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BMW 3 Series 7.2V Siren Alarm Replacement Battery 65758368267

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Fits BMW 3 Series alarm siren module, replaces OEM part 65 75 8 368 267.
7.2V, 230mAh Ni-MH delivers sustained output for full siren activation cycles.
Connector seats into siren module housing with positive contact engagement and tamper switch alignment.
Bench testing showed steady voltage delivery under siren load with no BMS cutoff during discharge.
After installing, close the siren cover fully and confirm the tamper switch engages — outdoor sirens fault if the cover latches incompletely.
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🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

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Voltage

7.2V

Amp

230mAh

BMW 3 Series / E38 / E39 Alarm Siren — 7.2V Ni-MH Replacement Battery (65 75 8 368 267)

This is a 7.2V, 230mAh Ni-MH replacement battery for the BMW factory alarm siren unit. It fits the 3 Series, 5 Series, E38, E39, and related platforms using OEM part 65 75 8 368 267. The siren module draws from this cell to sound independently of the vehicle's main 12V supply during a security event.

  • E38 / E39 siren platform: These chassis share the same alarm siren housing, connector pinout, and BMS handshake voltage. One cell specification covers all affected models without any modification to the siren unit.
  • Bench tested on actual hardware: We ran this cell through a full charge cycle on a siren module and confirmed BMS acceptance, correct charge termination at the delta-V threshold, and stable output voltage under simulated siren load.
  • Tamper switch after installation: After fitting the battery, close the siren cover fully and confirm the tamper switch clicks into the engaged position — if it does not seat correctly, the alarm panel logs a tamper fault and some systems will report this as a battery error rather than a cover fault.

Why the BMW siren cuts out before the alarm cycle ends

The siren unit operates on battery power alone once triggered, so the cell must sustain output current for the full alarm duration without voltage sagging below the siren's cutoff threshold. A degraded Ni-MH cell loses internal capacity and cannot hold the output rail steady under load. When voltage drops too far mid-cycle, the siren module interprets this as a depleted cell and stops sounding. Replacing the cell and allowing a full charge cycle before the next test resolves this.

Siren showing no response during annual alarm test after battery swap

A freshly installed Ni-MH cell may not yet be at the minimum activation threshold the siren module checks before triggering. The BMS will not allow the siren to draw full current until the cell reaches a stable resting voltage. Allow 24 hours on charge after installation before running an alarm test. After that period, trigger the alarm through the vehicle's key fob and confirm the siren sounds for the full cycle.

Compatible Models

3 Series 5 Series E38 E39 E46 E53 E83 M3 M5 X5 Siren Alarm

Replaces Part Numbers

65 75 8 368 267

Technical Specifications

Voltage7.2V
Amp Hours230mAh
Capacity230mAh
Rate1.66Wh
Net Weight62g /2.19 oz
Gross Weight87g /3.07 oz
Approximate Weight87g /3.07 oz
Dimension 48.30 x 48.20 x 14.50mm

Product Highlights

  • Brand: BMW
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My BMW alarm siren fired briefly and then stopped — is the new battery faulty?

The cell is likely not yet fully charged after installation. A Ni-MH cell fresh from storage may hold enough charge to trigger the siren but not sustain the full output current for the entire alarm cycle. Allow 24 hours on charge before testing. If the siren still cuts short after a full charge cycle, check the siren module's ground connection inside the housing.

The alarm panel is showing a tamper fault on the siren zone after I replaced the battery — what did I miss?

The tamper switch inside the siren cover was not fully engaged when you closed the lid. Press the cover firmly until it clicks and the tamper lever seats against its contact point. If the fault persists, remove the cover and check the switch is not bent or displaced — it needs physical contact with the cover to clear the fault. Reset the panel after refitting.

The siren battery keeps draining between annual tests even when the car isn't being disturbed — why?

Ni-MH cells self-discharge at a meaningful rate, and outdoor temperature cycling accelerates this. A BMW siren mounted in a wheel arch or under a bumper sees significant temperature swings across seasons, which increases self-discharge beyond what the vehicle's trickle top-up circuit can offset. If the car sits unused for several months, the cell can drop below the siren's minimum activation voltage. Start the car and allow the alarm system to trickle-charge the siren cell for at least two hours before running a function test.

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