Avaya FC4 Cordless Phone Compatible Battery 3.7V 700mAh
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Avaya FC4 Cordless Phone Compatible Battery 3.7V 700mAh - 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.
Avaya FC4 Cordless Phone Compatible Battery 3.7V 700mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.7V
Amp
700mAh
Avaya FC4 / IH4 / D4 Series — 3.7V Li-ion Replacement Battery (5010808000)
This is a 3.7V, 700mAh Li-ion replacement battery for Avaya DECT cordless phone handsets. It fits the FC4, IH4, D4, and D4 Office models, along with two additional handset variants sharing the same battery format. The OEM part number is 5010808000.
- FC4, IH4, D4, and D4 Office compatibility: These handsets share the same 3.7V Li-ion cell format, connector pinout, and BMS handshake requirements. One battery SKU covers the full range because the base station charging circuit and handset BMS treat all four models identically.
- Bench tested on actual hardware: We ran this battery through charge and discharge cycles on DECT handset hardware. The BMS held the correct 3.7V nominal rail, accepted charge from the base station without error flags, and maintained stable voltage through standby and active call states.
- First installation charge on DECT handsets: After fitting this battery, seat the handset in the base station cradle and leave it for a full charge cycle before use. Li-ion cells shipped in partial-charge storage states can read low on the handset indicator until the BMS completes its first full calibration charge.
Why the FC4 handset shows a low battery icon immediately after a new battery is fitted
Li-ion cells leave storage at around 40–60% charge to protect cell chemistry during transit. The handset BMS reads this as a low state of charge and displays the low battery indicator straight away. This is normal and not a fault with the replacement cell. Place the handset in the base cradle and allow the BMS to complete a full charge cycle — the indicator will clear once the cell reaches 4.2V.
Talk time noticeably shorter than the original battery after replacement
A new Li-ion cell can take two to three full charge and discharge cycles before the BMS accurately tracks capacity and the cell reaches its rated 700mAh output. If talk time is short after the first or second use, this is a calibration issue rather than a defective cell. Run the handset until the low battery warning appears, then return it to the base for a full charge. Repeat this two to three times and talk time will normalise.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Avaya
- 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 base station shows a charging error light after I put in the new battery — what's wrong?
The base station charging circuit checks for a minimum voltage before it begins charging. A Li-ion cell shipped from storage can sit below that acceptance threshold, causing the base to flag an error rather than charge. Remove the handset, wait 30 seconds, then reseat it firmly in the cradle — this triggers a fresh detection cycle. If the error clears and charging begins, the cell voltage was simply too low for the initial handshake; it will charge normally from that point.
The handset lost its DECT pairing after I swapped the battery — how do I fix it?
Some Avaya DECT handsets store pairing data in volatile memory backed by the battery. When power is fully removed during a battery swap, that pairing data can be lost. Re-register the handset to the base station using the subscription procedure in the handset menu — on most Avaya DECT systems, hold the base station registration button for three seconds, then navigate to the handset menu and select Register or Subscribe. The handset will reconnect to the base within 60 seconds.
The battery drains completely overnight even though the handset is sitting in the base — what causes that?
This happens when the handset is not making full contact with the base cradle charging pins. The handset appears docked but the charging circuit is not active, so the cell drains through normal standby draw. Remove the handset and check both the cradle pins and the matching contacts on the handset for dust or oxidation — clean them with a dry cloth. Reseat the handset and confirm the charging indicator light activates within a few seconds of docking.
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