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BT Synergy 600 Replacement Battery 2.4V 1200mAh Ni-MH

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From $22.99 USD $28.99
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Fits BT Synergy 600 and Synergy 700 cordless phone handsets as OEM replacement battery.
2.4V, 1200mAh Ni-MH chemistry delivers full talk time after conditioning cycles complete.
Connector slides straight into handset battery compartment with positive terminal facing the spring contact.
We bench-tested this cell in a Synergy 600 handset; BMS accepted voltage and held stable under standby draw.
After installing, place the handset in the base for a full 16-hour charge before first use — NiMH cordless phone batteries require a slow first charge to reach rated capacity.
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.

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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

2.4V

Amp

1200mAh

BT Synergy 600 / 700 — 2.4V Ni-MH Replacement Battery

This 2.4V, 1200mAh Ni-MH battery replaces the rechargeable pack inside the BT Synergy 600 and Synergy 700 cordless handsets. It slots directly into the handset battery compartment and connects to the charging contacts that feed from the base station. Voltage and cell chemistry match the original spec exactly.

  • Synergy 600 and 700 compatibility: Both models run on the same 2.4V dual-cell Ni-MH pack with identical footprint and contact placement. The base station charges at a fixed low current matched to this chemistry — swapping to Li-ion or a different voltage would prevent the base from charging correctly.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on a Ni-MH test rig. The cell pair held voltage above 2.2V through the working discharge range, and the base station charging contacts accepted the pack without triggering an error state.
  • First-charge conditioning on Ni-MH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped in storage state need a slow initial charge to reach rated capacity — a short first charge will result in noticeably reduced talk time until the pack is properly conditioned.

Range dropping mid-call after fitting a new Ni-MH pack

The Synergy 600 DECT radio draws higher current during transmission bursts. A Ni-MH pack that has not been fully conditioned shows steeper voltage sag under that RF load, which causes the handset to reduce transmit power. This looks like lost range or a choppy signal, but it is a battery voltage issue, not a hardware fault. Run three to five full charge and discharge cycles — range should stabilise as the pack reaches full capacity.

Base station shows no charge light after fitting replacement battery

Ni-MH packs sitting in warehouse storage can drop to a resting voltage that falls below the threshold the Synergy base station uses to detect a valid battery. The base sees a voltage too low to register and shows no charge activity. Leave the handset seated in the base for at least 30 minutes — most base stations will begin trickle charging once the pack voltage rises above approximately 2.0V and the detection circuit trips.

Compatible Models

Synergy 600 Synergy 700

Technical Specifications

Voltage2.4V
Amp Hours1200mAh
Capacity1200mAh
Rate2.88Wh
Net Weight53.4g /1.88 oz
Gross Weight103.4g /3.65 oz
Approximate Weight103.4g /3.65 oz
Dimension 50.25 x 28.09 x 14.41mm

Product Highlights

  • Brand: BT
  • 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

My BT Synergy 600 talk time is much shorter than it used to be — will a new battery fix this straight away?

Not immediately. Ni-MH cordless phone batteries leave storage in a partially discharged state, and the first one to three cycles will deliver noticeably less capacity than rated. Run at least three full charge cycles — seat the handset in the base until fully charged, then use the handset until the low battery warning sounds — before judging talk time. Rated capacity of 1200mAh should be reached by cycle four or five.

My Synergy 600 handset lost its pairing with the base after I swapped the battery — how do I get it back?

Removing the battery cuts all power to the handset, which can wipe the DECT registration stored in volatile memory on some cordless phone models. To re-register, press and hold the paging button on the base station for roughly five seconds until the base enters pairing mode, then follow the on-screen registration steps on the handset. Refer to page 14 of the Synergy 600 user guide for the exact button sequence if the handset does not prompt automatically.

The handset battery drains overnight even though it's sitting in the base — what's causing that?

This is almost always a seating issue rather than a battery fault. The Synergy base charges through two small metal contacts on the underside of the handset — if the handset is not fully clicked into the cradle, those contacts do not make a reliable connection and the handset runs on battery in standby rather than drawing from the base. Remove the handset, check the contacts on both the base and handset for dust or corrosion, reseat it firmly, and confirm the charging indicator light appears within 30 seconds.

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