Power Systems

Possible Causes

• •Battery age
• •Parasitic draw
• •Charging system fault
• •Sulfation (lead-acid)

Diagnostic Steps

1. 1.Measure battery voltage after 12 hours rest — below 12.4V indicates discharged or weak battery
2. 2.Check for parasitic draw with ammeter in series with negative terminal — more than 50mA is excessive
3. 3.Verify alternator or charger output voltage — should be 13.8–14.4V (12V system)
4. 4.Load test battery under rated current and measure voltage drop

Possible Causes

• •Undersized wiring
• •Corroded connections
• •Loose terminal
• •Undersized fuse holder

Diagnostic Steps

1. 1.Measure voltage at battery and at load simultaneously under full load
2. 2.More than 0.5V drop indicates wiring or connection problem
3. 3.Check all terminal connections for corrosion and tightness
4. 4.Inspect ground return path — high resistance ground causes same symptoms as undersized positive wire

Possible Causes

• •Battery has high internal resistance
• •Parasitic draw greater than charger output
• •Charger undersized for battery bank
• •Faulty charger

Diagnostic Steps

1. 1.Disconnect all loads and check if charger reaches absorption stage
2. 2.Measure charger output current — should taper off as battery approaches full charge
3. 3.Verify charger is sized for battery bank (minimum 10% of Ah capacity)
4. 4.Check battery temperature — excessive heat indicates internal fault