Does a larger battery give more POWER? Results inside...

[dwain]

A few times in recent months I have heard the opinion that larger batteries can actually give more power, no just longer runtime. It came up again in Javier's excellent video putting the new Bosch Hybrid Impact against the FUEL impact: http://professional-power-tool-guide.com/power-tool-forum/index.php?/topic/3851-bosch-vs-milwaukee-brushless-18v-impact-speed-challenge/

 

Being a skeptic of this, I decided to do some testing myself. I have a new respect for anyone who makes a decent video with a fairly scientific approach to testing, it is much harder than it looks. I just took some photos. Here's a couple of setup photos:

 

Everything was done in 4x4 rough cut treated pine (very soft). Screws were timed going in, not backing out. The 25mm auger bit tests were in and out. The batteries were always on 2 or 3 bars charge.

 

DCF886 Impact Driver driving 3 No. 8mm x 90mm lag screws. I did this test twice (one at the end of other tests since it was so different). Both batteries actually sheared the third screw at the same depth! Very uncanny. It didn't happen in the second run, which took much longer on the 2.0Ah for some reason...

2.0Ah - 59.7 secs & 99 secs

4.0Ah - 46.7 secs & 49 secs

 

DCD790 Compact Drill driving 3 No. 8mm x 50mm lag screws. The drill cut out every time as the head of the lag hit the washer.

2.0 Ah - 15.0 secs

4.0Ah - 15.3 secs

 

DCD985 Premium Drill drilling 4 No. Holes with 25mm auger bit. On both batteries I had to switch from 2nd gear to 1st gear on the third hole.

2.0Ah - 43.4 secs

4.0Ah - 44.5 secs

 

The results surprised me immensely! There was a clear power difference in the hand when using the impact driver with 4Ah batteries, but no difference with the drills (as reflected in the results). All scenarios were a big test for the tools. I would have guessed that the impact would be the least affected by battery size, but the results clearly disagreed.

 

The testing was not perfect, but I am definitely convinced of using larger batteries in an impact driver for large screws. It would be harder to measure, but an angle grinder and/or circular saw test would be interesting.

[Jimmijo]

Ha.. thats good to know. I would of thought the same. Didnt expect impact driver would give more clear power with the big pack. I would do the test on ciruclar saw. But it was missing for over amonth now. Might have to buy a used one somewhere soon. Good post tho.

[RedSionnach]

I did a lot of searching last night, I couldn't find any manufacturer listing their draw amps. It seems that almost every other tester found the same thing. I'm guessing that drill/drivers use a constant amount of power, assuming full trigger pull. While impacts or hammer are more as needed draw, and since the larger ah have a higher max discharge rate they can put out more torque.

[frankiegarcia19]

Good stuff man.. Now every reviewer should take that into account and use the same ah battery when comparing tools.i was wondering this and then a day later u got it. Nice job

[Javier]

That's interesting, I didn't know. I just assumed it would be the same performance with either battery as the manufacturers list same stats for either battery on the impact drivers.

[dwain]

Yeah I wouldn't take too much from my testing. I'm a bit concerned that heat of the batteries/drills could have played a part. I also wonder whether a battery gives more power at certain parts of its charge level, and I wasn't perfectly consistent on this

 

I was always fascinated by the tool fight TIA did between Milwaukee and Dewalt brushless tools. The milwaukee went faster at the start but slowed down so that the Dewalt caught up. These sort of experiences make it very difficult to be sure of any tools comparable output. http://professional-power-tool-guide.com/2012/08/friday-night-tool-fight-dewalt-vs-milwaukee-brushless-impact-drivers/

 

 

Ha.. thats good to know. I would of thought the same. Didnt expect impact driver would give more clear power with the big pack. I would do the test on ciruclar saw. But it was missing for over amonth now.

 

I could do one with my circ saw, but how do you think it would be best tested? I suppose I could push the through some framing timber as fast as it 'feels' possible (i.e. without slowing the blade so that it feels it will cut out). Could try it in some old hardwood too ....

[Conductor562]

Great little research project. I suppose maybe..... hell I have no idea. Great info though.

