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SLI and station batteries and charging methods

Short answer

SLI battery supplies high current for starting, lighting, and ignition in DG sets and vehicles; station battery is a float-charged DC bank for breaker tripping, protection, and emergency lighting. Charging methods include constant current, constant voltage, CC-CV, trickle, float, boost, and equalising.

What do you mean by starting, lighting and ignition and station battery in an industry? What are the different methods of battery charging system?

Starting, lighting and ignition (SLI) battery

An SLI battery is a lead-acid battery used in vehicles and engine-driven sets to:

  • Start the engine – supply a very high current (hundreds of amperes) for a few seconds to the starter motor;
  • Light – supply head lamps and other lamps when the engine is off;
  • Ignition – supply the ignition system of petrol engines.

In an industry, SLI batteries are used in diesel generator sets, fire-pump engines, forklifts and plant vehicles. They have thin plates with large surface area for high current; they are kept charged by the engine's alternator or by trickle charging when idle. Usual ratings: 12 V or 24 V, 80–200 Ah.

Station battery

A station battery is a large stationary battery bank (usually 24, 48, 110 or 220 V DC) installed in substations, power stations and industrial switchrooms to supply:

  • Tripping and closing coils of circuit breakers,
  • Protection relays, control and indication,
  • Emergency lighting and communication.

It must be completely reliable, so it is kept on float charge with the charger, battery and DC load in parallel. Thick-plate tubular lead-acid or Ni-Cd cells with long life (15–20 years) are used.

Methods of battery charging

  1. Constant-current charging – current held at about C/10 while voltage rises; two-rate variant reduces gassing.
  2. Constant-voltage charging – fixed 2.3–2.4 V/cell; current falls automatically.
  3. CC–CV (modified constant voltage) – constant current then constant voltage; used in modern chargers.
  4. Trickle charging – small continuous current to make up self-discharge of idle batteries (e.g. DG starting batteries).
  5. Float charging – charger feeds load and battery together at ≈ 2.2 V/cell (station batteries).
  6. Boost charging – high current briefly after deep discharge.
  7. Equalising charge – occasional overcharge to equalise all cells.
Station battery – float scheme
 AC ─►[Charger]──┬──────────┬──► DC bus (trip,
                 │          │    control, lights)
            [Battery bank]  │

✓ Answer checked by Claude Opus 5.5 (high effort)

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