battery pack

A battery pack is an assembly of individual battery cells connected in series, parallel, or a combination of both, designed to supply electrical energy at a specified voltage and capacity to a load or device. The cells are typically held in a plastic or metal housing with terminal connections, and in modern industrial applications, almost always paired with a battery management system (BMS) that monitors cell health, temperature, and charge state.

The configuration determines the electrical output. Series connection multiplies voltage: four 3.7V lithium-ion cells in series yield 14.8V. Parallel connection multiplies capacity and current capability while holding voltage flat: four cells in parallel at 3.7V still output 3.7V but deliver four times the amp-hour capacity. Industrial packs often use a mixed topology, sometimes called a 2S2P arrangement (two series strings, each string two cells in parallel), to balance voltage, capacity, and current delivery against cost and thermal management challenges.

Common chemistries and practical limits

Lithium-ion dominates industrial battery packs today because of high energy density, around 150 to 250 watt-hours per kilogram depending on chemistry. Older lead-acid packs, still found in uninterruptible power supplies and emergency lighting, deliver around 40 to 50 watt-hours per kilogram but cost far less and tolerate physical abuse better. Nickel-metal hydride packs appear in some industrial cordless tools and hybrid vehicles. The chemistry choice drives cycle life, self-discharge rate, operating temperature range, and safety behavior under fault conditions.

The battery management system is not optional in modern industrial packs. It measures individual cell voltage, pack current, and temperature using resistive sense networks and thermistors. The BMS enforces maximum charge voltage, prevents overdischarge, balances cell voltages to equalize wear, and cuts power if any cell exceeds safe operating limits. Without these protections, lithium-ion cells can enter thermal runaway, a chain reaction that generates heat, venting, and occasionally fire.

Battery packs appear everywhere industrial equipment demands portable or temporary power: forklifts, electric vehicles, backup power systems, power tools, and emergency exit lighting. A pack's usable life is measured in charge cycles, typically 500 to 3000 cycles for lithium-ion depending on depth of discharge and operating temperature. Capacity fades irreversibly as the electrolyte degrades and the electrodes develop resistance; a pack is often considered end-of-life when capacity falls to 80 percent of its original rating, though some applications tolerate further degradation.