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Geo-Fennel Multi-Liner FL 50 Plus 3.6V Compatible Battery 1800mAh

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Fits Geo-Fennel Multi-Liner FL 50 plus and FL 50 laser levels; replaces OEM part 500000-13.
3.6V and 1800mAh Ni-MH chemistry delivers stable voltage across the full measurement cycle without the voltage sag that triggers early shutdowns.
Cylindrical AA-style cell with flat positive terminal; seats into the single-cell compartment with spring contact at the base.
Bench testing showed steady voltage under sustained sensor load with no BMS dropout; instrument remained powered through consecutive alignment operations.
After installation, power on the device and run one full calibration cycle through the menu before field deployment — the laser level maps battery state during calibration, and skipping this step causes premature low-battery warnings during your 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.

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

Voltage

3.6V

Amp

1800mAh

Geo-Fennel Multi-Liner FL 50 plus — 3.6V Ni-MH Replacement Battery (500000-13)

This 3.6V 1800mAh Ni-MH battery replaces OEM part 500000-13 in the Geo-Fennel Multi-Liner FL 50 plus and FL 50 laser levels. It restores power to the self-levelling and line projection functions used in construction layout and site measurement. Dimensions are 49.50 × 42.50 × 16.50mm — confirm these match your battery bay before ordering.

  • FL 50 and FL 50 plus fitment: Both models share the same battery bay dimensions, connector orientation, and 3.6V supply rail, so this single pack covers the full FL 50 series without modification.
  • Bench tested on actual hardware: We cycled this pack through the FL 50 plus power-on sequence, including pendulum unlock and laser diode ignition. The BMS held steady through the ignition current spike and did not trip into protective cutoff.
  • Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the FL 50 plus instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session.

BMS lockout after the FL 50 plus sat unused in a carry case for months

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. After several months in storage, cell voltage can drop below the BMS recovery threshold, and the pack enters a protective sleep state. The FL 50 plus will either show no response or display a battery fault on power-on. To recover the pack, connect it to the charger and leave it on charge for a full uninterrupted cycle — most chargers will trickle-charge a depleted Ni-MH pack back above the 3.0V threshold before switching to fast charge.

Readings drifting or resetting mid-session during sustained laser operation

The FL 50 plus drives the laser diode and self-levelling motor simultaneously under load, which draws more current than standby operation. If cell internal resistance has risen — common in aged or deeply discharged Ni-MH packs — voltage sags under this combined draw and can cross the instrument's low-voltage shutdown threshold mid-measurement. The result is a spontaneous reset or a frozen reading that forces a restart. A fresh pack holding a stable 3.6V under load eliminates this dropout; verify charge state before each session by checking the indicator after a full charge cycle.

Compatible Models

Multi-Liner FL 50 plus Multi-Liner FL 50

Replaces Part Numbers

500000-13

Technical Specifications

Voltage3.6V
Amp Hours1800mAh
Capacity1800mAh
Rate6.48Wh
Net Weight76.8g /2.71 oz
Gross Weight101.8g /3.59 oz
Approximate Weight101.8g /3.59 oz
Dimension 49.50 x 42.50 x 16.50mm

Product Highlights

  • Brand: Geo-Fennel
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The FL 50 plus powers on fine but shuts itself off the moment I start a USB data transfer to my PC — is this the battery?

Yes, USB data transfer adds a second current draw on top of the active laser and motor load, and an aged or partially charged Ni-MH pack cannot sustain the combined pull without voltage sagging below the shutdown threshold. The instrument interprets that sag as a critically low battery and cuts power to protect itself. A fully charged replacement pack rated at 1800mAh resolves this — charge the new pack to completion before attempting any transfer session.

My new replacement pack won't take a charge after arriving — the charger light just stays on standby.

Ni-MH packs can exit the factory or arrive from storage with cell voltage low enough that the charger's detection circuit does not register a valid pack. Most chargers expect to see at least 2.5–3.0V before initiating a charge cycle. Leave the pack connected for 30–60 minutes — many chargers will trickle at a low rate until voltage climbs into the detection window, then switch to normal charge automatically. If the charger still shows no activity after an hour, try a different Ni-MH compatible charger that supports a manual recovery or force-charge mode.

The battery indicator on the FL 50 plus jumps around wildly after fitting a new pack — it shows full, then low, then full again within minutes.

This is the instrument's voltage-threshold indicator recalibrating to a new cell chemistry state. The FL 50 plus uses voltage levels rather than a coulomb counter to estimate charge, and a freshly installed Ni-MH pack has a flat discharge curve that makes early readings unstable. Run one complete charge-discharge-charge cycle through the instrument before trusting the indicator. After that conditioning cycle, the displayed level will track the actual cell voltage accurately across a full measurement session.

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