Cordless Circular Saw Runtime?

[Andrew More]

Just wondering what people's experiences are with run time on their cordless circular saws.

I've got the DeWalt DCS575 Flexvolt circular saw which runs the standard 7 1/4" blade. It comes with one 6 ah flexvolt battery, and I have a second 6 ah battery to swap to. I seemed to be getting pretty lousy runtime with this saw.

This weekend I tried to trim up some lumber I bought at a local sawyer. These are rough sawn 8/4+ hard maple boards, varying widths, between 7-9" wide. I was attempting to trim them down from their 12'+ sizes to something more managable for my project, of about 9' + whatever left over. I was able to make about 4-5 cuts before the saw stopped working, with 1 bar on the battery. At which point I swapped batteries, and was able to get maybe another 1-2 cuts before the saw seemly ran out of juice. Despite the material this seems to be pretty bad runtimes. I did check the batteries before this, and one was claiming fully charged, though it had been a while since it was on the charger. I could have had an issue with it binding up, but I've noticed similar problems with short runtime in the past cutting plywood, which is why I got a backup battery.

I ended up finishing with a 20V jigsaw, which had no issue cutting the remaining 6-7 boards to length.

What's a reasonable amount of runtime with this saws? Is mine defective, or is this just a limitation of the saw itself?

[Marc Fenneuff]

I have the same saw with two 6Ah and although I use it infrequently I get lots of runtime from the batteries. Your saw has a problem, maybe the batteries were old when you purchased it.

That said, DeWalt is playing a bit of game with the numbers, as the 6AH rating is when supplying 20V to a tool, not 60.

[Steve Rozmiarek]

We use a lot of these saws in the business, well mostly (5) the 577 "worm drive" and 1 of the 575 sidewinder. I'm a worm drive guy, so I use them mostly, they are a fantastic saw. I cut all the sheeting on a large roof with one battery just last month. I gave the 575 to one of the other guys, it has similar runtimes. We use these every day, a lot. Your experience is not normal.

You have a battery or saw issue most likely. I do have one battery that got dropped off a roof. It will show a full charge, then just crash. Sharp blades matter, but you probably have that under control. Something is definitely not right.

[Alan Gage]

My experience with battery indicators is that they indicate a full charge for a long time and that they fall off very quickly after showing a less than full charge. So I wouldn't assume that just because a battery showed a full 3 bars that it truly had a full charge.

You didn't indicate the state of charge of your 2nd battery (that only got 1-2 cuts).

8/4 hard maple takes a lot of juice. I believe these will also cut off due to excess heat, which is a possibility.

Alan

[Andrew More]

Okay, could be I have a problem with the batteries. I'm a bit hazy on details, but I believe the first battery showed 2 of 3 bars, and the second full 3 bars.
In a lot of cases I charge these batteries after use, and then they sit for a long period because I use the saw very infrequently (say a month or two). The point about the charge indicator not being great is a good one, this could be the issue.
Could also be an issue with binding and overheating, given the nature of the wood. The blade was used, but seemed to be in decent shape, and a 24 tooth blade.

[Mike Henderson]

If you get the same experience with two batteries, purchased at different times, I wouldn't suspect the batteries. I'd look to the saw, itself, or to the work you were doing.

If you get the same thing cutting plywood, that would cause me to suspect the saw, itself. Try a new blade first.

Mike

[Andrew More]

If you get the same thing cutting plywood, that would cause me to suspect the saw, itself. Try a new blade first.

Well with the plywood I was using a fairly new plywood blade. I started the cuts in the maple with this blade, and switched to a used cross cut blade. So that would be two different blades. So that leaves user error, saw problems, or mishandling the batteries.

I think I'm going to try again with some 2x12 scraps I've got and fresh from the charger batteries.

[Steve Rozmiarek]

Well with the plywood I was using a fairly new plywood blade. I started the cuts in the maple with this blade, and switched to a used cross cut blade. So that would be two different blades. So that leaves user error, saw problems, or mishandling the batteries.

I think I'm going to try again with some 2x12 scraps I've got and fresh from the charger batteries.

Andrew, just as a yardstick, I just cut three 19 step stringers from 2x14" LVL, cut 19 treads from 2x12, and 19 risers from 1x8, on one 9ah battery that wasn't fully charged, it showed down 1 bar. I changed batteries to build a 4x6 landing from 2x6 and 2x thick 3/4" subfloor. Second battery still shows full. I'm using a new 24 tooth Diablo blade. If my math is right, that's 133' of 2x cuts and another 30' of 1x for the first battery, and around 50' 2x and 50 1x for the second battery. Might help to compare what yours is doing.

[Jim Dwight]

I use a Skil cordless saw and it will cut a lot more than a few hardwood boards to rough length on a battery. I don't use it much but I think I've only charged the battery once. Power was surprising. I'd check the blade first and if it is in good shape, I'd question the batteries.

[Andrew More]

Did some testing tonight. Put on a new blade, cut everything, including the Hard Maple like butter. Went back to the old blade, burnt the maple to a crisp, took about 4x as long. Took another look at the blade, and sure enough it was the old blade that came installed in the previous circular saw. Doh!

Thanks for the feedback everybody, I think I'm going to replace my plywood blade as well.

[Steve Rozmiarek]

Did some testing tonight. Put on a new blade, cut everything, including the Hard Maple like butter. Went back to the old blade, burnt the maple to a crisp, took about 4x as long. Took another look at the blade, and sure enough it was the old blade that came installed in the previous circular saw. Doh!

Thanks for the feedback everybody, I think I'm going to replace my plywood blade as well.

Easy fixes are the best!