Thorn Voyager TwinSpot 4.8V 4000mAh Ni-CD Replacement Battery
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Thorn Voyager TwinSpot 4.8V 4000mAh Ni-CD Replacement Battery - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
Thorn Voyager TwinSpot 4.8V 4000mAh Ni-CD Replacement Battery - is backordered and will ship as soon as it is back in stock.
Voltage
4.8V
Amp
4000mAh
Thorn Voyager TwinSpot — 4.8V Ni-CD Replacement Battery (4VTD70 787296)
This is a 4.8V 4000mAh Ni-CD battery for the Thorn Voyager TwinSpot emergency lighting fixture. It provides backup power during mains failure, keeping the twin-spot heads active for safe evacuation lighting. The OEM references for this cell are 4VTD70 787296 and 621-0792.
- Voyager TwinSpot platform fit: The TwinSpot uses a dedicated 4.8V Ni-CD cell block that connects directly to the onboard charge controller. The cell voltage, connector orientation, and physical dimensions (130 × 62 × 32.90mm) match the original housing without modification.
- Bench tested on actual hardware: We cycled this cell through a full charge and load discharge on the TwinSpot controller. The BMS accepted the cell voltage on first connection, the charge indicator transitioned correctly, and the cell delivered rated capacity without thermal event.
- First-cycle conditioning for compliance testing: Run a full manual test within 24 hours of installation by holding the test button for the complete rated duration. This confirms the new cell accepts load under real conditions and lets the charge controller register cell capacity before the next scheduled compliance inspection.
Why the TwinSpot charge controller rejects a new cell straight out of the packaging
Ni-CD cells self-discharge during storage. By the time a replacement arrives, its resting voltage may sit below the float acceptance threshold of the TwinSpot charge controller — typically around 4.2–4.5V for a discharged 4.8V pack. The controller interprets this as a fault condition rather than a fresh cell needing charge. Leave the fitting powered with mains for 12–24 hours before testing. The controller will top-charge the cell into its acceptance window and clear the fault state on its own.
Emergency light dims noticeably partway through a duration test
This is a first-activation issue, not a cell defect. A Ni-CD cell that has not completed one full charge cycle from storage cannot sustain rated discharge current for the full test duration — voltage sags early under the twin-spot lamp load. The fix is a full 24-hour mains charge before the test. If dimming persists after one complete charge cycle, measure the resting voltage across the cell terminals: a fully charged 4.8V Ni-CD pack should read above 5.6V open circuit.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Thorn
- Manufacturer: CS
- Series: Standard
- Color: White
- Product Type: Ni-CD
- Battery Type: Ni-CD
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My TwinSpot fitting still shows the fault LED after I've installed the new battery and powered it back up — what's wrong?
Some TwinSpot fittings latch a fault LED in firmware and do not auto-clear when a new cell is connected. First confirm the cell voltage is within the charge controller's acceptance window by leaving it on mains for 12–24 hours. If the fault LED stays on after that conditioning period, press and hold the test button for three seconds to force a manual reset cycle. This clears the latched fault and allows the controller to re-register the new cell.
The emergency light passed installation fine but failed its three-hour duration test a week later — the new battery seems to drain too fast.
One full charge cycle from storage is not always enough to bring a Ni-CD cell to rated capacity. The first few cycles progressively restore the crystal structure inside the cell, increasing usable capacity each time. Run two additional full manual test cycles — allow 24 hours of mains charging between each — before scheduling the formal compliance test. If capacity still falls short after three conditioning cycles, measure cell voltage at the start of the test: it should be above 5.6V open circuit.
The replacement battery has been in the fitting for several months and the casing looks slightly swollen — is this a charging fault?
Swelling in a Ni-CD cell block is typically caused by prolonged overcharge from a continuous trickle charge at elevated ambient temperature inside the fitting. Check that the TwinSpot charge controller has dropped to float mode — the charge indicator should show green, not the active-charge amber or red. Inspect the fitting location: enclosures above 25°C accelerate this condition. Remove the swollen cell immediately, as a deformed cell can short internally, and replace it before returning the fitting to service.
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