did on the Cozy MKIV using two Odyssey batteries connected in-line with a busbar. A lead from the connecting busbar goes to the 12V master solenoid and the + terminal at the second battery goes to the 24V master solenoid. It works great on the Cozy. 24 volt handles the starter, fuel pump, landing gear, and the IP EFIS systems, radios, ect. The 12 volt side handles the interior lighting, power plug adapters for entertainment, and the 'el-cheapo automotive salvaged HID landing and taxi lights and some other 12 volt misc.. Used a standard Cessna style 3 pin aux power receptical wired to the 24V side for charging and emergency jump starting. It was a little weight penalty having the additional 12V heavy leads, extra solenoid, and an additional 16# battery, but there are absolutely no problems cranking over the engine due to a weak battery. On the 10, I flattened out the side lips of the supplied battery tray and rivited on 3/4" aluminum angle to form a boxed tray.. The solenoids are bolted to the angle and the dual batteries now fit perfectly side by side in the modified tray.

So you have the best of both worlds?

If I understand you correct you essentually wired them in series so depending on which battery you pull from gets you the voltage desired (i.e.12 or 24)?

David Clifford · #9 01-04-2009, 08:28 AM

Quote:

Originally Posted by mkmuch

So you have the best of both worlds?

If I understand you correct you essentually wired them in series so depending on which battery you pull from gets you the voltage desired (i.e.12 or 24)?

Yes. And wiring the AP receptical to the 24 volt side allows "standard" aviation jumping/charging when needed.

N395V · #10 01-04-2009, 06:07 PM

Using two 14 volt batteries in series and tapping one or the other for 14v is a recipe for early battery failure. One will be overutilized relative to the other causing a drain of the less used battery into the more used one.

If you are going to do this you shoud use a voltage equalizer such as this one... http://www.leab.de/english/dcdcwandl...zer/index.html