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frosh asks what is the advantage to negative grnd?

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Re: frosh asks what is the advantage to negative g

I'll echo Bill's comments. The generator/alternator can put out only so much power. If you try to tweak the regulator to allow greater current or voltage, you won't get much more power but you very likely will damage something.

The regulator really doesn't limit the output power; it limits the output voltage to prevent overcharging of the battery. Once the battery is fully charged, the regulator decreases the generator's output power (by reducing the field current). If more electrical power is required by the car's circuits, the battery voltage starts to decrease and the generator then provides whatever current it can, within its ability to do so, to bring the battery voltage back up. This means that it must provide enough current to meet the load demands and then, if it can, charge the battery too. If it can't meet the load demand, the battery will provide the extra power (until it goes flat, of course) and no charging will take place.

In short, the generator/alternator will put out whatever power it can to meet the loading and charging demands of the system. You can't do much to increase its capacity. So, if you need more power, the only really practical alternative is to get a bigger unit.
 
Re: frosh asks what is the advantage to negative g

Yep, except the CP 42 Dynamo is a 30+ amp machine which rquires the NCB 133 30 amp regulator for control. There is a higher rated one used on RR at 40 amps, however they are hard to find and expensive as the /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif---Keoke
 
Re: frosh asks what is the advantage to negative g

You were not wasting your time as the wire we all use has a positive resitive temperature coeficent, meaning that the resistance goes up rather dramatically with temp. Dave supplied us with resistances and if they were taken @ 70F ambient then you could expect a 140% increase @ 250F. 250F is realistic as the smaller wires heat up alot under load. The more copper/aluminum you can apply to the low voltage starter/charging circuit the better off you are. Dave is correct the drop is not great but with temp. increase, a weak starter and possibly a weak battery; you can use all the voltage and current carying capacity to your advantage. Dave also pointed out the load no load voltages and these result from the internal resistance of the generator (about which you can do nothing) but also the high temperature lead resistance from the generator to the 12v neg cable. You can increase the size of the latter. A simple test voltage reading while under normal driving conditions (lights, heater, radio, wipers) will show you how much of a loss you are experiencing with the stock connection. Sizeing the generator lead up to a 10g or 8g can help, (maybe no alot but it will help).
 
Re: frosh asks what is the advantage to negative g

Yep Bob, additionally, these wire table resistances define an uninsulated wire run in free space and must be corrected for when insulated, run in bundles as well as you noted under load and at non ambient temperatures.---Fwiw--Keoke
 
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