# Smart BatteryProtect 48V-10A — Alarm output inactive on startup when voltage already below threshold **URL:** \ **Category:** Q&A and troubleshooting\ **Tags:** battery\_protect, professional\ **Created:** [2 March 2026 08:51 UTC](https://community.victronenergy.com/t/smart-batteryprotect-48v-10a-alarm-output-inactive-on-startup-when-voltage-already-below-threshold/54230 "2026-03-02T08:51:23Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![mark86](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@mark86](https://community.victronenergy.com/u/mark86)\ **Post date:** [2 March 2026 08:51 UTC](https://community.victronenergy.com/t/smart-batteryprotect-48v-10a-alarm-output-inactive-on-startup-when-voltage-already-below-threshold/54230/1 "2026-03-02T08:51:23Z")
Hi everyone, I’ve been testing the Smart BatteryProtect 48V-10A and noticed a behavior difference in the alarm output depending on when the undervoltage condition occurs. I’d like to understand if this is intentional or a bug. Threshold = 46V and buzzer mode Test 1 — Voltage drops below threshold while system is already running: Start with power supply \> 46V (system running normally) -Decrease voltage below 46V -Wait 12 seconds → P3 displayed, alarm pin goes LOW (connected to GND) -Raise voltage back above 46V → alarm resets correctly Test 2 — System powered on with voltage already below threshold: Lower power supply below 46V Power on the system → E3 displayed, alarm pin remains inactive (NOT connected to GND) The datasheet states: “The alarm output is activated if the battery voltage drops below the preset disconnect level during more than 12 seconds.” The word “drops below” suggests a dynamic event (a transition), which could explain why the alarm doesn’t activate on startup. A customer of mine reports that older BatteryProtect units always triggered the alarm regardless of startup conditions. Is this behavior intentional by design, or is it a firmware bug? Thanks in advance for any insight!