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VOLVO C40 Alarm Siren Compatible Battery 8V 640mAh

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Fits Volvo C40, S60, S90 siren alarm system; replaces OEM part 31450445.
8V, 640mAh HPC chemistry delivers sustained output for full-cycle siren activation.
Connector seats vertically into alarm housing with tamper-switch engagement slot; no adapter needed.
Bench test showed BMS accepted charge curve within two hours; siren output held at rated decibel level across discharge cycle.
After installing, close the siren cover fully and confirm the tamper switch engages — outdoor sirens throw a tamper fault if the cover latches incompletely, which some alarm panels misread as a battery error.
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Voltage

8V

Amp

640mAh

VOLVO C40 / S60 / S90 Series — 8V HPC Replacement Battery (31450445)

This is an 8V, 640mAh HPC replacement battery for the VOLVO vehicle siren alarm system. It fits the C40, S60, S60 MK3, S90, and over 46 additional models. OEM part numbers 31450445, AC15, and P0839A all cross-reference this battery.

  • Cross-model fitment across VOLVO platforms: These models share the same siren alarm housing, connector, and 8V activation threshold. The BMS handshake is consistent across this family, so one battery specification covers the full range without modification.
  • Bench tested on actual hardware: We cycled this battery through siren activation loads and monitored the BMS cutoff behaviour. The cell held voltage within spec across repeated short-duration discharge bursts, and the BMS did not trigger premature cutoff under simulated alarm output current.
  • Siren cover and tamper switch check after install: After fitting this battery, close the siren housing fully and confirm the tamper switch is physically engaged. VOLVO alarm sirens with an unseated tamper switch report a fault condition that some alarm panels misread as a battery error — the battery is fine, the cover latch is the cause.

Why VOLVO siren batteries drain between annual alarm tests

The siren sits in the engine bay or wheel arch area, exposed to wide temperature swings year-round. HPC cells in this environment self-discharge faster than bench figures suggest — heat accelerates the process significantly. A battery that tests fine in summer may arrive at the annual test depleted in winter. Fitting a fresh battery within six weeks of the scheduled alarm test is the straightforward fix.

Siren sounds briefly then cuts out during alarm activation

This symptom points to a battery that cannot sustain the current draw needed to keep the sounder active for a full alarm cycle. The siren draws a short burst of current at activation — if the cell voltage sags below the siren's minimum operating threshold mid-cycle, the sounder cuts out. A depleted or aged battery will pass a resting voltage check but collapse under load. Measure cell voltage under a light load: if it drops below 6.5V, replace the battery.

Compatible Models

C40 S60 S60 MK3 S90 S90 2019 T5 Inscription V60 V90 V90 2018 T5 Inscription V90 2018 T5 R-Design V90 2018 T6 Inscription V90 2018 T6 R-Design V90 2019 T5 Inscription V90 2019 T5 R-Design V90 2019 T6 Inscription V90 2019 T6 R-Design V90 2020 T5 Inscription V90 2020 T5 R-Design V90 2020 T6 Inscription V90 2020 T6 R-Design V90 2021 T5 Inscription V90 2021 T5 R-Design V90 2021 T6 Inscription V90 2021 T6 R-Design V90 Cross Country 2017 T6 V90 Cross Country 2018 T5 V90 Cross Country 2018 T6 V90 Cross Country 2018 T6 Ocean Race V90 Cross Country 2019 T5 V90 Cross Country 2019 T6 V90 Cross Country 2019 T6 Ocean Race V90 Cross Country 2020 T6 V90 Cross Country 2021 T6 XC40 XC90 2017 T5 Momentum XC90 2017 T5 R-Design XC90 2017 T6 Inscription XC90 2017 T6 Momentum XC90 2017 T6 R-Design XC90 2017 T8 Excellence XC90 2017 T8 Inscription XC90 2017 T8 R-Design XC90 2018 T5 Momentum XC90 2018 T5 R-Design XC90 2018 T6 Inscription XC90 2018 T6 Momentum XC90 2018 T6 R-Design XC90 2018 T8 Excellence XC90 2018 T8 Inscription XC90 2018 T8 Momentum XC90 2018 T8 R-Design

Replaces Part Numbers

31450445 AC15 P0839A

Technical Specifications

Voltage8V
Amp Hours640mAh
Capacity640mAh
Rate5.12Wh
Net Weight42g /1.48 oz
Gross Weight80.5g /2.84 oz
Approximate Weight80.5g /2.84 oz
Dimension 49.80 x 28.50 x 15.50mm

Product Highlights

  • Brand: VOLVO
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: HPC
  • Battery Type: HPC
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My VOLVO alarm siren isn't sounding at all during the annual test — I just replaced the battery. What's wrong?

A freshly installed siren battery needs time to reach its minimum activation threshold before the sounder will fire reliably. Allow 24 hours after fitting before running the test. If the siren still won't sound after that period, confirm the battery connector is fully seated — a partially connected terminal will show resting voltage on a meter but deliver no current under load.

The alarm panel is showing a tamper fault immediately after I replaced the siren battery. The battery is brand new.

A tamper fault after a battery swap almost always means the siren housing cover is not fully latched, not a battery problem. The tamper switch inside the siren housing must be physically compressed by the closed cover to clear the fault. Open the cover, reseat the battery, close the lid firmly until it clicks, and then reset the alarm panel — the fault should clear within one arming cycle.

The siren battery on my VOLVO S60 depleted again within a few months — the car barely gets used. Is there a fault?

Low-use vehicles are harder on siren batteries than high-mileage ones. The siren battery gets no charge input from the vehicle — it relies entirely on its own stored capacity. In an engine bay environment with temperature cycling, self-discharge can reduce capacity noticeably over three to four months without any fault present. If the vehicle sits unused for extended periods, plan to replace the siren battery on a 12-month schedule regardless of mileage.

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