Archived from the Tools In Action forum (Dewalt). This thread is read-only.
I noticed that on Dewalts site the new 20v circular saw with 5.0ah battery kit has faster RPM’s than my saw I got when they first came out. 3700 rpm on mine. New one is 5250 rpm. If the new web page is correct it seems funny they are not publicizing the new improvement more that the simple spec change.
interesting. is the new saw geared different?
i thought higher amp hour batteries just provide longer runtime, not more power.
That’s a pretty big change in spec’s and higher Ah batteries never added more performance to Dewalt tools before. I think its an error on the Dewalt webpage.
Also, the dcs391 b bare and M1 4.0ah kit show 5250 RPM’s.
The dcs391 L1 3.0ah shows 3700 RPM’s says replaced by the M1 kit.
Like others have said, higher capacity batteries simply do not create higher motor speed.
More power
anyone figure this out if true?
Dewalt upgraded the motor and electronics back in Summer 2014. It wasn’t publicized. I think it was just a type change, new ones are probably type 2.
what really?!?! I need to check which one I have
Regarding higher power from battery size, it is technically possible. The total capacity of each cell determine the battery’s Ah rating, but the discharge rate of those cells determines how much juice the battery can put out at any one time (i.e. power).
i tested this on my Dewalt tools some time ago, with 4Ah and 2Ah batteries. The circular saw and drill saw no gain in power using the 4Ah battery, but the impact driver saw a sizeable gain in power. I have tested this with other manufacturers also, it explains why you see different power rating on manufacturer websites for different kits. It seems to me that impact drivers are made to make use of the extra discharge rate, while many other tools are not. I’d like to see a more comprehensive study on the subject.
so i was at lowes, and happened to look at this saw. it looks like dewalt really did change the rpms. is this blade or motor rpms? i imagine there was a gearing change as well, perhaps?
anyways i snapped a pic of the box. the specifications on the box is a sticker with the old specs underneath.
[External image (i.imgur.com), not copied]
Trim guy wrote:
Also, the dcs391 b bare and M1 4.0ah kit show 5250 RPM’s.
The dcs391 L1 3.0ah shows 3700 RPM’s says replaced by the M1 kit.
Like others have said, higher capacity batteries simply do not create higher motor speed.
Higher capacity batteries with higher possible amperage draw rates do create higher speeds.
Its because they used a motor that draws more amps than the battery can give it resulting in decreased power go try it plug in a sawsall to a 1.5 amp battery pull the trigger cut through a 2×4 then do the same with a 4 amp and there is a difference.
When you use a motor that is to strong for the batteries the motor only gets what the batteries can give so it slows down a bit but if the batteries are replaced with ones that can give more or give power faster then the motor uses full capacity. Eventually the motor will reach peak power and not speed up anymore, even if the batteries are changed to better ones.
I just bought the DCS391M1 kit with 4.0 amp battery in Dec 2014 but I didn’t keep the box to verify the 5250rpm.
But I can confirm that my saw performs differently depending on which battery I put in it. Looks like the motor was changed to take advantage of higher capacity batteries.
When I run the saw with a 2 amp vs a 4 amp battery, the saw definitely spins faster, has a higher pitched sound and feels like there’s more power with the 4 amp battery.
Unfortunately, it also seems that the battery drains a bit faster. After ripping 8 to 16 feet of 3/4″ plywood with a Diablo 40 tooth blade, it’s already drained 1 bar off of my 4 amp battery. I was expecting better battery life with a 4 amp battery but I do recognize that I’m using a finishing blade on the saw. On the other hand, the cuts are very smooth.
sweetpapa wrote:
I just bought the DCS391M1 kit with 4.0 amp battery in Dec 2014 but I didn’t keep the box to verify the 5250rpm.
But I can confirm that my saw performs differently depending on which battery I put in it. Looks like the motor was changed to take advantage of higher capacity batteries.
When I run the saw with a 2 amp vs a 4 amp battery, the saw definitely spins faster, has a higher pitched sound and feels like there’s more power with the 4 amp battery.
Unfortunately, it also seems that the battery drains a bit faster. After ripping 8 to 16 feet of 3/4″ plywood with a Diablo 40 tooth blade, it’s already drained 1 bar off of my 4 amp battery. I was expecting better battery life with a 4 amp battery but I do recognize that I’m using a finishing blade on the saw. On the other hand, the cuts are very smooth.
the rpms are printed on the label/decal on the saw.
anyone have any experience between the two different saws with different rpms?
my bare circular saw is rated at 5150 rpm Its a type 3.
Is this a brushless motor?