Aeroflex AE4000A Replacement Battery 7.4V 8700mAh Li-ion

Aeroflex AE4000A / E7000L — 7.4V Li-ion Replacement Battery (HYLB-1842)

This 7.4V 8700mAh Li-ion battery replaces the original pack in the Aeroflex AE4000A and E7000L portable RF and microwave test instruments. It supplies the sustained, stable current these units draw during field RF sweeps, signal analysis, and equipment diagnostics away from AC power. Capacity is 8700mAh (64.38Wh), matching OEM part numbers HYLB-1842 and HYLB-1842B.

• AE4000A and E7000L platform fit: Both instruments share the same battery bay dimensions, connector pinout, and BMS handshake protocol, which is why a single pack covers both models. The cell stack and protection circuit must satisfy the same voltage rail and communication requirements on either unit.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge sequences, monitoring BMS response during the high-current draw spike that occurs at instrument power-on and during active RF probe initialisation. The protection circuit held within spec across repeated cold starts.
• Pre-deployment calibration cycle: After installing this pack, run a full calibration cycle through the instrument's menu before heading into the field. The AE4000A and E7000L map battery state during calibration — skip this and the fuel indicator will trigger premature low-battery warnings mid-session even with charge remaining.

BMS lockout after the AE4000A sits unused in a carry case for months

Li-ion cells self-discharge over time, and if a pack drops below approximately 2.5V per cell during extended storage, the BMS enters a protective lockout state and will not accept a charge through normal means. The instrument won't power on and the charger shows no activity — this looks like a dead battery but is usually a recoverable BMS sleep state. Apply a low-rate trickle charge directly to the pack at around 0.1C until cell voltage climbs above 3.0V per cell, at which point the BMS re-initialises and normal charging resumes. If cell voltage reads zero and does not respond to trickle input after 30 minutes, the cells have reached an unrecoverable state and the pack needs replacement.

Instrument powers on but shuts off during USB data transfer to PC

USB data transfer adds a sustained secondary load on top of the instrument's active measurement draw — combined, the two can pull enough current to cross the BMS overcurrent threshold on a partially depleted pack. The BMS interprets this combined draw as a fault condition and cuts output to protect the cells. Charge the pack to full before any data transfer session, and where possible close active measurement processes before initiating the USB transfer. If the shutdown repeats even at full charge, check the USB cable — a resistive connection forces the instrument to draw harder from the battery to maintain data throughput, which pushes the load higher still.