On 11/28/2020 11:29 PM, Ian Molesworth wrote:

Seru=iously? SERIOUSLY??

If you are going to put a 'power limiter'

It's a VOLTAGE limiter, not a POWER limiter.

in the supply line then use
something linear not switching. Linear supplies dump extra power in
the form of heat. Switching power supplies make electrical noise
unless they are properly constructed and shielded ( ie expensive )
Knocking up a power regulator for this type of applicaion is barely
worth the effort.

Its not worth the effort as HE SHOULD USE AN APPROPRIATE BATTERY.
A PROPERLY DESIGNED switcher DOES NOT need to radiate noise!
A switcher designed by a moron, well that's another story...

One or even two simple diodes placed in series with the main
positive feed to those instruments rated at a lower maximum
voltage provides a safe and secure way to simply drop the voltage
into that device. As a side effect, you get additional reverse polarity
protection to your instruments!

Gee, I've recently documented a couple FIRES started that way!
Diodes DISSIPATE HEAT and WASTE ENERGY.
If they are not properly heat-sunk, YOU GET A FIRE.
Please do not try this at home.

YIKES.
Even for RAS...