[Jimmijo]

Hi Dwain, I put in some thoughts of how to do a fair test on the circular saw with the 1.5ah and 2.0ah xr vs. 3.0ah and 4.0ah xr big pack. I remember the most circular saw requiring to use the 3.0ah or above to get a better performance on the tool because the motor on circular draw much more amp power from the battery, not sure if I'm correct on that. And I also remember I used the 2.0ah xr small pack on the saw to make 2 5ft cut on a piece of 3/4" plywood forward by cutting some 2x4s with no problems and 2bars left on that 2.0ah xr battery. (Note: when I bought my set of the xr combo kit only come with 2x 2.0ah pack and Home Depot was running a deal for a free bare tool with the combo kit.) Thats how I got my circular saw free with the kit. Also remembered seeing the Y.T. video from TIA about the saw. Dan mentioned its better to use the 3.0ah on the saw to give better performance which it came with the kit. Thats why I went and bought a 3.0ah battery just for the saw. I'm not 100% on how to test them to be fair on this fact at the moment.

And I have been doing a lot of researching about powertool batteries lately. Trying to find out how they work and what's the best way to get the best use out of them. I have 5x 1.5ah, 2x 2.0ah, 2x 3.0ah and 2x 4.0ah total 11packs I have. But I only have 6 20v tools now included the missing circular saw 7tools and 3 changers. And I don't use all 6 or 7 tools all at once. So 8 batteries will be more than enough for me. Also heard if they dont get enough used or charge, its like it doesnt get enough work out for them. The batteries will go bad or shorten the lifetime by sitting and not being use. I'm has been trying to sell 3 of the 1.5ah or trade them for another bare tool. But no luck for the pass month and half. Anybody has any thoughts on the battery life or useage? Feel free to share your idea or experience by post a comment directly to me or here if Dwain don't mind. Thanks

[dwain]

OK, so I did a bit of a circular saw test today. I used an LVL offcut, 460mm long and 42mm deep, three runs with each battery. Each battery was on 3 bars charge.

 

 

Obviously there's a bit of difficulty with this one as user error plays a part (cutting straighter is easier on the saw), and i decide how hard to push the saw. I tried to push the saw to cut the length as fast as possible, which sometimes meant letting off the pressure to let the blade speed up again. I stopped the saw once on each battery.

 

4.0ah test - 78 secs

2.0ah test - 69 secs

 

Surprised again! Its true the 2.0ah batts are newer, but the 4.0ah's would still have much more capacity. Are you surprised?

[Jimmijo]

Nice update Dwain.

So, when using 2.0ah pack finished off and cut faster than the 4.0ah pack on the circular saw! Thats surprised me. Did you notice the difference on the battery useage somehow in the test?

[dwain]

nah, couldn't notice the difference really.

[Javier]

Now I'm confused

[NicholasShetley]

Something isn't right at all here. Could you try the test again?

[dwain]

the only things that could possibly be affecting the result are user error (which wouldn't be much), that i got the 4.0ah's second hand, or that the 2.0ah are US sourced, where the 4.0ah are Aus.

 

I could do it again, but I believe Dan & Eric may shed some light on it shortly

[Javier]

Now I want to know, if the capacity affects the performance then possibly the manufacturers would need to list performance ratings for either battery like they do with the fuel drills, I just find it strange that they only list differences on the drills and not anything else

[Jimmijo]

Hum. Thats strange the batteries wasn't a noticeable difference on the useage. My thought is since the circular saw draw higher amp power then the drill or impact driver. I assumed the the 2.0ah pack will be more noticeable decrease on the battery juice than the 4.0ah. I have heard using the 1.5ah pack on the circular saw would drain the pack way faster than the 3.0ah pack. For the fact I'm thinking it could because of the circuit board in the pack is pushing more power using higher amp to spin the motor faster than and create higher speed. I dont know it could cause the small pack cut faster on speed thou.

I find something are kinda interesting me on how all tools brand use different brand cells. Like Sony, Sanyo and Samsung 18650 lithium ion cells. Feel free to check out this link to get some ideas. http://toolguyd.com/power-tool-brands-dont-make-their-own-batteries/

[Guest The carpenter]

Milwaukee actually advertises that their 4.0 ah batteries increase the performance (speed and torque), not just runtime, of all of their M18 tools.  So I got curious and asked a Dewalt rep if their 4.0 ah batteries did the same and he said no, they did not.  It seems like if it were true for one manufacturer it would be true for another, unless its something having to do the the internal circuitry of either the batteries or the tools themselves?   

