run time only..
Overview of the new XC5.0 battery pack from Milwaukee:
"Upgrade to the M18™ REDLITHIUM™ XC5.0 Battery Pack to instantly increase the run-time and durability of your M18™ cordless tools"
"Delivers up to 2.5X more run-time, 80% less money in your wallet than standard 18 volt lithium-ion batteries.
Is 5% even really a difference you would see or feel in use? I night my impact with a battery kit since it was the first Milwaukee product I bought, so that's why I have the 2.0. Wondering if it's worth the upgrade. I love the weight of the packs.
Not to hijack: But speaking of MIL lion batteries, other than the one or two we use frequently, do we store the new, unused ones in a cool place until we need them? Months maybe?
i run all mil m-12 stuff drills impacts sawzall and attended a tool expo that they hosted, the only diff in the 2.0 battery and the 4.0 battery is like 2 gallons of gas compared to 4. they deliver full power till dead and they shut them selves right off to be easier on the motor not delivering enough current. unlike other drills drivers that wind right down to nothing
I asked the M18 product manager that very question on a conference call before...and he said "the 4.0XC batteries will give you roughly 5% more power than the 3.0 or compact packs".
I asked the M18 product manager that very question on a conference call before...and he said "the 4.0XC batteries will give you roughly 5% more power than the 3.0 or compact packs".
I have a 5.0 pack also, but it seems to be the exact same as the 4.0 in power/weight....runtime being the only difference that I can see physically from the outside. That & they did stamp a lightning bolt on the top of the housing.
Even on FUEL devices?
NLithium's power decline is very linear and almost flat till the end. Off the charger, 1.5 to 5.0 ah batteries will all be the same power. As the batteries drain, the bigger batteries will retain closer to 100% voltage than the smaller batteries, but in all cases, these drops are very small with lithium's and might equate to 5% when they are close to empty.
I'm pretty sure it's a chopper circuit so higher voltage will mean less current and, therefore, less heat the same power. FUEL also regulates power based on heat, as I understand, so the larger battery creating more power does make sense but I can't imagine the effect is all that significant.
More available amps is not a concern if the 2.0AH battery already supplies enough juice. I highly doubt the Milwaukee 2654 is being strained by the 2AH battery. You can have more available amps, but it doesn't mean the motor will take it. It only takes what it needs.
Milwaukee claims that the 2603-22ct, which comes with the 2.0 batteries, has 650 in-lbs of torque. The 2603-22, same drill but comes with the XC 4.0 batteries, has 725 in-lbs of torque. Milwaukee claims the impacts get the same power with either battery.
i run all mil m-12 stuff drills impacts sawzall and attended a tool expo that they hosted, the only diff in the 2.0 battery and the 4.0 battery is like 2 gallons of gas compared to 4. they deliver full power till dead
As a simple response for that PM to not get into details, this is sort of true. Being that he is a PM and not an engineer, he might not be able to explain that answer and is just quoting what he hears.
So explain this...
It's electronically limited by the RedLink circuit. The battery cells can handle the load no problem, but you reduce cell life by drawing closer to the max discharge rate. Seems like Milwaukee took the conservative approach, which is not surprising.
My understanding is that the 5% difference figure is related to battery's internal resistance rather than any differences in the state of charge. That is, even for both packs fully charged the 4AH one could still provide slightly more grunt if you're really trying to pull a lot of current.
A ballpark figure for the internal resistance for a single Li-Ion cell is somewhere around 20 m-ohms, and an 18V pack has 5 cells in series. So that's about 5x0.02 which comes to 0.1 ohms internal resistance.
I believe that most 4AH packs use the same cells as the 2AH packs, but with 2 cells in parallel to get the added capacity. This however also halves the internal resistance! So if for example the 2AH pack had 0.1 ohms then the 4AH pack would only have 0.05 ohms.
Now consider something that's pushing the battery fairly hard. Say a circular saw pulling about 10 amps (180 watts). The voltage drop due to the 0.1 ohms of the 2AH pack would be 10*0.1 = 1 volt whereas that for the 0.05 ohm 4AH pack would only be 10*0.05 = 0.5 volts.
So given a no load voltage of say 19 volts, the 2AH pack would put out 18.0 volts while the 4AH pack would hold 18.5 volts under this load. Since power is proportional to voltage squared, this would equate to a difference in power applied to the tool in the ratio of (18.5/18.0) squared, which actually comes out quite close to 105% (a 5% increase).
If the 2.0 and 4.0 batteries have the same C rating then that means the 4.0 can discharge at twice the rate, thereby providing more power to the tool, so it becomes more than just a gas tank thing. The analogy would be the larger battery has a larger gas tank (more capacity) but it might also have larger injectors (more flow).
It's electronically limited by the RedLink circuit. The battery cells can handle the load no problem, but you reduce cell life by drawing closer to the max discharge rate. Seems like Milwaukee took the conservative approach, which is not surprising.
That's assuming that the 2.0/4.0/5.0 use the same Redlink circuit. Which they don't. They are calibrated to the battery capacity. So, say the 2.0 will be limited to 4A discharge, the 4 to 8A discharge, and the 5 to 10A. I'm not sure if those are the numbers but the circuitry needs to be matched to the battery.