Brushless Motor

[Dave Lehnert]

Keep seeing tools advertised with "Brushless motor"

What is the advantage?

[mark mcfarlane]

More power, potentially longer battery life, more expensive to build.

whats-so-great-about-brushless-motor-power-tools/

[Dan Friedrichs]

No brushes, obviously

More energy efficient
More power per volume and weight
No consumable parts (brushes)

Brushless motors are basically just "regular" AC motors, and they contain electronics to turn the DC battery current into AC (compared to a "brushed" motor which uses the brushes and a commutating ring to mechanically turn the DC into AC). They are clearly the "way of the future", and I would definitely prefer them over brushed motors, even at a large price premium.

[Mike Henderson]

Universal motors are series wound motors where the stator winding is in series with the rotor winding. The way you get power to the rotor winding is through brushes and a commutator.

A brushless motor uses permanent magnets for the rotor so no power has to be brought to the rotor. To make the field function so that the magnetic field of the stator drives the rotor, the power into the stator must be switched at the rate of the rotation. This is accomplished by monitoring the position of the rotor and using electronics to switch the power to the stator.

Others have give you the advantages and disadvantages. I expect that brushless motors will eventually be used in all small motor applications, except where cost is a major factor (Harbor Freight tools, for example).

I have some tools with brushless motors and they work well. But I don't see a whole lot of difference in use compared to brushed motors. However, if the cost difference is not too much, I'd buy brushless motors.

Mike

[William Shelley]

To give an idea of the fantastic life span of brushless motors: almost all fans used for computers and electronics are brushless DC, and a life span of 80,000 to 100,000 hours is pretty common.

[Bruce Page]

Brushless tool design can also mean more power in a smaller package. My brushless 20v DeWalt drill is much smaller than my old DeWalt 14v.

The only gripe I have with the DeWalt brushless is that the motor stops so quickly when you release the trigger that the chuck will loosen on the drill bit.

[Mike Henderson]

To give an idea of the fantastic life span of brushless motors: almost all fans used for computers and electronics are brushless DC, and a life span of 80,000 to 100,000 hours is pretty common.

You're absolutely correct. But how many of you have changed the brushes on a cordless drill (for example). Most people just don't use cordless tools (especially for home use) that much.

I suspect the cost difference is not that bad compared to tools that already have electronics, such as a soft start router. Soft start requires a position sensor on the rotor and electronics to control the power. And, as we've seen with other electronics, once the volume gets up, the cost really goes down.

I like brushless tools but they aren't head and shoulders above tools with brushes - for most uses.

Mike

[Frank Pratt]

One of the magazines (FWW?) did testing comparing conventional and brushless tools & there wasn't a huge difference in power or efficiency. I've been using cordless tools, both at work and home, for over 30 years. I've never had to change brushes. The tools have either broken, worn out, or been rendered obsolete by battery costs.

That said, if there's a sale & the cost of brushless isn't much more, that's what i'll go with.

[Sebastien La Madeleine]

I would like to add a few practical observations about brushless.

I currently use 2 different set of Dewalt 20V drill/impact combo. The first one is brushed and older, the second one is brushless. Both impacts and drills are of the same category (impact driver/hammer drill).

1 - On the brushless kit, you can definitely feel the steps between the speeds, where as the brushed motor is seamless. At high speeds not so much a problem, but if I need to finesse something at low speeds, I still need to use the brushed one. (mostly because of the third point below)

2 - Another annoyance of the brushless is when you go beyond the torque limit (without the clutch), it will hold for a while and suddenly it will let go. This has caused me to hit my knuckles quite a few times. Mostly when drilling bigger holes (1/2 or 5/8) through steel or concrete and binding the bit for some reason. The brushed model on the same interaction will bind and keep the torque up, until you release the trigger so you kind of control the release action of the torque. If you are using the clutch, both are fine.

3 - And here's my final gripe, you don't get as much feedback or speed drop from the resistance of the screw due to the greater torque characteristics of the brushless motor, so I've over driven quite a few screws with the brushless that I would get just right with the brushed one. This might get better with time, but being that it's been a struggle for 6 months already, I doubt it now.

