--- title: "Battery charging schemes and most effective" subject: "Industrial Power Distribution and Illumination" chapter: 9 key: "semester_6/industrial_power_distribution_and_illumination:battery-charging-schemes-effective" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/battery-charging-schemes-effective site: BCT Engineering --- # Battery charging schemes and most effective Industrial Power Distribution and Illumination · Chapter 9: Emergency and Backup Supply Systems - Asked in: 2073 Bhadra, 4 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/battery-charging-schemes-effective - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-9 ## Question What are different types of battery charging scheme? Describe each of them with their specific purposes. Which method is most effective? ## Short answer Schemes are constant current, constant voltage, trickle, float, boost, and equalising. The most effective is modified constant voltage (CC-CV): constant current, then constant voltage, then float, giving fast charging without overgassing; for standby duty float charging is best. ## Answer Battery charging schemes differ in how current and voltage are controlled during charging. 1. **Constant-current charging** – current fixed at about C/10. *Purpose:* first charge of new batteries, accurate restoring of known Ah; used in battery workshops. 2. **Constant-voltage charging** – fixed voltage ≈ 2.3–2.4 V/cell; current falls as battery charges. *Purpose:* fast, self-limiting charging, e.g. vehicle alternator charging. 3. **Trickle charging** – tiny continuous current equal to self-discharge. *Purpose:* keep idle standby batteries (emergency lights, alarms, DG starting) always full. 4. **Float charging** – charger, battery and load in parallel at ≈ 2.2 V/cell. *Purpose:* no-break DC supply in substations, telecom and UPS; battery takes load at mains failure. 5. **Boost charging** – high current for a short time. *Purpose:* quick recovery of a deeply discharged battery. 6. **Equalising charge** – periodic controlled overcharge. *Purpose:* equalise voltages and specific gravity of all cells in a string. **Most effective method:** the **modified constant-voltage (CC–CV) method** – constant current at first, then constant voltage, then float. It charges fast without overcharging or excessive gassing and gives the longest battery life, so it is used in most modern chargers. For standby duty, **float charging** is the most effective in practice. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In constant-voltage charging at about 2.3-2.4 V/cell, how does the charging current behave? A. It stays fixed at C/10 B. It falls as the battery charges, making the method self-limiting C. It rises as the battery charges D. It is zero until the battery is fully discharged Answer: B. With fixed voltage, the current falls as battery emf rises, so charging is fast at first and self-limiting. (Key point: Constant-voltage charging) 2. What is the arrangement and purpose of float charging? A. A high current used briefly to recover a deeply discharged battery B. A periodic overcharge to equalise cells C. A tiny current equal to self-discharge to a disconnected battery D. Charger, battery and load in parallel at about 2.2 V/cell for a no-break DC supply Answer: D. In float charging the charger carries the load and keeps the battery full, which takes over when mains fails. (Key point: Float charging) 3. What is the purpose of an equalising charge? A. Controlled periodic overcharge to equalise voltage and specific gravity of all cells B. Quick recovery of a deeply discharged battery C. Charging a new battery for the first time D. Supplying the load during mains failure Answer: A. Cells in a string drift apart; a periodic controlled overcharge brings them to the same state. (Key point: Equalising charge) 4. Which method is described as most effective for general charging, and why? A. Boost charging, because it is fastest B. Trickle charging, because it never overcharges C. Modified constant-voltage (CC-CV), because it charges fast without overcharging or excess gassing D. Constant-current charging, because it needs no control Answer: C. CC-CV starts with constant current, then constant voltage, then float, giving fast charging and long battery life. 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