Milwaukee Impact Power vs Battery Drain

[JacksoNRolyaT]

Hey guys, tried to do some searches and google research but didn't find too much. I have a Milwaukee 1/2 High Torque Impact (2763-22) and I absolutely love the thing. Everyone at work loves it too. 9 times out of 10 it takes whatever I ask of it off but yesterday I ran into an interesting problem that, until then, I didn't realize was happening.

So at work we had an Audi come in for 1 tire. Okay, get the gun, get the socket, start taking lug nuts off. Got to the last two and it wouldn't take them off. Instead of hammering and taking them off the gun would hammer and vibrate more profoundly than it usually does when loosening a bolt. That's when I realized my battery was on the last dot of the four dots.

So that got me wondering, how much torque does the gun lose when the battery is lower vs when it is fully charged. Or does it even lose any torque power when the battery is low. Gun has Redlithium XC4.0 batteries.

 

[crewchief888]

my fuel 3/8" dr gun stays pretty consistent until the battery light starts to flash.

 

[rlitman]

my fuel 3/8" dr gun stays pretty consistent until the battery light starts to flash.

The compact impact (like my Fuel 1/4" hex) supposedly has the same power output on the small and large batteries, and I have not felt any loss of power on the last dot. The 1/2" Fuel drill and full size 1/2" Fuel impact supposedly put out more torque using the large batteries, so I'd guess that the voltage dropoff may be more felt on some tools than others.
I don't own the full sized 1/2" impact, but I've felt a drop in power on the last dot with the drill.

Running lithiums down too low is not good for them. Neither is charging them too much.
I try to wait until they're at 2 lights before putting them on the charger when working at home. If I'm going somewhere, of course, I try to bring charged batteries with me.

 

[Ign]

Yes, power of the tool relative to battery charge is more pronounced on certain tools. Li-ion is supposed to have "fade-free" performance, but that's really only relative to old ni-cads that would gradually run down to ~1 rpm (or less).

My M12 2438 sander/polisher, I can tell when it nears one light on the charge indicator. Same for my M18 Fuel grinder, 2604 hammer drill, and even the little M12 drills w a 3/8" chuck (2410/2407) have noticeably more "whirr" with a full battery.

Not Milwaukee but I can also tell when my Ryobi 40V string trimmer is nearing the end of its charge.

The 12V Nextec stuff seems to suffer from battery fade even more, which I've always guessed was simply Craftsman putting less R&D or electronics in the tools to keep cost down.

I virtually always run my batteries down until they automatically cut out, and I leave them on the charger for weeks. I also leave them in my unheated shop, and do anything else that is NOT considered "best practice" w li-ion. I've never had a premature battery failure.