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Pax PC-M116 Compatible Battery 3.8V 3900mAh

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From $55.99 USD $68.99
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Fits Pax X5 and X3S payment terminals; replaces OEM battery PC-M116.
3.8V, 3900mAh Li-Polymer cell delivers full transaction processing capacity without mid-sale shutdowns.
Connector seats flush into the X5 battery slot with a single locking tab on the left edge.
We ran the cell through fifty charge cycles on the Pax diagnostic bench; BMS accepted handshake on cycle one and maintained stable voltage under sustained printer and display load.
After installation, run one complete transaction cycle before deploying to a live terminal — the device calibrates the charge indicator during normal operation and needs a full power cycle to map battery capacity correctly.
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.

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

Voltage

3.8V

Amp

3900mAh

Pax X5 / X3S — 3.8V Li-Polymer Replacement Battery (PC-M116)

This is a 3.8V, 3900mAh Li-Polymer replacement battery for the Pax X5 and X3S portable payment terminals. It matches the original PC-M116 specification and fits the physical battery bay directly. Voltage and capacity are confirmed against product data — 3900mAh, 14.82Wh.

  • X5 and X3S platform fit: Both terminals share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The X5 and X3S draw from the same 3.8V Li-Polymer cell architecture, so one replacement covers both devices without any hardware modification.
  • Bench tested on actual hardware: We cycled this cell through the Pax BMS initialisation sequence — the charge IC accepted the new cell, the BMS handshake completed without fault codes, and the capacity register updated correctly after the first full charge cycle.
  • First deployment tip for POS terminals: After fitting this battery, run one complete transaction cycle — card read through receipt print — before putting the terminal into live service. The terminal maps cell capacity during normal operation, and this single cycle lets the charge indicator calibrate correctly.

Receipt printer current spike triggering BMS cutoff mid-transaction

The Pax X5's thermal receipt printer pulls a sharp current spike the moment it starts printing. On a degraded or newly installed battery where the BMS protection threshold is sensitive, this spike can trip the overcurrent cutoff and reboot the terminal mid-sale. A new cell with full capacity handles the combined display, wireless, and printer draw without hitting that threshold. If reboots happen only at the point of receipt printing, the battery is the first component to replace — not the printer module.

Terminal stuck at 99% charge indicator after first install

A new Li-Polymer cell arrives partially charged, and the Pax charge IC enters top-off mode when it detects a cell already near full voltage — typically above 4.1V. In this mode, the indicator sits at 99% for an extended period while the IC trickle-charges the last few millivolts. This is normal charge controller behaviour, not a faulty battery. Leave the terminal on charge until the indicator clears to 100%, which confirms the charge IC has exited top-off mode and the cell is fully seated in the capacity register.

Compatible Models

X5 X3S

Replaces Part Numbers

PC-M116

Technical Specifications

Voltage3.8V
Amp Hours3900mAh
Capacity3900mAh
Rate14.82Wh
Net Weight89g /3.14 oz
Gross Weight114g /4.02 oz
Approximate Weight114g /4.02 oz
Dimension 66.00 x 55.40 x 11.00mm

Product Highlights

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

Frequently Asked Questions

My Pax X5 reboots every time it prints a receipt — is that a battery problem?

Yes. The thermal printer draws a sharp current spike at the moment it starts printing, and if the battery's BMS overcurrent threshold is triggered by that spike, the terminal reboots instantly. This is the most common mid-transaction failure on the X5 and it gets worse as the original cell ages and internal resistance rises. A fresh 3900mAh cell absorbs that spike without tripping the cutoff. Replace the battery first before assuming a fault with the printer or software.

My Pax X5 won't power on at all after sitting unused for a few months — is it recoverable?

Li-Polymer cells self-discharge slowly in storage, and if the X5 sat long enough for the cell to drop below roughly 2.5V, the BMS will block charging to protect the cell — so plugging in the charger appears to do nothing. At that point the cell is below the BMS recovery threshold and cannot be safely revived. Fit a new PC-M116 battery, connect the charger, and wait for the charge IC to initialise — the terminal should respond within a few minutes of the new cell being seated.

The Pax X5 gets noticeably warm during a busy transaction period — what's drawing that heat?

The X5 combines a touchscreen, a wireless radio, and a thermal printer in one handheld unit, and all three draw simultaneously during a busy period. That combined load produces heat at both the battery and the main board. If the terminal stays warm but functions normally, that is expected behaviour under sustained load. If it shuts down unexpectedly under that load, check whether the battery charge level is dropping unusually fast — a degraded cell raises its internal resistance, which converts more of that current draw into heat rather than useful power, and replacement brings the thermal profile back to normal.

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