Starter/Generator load

bronsonj

Hello all,

Just wondering, what kind of load does a Starter/Generator place on the engine when it's generating full power? I know that as the battery gets recharged the resistance will go down, but will this rob me of 1hp when under full load? 2hp? or worse?!?!

Lastly (and most embarrasing ). I *thought* I printed off all the info from my PMs on the starter generator I have so I could look up the wiring later. But when I got back into it this past weekend, my printoff wasn't there and by now the PMs have been erased... How do I figure out what Starter/Gen I have so I can look up the threads on here about wiring them? I don't remember make/model/anything about it.

BGW

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slonomo

I'm not sure about 1hp, but they certainly rob h.p. This is why some drag race vehicles don't run charging systems. With that said, I don't think a normal operating starter/gen will drain very much power. Could it be measured? Sure, but your drivetrain is probably sucking more power than the charging system, to the tune of 20-30%.

bronsonj

OK, thanks for the input slo.
The worst would be shortly after startup when the battery was just depleted anyway. So I should be fine.

I will get some pics of the starter generator so hopefully someone here can help identify.

sho305

A gen does not generate much power at low speed like an alt can, so it wont load until over 2000 rpm or so. I can see my lights get brighter above that rpm in fact with the yamaha. Seems like you could put a switch on the VR to stop it from generating, since the VR excites the field to cause it to generate. You would still lose a little to spin the belt and such but not much, then turn it on to charge. If you run a clone with a mag ignition they have and don't use lights/radio/etc you don't need to charger very often. You could turn it on once a week for a while or something, etc., turn it on at night for lights use. Maybe pick up a cheap voltage gauge on a momentary switch to check it once in a while. It depends on how often you start/crank the engine. If you can find a cogged belt for the gen (I have one from CPP) that might save you a fraction of a HP. Lot of the wiring is posted here if you figure out what brand it is.

bronsonj

Time for a really daft question...

I found a key switch that will handle a 75amp continuous load at 14v . It has what looks like a unique key, it has accessory, off, accessory/ignition and a momentary start, in that order. I am unsure if the key is actually unique or just looks that way.

http://products.pollakaftermarket.co...purpose-switch

My plan is to run the starter/gen in the accessory/ignition position.
So my question is, would that be too much for the switch to handle without a solenoid?

I found that switch online for $15 to $20.

bronsonj

Doh! That's a three position switch. Their 31-499 switch is 4 position and high current. It looks like $25 is the going rate online for the 4 position.

sho305

The gen puts out 15A max current, but I would not run that to the key, and it should be larger gauge wiring. I would get a normal key and use a constant duty relay. But IIRC you can manage charging with the field wire anyway the one the VR uses to make it charge or not. No field and it will just spin and not charge.