my dewalt 20v circular saw just stopped in the middle of a cut and won't start again, the battery is charged.

Diagnosis

The DCS570B utilizes an electronic overload protection circuit designed to prevent the brushless motor from burning out during high-torque scenarios. When you hit a dense knot in the lumber or force the saw too quickly through a thick piece of material, the motor draws an excessive amount of current. The control board detects this spike and instantly severs the connection between the battery and the motor to prevent catastrophic winding failure. This is often accompanied by a "dead" feel where the trigger has no tactile response and the blade remains motionless despite a fully charged battery. To confirm this is the issue, check if the saw was running hot to the touch near the motor housing or if you felt the RPMs drop significantly just before the shutdown. If the saw stopped abruptly without a slowing period, the electronic trip is the primary culprit.

How to Fix It

Follow these specific steps to reset the electronic control module and restore power to the motor:

1. Immediately release the trigger and remove the saw from the workpiece to ensure there is no physical resistance on the blade.
2. Remove the 20V Max battery pack entirely from the tool housing. This clears the temporary memory of the overload circuit.
3. Inspect the battery terminals on both the battery and the saw for any sawdust buildup or debris that could be causing a poor connection. Use a can of compressed air to clear the terminal slots.
4. Wait exactly 60 seconds. This allows the internal capacitors on the control board to fully discharge and the thermal sensors to cool down.
5. Re-insert the battery, ensuring it clicks firmly into place.
6. Squeeze and hold the trigger for 3 full seconds without attempting to cut anything. This "wakes up" the logic board.
7. If the blade begins to spin, gradually increase your feed rate during the next cut to avoid triggering the protection again.

If That Didn't Work

• Test with a high-capacity battery. If you are using a 2.0Ah or 4.0Ah battery, swap to a 5.0Ah or 6.0Ah pack. The DCS570B has a high current draw; if the battery cells are degraded, they may drop voltage under load, triggering a low-voltage cutoff that mimics an overload trip.
• Check the blade for "binding" or warping. If the blade is bent or the arbor nut is over-tightened, the motor may be drawing too many amps just to overcome the friction, causing it to trip immediately upon startup. Loosen the arbor bolt and ensure the blade spins freely by hand (with the battery removed).
• Inspect the trigger switch for mechanical failure. If the trigger feels "mushy" or doesn't click, the internal plastic actuator may have snapped. You can test this by checking if the saw starts when the battery is partially inserted (though this is risky and should only be done briefly).
• Examine the carbon brushes (if applicable to your specific production run) or the brushless controller for burnt smells. If you smell ozone or burnt plastic near the rear vents, the MOSFETs on the control board have likely failed, requiring a replacement of the motor assembly.

Heads Up

• Avoid "forcing" the cut. If the saw begins to slow down, back off the pressure and let the RPMs recover. Forcing the blade leads to premature trigger failure and frequent overload trips.
• Keep the motor vents clear. Use compressed air every 5-10 cuts to blow sawdust out of the motor housing; accumulated dust traps heat, which makes the electronic overload protection trip much faster.
• Use a sharp, high-quality carbide blade. A dull blade increases the friction and load on the motor by up to 40%, significantly increasing the likelihood of a mid-cut shutdown.
• Store your batteries in a cool, dry place. Extreme heat can cause the battery's internal BMS to shut down power to the tool to prevent cell damage, which looks exactly like a tool failure.