Some interesting views above but I don’t think that anyone will convert a 12VDC aircraft to a 24VDC aircraft its a lot of work to do just for one aircraft . Cessna did this as part of the C150 sorting out program that became the C152 but that was for a lot of units and IMO was a very good move if only to reduce the chances of students flattening the battery during starting ( to make it practically impossible you have to fit a slickstart )
Comments about car batteries are in invalid as like a someone above I got eight years out of a OM car battery and could get a very cheap replacement that would be lucky to see three winters before failure, if you want the OM quality battery and the eight year life the price is comparable with an aircraft battery.
As said above large aircraft use three phase 400Hz 110 or 115 V depending on how you mesure the voltage.
You know the next Q 
Peter, it actually mentions ETSO-C173a or equivalent.
Given all candidate vendors are American, I wonder what exactly that means?
What is the application process, and is “AML TSO” possible?
Peter wrote:
Does CS-STAN cover battery replacements with a different type?
Not the present issue, but the proposed new issue will. A condition is that the battery manufacturer declares that the new battery complies with ETSO-C173A.
I think it’s regulation that keeps battery prices high. If everyone could bolt in an odyssey battery into a Cessna (and many people have) straight away the cost drops by 50%
Are 24V batteries less robust that 12v ones? Ive known many aircraft where the students flattened the battery so it’s been started by prop swinging and my observations is the 24 volts seem more likely to fail shortly after.
@AJ you are looking at one of these. These battery conditioners apply current pulses to the battery and strip off the sulphide layer, or something like that. I have one too and it works great for my Concorde battery; I posted about it in the linked thread.
What supports high GA battery prices is lower volumes plus a belief that a battery model cannot be changed for a different one unless the new one has an STC. Sometimes that is true but usually it isn’t, especially in the FAA world where changing from e.g. a Gill to a Concorde is generally regarded as a Minor Alteration. That misbelief results in a lack of competition because it is hard to enter the marketplace.
Basic problem for GA is lack of production volumen compared to many other industries including auto parts. With increasing production volume price per unit drops. Add to this cost of certification and lack of competition on parts in many cases. Fx compare prices on same product certified and non-certified (expimental), gives an idea about high certification cost. Money is limited for RD in GA. In the low end of ga market (piston) the quality of components is really not that great, much of the stuff used there is still 60’s and 70’s technology. Best course for GA is to use technology from other industries, mostly auto. LED lights is a good example. But things generally have to be adapted to larger temperature changes, pressure changes, vibration, g-load etc, which they where never designed for in auto applications.