On the plus side, the batteries do last significantly longer. I recently screwed about 1000 2 1/2 inch wood screws in pine and did not even need to swap battery. With the brushed impact, I rarely managed more than 500. Not scientifically tested, but by my average use, nice improvement. Though, with a spare battery, not a deal maker/breaker either way. The tools also keep a lower temperature, not a big deal, but after drilling a couple holes in 1/2 steel, it's the difference between being able to wrap your hand around the motor or not. Last point, not brush dust.

Keep in mind that I have not tried other brands or models, it might be different.

Not trying to ramble too much, hoping to warn others that the differences are there, though subtle.

[Greg Parrish]

I have 18v makita brushless hammer drill and impact that I've used heavily. They replaced the prior makita 18v brushed models that I simply wore out. I love the new brushless models for general construction and building duties, but they get heavy fast. As mentioned above, I've built an entire deck using just a single charge on my impact driver and only needing to recharge a few times for the circular saw.

The above said, I just picked up a combo set of 12v max Bosch drill/impact tools. I bought them to supplement the makitas for lighter weight and for use in the workshop. I've been second guessing my decision since they are not brushless but for the price they seemed a good bargain. While the batteries are getting their initial charge I've looked at the various 12v brushless tools but am not sure I would see the real improvement. Should I have gone with another brand brushless to get a combo set or is it worth the difference to buy the bosch set a separates? Are they that much better? I'm not sure, but if it were my 18v general set I would get them no question, but for light weight use around the shop I'm not sure.

[mark mcfarlane]

I would like to add a few practical observations about brushless.

...
2 - Another annoyance of the brushless is when you go beyond the torque limit (without the clutch), it will hold for a while and suddenly it will let go. This has caused me to hit my knuckles quite a few times. Mostly when drilling bigger holes (1/2 or 5/8) through steel or concrete and binding the bit for some reason. The brushed model on the same interaction will bind and keep the torque up, until you release the trigger so you kind of control the release action of the torque. If you are using the clutch, both are fine.
...

Very interesting. That might be why I am now wearing a wrist brace after my 18V brushless Makita took off on me a few days ago drilling 1.25" holes through double 2*4's.

I'm going to try tomorrow to drill in clutch mode and see if it has enough torque but doesn't 'jump' on me.

Keep that bit straight and don't hit any nails...

[Frank Drew]

You're absolutely correct. But how many of you have changed the brushes on a cordless drill (for example). Most people just don't use cordless tools (especially for home use) that much.

Mike,

If we're talking about drills, all I see are cordless.

[William Shelley]

Visit any hardware store in the US, and the area of corded drills is basically just "this is what you buy if you need a drill for mixing mortar or drywall mud", everything else is cordless.

[Frank Drew]

To give an idea of the fantastic life span of brushless motors: almost all fans used for computers and electronics are brushless DC, and a life span of 80,000 to 100,000 hours is pretty common.

A neighbor gave me a new but inexpensive pedestal fan around the time I opened my shop, so back in 1981-1982. Between my shop and my home, where I now use it, it has run at least 8 hours a day every day since then. If my math is correct, that's a bit over 100,000 hours. A few of the plastic fittings around the foot assembly have fallen off but that motor just keep purring along. Aside from the motor,.I'm astonished that the bearings have lasted this long.

[Mike Henderson]

Mike,

If we're talking about drills, all I see are cordless.

Cordless drills have brushes - unless the motor is a brushless motor. It doesn't matter where the power comes from, the motor is the same.

A corded drill - they do still sell such things - would likely have brushes, but it's possible to make a corded brushless drill. I guess since the market for corded drills is so small it's not worth it to make a brushless corded drill. Also, one of the selling points for brushless motors is lower power consumption, which is more important in cordless tools than in corded tools.

Brushes can last a long time, as Frank pointed out about how long his fan has lasted (which is almost certainly a brushed motor).

This is a side comment about brushless motors. Since the rotor uses permanent magnets, I suppose there's some HP level to the motor where the magnets get too big or too expensive or whatever. In any case, the only brushless motors I see are small ones.

Mike