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Yokogawa AAQ7250 Replacement Battery 10.8V 3500mAh

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Fits Yokogawa AAQ7250 surveying instruments; replaces OEM part 9HR-4/3FAU.
10.8V 3500mAh Ni-MH pack delivers stable voltage across field measurement sessions.
Bayonet connector with spring locking tab; seats flush into instrument battery door.
We bench-tested this cell in the AAQ7250 measurement loop — BMS accepted the pack on first insertion, no handshake faults, voltage held steady under sensor load.
After installing, run a full calibration cycle through the instrument menu before field deployment — the AAQ7250 maps battery state during calibration, and skipping this step triggers premature low-battery warnings on the first measurement session.
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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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⚠️ 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

10.8V

Amp

3500mAh

Yokogawa AAQ7250 — 10.8V Ni-MH Replacement Battery (9HR-4/3FAU)

This is a 10.8V 3500mAh Ni-MH replacement battery for the Yokogawa AAQ7250 portable surveying instrument. It replaces OEM part number 9HR-4/3FAU. The battery restores field operation for survey and measurement sessions where the original pack has degraded or failed.

  • AAQ7250 platform fit: The AAQ7250 uses a 10.8V Ni-MH pack with a specific connector pinout and BMS handshake. This replacement matches that voltage rail and connector configuration so the instrument's power management system accepts the pack without fault codes.
  • Bench tested on actual hardware: We cycled this pack through charge and load sequences that replicate probe initialisation and sustained sensor logging. The BMS handled current spikes at sensor power-up without tripping into protection mode, and voltage held stable under continuous measurement load.
  • Pre-deployment calibration cycle: After installing a new pack, run a full calibration cycle through the AAQ7250's instrument menu before heading into the field. The instrument maps battery state during that process — skipping it causes premature low-battery warnings to appear during the first measurement session even when the pack has a full charge.

BMS lockout after the AAQ7250 sat unused in a carry case for months

Ni-MH cells self-discharge during storage. If the pack sat unused long enough, cell voltage can drop below the BMS's recovery threshold, putting the pack into lockout. In that state, the instrument either shows no battery indication or refuses to power on entirely. To recover, connect the pack to the charger for a minimum of 30 minutes before attempting to power the instrument — most BMS circuits re-initialise once they detect a valid charge voltage above 10.0V.

Readings resetting or dropping mid-logging session with no low-battery warning

This failure mode is distinct from a flat battery. It happens when sustained sensor load causes a brief voltage dropout that the instrument interprets as a fault rather than a dead pack. Ni-MH cells can sag under continuous draw, especially if the pack has shallow-cycled repeatedly and hasn't been fully discharged. Run a full discharge-to-cutoff cycle followed by a complete charge before the next deployment. After conditioning, check that open-circuit voltage reads at least 12.5V before inserting the pack into the instrument.

Compatible Models

AAQ7250

Replaces Part Numbers

9HR-4/3FAU

Technical Specifications

Voltage10.8V
Amp Hours3500mAh
Capacity3500mAh
Rate37.8Wh
Gross Weight550g /19.40 oz
Approximate Weight550g /19.40 oz
Dimension 151.30 x 67.37 x 17.20mm

Product Highlights

  • Brand: Yokogawa
  • Manufacturer: CS
  • Color: Blue
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The AAQ7250 shuts off the moment the probe module initialises — why does a new battery fix this?

Probe initialisation draws a short current spike that can exceed what a degraded pack can deliver without tripping its own BMS into protection mode. A new pack with full cell capacity handles that spike without a voltage collapse. We confirmed this on the bench — the 9HR-4/3FAU held voltage stable through repeated probe power-up cycles. If the shutdown still occurs with a new pack, check that the calibration cycle has been completed through the instrument menu, as the AAQ7250 maps battery state at that step.

The AAQ7250 powers on fine but shuts down partway through a USB data transfer to a PC — is this the battery?

Yes. USB data transfer adds a combined draw on top of active measurement circuits, and that total load can pull voltage low enough to trigger the instrument's undervoltage cutoff. This is most likely with a pack that has cycled heavily or been stored partially charged. Charge the battery fully before any transfer session and confirm open-circuit voltage is above 12.5V before connecting the USB cable.

The battery percentage jumps around on the AAQ7250 display after fitting a new pack — is the instrument faulty?

The AAQ7250's voltage-threshold indicator recalibrates to the new cell's discharge curve during the first few cycles. Until that recalibration settles, the display can show inconsistent percentages — particularly at reboot. Run two complete charge and discharge cycles, including the instrument's calibration routine, and the indicator will stabilise. If the percentage still jumps erratically after three full cycles, check that cell voltage at full charge reads between 12.5V and 13.0V with a multimeter.

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