FLEX 445894 18V Cordless Circular Saw Compatible Battery 3000mAh
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FLEX 445894 18V Cordless Circular Saw Compatible Battery 3000mAh - 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.
FLEX 445894 18V Cordless Circular Saw Compatible Battery 3000mAh - is backordered and will ship as soon as it is back in stock.
Voltage
18V
Amp
3000mAh
FLEX 517674 CS 45 18.0-EC C — 18V Li-ion Replacement Battery (445894)
This is an 18V, 3000mAh Li-ion replacement battery for the FLEX 517674 CS 45 18.0-EC C Compact cordless circular saw. It also fits the RFE 40 18.0-EC Cordless gutter bracket slot cutter. The OEM part number is 445894.
- CS 45 and RFE 40 platform fit: Both tools share the same 18V rail, slide-in connector, and BMS handshake protocol — one battery covers either tool without modification or adapters.
- Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on a CS 45 platform. The BMS correctly handled motor-start inrush current at trigger pull and held cell voltage within the expected 18V nominal range under sustained load.
- Motor inrush conditioning on first use: Run the saw at half load — shallow crosscuts through softwood — for two cycles before tackling full-depth hardwood rips. This lets the BMS profile the motor's inrush draw and set overcurrent thresholds accurately before maximum torque applications.
Thermal cutoff under sustained circular saw load
The CS 45's enclosed battery housing traps heat from both the motor and the cells during extended cuts. When cell temperature exceeds the BMS upper threshold — typically around 60°C on Li-ion packs — the BMS shuts the pack down to protect the cells. This is not a fault; it is the protection circuit doing its job. Let the pack rest off the tool for 10–15 minutes and allow both the housing and cells to cool before resuming.
Saw bogs and loses power mid-cut under load
A bogging saw that slows under load but does not fully cut out usually points to voltage sag — rail voltage drops during high current draw because contact resistance at the battery terminals is too high. Pull the pack, inspect the slide-in contacts for sawdust compaction or corrosion, and clean them with a dry brush. Reseat the pack firmly and retest; rail voltage under load should recover to above 16V on an 18V nominal pack.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: FLEX
- 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
My FLEX CS 45 cuts out the instant I pull the trigger — why does it die on startup?
The trigger-pull inrush current spike from the circular saw motor can exceed the BMS overcurrent threshold on a cold or storage-rested pack. The BMS trips as a protection response, not a defect. Warm the pack to room temperature and attempt a no-load trigger pull first — spinning the blade free before engaging a cut lets the BMS log a lower baseline inrush reading. If the saw runs freely but cuts out under wood contact, check terminal cleanliness and reseat the pack.
My charger blinks red and won't accept this new pack — what's happening?
A pack that has sat in storage can drop below the charger's acceptance voltage floor, typically around 12–13V on an 18V Li-ion unit. Most FLEX chargers require the cells to be above that threshold before the charge cycle starts. Leave the pack on the charger for 20–30 minutes — some chargers run a trickle recovery mode that slowly raises cell voltage until the pack clears the acceptance threshold and the full charge cycle begins. If the red blink persists past 30 minutes, measure pack voltage at the terminals; a reading below 10V indicates a cell-level issue.
The CS 45 runs fine in summer but bogs badly in cold weather — is the battery failing?
Cold temperatures raise the internal resistance of Li-ion cells significantly — below 5°C, a healthy pack can behave like a partially depleted one. The saw bogs because the cells cannot sustain high current delivery when cold. Store the pack indoors before use and keep it in a jacket pocket between cuts on cold days. Once the pack is back above 10°C, normal power delivery resumes without any reset or intervention needed.
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