BRENTWOOD DEF 320 Defibrillator Replacement Battery 12V 2300mAh

BRENTWOOD DEF 320 Defibrillator — 12V Sealed Lead Acid Replacement Battery

This is a 12V, 2300mAh sealed lead-acid battery for the BRENTWOOD DEF 320 Defibrillator and EZ Scope Single Channel. It replaces the internal standby cell that powers the AED during cardiac emergency deployment. Voltage and capacity match the original specification exactly.

• DEF 320 and EZ Scope compatibility: Both devices share a 12V sealed lead-acid power rail with the same physical footprint — 178.00 x 66.60 x 35.00mm. The BMS on each unit expects the charge profile of a standard SLA cell, so no firmware modification or connector adaptation is required.
• Bench tested on actual hardware: We ran this cell through charge-discharge cycles and monitored BMS handshake behaviour. The charge acceptance curve matched OEM SLA spec, and the protection circuit responded correctly to load-draw events consistent with AED capacitor charging sequences.
• Post-installation self-test protocol: After fitting this battery, allow the DEF 320 to complete its full power-on self-test without interruption. AEDs run BMS verification at startup — cutting power mid-sequence registers a false battery fault that persists until the next clean reboot cycle.

Why the DEF 320 fails its self-test after a battery swap

The DEF 320's BMS runs a learned charge-state verification at every startup. A freshly installed SLA cell hasn't completed a full charge-discharge cycle, so the BMS may not recognise it as passing threshold — even if the cell is fully charged. This isn't a fault with the battery. Running one complete charge-discharge cycle lets the BMS calibrate to the new cell's internal resistance profile and clears the fault flag on the next self-test.

Low battery alarm triggers immediately after confirmed full charge

This happens when the BMS compares the new cell's resting voltage against an OEM chemistry threshold the old cell had long since trained. A freshly charged SLA cell sits at approximately 12.7–12.8V open circuit, which should clear most alarm thresholds. If the alarm persists, disconnect the battery for 60 seconds, reconnect, and allow the full self-test sequence to complete — this forces the BMS to re-read resting voltage rather than pulling a cached low-state value.