Reply to thread

Message: <blockquote data-quote="stormsearch" data-source="post: 6681591" data-attributes="member: 615664">What bub is saying is all true.  I will add a couple notes.  Putting in a larger battery will only help if the alternator cannot keep up with the system voltage that the amps are continuously pulling for a set timeframe.  BUT, after a short period of time, the larger battery will be no better than the one replaced since it has output enough current to drop it's capacity.  A bigger battery will help in longer run times while the engine is off.  A bigger battery will help to start vehicles that struggle particularly in colder climates (assuming a weak battery to begin with).  Battery acts like a capacitor in the system to absorb voltage spikes (either from vehicle electronics or sound system) - a larger battery will not really help here.Running your power wire to the alternator B+ stud is actually not a bad idea - since you would bypass the alt B+ to battery B+ cable run.  But that will work the opposite way if the engine is off.  However, powering away from the battery reduces its affect to help deal with the amp power spikes (it needs to overcome the added impedance of the wire from batt to alt vs. dealing with a power spike directly at the batt b+).  Hence reason people like to add a 2nd battery in the rear near their amps.  The alternator is a noisy machine (electromagnetic noise) so keeping power wires from it is preferred.Also note, that the alternator operates to control voltage near the battery B+ terminal.  There is a feedback wire that likely terminates near the batt b+ (fuse box or other power distribution type box).  This ensures proper battery voltage based on temperature and provides longer battery longevity.  Batteries have an optimal charge voltage dependent on temperature.  Pulling power at the alt b+ will obviously provide a higher operating voltage to compensate for the voltage drop across the batt to alt wire.Resting voltage of a battery is 12.7v (12.6v if you consider some of non-wet cell batteries), 100% SOC.  If the resting voltage of the battery is at 12.5v, it is around 50% SOC.  At 12.0v, battery is considered dead.  This only relates to when a battery is not receiving or providing any current (resting voltage).  Battery voltage will drop significantly during high power loads like starting your vehicle.  Dropping to 8v is not uncommon for the very short period of time.</blockquote>

Verification

Top

What's new

Forum list