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NorthWestern Bell 35858 Cordless Phone Ni-MH Replacement Battery 3.6V

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From $205.99 USD $253.99
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Fits NorthWestern Bell model 35858 cordless handset; replaces original 3.6V Ni-MH pack.
3.6V, 700mAh Ni-MH chemistry delivers rated capacity for standard talk and standby duty cycles.
Connector slides into handset battery cavity with positive terminal facing the contact spring.
We bench-tested the pack across five charge cycles; BMS accepted 3.6V input without fault codes.
After installation, 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.

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

Voltage

3.6V

Amp

700mAh

NorthWestern Bell 35858 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 700mAh Ni-MH rechargeable battery for the NorthWestern Bell 35858 cordless phone handset. It replaces the original pack when the handset no longer holds a charge or stops powering on from the cradle. Dimensions are 46.00 x 31.00 x 10.50mm — confirm against your existing cell before installing.

  • 35858 handset fit: The 35858 uses a single-cell 3.6V Ni-MH pack matched to the handset's charge circuit voltage rail. Swapping chemistry or voltage will confuse the base station's trickle-charge logic and shorten pack life.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on a cordless phone test rig. The BMS held stable voltage throughout, and the base station accepted the pack without triggering a charge fault.
  • First charge on NiMH 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 700mAh capacity — a short first charge will leave you with noticeably less talk time from day one.

Range drops after battery swap on the 35858

The 35858 handset adjusts RF transmit power based on available voltage from the battery. A Ni-MH pack that hasn't been fully conditioned sags under the RF load, causing the handset to reduce transmit strength mid-call. This shows up as static, dropped range, or calls cutting out at distances that worked fine with the original battery. Run three to five full charge-discharge cycles and the voltage curve stabilises — range returns to normal after conditioning.

Base station shows no charge light after installing new pack

Ni-MH packs stored before shipping can drop to a voltage the base station's charge controller reads as an error or open circuit. The base expects to see at least a minimal voltage on the contacts before initiating its charge sequence. If the charge indicator stays off or flashes an error, remove the handset, wait 10 seconds, and re-seat it firmly — the contacts need a clean connection. If the fault persists, check the handset battery contacts for debris and confirm the battery voltage reads above 3.0V with a multimeter before assuming a faulty pack.

Compatible Models

35858

Technical Specifications

Voltage3.6V
Amp Hours700mAh
Capacity700mAh
Rate2.52Wh
Net Weight37g /1.31 oz
Gross Weight62g /2.19 oz
Approximate Weight62g /2.19 oz
Dimension 46.00 x 31.00 x 10.50mm

Product Highlights

  • Brand: NorthWestern Bell
  • 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

Talk time on my 35858 is way shorter than it used to be — is the new battery faulty?

Not likely faulty — Ni-MH cordless batteries need three to five full charge-discharge cycles before they reach rated capacity. Most packs ship partially discharged, so the first cycle often delivers noticeably less talk time than the 700mAh spec. Run the handset down until it beeps for low battery, then return it to the base for a full charge, and repeat. By cycle four or five, talk time should stabilise close to the original handset spec.

My 35858 handset stopped pairing with the base after I swapped the battery — how do I fix this?

Some DECT cordless phones lose their pairing data when power is fully removed from the handset, which happens during a battery swap. The fix is to re-register the handset from the base station menu — on most Northwestern Bell models this means holding the Find/Page button on the base for several seconds until the handset enters registration mode. Check your handset manual for the exact key sequence. Once re-paired, the handset should operate normally without any further resets.

The handset battery is nearly dead every morning even though I put it in the cradle each night — what's draining it?

Overnight drain on a seated handset usually means the handset isn't making a solid connection with the base charging contacts. If the contacts on either the handset or the base are oxidised or slightly bent, the charge circuit doesn't complete and the handset runs on standby draw all night. Clean both sets of contacts with a dry cloth, then press the handset firmly into the base — you should see the charge indicator light activate within a few seconds. If the light still doesn't come on, check that the base itself has power and the adapter is seated.

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