12V DC voltage stabilizer

I'm looking for a circuit diagram for 12V DC voltage stabilizer for my car.

I found that every time when I start my car, the starter motor will draw so
much current that cause the voltage over the ignition coil to drop
tremendously.

Most circuits I found need higher input voltage to produce a lower stable
voltage, but the only voltage source in a car is from the battery. So it's a
12V-12V DC voltage stabilizer that I'm looking for. Any recommendation?

Thanks,
Newbie

 

The battery needs replacing.

Graham

 

ISO 7637-1 (12V vehicles) specifies the voltage droops you may expect
to encounter during engine crank (amongst other things)

Although I agree with Graham your battery may need replacing, during
cranking the battery feed may droop to as low as 5V, then raise to
between 6V and 9.5V once the starter motor is running. Once the starter
motor is disengaged, things should recover to normal.

As the only feed during that time is the battery, you would need to
have a circuit that can take 5V ->14V in and produce your clean power
for whatever it is you are trying to operate. (Think SEPIC converter).

Cheers

PeteS

 

Yeah, and the additional current drain on the battery will drag it down
even more.

Does the car not start reliably? They're generally engineered to take
all of those factors into account.

IOW, if it ain't broke, don't fix it.

Good Luck!
Rich

 

The battery is a new one. The car, it's an antique car, 1963 moris mini. I
find it hard to get started at times. Anyway, thanks for all the advice.

Regards,
Newbie

 

Look for rust/corrosion on connections in the
coil circuit, particularly the grounding cable
from the battery to the engine block.

Ed

 

I might build or buy a Capacative Discharge Ignition for it ...
although those older Brit cars are famous for electrical problems.

 

Ahhh.

The battery in that may be slightly undersized by today's standards.

Graham

 

ANTIQUE????!?!?!??!?!!!! 1963??!?!?!??!??

Hey, that's when my family got our first convertible! A Ford Galaxie
500, in "Anniversary Gold", with a red top and red interior. That was
the one I learned to wreck cars in. ;-p

Anyhoo, I'm the one who said "If it ain't broke, don't fix it," but
since you've admitted it's a Brit car, here's what I'd do: First,
as someone else has posted, make sure you have very good electrical
contacts, both at the battery posts and at the lugs where the
cables bolt to the frame/engine block and to the starter or
solenoid. Clean them very aggressively with a wire brush, but
avoid chemicals. Don't grease them right away - bolt them up,
and grease them all around. I don't know what kind of battery
terminals you have, but I have had the kind with the vertical
lead posts, and the lead lugs that always get torn up when
people loosen them with pliers and stuff. Well, I got a post/
lug cleaner at the auto parts for about two bucks - it was
two very stiff wire brushes: one to go inside the lug, and
one to go around the post. I also got new cables, with new
leaden lugs, and stuck washers under the bolt head and nut
so I wouldn't tear up the lug when I had to loosen them.

Which, as it turns out, I didn't have to do very often. ;-)

Now, I have the kind with side terminals, and I just keep the
mating surfaces clean and shiny, and keep a 7MM wrench in its
own special place in the trunk.

Good Luck!
Rich

 

Most older cars use a simple series resistor to the coil which is
shorted out when cranking.
Easy to implement and very reliable.

 

"Lucas", Prince of Darkness.