12v Starter Slower To Crank

So I had a 6v starter on a 12v system. Foot pedal starter style.

Now I have a12v starter I installed. Engine is cranking slower and I can tell it's having a harder time getting started.

What can I do? More CCA?

 

12 Volt should require half as many amps. V=IR. It will crank slower, because the six volt unit was being over-revved on twelve volts.

Otherwise, check and clean all the connections, including the switch, ground to the frame, etc. Is the foot pedal link and starter switch button adjusted correctly to give firm contact with the new starter?

I'd try also the starter with a jumper direct from the battery, to be sure the starter itself is okay.

 

We're no longer using the foot switch.. keyed starter now.

 

Did you go with the newer gear reduction starter?
They are the cat's meow?
If everything is clean, good cables, should start right up?
As PeteL said needs have the amps because of the higher voltage, you really can use a 6 volt starter and then put 12 volts to it and work great as long as the brushes are good, etc?
I also would check it with a jumper to see if it is the same, sounds like the new starter is not good?

 

just slower. I can here a difference in the pitch.

 

Well, this just threw my understanding of voltage and amps straight out the window."


Throws my understanding of math right out the window, too. Although a very small window would be adequate.

Howard, I believe your hands-on finding, but surely your electrical formula means twice the volts equals half the amps, for the same HP/watts?

 

Could it be wired incorrectly?

 

Mine too, and I am a high voltage test engineer, but then again, that is AC volts (lol)

Do me a favor and tell me what the voltage is that accompanies that current draw when you roll your starter...

If you are drawing an average of 170 amps when you hit the starter at 12 volts, which actually drops to around 10 volts max on a good battery, you are drawing a total of 1700 volt-amperes or higher, if your battery voltage stays up, which is the same value as watts in DC circuits. This sounds awfully high for a 12 volt starter motor. I don't know what the hp rating for a standard starter motor is or I could tell you what your battery voltage is when your cranking. For example, if your starter motor is 1 hp, you would be dropping your battery voltage to around 4 volts if you are drawing this kind of amperage. When I am starting my jeep, my voltage never even hits 10 volts when cranking, and my current is much, much lower than that... 1 hp = 748 watts (volt-amperes)

 

A stalled motor with 12v battery will draw more current than a free-turning motor with 12v battery. Counter-electromotive force (CEMF), which is sometimes called generator action in a motor. It's what causes a long piece of copper wire (windings) from being a dead-short. But a stalled motor has no CEMF so it does become nothing but a short-ciucuited ball of copper wire. That's why a stalled motor burns up.

That's why the Ohms Law doesnt exactly line up when there are motors involved.

And as was already suggested, there is voltage droop in the battery due to internal resistance.