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Old 02-02-2019, 04:27 PM   #1
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Question about Dewalt 20V cordless batteries


I recently bought a Dewalt 20V 1/4 inch impact driver. It came with 1.3 ah battery. Someone on youtube suggested i would get more "power" from higher amp batteries. He said the tool would struggle less with tight fasteners with a 3 ah battery.

This seems doubtful to me, as the capacity of all the batteries is 20V and the amp hour rating reflects longer run time, not power output. A 1.3 ah battery might need to be recharged more frequently than a 3 ah battery, for example, but their power output is the same. Is this correct? Thanks!
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Old 02-02-2019, 04:54 PM   #2
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Re: Question about Dewalt 20V cordless batteries


Thatís correct. Although some folks claim more power from higher aH batteries I havenít found that to be the case. My Milwaukee impacts and saws and what not seem to run the same whether I have my 4.0 or my 9.0 aH batteries installed.
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Old 02-02-2019, 05:59 PM   #3
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Re: Question about Dewalt 20V cordless batteries


I have many 20 volt tools and batteries.
I have the 1.3, 3 and 5 AH batteries.
The 5 AH come with the yard tools, blower, weedeater, and chainsaw.

The only difference I see is the run time and the weight.
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Old 02-02-2019, 06:33 PM   #4
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Re: Question about Dewalt 20V cordless batteries


Amp hour rating is the battery's reserve power, or how long the tool will run on a single charge. The amp hour rating has little to no effect on the power output of the tool. It might seem to help very slightly on high draw tools because the larger cells can better handle the high drain conditions under full load. Your impact driver is really only rated at about 150 lb ft of torque and you'll actually lose some of that because the little 1/4 driver bit will flex quite a bit which consumes some of the torque.

This same impact driver is also sold as an actual impact wrench with a 3/8" or 1/2" anvil instead of the bit drive. It has the same motor but does a better job because the larger diameter, shorter anvil provides better power transfer to the fastener. The 1/4" impact driver is meant for driving screws or small bolts.

When you need to break loose larger fasteners you need a heavier tool. These will have larger and heavier hammers inside and a much higher torque. For comparison the big 1/2" drive brushless impact is rated at around 1200 lb ft for breakaway.
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Old 02-02-2019, 06:41 PM   #5
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Re: Question about Dewalt 20V cordless batteries


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Originally Posted by Bigplanz View Post
A 1.3 ah battery might need to be recharged more frequently than a 3 ah battery, for example, but their power output is the same. Is this correct? Thanks!

In theory yes. In practicality it's another story. I have 1.5 and 4AH batteries in my line up. Whenever I have demanding tasks, I always reach for the 4's.
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Old 02-04-2019, 11:56 AM   #6
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Re: Question about Dewalt 20V cordless batteries


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In theory yes. In practicality it's another story. I have 1.5 and 4AH batteries in my line up. Whenever I have demanding tasks, I always reach for the 4's.
My knee-jerk reaction is to be skeptical of this, but thinking about it I could imagine a couple of ways in which it could be true.

Strictly speaking, amp-hours are the maximum amount of charge stored in the battery (pedantry: charge, energy, and power are three different things, and there's no such thing as "stored power"). So people are correct in that, if we view the battery as a monolithic "black box" with only a voltage and an amp-hour rating, the only difference will be run time.

However, a battery isn't a monolithic "black box." An 18V-- or "20V MAX" if you're a marketing douche from Stanley (the actual voltages are the same)-- battery is made of individual (if I recall correctly) 3.6V cells. The cells are arranged in strings of 5 to get the nominal 18V, and then a number of those "strings" are wired in parallel to get the desired capacity.

If we ignore, for the moment, the electronics in the tool and the battery and just view the battery/tool combination as the cells connected to a static load, then you absolutely will get more power from a higher capacity battery. The reason for this is that having more 18V "strings" in parallel reduces the total equivalent resistance due to the internal resistance of each cell.

That being said, we shouldn't ignore the electronics. There's a fair amount of wizardry going on there. It could be that the battery is controlled with some sort of magic PWM scheme or something (boost converter?) in a way that makes the internal resistances moot, I really don't know (batteries are expensive enough that I haven't been willing to risk breaking one opening it to poke around). On the other hand, it could be that a larger battery communicates to the tool "hey, I've got all this extra energy so it's okay to turn it up to 11."

