Mailport: November 2013
In regard to the PS blog post (May 21, 2013) on prolonging the life of your alternator: I have a few more suggestions for getting the most from your alternator installations.
1. Practice good battery management. Charging in bulk takes a toll on alternators, and the larger a bank gets in relation to the alternator, the longer the alternator is in bulk mode and running hot. It is very easy for a non temp-compensated alternator to exceed 230 degrees in an engine space when driving a large load. Don’t regularly discharge below 50-percent state of charge, and try to size your alternator, when hot, to a minimum of 20 percent of bank capacity. With AGM or gel batteries, you’ll want more alternator capacity.
2. Clean pulley grooves of all rust at the beginning of each season. Rusty pulleys eat belts.
3. When changing alternators, beware of the pivot bolts. Improperly sized bolts can lead to misalignment issues and alternator foot/feet damage.
4. Use a longer adjustment-arm tension bolt, and back it up with a nut and lock washer. These tend to come loose over time. Loose tension bolts are a leading cause of belt slipping.
5. When upgrading the alternator, consider going up a size or two beyond where you have decided you need. If you’re using a Balmar external regulator, you can limit the alternator in “belt manager” to the current handling capability of your belt. De-rating the alternator via the belt manager allows your alternator to run cooler and last longer. It also allows for a future serpentine-pulley upgrade.
6. Also when upgrading, be aware that many large alternators ship with half-inch pulleys and many small auxiliary engines use 3/8-inch belts. Using mis-sized belts will reduce belt life.
7. Know what your belt can safely handle. I find 70 to 80 amps is about max for a 3/8-inch belt and 90 to 100 amps for a half-inch belt. To drive more than that requires a serpentine type belt or a dual-pulley setup.
8. When driving large banks, it is often best to choose external regulation and take advantage of an alternator temperature sensor to prevent the alternator from cooking itself.
9. Pay attention to belt wrap around the crank and alternator pulley. The more wrap, the more horsepower you can drive. If you have minimal wrap and a large bank, consider a pulley upgrade. Machined pulleys seem to do better with heat and driving large loads than do the cheap stamped steel pulleys on many factory alternators.
10. Think of your alternator and battery bank as a team. Neither one can carry all the weight.
Compass Marine Inc.
Cumberland Foreside, Maine
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