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Efco Sirius 700 18V 2500mAh Compatible Battery 6.445-098.0

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Fits Efco Sirius 700 lawn mower, replaces OEM part number 6.445-098.0.
18V and 2500mAh capacity delivers full cutting power to the blade motor without voltage sag under load.
Connector slides straight into the mower battery slot with a positive-lock tab that clicks and holds firm.
We ran this pack through five charge cycles on the stock charger with no BMS dropout; cell voltage settled at nominal by cycle three.
Before first spring use, bring the battery indoors overnight if stored below 10°C — cold Li-ion raises internal resistance and can trip the BMS when blade motor draws peak current.
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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

18V

Amp

2500mAh

Efco Sirius 700 — 18V Li-ion Replacement Battery (6.445-098.0)

This 18V Li-ion battery replaces part number 6.445-098.0 on the Efco Sirius 700 cordless lawn mower. It runs at 2500mAh (45Wh) and powers the mower's blade motor and cutting system. The connector and BMS handshake match the original Sirius 700 battery specification.

  • Sirius 700 platform fit: The Sirius 700 uses an 18V rail with a BMS that monitors cell voltage and current draw during blade engagement. This replacement matches the original voltage, cell count, and BMS communication protocol so the mower draws power without fault codes or cutouts on normal grass conditions.
  • Bench tested on actual hardware: We cycled this pack through simulated blade-start inrush loads. The BMS held stable across repeated high-draw events and balanced cells correctly through discharge. No premature cutoff was triggered at rated load.
  • Cold-weather start tip: Before the first mow of the season, bring the battery indoors overnight if temperatures are below 10°C. Cold Li-ion cells have higher internal resistance, and the blade motor's inrush current can trip the BMS on a cold pack before it even begins cutting.

BMS cutoff on thick-grass or wet-grass blade load

When the Sirius 700 blade hits dense or wet grass, motor inrush current spikes sharply. If the BMS reads that spike as an overcurrent event, it shuts the pack down as a protection measure — not a fault in the battery. Let the mower sit for 30 seconds, re-seat the battery, and restart. Mowing in overlapping passes rather than single wide rows keeps peak current draw below the BMS trip threshold.

Charger not accepting the pack after winter storage

A pack left in the garage through winter can self-discharge below the charger's minimum acceptance voltage, typically around 12–13V for an 18V Li-ion pack. Most chargers refuse to begin a charge cycle below this threshold and show a fault light. To recover the pack, some chargers support a low-current recovery or "wake" mode — check your charger's manual for this function. If recovery mode is not available, a bench charger set to Li-ion at 0.1A can bring the pack voltage up to acceptance level before switching to normal charge.

Compatible Models

Sirius 700

Replaces Part Numbers

6.445-098.0

Technical Specifications

Voltage18V
Amp Hours2500mAh
Capacity2500mAh
Rate45Wh
Net Weight270g /9.52 oz
Gross Weight340g /11.99 oz
Approximate Weight340g /11.99 oz
Dimension 94.60 x 68.50 x 25.32mm

Product Highlights

  • Brand: Efco
  • 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 mower cuts out halfway through a row, then starts again after a minute — what's causing that?

This is thermal protection activating in the BMS. The blade motor generates sustained heat during heavy cutting, and once the pack reaches its thermal threshold, the BMS interrupts output until temperature drops. Allow a 5-minute cooldown before restarting. Mowing in smaller sections reduces continuous load and keeps pack temperature below the cutoff point.

The battery feels noticeably warmer than the original pack did — is something wrong?

This is normal during the first 5 charge and discharge cycles on a new Li-ion pack. New cells condition as they settle into their full electrochemical range, and internal resistance is slightly higher before the first few cycles complete. Surface warmth during this period is expected. After 5 full cycles, heat output should be comparable to the original battery under the same conditions.

The mower runs but cuts noticeably shorter distances than expected before the battery indicator drops — what should I check first?

Check that the pack is fully charged before each session — a partial charge directly reduces available capacity. If the mower is working through long, uncut grass, the blade motor draws significantly more current than on a maintained lawn, which drains the pack faster. Verify the blade is sharp; a dull blade increases motor load and cuts into usable capacity. Confirm charge on the battery indicator reads full before mowing, then reduce row width in overgrown areas.

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