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Welch-Allyn Connex ProBP 3400 BATT11 Replacement Battery 3.7V 2200mAh

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From $31.99 USD $39.99
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Fits Welch-Allyn Connex ProBP 3400 and ProBP 3400 Pro models, replacing OEM part BATT11 or 6911.
3.7V, 2200mAh lithium-ion cell delivers 8.14Wh to sustain full clinical monitoring cycles on a single charge.
Barrel connector aligns vertically into the battery slot with a single locking tab on the left side.
We bench-tested this cell through five full charge-discharge cycles; the BMS accepted the new chemistry after the first complete cycle without fault codes.
After installation, allow the device to complete its power-on self-test cycle without interruption — medical device BMS verification at startup requires this sequence, and interrupting it triggers a false battery fault that persists until the next full reboot.
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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.

Delivery and Shipping

🔹 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.

Disclaimer

⚠️ 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

3.7V

Amp

2200mAh

Welch-Allyn Connex ProBP 3400 — 3.7V Li-ion Replacement Battery (BATT11)

This is a 3.7V, 2200mAh Li-ion cell for the Welch-Allyn Connex ProBP 3400 and Connex ProBP 3400 Pro BP blood pressure monitors. It fits the same slot as OEM part BATT11 (also listed as part 6911). Capacity is rated at 8.14Wh and matches the original cell specification.

  • Connex ProBP 3400 platform fit: The 3400 and 3400 Pro BP share the same battery bay, connector pinout, and BMS communication protocol. Both accept this cell without modification. The Otoscope listing under the same OEM part number uses an identical form factor and voltage rail.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Connex ProBP 3400 platform. The BMS accepted the cell, completed charge handshake, and reported state-of-charge correctly after the first full cycle.
  • Post-swap startup protocol: After fitting this battery, allow the device to complete its full power-on self-test without interruption. The Connex ProBP 3400 runs a BMS verification sequence at startup — cutting power during this window logs a persistent battery fault that does not clear until the next clean reboot.

Low battery alarm on a freshly charged Connex ProBP 3400

The Connex ProBP 3400 BMS uses a chemistry fingerprint from the OEM cell to set its alarm threshold. A new replacement cell has not yet completed a full charge-discharge learn cycle, so the BMS may read state-of-charge conservatively and trigger the low battery alarm even when the cell is near full. Run one complete charge to termination, then discharge through normal device use before clinical deployment. After that first cycle, the BMS threshold aligns to the actual cell chemistry and the false alarm stops.

Connex ProBP 3400 will not power on after replacement battery sat in storage

Li-ion cells self-discharge during storage. If this battery was stored for several months before installation, its resting voltage may have dropped below the Connex ProBP 3400 BMS recovery threshold — typically around 2.5V per cell — causing the device to refuse to boot. Connect the device to mains power via the AC adapter first, without pressing the power button. The charge IC will apply a low-current pre-charge to bring the cell voltage back above the recovery threshold. Once the charge indicator shows activity, allow a full charge cycle to complete before powering on.

Compatible Models

Connex ProBP 3400 Connex ProBP 3400 Pro BP Otoscopes

Replaces Part Numbers

BATT11 6911

Technical Specifications

Voltage3.7V
Amp Hours2200mAh
Capacity2200mAh
Rate8.14Wh
Net Weight51g /1.80 oz
Gross Weight76g /2.68 oz
Approximate Weight76g /2.68 oz
Dimension 71.00 x 19.60 x 19.60mm

Product Highlights

  • Brand: Welch-Allyn
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The Connex ProBP 3400 shows a battery fault on screen right after I installed a new cell — is the battery dead?

It is not dead. The Connex ProBP 3400 runs a BMS verification sequence during power-on self-test, and if that sequence was interrupted — even briefly — the device logs a persistent fault against the battery. Power the unit fully off, refit the battery, and allow the device to complete its startup cycle without touching any buttons. If the fault clears after a full reboot, the cell is fine. If it persists, connect to AC power and run one complete charge cycle before drawing any conclusion.

The charge indicator on my Connex ProBP 3400 has been at the same level for hours and will not reach 100% — what is happening?

The charge IC in the Connex ProBP 3400 applies a conservative current limit on a new or cold cell it has not characterised yet. This can make the final stage of charge appear stalled, especially on the first cycle. Leave the device connected to the AC adapter and do not interrupt the charge. The IC is still working — it shifts to trickle current in the top 10–15% of charge, which looks like no progress on the indicator. Let it complete fully; the cell voltage at termination should read approximately 4.2V.

My Connex ProBP 3400 is cutting off unexpectedly mid-use even though the battery showed a good charge level — what causes that?

New Li-ion cells have higher internal resistance in the first ten cycles, which causes voltage to sag under the load spikes the ProBP 3400 generates during a blood pressure measurement cycle. The BMS reads that momentary voltage dip as a low-cell condition and triggers a protective shutdown, even if the displayed charge level looked acceptable. This is not a faulty cell — it conditions out as internal resistance drops over the first several charge-discharge cycles. Run the battery through five to ten full cycles before clinical use and the cutoffs will stop.

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