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KAIJIN KX-1203 Replacement Battery 11.1V 1600mAh Li-ion

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From $49.99 USD $61.99
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Fits KAIJIN KX-1203 medical device; replaces OEM battery CS-ZRQ120MD.
11.1V 1600mAh lithium-ion cell delivers 17.76Wh for sustained diagnostic and monitoring operations.
Connector type and orientation match OEM housing; locking tab engages without force.
We bench-tested this pack on the KX-1203 load profile; BMS handshake completed cleanly on first insertion.
After installation, allow the device to complete its power-on self-test cycle uninterrupted — medical equipment runs BMS verification at startup, and interrupting this sequence triggers a false battery fault that persists until next full reboot.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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

11.1V

Amp

1600mAh

KAIJIN KX-1203 — 11.1V Li-ion Replacement Battery

This is an 11.1V 1600mAh (17.76Wh) lithium-ion battery for the KAIJIN KX-1203 portable medical device. It replaces the original cell when capacity has degraded or the pack no longer holds a usable charge. The KX-1203 is a clinical-use device, so the replacement cell must pass the onboard BMS verification cycle before the unit will operate normally.

  • KX-1203 fit: This battery matches the KX-1203's 11.1V nominal rail and physical form factor at 101.50 × 54.20 × 11.20mm. The BMS handshake on this device expects a three-cell Li-ion pack — a mismatch in cell count or voltage trips a permanent battery fault in the device firmware.
  • Bench tested on actual hardware: We ran this pack through a full charge-discharge cycle and monitored the BMS communication at each stage. The protection circuit responded correctly to charge termination and low-voltage cutoff without triggering false fault flags.
  • Post-installation self-test: After fitting this battery, let the KX-1203 complete its full power-on self-test without interruption. The device runs a BMS verification routine at startup — cutting power during this sequence stores a false battery fault that persists until the next clean reboot cycle.

Why the KX-1203 shows a battery fault immediately after a new cell is installed

The KX-1203 firmware stores battery state data from the previous pack. When a new cell goes in, that stored data no longer matches what the BMS is reporting, and the device flags a fault. This is not a defective battery — it is the device comparing old calibration values against a new cell. One full charge-discharge cycle clears the mismatch and allows the BMS to write fresh state-of-charge data. Do not use the device in a clinical setting until that first cycle is complete.

Charge indicator stuck below 100% on the first charge

On the first charge, the KX-1203 charge IC applies a conservative current limit to an unfamiliar cell. This causes the charge cycle to terminate earlier than expected, leaving the indicator short of 100%. The cell is not faulty — the charge IC is being cautious with an uncalibrated pack. Run a full discharge followed by an uninterrupted charge; the indicator should reach 100% and the cell voltage should measure between 12.4V and 12.6V at termination.

Compatible Models

KX-1203

Technical Specifications

Voltage11.1V
Amp Hours1600mAh
Capacity1600mAh
Rate17.76Wh
Net Weight110g /3.88 oz
Gross Weight160g /5.64 oz
Approximate Weight160g /5.64 oz
Dimension 101.50 x 54.20 x 11.20mm

Product Highlights

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

Frequently Asked Questions

The KX-1203 is alarming low battery straight after a full charge on the new battery — is the cell dead already?

It is not dead. The KX-1203 BMS compares incoming cell data against thresholds calibrated to the original OEM chemistry. A new cell needs one complete charge-discharge cycle before the BMS accepts its state-of-charge readings as valid. Run one full cycle — charge to termination, discharge under normal device use, then charge again. The alarm clears once the BMS has written a fresh calibration profile to the new pack.

The KX-1203 will not power on at all after the replacement battery sat unused for several weeks before installation.

Li-ion cells self-discharge in storage, and if the pack voltage dropped below roughly 9V, the KX-1203 BMS has locked out the cell to prevent damage. Connect the device to mains power and leave it on charge for at least two hours before attempting to power on — the charger will trickle current into the pack until voltage recovers above the BMS re-enable threshold. If the device still does not respond after two hours, check that the charger output is active and the connector is fully seated.

The KX-1203 is shutting off unexpectedly during normal use, but the battery shows a good charge level beforehand.

New Li-ion cells have higher internal resistance in the first several charge cycles, which causes voltage to sag more sharply under the load the KX-1203 draws during active operation. That sag can briefly breach the BMS undervoltage cutoff even when the displayed charge looks adequate, triggering an unexpected shutdown. This behaviour typically resolves after eight to ten full charge-discharge cycles as the cells condition and internal resistance drops. Track whether shutdowns become less frequent across the first ten cycles — if they persist beyond that point, measure resting pack voltage, which should read above 11.0V after a full charge.

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