There's a lot of anecdotal evidence floating around the Internet to support either position, both sides having people who are absolutely adamant that it does/doesn't make a difference. As far as I know the manufacturers are silent on the issue. Maybe somebody has done actual testing?
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Old 02-05-2019, 07:21 AM   #7
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Re: Question about Dewalt 20V cordless batteries


^ This. Just remember that Dewalt's 20v batteries are the same as others' 18 v batteries due to their creative rating that uses hot off the charger voltage instead of nominal voltage which is 3.7v per cell. Some other mfgs play the same game like EGO "56v" which are nominally 52v.
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Old 02-05-2019, 02:23 PM   #8
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Re: Question about Dewalt 20V cordless batteries


Yeah, I know about the marketing department's 20V scam. Sheesh!

This was a kit, priced at $100 for the tool, charger and the smallest battery they make. More marketing, to get you in their tool line. Works fine though, and I can get a 4 aH dewalt battery from Amazok for $60 if really feel the need.
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Old 02-05-2019, 04:15 PM   #9
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Re: Question about Dewalt 20V cordless batteries


Don't forget that Dewalt does still maintain the old 18v tool line that is incompatible with the new 20v slide on packs. It would be pretty confusing for consumers if they had called both 18v but they don't fit together. The new style, slide on batteries CAN be used on the old tools but requires the help of an adapter. The 20v Max name may be a bit of a marketing ploy, but the name change also differentiates the two lines. They don't hide the fact that they are still 18v tools.

Nothing wrong with the compact batteries, they certainly have their place. They are desirable and work great for low demand tools to make them both lighter and more compact. Also a little more budget friendly for homeowners that may not need to own the big contractor grade batteries.

They offer compact batteries in 1.5, 2.0 and 3.0ah, full sized packs in the 3.0, 4.0, and 5.0ah batteries and oversized batteries in 6.0ah. You can also step up and use the flexvolt 20/60v batteries in 6.0, 9.0 and 12.0 ah. You can choose the batteries that work best for you, the way you use your tools and the tools that you own. They also sell your impact driver kit with the larger batteries if you had chosen to go that way, it just costs a little more.
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Old 02-05-2019, 07:32 PM   #10
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Re: Question about Dewalt 20V cordless batteries


I run the makita cordless line. My drill and driver came with the 1.5 ah battery, ran fine. My skil saw came with a couple of the 3.0 ah battery and wouldn’t run on the little ones. Just for consistency, I started using the larger battery for everything...and I now use the same for the angle grinder, planer, recip saw, etc. actually gave the two little batteries to a friend last summer. So, not being up on the details of how they work, I never have the wrong battery at hand and have no concerns about run time.
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Old 02-06-2019, 07:53 AM   #11
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Re: Question about Dewalt 20V cordless batteries


With Li-ion batteries a larger capacity battery can discharge more current. So in theory the 3.0 Ah battery can delivery more current to the drill's motor which translates to more power. Again that's in theory. Just my 2 cents.

May be some can try that out and chime in to confirm

As others pointed these batteries are by no means 20 V. It's a marketing gimmick. It may be 20 V momentarily one first use after charging. But the nominal voltage is 3.7 V per cell in the batteries. A true 20 V systems would delivery a bit more power.

I currently have the dewalt '20V' impact driver and drills (the ones with the brushless motor). IMO they are way over-rated for the price but for they do the job
Prior to this I had the much cheaper Ryobi unit. They did the job too.

Last edited by 007noob; 02-06-2019 at 08:02 AM.
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Old 02-06-2019, 10:57 AM   #12
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Re: Question about Dewalt 20V cordless batteries


I have the Porter-Cable 20v drill and impact driver kit. It came with 1.3 amp batteries and I have since bought 4.0s. As others have pointed out, I get longer run time but no increase in power.
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Old 02-14-2019, 01:24 AM   #13
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Re: Question about Dewalt 20V cordless batteries


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Originally Posted by ront02769 View Post
I run the makita cordless line. My drill and driver came with the 1.5 ah battery, ran fine. My skil saw came with a couple of the 3.0 ah battery and wouldn’t run on the little ones. Just for consistency, I started using the larger battery for everything...and I now use the same for the angle grinder, planer, recip saw, etc. actually gave the two little batteries to a friend last summer. So, not being up on the details of how they work, I never have the wrong battery at hand and have no concerns about run time.
I did the same think. After daliances with the other colors of tools, I finally returned back to the brand who began the cordless tool revolution... Makita. One of the neat things about Makita batteries is that their 3.0 ah, 4.0 ah, 5.0 ah, and 6.0 ah batteries are all the same exact physical size, where the 6.0 is no bigger in any physical dimension than their 3.0.

