Managing Battery Health and Charging on the Caterpillar 955L Track Loader

[MikePhua]

The Legacy of the Caterpillar 955L
The Caterpillar 955L crawler loader, introduced in the mid-1970s, was part of Caterpillar’s evolution from cable-operated machines to fully hydraulic systems. Built in Peoria, Illinois, the 955L featured a 3304 four-cylinder diesel engine producing around 100 horsepower, paired with a torque converter transmission and a hydraulically controlled bucket. With an operating weight of approximately 30,000 pounds, the 955L was designed for rugged earthmoving, land clearing, and quarry work. Caterpillar, founded in 1925, had by then become a global leader in heavy equipment, and the 955L contributed to its dominance in the track loader segment. Tens of thousands of units were sold worldwide, many still in use today due to their mechanical simplicity and robust construction.
Terminology Annotation

• Smart Charger: A battery charger that automatically adjusts voltage and current based on battery condition, preventing overcharging and sulfation.
  
• Parasitic Draw: Electrical current consumed by components when the machine is off, which can slowly discharge batteries.
  
• Group 31 Battery: A common heavy-duty battery size used in industrial equipment, typically rated at 950–1,100 cold cranking amps (CCA).
  
• Voltage Regulator: A device that maintains consistent output from the alternator to prevent battery overcharge or undercharge.
  

Battery Configuration and Charging Challenges
The 955L typically uses two 12-volt batteries wired in parallel to provide sufficient cranking power for the diesel engine. Over time, operators have upgraded to Group 31 batteries for improved cold-start performance and longer reserve capacity. However, maintaining battery health in older machines presents challenges, especially when the equipment sits idle for extended periods.
Smart chargers have become a popular solution, offering automatic float charging and desulfation cycles. These chargers can be left connected indefinitely, keeping batteries at optimal voltage without risk of overcharging. However, compatibility with older electrical systems must be considered. Machines like the 955L may have residual parasitic draw from gauges, relays, or aftermarket lighting, which can interfere with charger operation.
Common Symptoms and Diagnostic Steps
Operators may notice that even with new batteries, the machine struggles to crank after a few days of inactivity. This often points to:

• Parasitic draw exceeding 50 milliamps
  
• Faulty voltage regulator allowing backfeed
  
• Alternator diode leakage
  
• Poor ground connections at the frame or starter
  

To diagnose, technicians should:

• Use a multimeter to measure current draw with the key off
  
• Disconnect one battery terminal and insert an ammeter in series
  
• Inspect wiring for corrosion, especially near the starter solenoid
  
• Test alternator output and diode integrity
  

Anecdote from a Quarry Operation
In 2012, a quarry operator in Pennsylvania upgraded his 955L with two new Group 31 batteries and a smart charger. Despite the upgrade, the machine failed to start after sitting for a week. After tracing the issue, he found a corroded ground strap between the battery box and the frame. Replacing the strap and installing a battery disconnect switch resolved the problem. He later added a solar trickle charger for off-grid maintenance, which kept the batteries topped off even during winter shutdowns.
Recommended Solutions and Upgrades
To improve battery reliability and charging efficiency:

• Install a battery disconnect switch to eliminate parasitic draw during storage
  
• Use smart chargers with temperature compensation and AGM compatibility
  
• Replace ground straps with braided copper and seal connections with dielectric grease
  
• Upgrade to sealed AGM batteries for reduced maintenance and better vibration resistance
  
• Add a voltmeter to the dash for real-time battery monitoring
  

Preventative Maintenance Strategies

• Clean battery terminals monthly and check for corrosion
  
• Test battery voltage before and after charging to verify float levels
  
• Inspect alternator belts and tension quarterly
  
• Replace voltage regulators every 2,000 hours or if output fluctuates
  
• Store machines indoors or use insulated battery blankets in cold climates
  

Design Considerations and Future Improvements
While the 955L’s electrical system is simple, it lacks modern safeguards against battery degradation. Future retrofits could include:

• Solid-state voltage regulators with low standby current
  
• Integrated battery monitoring systems with Bluetooth connectivity
  
• Automatic disconnect relays triggered by inactivity
  
• Solar charging ports for remote maintenance
  

Conclusion
Managing battery health on the Caterpillar 955L requires a blend of modern charging technology and old-school electrical discipline. Smart chargers offer a valuable tool for maintaining voltage, but they must be paired with clean wiring, solid grounds, and protection against parasitic draw. With proper upgrades and routine checks, operators can ensure reliable starts and extend battery life, keeping this classic track loader ready for work even decades after its debut. The 955L remains a testament to Caterpillar’s engineering legacy—mechanically tough, electrically simple, and still pushing dirt across generations.