Battery charger Voltcraft BC4 for Li-ion and NiMH cells — AA, AAA, C, Sub-C, 18650, 21700

Voltcraft BC4 is a universal battery charger designed for Li-ion and NiMH cylindrical cells. It supports common sizes including AA, AAA, C, Sub-C and larger lithium cells such as 18650 and 21700. The charger provides selectable charging for single or multiple cells and is intended for recharging and maintaining batteries used in household devices, flashlights, power tools and portable electronics.

Advantages

The charger accommodates both Li-ion and NiMH chemistries and automatically adapts to cell length and diameter within supported formats. Its design allows independent charging channels so cells of different charge states can be charged simultaneously. Built-in safety features include protection against reverse polarity and short-circuit conditions, with temperature monitoring to prevent overheating during extended charging. The compact footprint and clear status indicators make it suitable for desktop or workshop use.

Suitable for

• Recharging AA and AAA NiMH rechargeable batteries used in remotes, toys and clocks
• Charging C and Sub-C cells for portable radios, emergency lights and hobby devices
• Charging 18650 and 21700 Li-ion cells for flashlights, e-bikes and power banks (compatible cylindrical cells only)
• Maintaining partially discharged cells for storage or intermittent use

Key specifications

• Supported chemistries: Li-ion (cylindrical) and NiMH
• Supported cell formats: AA, AAA, C, Sub-C, 18650, 21700
• Independent charging channels with per-slot monitoring
• Safety features: reverse polarity protection, short-circuit protection, temperature monitoring
• Status indicators: per-slot LED or display showing charge progress
• Input: mains-powered charger (AC input compatible with household outlets)

How to use

Insert batteries into the slots ensuring correct polarity. Connect the charger to a compatible mains outlet; charging will begin automatically for supported cells. Monitor the status indicators to determine charge progress and wait for the indicator that signals a finished or maintained charge. Remove cells once charging is complete or when the maintenance/standby mode is active. For best results, use on a stable, flat surface and avoid exposing the charger to prolonged direct heat or moisture.

Usage recommendations

Use only cylindrical Li-ion and NiMH rechargeable cells in the supported sizes. Do not attempt to charge damaged, swollen, or non-rechargeable batteries. For storage, fully charge NiMH cells before long-term shelving and store Li-ion cells at around 30–50% charge. If charging multiple cells of different chemistries is necessary, consult the device indicators and manufacturer instructions; avoid mixing chemistries in a single slot.