Cordless Tool Batteries

Broke out my Milwaukee angle grinder, with a cut off wheel attached, to cut up some old scrap polycarbonate roofing panels. Stacked a few panels on top of each other, then went at it. Worked okay, but after a few minutes the battery overheated, and the tool shut down. Too much current flow, apparently. I switched batteries, and went back to work, and the same thing happened with battery #2. Got the job done by switching back and forth between the batteries, using one while the other cooled.

I suppose I should be happy that the system monitors temperature and shuts down to protect itself, and me! Nice technology. Have to admit, though, battery powered angle grinders have limitations.
 
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Nessism1 said:
Broke out my Milwaukee angle grinder, with a cut off wheel attached, to cut up some old scrap polycarbonate roofing panels. Stacked a few panels on top of each other, then went at it. Worked okay, but after a few minutes the battery overheated, and the tool shut down. Too much current flow, apparently. I switched batteries, and went back to work, and the same thing happened with battery #2. Got the job done by switching back and forth between the batteries, using one while the other cooled.

I suppose I should be happy that the system monitors temperature and shuts down to protect itself, and me! Nice technology. Have to admit, though, battery powered angle grinders have limitations.
Click to expand...

What battery are you using? I've only hit the duty cycle a few times with the M18 inflator but that's after inflating 8 tires one after another, and thats the tools duty cycle, not the battery. and a Ryobi die grinder carving some gokart engine plate holes.
 
cptbarkey said:
What battery are you using? I've only hit the duty cycle a few times with the M18 inflator but that's after inflating 8 tires one after another, and thats the tools duty cycle, not the battery. and a Ryobi die grinder carving some gokart engine plate holes.
Click to expand...
M18 5Ah batteries. I'm glad they didn't fry. Charged them back up later that day, and they seem perfectly normal.

Interestingly, when they overheated, and pressing the charge light on the battery, the LED's flashed all about. Apparently that's the signal for either malfunction and/or overheat.
 
willbur said:
no- its the power (watts) that produce heat.
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No, you're close Wilbur, but not quite there.....since we're getting "technical".....

It's actually not the watts......it's the friction of the electrons transferring the current that causes the heat. We measure that in Watts as power.

;)
 
MaximumMini said:
No, you're close Wilbur, but not quite there.....since we're getting "technical".....

It's actually not the watts......it's the friction of the electrons transferring the current that causes the heat. We measure that in Watts as power.

;)
Click to expand...
“Friction of electrons”!!??

😂😂😂
 
MaximumMini said:
No, you're close Wilbur, but not quite there.....since we're getting "technical".....

It's actually not the watts......it's the friction of the electrons transferring the current that causes the heat. We measure that in Watts as power.

;)
Click to expand...
nah- I use low friction electron additives in all my stuff.
In all my upper level physics classes, electron friction was never mentioned for electric circuit, just watts. No one sat around and calculated heat from electron friction in design, just watts that had to be dissipated and not blow out the device. Are you sure about this or something google told you and trying to be "the smartest guy in the room" LOL
 
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willbur said:
which is a formula for power (watts)
Click to expand...
You’re conflating two things.

Watts of useful work from a machine, versus watts of waste heat due to resistance (“friction” as someone said).

The two certainly correlate, since doing more shaft work requires more amps. But one rises linearly (V*A) while the other is the square of the current.

Obviously there is much more to it, especially when we talk more complex factors. KISS principle applies here.

The context of your first reply was relative to shaft work:
IMG_1351.webp


Higher battery voltage results in lower current for the same shaft work (V*A), with that lower current impacting battery heat generation internally (I^2 R).

Which is the implication here:

IMG_1352.webp


willbur said:
nah- I use low friction electron additives in all my stuff.
In all my upper level physics classes, electron friction was never mentioned for electric circuit, just watts. No one sat around and calculated heat from electron friction in design, just watts that had to be dissipated and not blow out the device. Are you sure about this or something google told you and trying to be "the smartest guy in the room" LOL
Click to expand...
Huh?!? Yes, watts of resistive heating due to I^2R. I’ll let @MaximumMini defend their comment, but I take the “friction” term as a resistance/impedance.

And for any practical design, that is always calculated. So not sure what argument you’re trying to win.

Work from a motor is in watts.
Waste heat dissipated from impedance is in watts.
My electric heater in my house is in watts.
My car engine is rated in watts.
My lightbulbs are rated in watts.
My bicycle tells me how many watts of power I’m generating.

So what?!?

Use the term as it is intended for the situation at hand.

That is, a higher battery voltage results in lower current for the same power, which reduces self-heating in the power tool battery (subject of this thread).
 
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