those with car starter experience

[dcastillo]

So as usual when I get into a hobby my brain goes nostop and sometimes I really need to get focused (just ask my wife)

currently I have a treadmill motor in my cart, on my work bench is a broken golf cart motor (2kW) Im trying to fix, and on the floor in my cubicle is a giant servo type motor (that being honest with myself, will never fit in my cart and if it did needs a crazy almost 1 to 1 gear ratio to work)

In light of the fact I dont have tons of free time..
so should I just stop the tinkering and buy a my1020 1000W motor for $100 or go the route of a used starter for $20-30 and spend one evening modifying it for my cart?

most of the small starters are 12V, around 1K-1.5K watts meaning around 100A. My controller can do 24-48V at continuous 80A, peak 200A.
would I just set it up at 24V and set the controller current limit, or would I need to overvolt it to 48V with the controller on current limit?


sorry for the rambling... I guess my question is, should I just get a used starter and if so how much power would i need to hit it with to get the performance I need... (guessing at least 1000W is good for me, Im only getting about 800W now)

thanx for all the great advice
-Danny

 

[OzFab]

All I can say (because electrics is one thing I know little about) is 1kW = 1.34hp. Are you sure 1.3-2hp will be enough?

 

[dcastillo]

yep
Im running a treadmill motor now, its rated at 2.5 Hp, but Im powering it at half voltage...

so probably about the same power.
FYI, is on a small two seater cart made for my kids, so it only does 12mph and struggles in grass with me on it, just a little though...

if the starter is 1kW at 12V, then I should be fine since Ill be hitting it with 24V minimum, just have to limit my current and watch out for to much heat...
thanx for the input though

 

[itsid]

Get a truck starter rated 24V not a car starter.

You pretty much cannot overvolt them because they might be rated 2kW (and way up) but that's for a runtime of about 10 seconds, much longer and they will get too hot and burn out.
So get the biggest you can find for a small amount of money (biggest I've seen is 9kW)
but I guess anything above 3kW will do.
do not apply the full amperage, but run it at 50% (maybe 75% for a short time)
to prevent frying the coils.
Or, you'll need a cooling system, and that is going to be a tough task I guess

'sid

 

[machinist@large]

Like 'sid said, cooling would be the deal breaker if you wanted to try using a started motor; they're not rated for continuous use, and will quickly fry if run that way. Another problem is that a great majority of the starters out there use simple bronze bushings instead of ball bearings, again limiting their usefulness as continuous duty power source.

That isn't to say that you couldn't scavenge the rotor and windings for something, it's just that you would have to have fairly extensive machining capabilities at your disposal to fabricate a new housing that had proper bearings and some form of cooling system to make it work. Is it doable? Most likely yes. Would it be easy? No.

Pat

 

[itsid]

but according to this video, it looks like a truckload of fun :
http://www.youtube.com/watch?v=C5lp3fP1WKo



'sid

 

[dcastillo]

I saw that this afternoon as well.. Full on power, that guy is crazy....

So as long as i used a pwm controller to limit my current i should be good... Just need one rated at double the power i need so i can run it at half power....

 

[itsid]

I saw that this afternoon as well.. Full on power, that guy is crazy....

So as long as i used a pwm controller to limit my current i should be good... Just need one rated at double the power i need so i can run it at half power....

I would say so..
I can't tell for sure how long a starter will last, but as long as you still check every now and then if it's getting too hot,
I'd say it's pretty much safe to run it at half it's power for a while.

'sid

 

[fowler]

Yep

Most trucks have brass bushings

And they are wound to allowance amps
U wil drain 2 1600cca batts in a few mins without a dam good controller of some type

U will also have to remove the soliniod as well
As this will move the pinion in and out and it is a large cause of all the heat

The motor doesn't release too much heat but it won't last long either way

 

[machinist@large]

but according to this video, it looks like a truckload of fun :
http://www.youtube.com/watch?v=C5lp3fP1WKo



'sid

I have to fully agree there!!! If you were trying to justify it as along term, bullet proof reliable unit, it would fail. If you look at it the same way you would look at a demolition derby car, i.e. it's probably not long of this earth, let's go have a blast before it goes, then all you have to do is rationalize the up front cost.

Lets see; all you would need to spend real money on would be the kart chassis. All you would need to make sure of is that your choice of batteries and the starter motor were well connected and properly safeguarded. If you size the batt's correctly, and actually do all the correct preventative maintenance to help extend their life, then the starter motor and the remote mounted solenoid should be the first items to potentially fail. And if you're on good terms with the local wrecking yards, that can also lower the cost of play.

I would say so..
I can't tell for sure how long a starter will last, but as long as you still check every now and then if it's getting too hot,
I'd say it's pretty much safe to run it at half it's power for a while.

'sid

With a design that basic, and my thoughts as listed above, I think we all are probably in agreement that good fun can be had....

Yep
The motor doesn't release too much heat but it won't last long either way

Quite true, but depending on what the local scrap yards are charging for savaged starters, it still falls in the realm of "Reasonable Cost".

Pat

 

[dcastillo]

Well...
Ive already got the cart, batteries and a 200A controller... so the only money Id be spending is for the starter and then time to modify it (which looks like one evening)... only thing im not sure of it how the sprocket mounts to it...

Im guessing I can get reasonable life out of the starter if I run it at about 1/3rd power since its just for my kids... say a 6kW starter ran at 2kW?
(ofcourse when they arent with me I may overvolt it and run all 200A for a few seconds just to see what she can do )