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After another stimulating conversation with Dan Pires of Lewco Electric in Newport Beach I have more info to share on regulator behavior, specifically alternator mounted and internal fixed point regulators.
He said it's normal to see voltage variations as much as 0.3 ~ 0.5 volts depending on the state of charge of the connected battery and that variation can be different depending on the physical construction of the alternator itself. The reason: heat.
The fixed point regulators don't do this by design, they're trying all they can to maintain a set voltage output but there's a degradation of regulator components as they heat up causing the performance variation. Further, the construction of the alternator affects heat buildup too. The more heat, the more degradation and the more pronounced the voltage variation.
For example, our stock Motorola alternator with the regulator mounted on the back encapsulating the spark producing components (ignition proof) allows air to flow through the alt with minimal restriction making for efficient cooling. In contrast the Delco style with the internal regulator has spark arresting screens front and back restricting the airflow somewhat. This is more apparent at low RPM operation when the cooling fan is turning the slowest.
The alternator I dropped off at Dan's shop was a Delco single wire self exciting type. In addition to the modifications he's making he asked if I would like to add an exciter wire so the alternator would kick in at lower RPM. I said no thanks. After learning about the variations caused by heat and the fact I have the restrictive screen type ignition proofing I'd just as soon have the cooling fan spinning at a decent RPM before the alternator gets to work. He smiled and nodded in agreement.
He said it's normal to see voltage variations as much as 0.3 ~ 0.5 volts depending on the state of charge of the connected battery and that variation can be different depending on the physical construction of the alternator itself. The reason: heat.
The fixed point regulators don't do this by design, they're trying all they can to maintain a set voltage output but there's a degradation of regulator components as they heat up causing the performance variation. Further, the construction of the alternator affects heat buildup too. The more heat, the more degradation and the more pronounced the voltage variation.
For example, our stock Motorola alternator with the regulator mounted on the back encapsulating the spark producing components (ignition proof) allows air to flow through the alt with minimal restriction making for efficient cooling. In contrast the Delco style with the internal regulator has spark arresting screens front and back restricting the airflow somewhat. This is more apparent at low RPM operation when the cooling fan is turning the slowest.
The alternator I dropped off at Dan's shop was a Delco single wire self exciting type. In addition to the modifications he's making he asked if I would like to add an exciter wire so the alternator would kick in at lower RPM. I said no thanks. After learning about the variations caused by heat and the fact I have the restrictive screen type ignition proofing I'd just as soon have the cooling fan spinning at a decent RPM before the alternator gets to work. He smiled and nodded in agreement.
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