Advantage/Disadvantage 12v vs 24v electrical system?

[Pilot135pd]

I've always owned 12v aircraft so I'm interested in learning the pros and cons of the 12v system over a 24v system. Everyone has 12v chargers and 12v accessories are more readily available, although that's changing and now most everything works from 11 to 30vdc.

1- Would it be just basically changing the alternator, regulator, and starter, or is it more complicated and I would need to change more things?

2- Is there any advantage to keeping the 24v vs changing it to 12v? Since all my avionics work from 11v to 30v, if I keep it 24v and that voltage is basically only used for starting, if I lose my alternator in some remote place out in the back country, I'm thinking it could be hand propped to start and my avionics should last a whole lot longer as the voltage in those batteries slowly decreases from 24v down to something where the avionics would stop working below 11 volts, or am I not understanding how the 24v avionics work?

Here's my setup:

My new-to-me plane has a 24volt electrical system. It used to have an old Russian radial engine and now it has a Lycoming IO-540 (with a modern brand new alternator and starter). It's a VFR plane with bare minimum avionics: G5, MGL engine monitor, radio, portable Garmin 696 and Aera 660, manual flaps and trim. It also has a IO-540 with 3 blade C/S prop.

It currently has two bigass & heavy 12volt batteries that came from an old tech jet that uses 4 batteries and my plan is to replace them with two very much lighter Odyssey 680s. I read in another thread here of at least one RV with an IO-540 using a single Odyssey 680 so I don't expect any starting problems doing that swap.

 

[riseric]

I have a 24V Cessna
Rapidely, what I can observe first hand is this:
Because a 24V is somewhat a less frequent system, part availability can be an issue and cost is always higher. i.e. starter and batteries.

Keep in mind that one advantage of higher voltage is that for a given need in watts (say for an element drawing 120W as a light or Pitot heater, you will need 10A in a 12V system, or 5A in a 24V system), the wiring can be smaller, thus less overall weight/cost for all the electrical system.

If you choose to convert a 24V system to a 12V system, beware that all or some of the wiring system might not be able to handle the extra Amps??
Others might think of extra issues?

 

[BillL]

I looked at this decades ago, but never did a change over. The advantage is lighter wiring due to lower demand amps. Also fixed resistance things in the system have lower power losses.

If you have a minimalist system, then an alternator, and new power wiring to high demand devices would be in order. If you go this direction the intervention in the wiring system, selection of wire, sizes and termination could yield a more reliable flying machine in the end. A double advantage.

 

[bmellis11]

Here's a link you may find useful on this topic: http://www.aeroelectric.com/articles/richter/response_1.pdf

 

[BobTurner]

Your thinking that your 10-28 volt avionics would keep running longer on a 24 volt battery vs a 12 volt battery, following an alternator failure, is incorrect. All batteries have an ‘amp hour’ rating. Once you exceed that, the battery will no longer supply a useable current - even if it still shows, say, 15 volts.

 

[Pilot135pd]

Thanks for all the replies, they did jog my memory to basic electrical things I had forgotten.

The plane has all LED lighting and as you can see in the picture practically no avionics, plus no additional motors. Manual trim, manual flaps, no landing gear or cowlings doors, etc.. It doesn't even have a transponder, which would be the highest current draw on the panel. Good old Polish/Russian engineering so everything is manual and the only thing that uses a lot of current is when starting the IO-540.

Aside from the engine starting, everything else electric (avionics and lights) has a very low current draw so I don't think I'd need to change much wiring, specially because there isn't much wiring in the plane as it is now.

I'll replace the heavy batteries with 680s and leave it as it is for now, until something major like the starter or the alternator go south (they're both new) and then I'll revisit just in case.

Thanks again.