So I got all 6.0 batteries, and kept one 2.0 battery (which is smaller, about half the height) just to use in tight spaces. The consistency of having all the other batteries be the same ah makes it easier to know what the battery meter means when it says 2 bars vs 3 bars. And no matter which battery I grab, the performance and predicted run time is the same.

I also like Makita's X2 (pair of 18v batteries) over the huge honkin 12 ah red battery or the giant 60v yellow battery. To run Makita's higher voltage tools, I can still grab the first two 6 ah batteries I run across in my mess, stripping them off of other tools that aren't being used in that moment, rather than waiting for the one big giant battery to charge.

One of the benefits to higher amp hour batteries (especially if they are the same size as the lower amp hour batteries so there is no size or weight penalty) has nothing to do with the magic inside the black box of the battery.

It has to do with LOAD.

Some people say they see no performance difference between a 1.3 ah battery vs a 4.0 ah battery. Well, when driving 6" long self drilling Timberlok screws, where the friction is so hot that a wisp of smoke floats away from the penetration juncture... that higher amp hour battery doesn't argue like the little battery does. Higher loads tax the smaller batteries much quicker. This could account for the discrepancy in anecdotal reports. No account is made of the loads being driven. Higher loads demand and therefore deplete available current quicker.
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Last edited by Bent Nail; 02-14-2019 at 01:30 AM.
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Old 02-14-2019, 12:42 PM   #14
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Re: Question about Dewalt 20V cordless batteries


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Originally Posted by Bent Nail View Post
One of the benefits to higher amp hour batteries (especially if they are the same size as the lower amp hour batteries so there is no size or weight penalty) has nothing to do with the magic inside the black box of the battery.

It has to do with LOAD.

Some people say they see no performance difference between a 1.3 ah battery vs a 4.0 ah battery. Well, when driving 6" long self drilling Timberlok screws, where the friction is so hot that a wisp of smoke floats away from the penetration juncture... that higher amp hour battery doesn't argue like the little battery does. Higher loads tax the smaller batteries much quicker. This could account for the discrepancy in anecdotal reports. No account is made of the loads being driven. Higher loads demand and therefore deplete available current quicker.
Are you suggesting that driving a single 6" Timberlok will deplete a 1.3Ah battery? Otherwise your statement would seem to support the hypothesis that the higher capacity batteries actually put out more power.
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Old 02-15-2019, 11:31 AM   #15
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Re: Question about Dewalt 20V cordless batteries


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Are you suggesting that driving a single 6" Timberlok will deplete a 1.3Ah battery? Otherwise your statement would seem to support the hypothesis that the higher capacity batteries actually put out more power.
Higher capacity batteries DO actually put out more power... over a period of time. And the higher the loads, the shorter the time. The smaller the battery, the quicker it depletes.

Low, light duty, non demanding loads would not reveal any practical performance differences between battery sizes in real world usage.

And that's the key... and the problem... with anecdotal reports about whether or not battery size makes a difference. These are construction tools used to build and repair stuff in homes and job sites. We are not talking about instrumented tests in a controlled laboratory. Who knows what the state of charge or rate of depletion was for any given person reporting experience. And when I'm in a situation where I'm needing to drive 6" TimberLok's, it's never just one.

As a practical matter, if I bring tools to a task that can be constructed or repaired with say, a dozen TimberLoks, I'm going to slide on a fat battery, because the probability is higher that the skinny battery will run out of juice before the job is done. Been there done that, and made the round trip down and up the ladder for it.

The higher workload accelerates the time to battery depletion, because more energy is being demanded, and the demand is continuous duty, due to the long length of the screws. With continuous loads, heat dissipation, heat distribution over the number of individual cells, and thermal measurement and management by the electronics within the battery enter into the equation. But none of that is my concern. I just want to get all the screws in, all the way down, so I'm going to pick the fat battery from the get go.

On the other hand, if I'm installing a little shelving system with 1 1/2" screws, I know that the neither the tool, the battery, or even the screws will heat up much. Any size battery will do, and neither size battery will reveal any apparent difference in performance over the time period of that job.

Last edited by Bent Nail; 02-15-2019 at 11:37 AM.
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