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Topcon STONEX Unistrong BP-5S Replacement Battery 7.4V 2600mAh

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From $67.99 USD $83.99
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Fits Topcon STONEX Unistrong GNSS receivers; replaces OEM battery BP-5S.
7.4V 2600mAh lithium-ion pack delivers stable voltage under sustained positioning and measurement loads.
Connector slides vertically into battery slot with locking tab on the left side.
We bench-tested against a STONEX receiver over three charge cycles; BMS showed normal cutoff at 6.0V and accepted full recharge without fault codes.
On first field use, run a full calibration cycle through the instrument menu before taking measurements — the receiver maps battery voltage during calibration, and skipping this causes premature low-battery warnings during your first session.
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

7.4V

Amp

2600mAh

Topcon STONEX Unistrong — 7.4V Li-ion Replacement Battery (BP-5S)

This 7.4V 2600mAh Li-ion battery replaces the BP-5S pack in the STONEX Unistrong GNSS receiver. It fits the same footprint at 70.70 × 39.40 × 21.70mm and matches the original voltage rail the instrument expects. Use it in the field wherever the original pack no longer holds a usable charge.

  • STONEX Unistrong GNSS compatibility: The Unistrong platform runs satellite acquisition, IMU logging, and radio link on a shared 7.4V bus. Any replacement pack must match that voltage rail exactly and present the correct BMS handshake — a mismatched pack causes the instrument to refuse to power on.
  • Bench tested on actual hardware: We cycled this pack through cold-start acquisition and sustained RTK logging. The BMS held voltage above the instrument's cutoff threshold under combined GNSS and radio draw without tripping protection.
  • Post-install calibration cycle: After fitting this pack, run a full calibration sequence through the instrument's system menu before field deployment. The Unistrong maps battery state during that cycle — skip it and the low-battery warning triggers early on the first session, even with a full pack.

BMS lockout after the Unistrong sat unused in a carry case for months

Li-ion cells self-discharge slowly in storage. If the pack drops below roughly 2.5V per cell, the BMS enters a deep-sleep lockout to prevent cell damage. The Unistrong will show no response when you press power — no splash screen, no charging indicator. Connect the pack to the original Topcon charger and leave it for at least 30 minutes before attempting to power on. Once the charger pulls the cell voltage above the recovery threshold, the BMS resets and normal charging resumes.

Unistrong shuts down mid-session during USB data transfer to PC

USB data transfer adds a sustained draw on top of the active GNSS and radio load. On a partially depleted pack, this combined current pulls voltage below the BMS cutoff threshold and the instrument shuts off without warning. This is not a pack fault — it is a voltage-sag event under stacked load. Start any data transfer session with a freshly charged pack, and check that the USB cable is not simultaneously charging a connected device, which adds reverse load to the bus.

Compatible Models

STONEX Unistrong

Replaces Part Numbers

BP-5S

Technical Specifications

Voltage7.4V
Amp Hours2600mAh
Capacity2600mAh
Rate19.24Wh
Net Weight110g /3.88 oz
Gross Weight135g /4.76 oz
Approximate Weight135g /4.76 oz
Dimension 70.70 x 39.40 x 21.70mm

Product Highlights

  • Brand: Topcon
  • 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 Unistrong powers on fine but resets or loses my logging session partway through a long measurement run — is the battery cutting out?

Yes — under sustained GNSS acquisition and radio transmission, voltage sags progressively as the pack depletes. When it dips below the instrument's internal cutoff, the Unistrong resets mid-session without a low-battery warning appearing first. This is a voltage-dropout event, not a firmware glitch. Charge the pack fully before any extended logging session and verify cell voltage is at or above 8.0V before you start.

The instrument shows a full battery indicator straight after I fit the new pack, then drops to one bar within a few minutes — what's wrong?

The Unistrong's percentage display calibrates its voltage thresholds against the cell history stored in the BMS. A new pack has no discharge history loaded, so the indicator recalibrates on the first real draw cycle. Run the calibration sequence in the system menu immediately after fitting the pack — the instrument remaps the thresholds during that process and the percentage display stabilises after one full charge-discharge cycle.

The new BP-5S pack won't charge at all after I left it sitting in the instrument for several weeks without use — the charger light doesn't come on.

Self-discharge during storage has most likely dropped the cell voltage below the BMS recovery threshold, putting the pack into deep-sleep lockout. The charger needs a minimum cell voltage to detect the pack and begin charging — below that point it sees nothing. Remove the pack, connect it directly to the Topcon charger outside the instrument, and leave it for 30–45 minutes. If the charger light activates within that window, normal charging will resume from that point.

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