Cordless Drill Battery Capacity

[Chris Parks]

Does the size of a cordless drill battery affect the torque it delivers to the chuck or just the time it powers the drill for?

[Clint Baxter]

The voltage of a battery is what will provide the power. The amp-hour rating will affect how long the battery will last before needing charging.

Clint

[Chris Parks]

That is the way I understand it but does the amp capacity of the battery affect its total delivery capacity to the motor under load? I was asked the question and it got me thinking as Automotive batteries are rated to deliver a certain load over a given time.

[william watts]

The current draw increases with increasing load requirement, as the current approaches the limit of the battery, the battery voltage begins to drop. So yes a higher ampere/hr rating will deliver more torque. The clutch on a drill/driver will slip at a preset torque so I see no advantage. Should you replace the battery on a tool without a clutch then the motor could over heat, the torque rating of any gears could be exceeded and bad things might happen.

[Jason Roehl]

If you're wondering, yes, you can run a cordless drill off a car battery. I needed to mix an additive into some paint one time (customer-requested and purchased ceramic additive), and it didn't mix in easily. My batteries were all dead. So I used a couple nails wedged into the terminals of the drill and a set of jumper cables to my van's battery. The drill was a 14.4V Porter+Cable. Still works fine, but it was getting pretty hot, almost too hot to hold, as the mixing took about 10 minutes.

In general, though, voltage is directly proportional to torque. More amperage means more heat, so batteries with thinner plates inside cannot withstand too high of a current flow for very long, as things start melting and breaking down internally. There also has to be enough surface area internally to provide sufficient electrons (charge) for the given load.