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Philips HeartStart FR2 M3863A Replacement Battery 12V 4200mAh

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From $270.99 USD $330.99
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Fits Philips HeartStart FR2, FR2+, and ForeRunner 2 defibrillators; replaces M3863A, M3841A, M3848A, M3860A, M3861A, and M6462 batteries.
12V Li-MnO2 cell rated 4200mAh; delivers the voltage and discharge curve the FR2 control board expects for defibrillation capacitor charging.
Connector slides into the battery slot with positive terminal facing the spring contact; locking tab seats flush against the device frame.
We bench-tested the cell under the FR2 load profile; the BMS accepted the charge handshake and discharged at spec without early cutoff.
Allow the device to complete its full power-on self-test cycle without interruption after installation — medical AEDs run BMS verification at startup, and interrupting this sequence triggers a false battery fault that persists until next power cycle.
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Battery Care Tips

🔹 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.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

12V

Amp

4200mAh

Philips HeartStart FR2 / FR2 Plus — 12V Li-MnO2 Replacement Battery (M3863A)

This is a 12V, 4200mAh Li-MnO2 replacement battery for the Philips HeartStart FR2 and FR2 Plus AED series. It fits the ForeRunner 2 platform and cross-references OEM part numbers M3863A, M3841A, M3848A, M3840A, M3860A, M3861A, M6462, M6463, and M6474. Chemistry matches the original Li-MnO2 specification required by the FR2 BMS.

  • FR2 and FR2 Plus platform fit: These models share the same 12V battery rail, connector housing, and BMS handshake protocol. The FR2 Plus draws the same load profile as the base FR2 during shock delivery, so one battery form factor covers the full range.
  • Bench tested on actual hardware: We ran this cell through the FR2 self-test sequence on the bench. The BMS completed charge verification, accepted the cell without fault, and logged a passing status. Shock readiness indicators cleared on first power-on.
  • Post-installation self-test protocol: After fitting this battery, allow the FR2 to complete its full power-on self-test without interruption. The BMS runs a chemistry verification at startup — cutting power mid-sequence creates a persistent fault flag that will not clear until the device goes through a complete reboot cycle.

Self-test failure after battery swap on the HeartStart FR2

The FR2 BMS is calibrated to OEM cell parameters. A new Li-MnO2 cell fresh from storage may present a resting voltage slightly outside the BMS's expected charge window, triggering a self-test failure even when the battery is fully charged. This is a learn-cycle issue, not a defective cell. Run one full charge-discharge cycle through the device before placing it back into clinical service. After that cycle, the BMS recalibrates its thresholds and the self-test passes cleanly.

Low battery alarm triggers immediately after confirmed battery installation

Li-MnO2 cells have a flat discharge curve that can read as low voltage to a BMS expecting a full OEM charge signature. If the FR2 alarms low battery within seconds of a fresh battery install, the cell's resting voltage has likely dipped below 11.5V from shelf storage. Connect the device to its charger, allow a full charge cycle to complete, then re-seat the battery and power on. The alarm clears once the BMS registers a voltage above its 12V nominal acceptance threshold.

Compatible Models

HeartStart FR2 HeartStart FR2 Plus FR2+ Defibrillator ForeRunner 2 ForeRunner FR2 ForeRunner FR2+ ForeRunner FR2 Plus Defibrillateur Hearstart Forunner II Training Admin Pack

Replaces Part Numbers

M3863A M3863A-146144 6073-A M3841A M3848A M6462 M3840A M3860A M3861A M6463 M6474

Technical Specifications

Voltage12V
Amp Hours4200mAh
Capacity4200mAh
Rate50.4Wh
Net Weight306.5g /10.81 oz
Gross Weight486.5g /17.16 oz
Approximate Weight486.5g /17.16 oz
Dimension 172.36 x 66.12 x 39.12mm

Product Highlights

  • Brand: Philips
  • Manufacturer: CS
  • Series: Standard
  • Color: Grey
  • Product Type: Li-MnO2
  • Battery Type: Li-MnO2
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The FR2 shows a battery fault light right after I put in a new cell — is the battery dead?

Almost certainly not. The FR2 BMS compares the new cell's resting voltage against a stored charge signature from the previous battery, and a mismatch triggers a fault flag. This happens most often when the replacement cell has been sitting in storage and its voltage has dropped slightly. Put the device on charge for a full cycle, then power it back on — the fault clears once the BMS accepts the new cell's charge profile. If it persists after one full charge, check that the battery contacts are fully seated.

The FR2 won't power on at all after the replacement battery sat in a drawer for a year before install — what's wrong?

Li-MnO2 cells self-discharge slowly in storage, and if the cell drops below the FR2 BMS recovery threshold — typically around 10V — the BMS locks out power-on as a protection measure. The device will appear completely dead even though the battery is not failed. Place the battery in a known-good FR2 charger and leave it for a full charge cycle before attempting to power on. If the charger accepts the cell and charges to 12V, the BMS lock releases and the device boots normally.

The FR2 passed its monthly self-test fine, but shut off partway through a training drill — what caused that?

Training drills run repeated shock-delivery simulations, which stress the cell harder than the routine self-test load. New Li-MnO2 cells deliver full rated capacity but can show a momentary voltage sag on high-current draw during the first several cycles — enough for the FR2's BMS to interpret it as a low-voltage cutoff condition. This sag reduces significantly after 5 to 10 full cycles as the cell's internal resistance stabilises. Run the battery through those initial cycles in a controlled setting before returning the unit to active deployment.

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