[Sauropod55]

I would think the real test is how many holes are rilled and how many screws are driven. The speed is a function of the gearing etc while the longevity is a function of the available power (amperage).

[dwain]

I would think the real test is how many holes are rilled and how many screws are driven. The speed is a function of the gearing etc while the longevity is a function of the available power (amperage).

 

no doubt the runtime is the biggest gain in performance from larger batteries, everyone accepts that, and most tests done by TIA are about runtime (total screws etc.).

 

But the question here is whether a bigger gas tank (i.e. 4AH) also affects power (which is not the same as speed). I think many people (myself included) expected that the power would not be affected by battery size, and that if it did, it would be the higher draw tools (like circular saw). My testing has given exactly the opposite results.

[RedSionnach]

The 4ah batteries do have higher max discharge than 2ah. Some manufacturers, with some tools, seem to take advantage with boosted performance while sacrificing at least some of the run time advantage.

I would assume that a circular saw would be a conatant draw, so that blade rpm wouldn't be affected.

I'm not hacking on your saw test, but there is a lot to consider with a saw. In order for a truely accurate test you would need a new blade for each test to account for dulling. Then there's density of material, and a constant pushing speed/pressure.

[dwain]

yeah there is a lot to consider. Re: the saw test, it was only 1.2m of cutting each test, and on a used (but reasonably new) blade, i don't think that would be significant. In any case, I did the 2ah cuts second. LVLs would be fairly consistent in density, but the user push is the hard to control aspect...

 

where can you find the discharge rates of batteries?

[Jimmijo]

I did many reseach about that. But no one seems to know what exact cell they use for them. Best I came across is dewalt using the red Sanyo 18650 2000mAh 20A max high discharge rate cells. But I heard the older one use even higher discharge rate cell. (Not meaning the pack is going to be on 20A discharge all time, it's depending on circuit board control when different temperature, how warm up is pack and many other facts.) I also think that could be one of the reason the result came out kind of strange. I remembered you mentioned about one of the battery pack is from US and the other pack you bought it used. It could to cause some strange result as well. Im not sure tho.

[Jimmijo]

Here are part of the article I copy and paste from the link I put in my preview post,

Maximum discharge rate. One brand’s latest 18V battery packs are built with cells advertised as having a 20A max discharge rate (22A on paper), and their previous battery packs were built with cells rated with a 25A max discharge rate (23A on paper).

A homeowner brand will not equip their tools with Li-ion batteries rated for 20A+ max discharge rates, and pro-grade brands will not equip their tools with cells rated much lower than that.

As a reference reminder, a battery with a 2.0Ah rated capacity can deliver a 2A discharge rate for 1 hour. Thus, a 20A discharge rate would deplete the battery charge in 6 minutes.

When is the last time you saw a consumer-grade cordless rotary hammer? Angle grinder? Band saw? Consumer-grade cordless tools don’t have the same power requirements as pro-grade tools, and so they don’t require top-dollar battery cells that can deliver the highest maximum discharge rate.

Minimum operating temperature, or rather minimum operating temperature and battery performance at those temperatures. The best rechargeable Li-ion batteries I have seen thus far can deliver 60% of their rated capacities at -4°F, and 80% at 32°F at a 10A discharge rate. A 10A discharge rate would deplete a 2.0Ah battery in 12 minutes at room temperature (100% capacity).

Battery packs that probably won’t be used outdoors in all weather conditions don’t need cells with good cold weather performance.

Life cycle. Samsung’s recent INR batteries maintain 60% or greater charge capacity after 250 charge cycles. More life cycles means longer usability and less frequent replacement schedule.

Minimum/standard capacity. A 2.0Ah battery won’t necessarily deliver 2.0Ah charge capacity under load. 2.0Ah is the nominal capacity, but during high drain discharge, the actual capacity might drop.

Charging time. Higher performance batteries can usually be charged at higher rates, although active cooling is required to achieve the maximum charging rate.

[Sauropod55]

I missed in your intro that you got the larger batteries second hand. That should play into the results somehow. I know that nicads develop an unchargeable area over time and tha has a huge impact.

[dwain]

I missed in your intro that you got the larger batteries second hand. That should play into the results somehow. I know that nicads develop an unchargeable area over time and tha has a huge impact.

 

it wasn't in the intro I'm not sure it would affect the results greatly, as they haven't been out in Aus for that long, and the Li-Ions should hold their charging capacity pretty well in the first couple of years...