v8zracer260z

It is normal to see some fluctuation in the voltmeter depending on the condition of he battery and the loads on the system. Typically 13.0 to 14.5 is a normal range. Though low voltage indicates a non charging symptom ie alternator or regulator problem and over charging sytem can cause more problems. Over charging of more than 15-16 volts can blow out lights and fry computors leading to expensive repairs. In addition to checking the level of the fluid I would recommend checking the specific gravity of the battery acid with a hydrometer found at any local auto parts store. This is a better indicator of battery health. Water has a specific Gravity (SG) of 1.000 in a Sulfuric Acid battery A SG of 1.265 is ideal and it can be slightly higher or lower in each cell but if you have one or more cells showing close to 1.000 indicates a dead or shorted cell it's time to replace the battery. Also since you have a wavering idle that in itself may be causing your voltage to drop. Your alternator puts out very little charge if any at idle. Dropping below that rpm may cause a significant drop in charging voltage. You may not have anything wrong with the charging, but have an idle conrol issue. Just a little advice from a prior F/A 18 Avionics Tech Hope this helps you guys out.