Richard Bell wrote:
> In article > ,
> Bruce Chang > wrote:
> >
> >"sdlomi2" > wrote in message
> ...
> >> Help! Got a '55 Studebaker. Aftermkt. mp3/cd/amfm radio. If
I set
> >> stations, it remembers fine going from on to off to access to off.
But!
> >> When I start i, the starter seems to drop the "voltage
threshold"(at least
> >> that's what I visualize) such that all memory settings are lost.
> >> Ideas, please? Thank you, s
> >>
> >>
> >>
> >
> >Maybe a small 12V battery or large capacitor that's hooked up with a
diode
> >between it and the car battery so voltage to the stereo won't drop
when the
> >car battery voltage drops significantly.
> >
The large capacitor will cause a voltage
> spike, just after the motor starts, so a choke coil will be needed to
> protect the sound unit.

Inductors generate spikes, not capacitors. The best
arrangement has a choke in the supply line, with a capacitor between
the hot side of the choke and ground. That'll swallow most
interference. It would take a pretty big capacitor to keep a stereo
happy.
Spikes are generated by the starter solenoid and by the starter
itself when the current is cut off. A capacitor cannot provide any
higher voltage than it was provided with in the first place, but an
inductor like a solenoid can make a 600-volt spike. I've measured it.
It's the principle behind the ignition coil.

> Here, in the Great White North (How's it goin', eh?), we would advise
you that
> your battery is seriously short of cold cranking amperage and that
you
> should buy the biggest battery that will fit in the tray. However,
being
> designed for old-tech batteries, you should accept anything that
covers half
> of your '55 studebaker's battery tray. While cold weather starting
may be
> the least of your worries, a larger battery is the simplest (if not
the
> cheapest) solution to your problem.

A 35-watt electric battery blanket will make that battery
perform. Some guys use them instead of a block heater. A battery loses
something like 60% of its capacity at -25 degrees C.

Dan