Cordless Impact Wrench Performance vs Battery (Max Current vs. Capacity)

[YoshiMoshi]

Milwaukee makes a cordless right angle impact wrench, 2565-20. As part of their M12 line of power tools. A YouTube channel tested the performance of the tool, with their different batteries. I'm having difficulty in understanding the observations. It seems that higher output current batteries do not necessarily mean higher performance.

The Data collected from the video:

• CP 1.0 peak torque 131 ft lb
• CP 2.0 peak torque 144 ft lb
• XC 4.0 peak torque 159 ft lb
• XC 6.0 peak torque 182 ft lb

Now the internals of the batteries:

Combining the data

1. CP 1.0, 1 Ah, Peak Torque 131 ft lb
   1. 3x Samsung 13Q, Total Max Continuous Discharge Current From Battery Pack = 15 A
   2. 3x Moli IMR-18650E, Total Max Continuous Discharge Current From Battery Pack = 20 A
   3. 3x Samsung 15M, Total Max Continuous Discharge Current From Battery Pack = 23 A
2. CP 2.0, 2 Ah, peak torque 144 ft lb
   1. 3x Samsung 20R, Total Max Continuous Discharge Current From Battery Pack = 22 A
   2. 3x LG HG2LGDAHD41865, Total Continuous Discharge Current From Battery Pack = 20 A
3. XC 4.0, 4 Ah, Peak Torque 159 ft lb
   1. 6x LG HG2LGDAHD41865, Total Continuous Discharge Current From Battery Pack = 40 A
4. XC 6.0, 6 Ah, Peak Torque 182 ft lb
   1. 6x Samsung 30Q, Total Continuous Discharge Current From Battery Pack = 30 A

Taking the best configuration for each battery (the video didn't specify):

1. CP 1.0, 1 Ah, 23 A, Peak Torque 131 ft lb
2. CP 2.0, 2 Ah, 22 A, Peak Torque 144 ft lb
3. XC 4.0, 4 Ah, 40 A, Peak Torque 159 ft lb
4. XC 6.0, 6 Ah, 30 A, Peak Torque 182 ft lb

Well I don't get this:

• CP 2.0 had better performance than the CP 1.0, despite delivering less current to the tool of 1 A. The difference is that the 2.0 has a larger capacity of 1 Ah. But why does the increase capacity result in better performance?
• XC 6.0 had better performance than the XC 4.0, despite delivering less current to the tool of 10 A. The difference is that the XC 6.0 has a larger capacity of 2 Ah. But why does the increase capacity result in better performance?

I would presume that a battery pack that is able to discharge more current, would result in better performance. But that doesn't seem to be the case here. It seems that larger capacity battery pack increases performance more than a battery pack that draws more current. I don't really understand why. Thanks for any help!

Also, I was looking into custom battery packs. Am I right that say for example the XC 5.0 has a maximum continuous discharge current of 50 A, but the power tool will only consume the maximum amount of current it needs. So while the battery pack may support a maximum of 50 A, the power tool may not necessairly consume 50 A. There is some sort of maximum, at which a battery pack that can output more current won't result in any difference in performance?

 

[Baluncore]

Energy usage is also dependent on the number of impacts per second. Where is that in your analysis?

Be aware that impact drivers may destroy some low-cost or generic battery packs, by fracturing the internal connections.

 

[YoshiMoshi]

I don't have that data. But if the same tool is used, is it safe to assume it's the same?

These are official battery packs from the manufacture and not the cheap knock offs.

I just find it interesting, battery packs whose cells that can output less current, but have a higher capacity, result in better performance in the tool.

I would have thought battery capacity would just have longer run time, and not better performance, and that batteries that can output more current, would result in better performance.

I don't really understand it. Unless, batteries with a higher capacity can have more impacts pet second? But I don't know why this would be the case.