Thread: 12v alternator rebuild?

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I have a race car that I'm considering running a 16v battery instead of a 12v battery since I have alot of devices, i.e. transbrake, rollstop, fans, fuel pumps, etc. I understand that it's not the voltage of the alternator or battery that provides power, but the amps it puts out. So, running a 12v system with high amps, i.e. 95amps, should be sufficient? It seems that running a 12v battery is more practical.

Any feedback would be appreciated.

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

Glen

Thanks very much for your thorough explanation...it's much clearer.

So, if I've not had any problems starting my motor with a 12v, and my only concern is getting enough current to my electrical devices while the motor is running, i.e. MSD box, fans,fuel pumps, etc., then I should be okay to run a 12v battery but with an alternator that puts out enough amps, i.e. 95 or so?

Ron

Originally Posted by Ron Lee

Glen

Thanks very much for your thorough explanation...it's much clearer.

So, if I've not had any problems starting my motor with a 12v, and my only concern is getting enough current to my electrical devices while the motor is running, i.e. MSD box, fans,fuel pumps, etc., then I should be okay to run a 12v battery but with an alternator that puts out enough amps, i.e. 95 or so?

Ron

That would be true. A 16v battery could and would do harm to all of your 12v accessories.

Thanks for the info. So, can my current alternator, which is 12v 40amp, be converted to a higher amp, i.e. 95 or so without any problems, or would I be better off purchasing one, i.e. Powermaster, Denso, etc?

Ron

I would purchase one new.

I concur w/NTFDAY - new 100 amp one wire unit are about 100 dollars from Summit - http://summitracing.com/parts/SUM-G1667A/

one wire units are a nice quick fix, but they actually don't regulate power as well, you are better off with a three wire if you really want optimal power to your many accessories.