So are we saying that my stock Hitachi 35 amp internally regulated alternator, which looks pretty automotive, and is being called upon to charge 3 12v Lifeline AGMs, is a better bet to last than the 80 amp internally regulated aftermarket because of potential overheating issues?
Not saying that at all. Saying quite the opposite... Stock alts set up to run with external regulation need to utilize Belt Manager (which is current limiting) unless the bank is really tiny. This is in order to not burn up the alt asking it for full output for long periods..... Many stock alts, including Hitachi's, internally self protect by reducing the voltage as the alt heats up. With an external regulation you still need to protect it from going over 220F.... Using the alt temp sensor to do this can dig into performance gains so the best bet is to limit the max field potential via the regulator using Belt Manager.
High output, purpose built, small case alts cool better, deliver better current at low RPM and last longer in deep cycling applications all will delivering more power than a stock alt asked to do the same. I have a Hitachi apart on my bench right now and they are very lightly built compared to a Balmar, Grasser, Electromaax or my own Compass Marine alts.........
These are some of the features I build into my own alternators which are well above and beyond factory alternators:
*Hand wound stators using the highest quality 14GA magnet wire means better cooling.
*Precision machined rotor and slip rings for greater contact at all RPM.
*Tighter tolerances for the stator/rotor gap for better performance. A feature not found in standard alternators.
*Precision milled stator utilizing a special dacron/mylar insulator. The industry norm is paper..
*Rotor is precision balanced to .025 ounce inches. Industry norm is .050 - .090. This means SMOOTH operation and less harmonics...
*Motorola 50A press fit diodes. Industry standards are no-name Chinese button diodes and 30A rated. These Motorola diodes carry a performance rating to 300F.
*Internal wire leads are ultra high temperature acrylic coated fiberglass insulation sleeves not cheap rubber sleeving.
*Brushes are high copper content composite not run of the mill carbon brushes. This yields superior conductivity and considerably longer life.
*Billet machined pulleys for better belt grip. This means less thermal expansion of the pulley when hot, which leads to less belt slippage.
*Alternators are isolated ground and the neg terminal is 100% isolated from the case. This is a significant upgrade over cheap case ground alternators. Both the positive and negative studs are 5/16" not wimpy 1/4" or #10 studs. These studs are bolted, not press fit or friction fitted, directly to the rectifier bridge for the best possible connection. Industry standard is a compression/friction fit.
*Rectifier and alt case are precision machined for proper mating and the best possible heat transfer. High temp heat transfer paste is used for the best heat dissipation.
High output alts can deliver more power for longer durations at lower temps.... Using a factory 80A alt and a high output 80A alt the factory using the same regulator will need more current limiting and will deliver lower performance. Can they work? Yes absolutely, but don't expect anywhere near 80A of performance, more like 40-45....
