Please tell me if I am in the wrong Forum?

A Car Battery is Ratted 12 Volts at whatever Cold Cranking Amps you Buy.

Cold Cranking Amps is how many Amps the Battery can give for 30 Seconds in the Cold to Start the Car.

What I do not understand is when you start the Car does the Battery have to give the most Amps for 30 Seconds?

What is going on?

Thanks for the help.

 

What I do not understand is when you start the Car does the Battery have to give the most Amps for 30 Seconds?

It's the engine starter that takes that high amperage so the battery has to provide those amps for however long it takes for the starter to start the engine.

 

A Lead-Acid-Battery will tend to lose it's ability to provide high peak-Currents as it's temperature gets lower.

To add to this problem,
the Engine-Oil tends to substantially increase in viscosity when it's extremely cold,
this causes additional drag on the Starter, requiring extra-heavy Current from the Battery.
.
.
.

 

Turning over a cold engine, fast enough to promote a start, requires a substantial amount of work. As your vehicles electrical system is only 12 volts, large currents are required to meet the demand. The batteries rating will give you an idea as to how it can perform, supplying that demand. A vehicle out of tune, may require extended cranking times. In the carbureted days, extended cranking was not uncommon. Electronic ignition has brought that down.

 

The 30 seconds is for a carburetor fuel system that needs air flow to bring in the fuel. Injectors deliver the fuel almost immediatley.

 

Turning over a cold engine, fast enough to promote a start, requires a substantial amount of work.

The much older vehicles that had the back up option of a hand crank, If kept tuned up could be started with a couple of cranks!
(Also handy if stuck on a patch of ice, stick it in 1st or rev, and 'wind' it out) .

 

Evidently Max is a lot older that the photo implies, to recall cranking a car engine from in front. My grandfather had mentioned that a backfire could spin the crank backward and cause injuries, if the reverse drive "kickout"failed to disengage. That "Kickout" was a very simple Over-running disengagement arrangement, intended to only allow cranking the engine in one direction. Evidently road salt would make them rust and bind.

 

So, seeing as human powered crank can maybe provide a few hundred Watts, why do we need 2400W of cold cranking power?

(no need to answer this)

 

Evidently Max is a lot older that the photo implies, to recall cranking a car engine from in front. My grandfather had mentioned that a backfire could spin the crank backward and cause injuries, if the reverse drive "kickout"failed to disengage. That "Kickout" was a very simple Over-running disengagement arrangement, intended to only allow cranking the engine in one direction. Evidently road salt would make them rust and bind.

I've cranked a car engine and I'm not quite 60 years old yet. This was back in the 1980 time frame. Granted, the car I cranked was a long shot from being a new car at the time.

 

Those hand cranked engines were low compression four cylinder machines. A tight V8 or even six cylinder engine spinning much faster does take a lot more torque. Also, the starter motor is also spinning the torque converter as well.
AND, besides all of that, it makes a lot more sense to have a fair amount of reserve power. Designing for "Just Enough to work under best conditions" is a poor scheme.

 

Another useful use for the crank, when in H.M army in the Libyan desert, got stuck on a dune, and the hand crank slowly wound us out.

Evidently Max is a lot older that the photo implies,

Actually Max is a computer generated entity, so timeless!
(ref: BBC TV)

 

You could always pull start the car…

…with a horse.

 

You could always pull start the car…

…with a horse.

So you are saying that 745.7W will do it?

I do remember people push starting their cars if the battery was dead. My first car weighed only 1500 lbs. On a flat surface I could open the driver side door, stand outside, holding the steering wheel, and push it until I reached a trot, and then jump in and, put it in first and get it started. And at 152 lbs, I am no horse!

 

The 30 seconds is for a carburetor fuel system that needs air flow to bring in the fuel. Injectors deliver the fuel almost immediatley.

Actually, the carburetor often delivered fuel before electronic would, as a result of the operator giving the appropriate number of pumps to the accelerator before cranking. Canadian winters demanded that drivers learnt the specific needs of their engines, to accomplish severe cold starts. A pump too many, or not enough, led to extended cranks, in an environment that restricted those resources. Manual chokes added that extra opportunity to screw it up.

As younger fellows back in the day, we’d tinker with any setting we could, distributors vacuum/mechanical advance, timing, chokes, jets, whatever. We necessarily carried an inventory of batteries to keep us going.

 

I recall a rainy trip with friends in a Rambler with a dead battery, and the group riding with only enough money for gas. And when the engine stalled at a light, we were ready to jump out and push when the light went green. We did that quite a few times that day, did not get hardly wet, we were so fast. BUT that was a thoroughly warmed engine and a quick footed driver. it was the others that gave it the push to start. Fun times back in 1968.