Thread: 12v alternator rebuild?
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07-02-2009 11:20 PM #2
Sounds good Ron, but you’ll need another source to properly charge a 16 volt battery. A typical 12 volt automotive application is made up of; an alternator, a 12 volt (six cell) lead acid battery, starter motor, ignition system, and all the “other” electric accessories.
The alternator actually produces the power required by the electrical system when the engine is running. The alternator converts mechanical energy from the engine and produces current to charge the battery as well as powering the remaining electrical components. The battery’s purpose is to serve as an energy source to start the engine and to power electrical components when the engine is not running (door locks, windows, etc). When the engine is running, the alternator re-charges the battery and provides the electrical power for the ignition and all of the other electrical stuff.
Typically, the starter motor draws the greatest current as it provides the necessary torque to the crankshaft (via the flexplate/flywheel) to start the engine. As such, a battery must be large enough to meet the electrical (current) requirements of the starter motor. Some external factors cause the starter to draw more current, such as low temperatures when oil’s viscosity is “thicker” which requires greater starting torque. Engine modifications that increase an engine’s compression ratio will also tax the starter – requiring greater starting torque and draw more electrical current. Higher torque (or gear driven) starters are helpful when restarting a hot high-compression engine. We’ve all heard that awful “wuuu, wuuu, wuuhhhh” sound, eh?
The increased torque required to start a modified engine requires an increase in the current required to operate the starter motor. This increased current in the starter circuit of the vehicle results in voltage drop due to resistive dissipation (of energy – ever felt “warm cables”?) in the battery cables, starter motor armature, and in the internal resistance of the vehicle battery. To address this voltage drop, some racing applications use 16 volt batteries having eight cells.
Lead acid batteries are the most common type used in automotive applications. These batteries must be recharged to replace the energy taken from the battery and maintain the specific gravity of the liquid electrolyte. Under-charging or over-charging greatly reduces the effectiveness and life of a battery. Lead acid batteries typically recharge between 2.3 and 2.5 volts per cell. The charge voltage required for a lead acid battery is dictated by the number of cells in the battery. The “standard” alternator is designed to charge 12 volt (6 cell) and usually puts out between 13.8 and 15 volts. They cannot be modified (easily) to charge 16 volt (8 cell) batteries which need, at a minimum 18.4 volts to charge.
You could run a 200 amp alternator designed for 12 volt system and it would not charge your (expensive?) 16 volt battery.
To properly charge you’ll need a new alternator (like an XS VOLT), see: url]http://www.powermastermotorsports.com/spl_alternators.html[/url]
Good Luck,
Glenn"Where the people fear the government you have tyranny. Where the government fears the people you have liberty." John Basil Barnhil
I saw last night on fb about John. The world sure lost a great one. I'm going to miss his humor, advice, and perspective from another portion of the world. Rest in Peace Johnboy.
John Norton aka johnboy