Lithium-ion batteries

Large lithium-ion batteries usually come in battery packs which are multiple cells connected together. They need to be monitored electronically (voltage, current, temperature, etc.) on a constant basis to ensure their safe operation and protect the lithium-ion cells against damage. These tasks are carried out by an integrated battery-specific battery management system (BMS).

‘HOPPECKE sun | powerpack premium lithium-ion’ battery.

Key: ① housing; ② lower battery stack; ③ upper battery stack; ④ battery management system (BMS); ⑤ display unit; ⑥ connector; ⑦ service interface.         

Technologies: Prismatic cells, lithium iron phosphate (LiFePo).

Nominal capacity: 50 Ah (C3) 5 kWh or 78 Ah (C3) 7.5 kWh system.

Nominal voltage: 3.2 V/cell (51.2V battery system.

The unit is about the size of a large suitcase.

Lithium-ion batteries have several advantages over lead-acid batteries. They generally have a longer service life. Energy and power densities are significantly higher than their lead-acid counterparts, which results in smaller battery banks (in terms of volume and weight). They are less sensitive to deep-cycle discharging than lead-acid batteries. They also have higher round-trip cycling efficiencies than lead-acid batteries, so less energy is lost during charging and discharging. However, they are significantly more expensive and not yet available everywhere.

Lithium-ion batteries are extremely sensitive to low and high temperatures. The desired operating temperature for most lithium-ion batteries is 20° C to 30 °C (refer to specifications). Active or passive cooling or heating can be required for optimal performance.