Automobile starter motor

Hi group,

I have a couple of questions. I am aware that the duty cycle of automobile starter motors is insufficient for continuous duty, but does anyone out there have any real world experience with them?

A couple of guys at work were thinking of making electric go karts to race during break time, and there is only about 5 good minutes of race time, between loading and unloading.

Questions that come to mind are: Are they PM or series wound? Can they be easily re-timed for bidirectional rotation? any cheap digital circuits out there for 100+ amp PWM?


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The Delco starter I took apart was series wound. I reversed the polarity of the field coil with respect to the armature to get it to run the opposite direction.

I got the impression that it was grossly inefficient. The only thing I had at the time that would make it turn (no load) was a 50A battery booster. I never ran it for more than a few seconds at a time, but I suspect that after a minute or so it might start to smell funny.

Another idea. I was looking through my dad's fishing stuff last weekend. He has one of those electric trolling rigs. That thing has a seriously beefy motor to turn the prop.


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Jeff Shirley

Here's a link on the subject...

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A car starter motor is a grossly underdesigned contraption. It's designed to handle massive power input and generate massive power output as a result for a very short time. Overrunning its duty cycle is begging for trouble. It's great for a short boost, but for any kind of load or no-load condition lasting over sixty seconds or so, it will give up the ghost in short order. The main problem is that there is virtually zero built-in faculty for cooling. It's designed to run hard, quick, then rest a good long time. Long runs will overheat it and melt something best not melted.

If you can solve the cooling problem with massive airflow or some kind of liquid jacket, you might be on to something.


Reply to
Sean Leistico

Well, here is part of the idea, we only have about 5 minutes during break time. A water jacket would certainly aid in cooling.

The other part of the idea is that a starter motor is dirt cheap from a junk yard. My idea was to build a bucket around it, that shared as much surface area with it as possible.

The 3rd part of the formula, is that the course we would be racing would only allow for intermittent bursts.

For throttle, it looks like we will be running stepped current limiting resistors, and shunt them out with the "gas" pedal.

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Several years ago my job was to service heavy equipment in remote locations. We used a starter motor attached to a small pump to add hydraulic oil and transmission oil to the heavy equipment. Using a 12 volt battery I could pump 55 gallons of hydraulic oil in about 10 minutes. Several times I was required to pump 110 gallons of oil/fluid. Most of the time the I would only pump about 20/30 gallons of oil/fluid a day. We had to replace the starter motor about 3/4 times a year.


-- Bob Houston

1759 Cuba Road Bridgeport, Texas 76426

e-mail--do let the dogs out

The Vulcan Neck Pinch isn't half as powerful as the Vulcan Groin Kick, but it is more politically correct!

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Robert Houston

You're beating a dead horse, I mean a dead motor (if you use a car starter). As the others have said, they are just not designed for continuous operation. If you really want to kick their butts, try one of these:

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I know they are not cheap, but hey 6+ HP! BTW, this place is a good source for other EV stuff. Have fun.

Reply to
Shawn Brown

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