On cordless electric impact wrench or akin, power sourcing

[abdulbadii]

How's actually the working mechanism of the cordless electric powered impact wrench or other cordless of kinds such nowadays? Why can't they bypass directly to source the mains 110/220V AC either with or without adapter ?
as sellers say 'it can't', so confusing

 

[rjenkinsgb]

The motor or drive system is designed for low voltage DC, eg. 18V or whatever, and operating from high-current capable lithium cells.

The tools could theoretically work through a suitable AC to DC power supply, but it would need one with the DC output rated within the battery voltage and able to supply anything from 30A to possibly 100A, depending on the tool type and ratings.

Plus connecting cables from that to the tool with high enough current ratings to not cause an excess voltage drop at full load current.

A suitable power supply with cables and connectors etc. is likely to be more expensive than just buying the AC version of the tool! The much higher voltage supply from AC power means the currents are proportionally lower with tools designed for direct AC connection.

Suitable batteries can easily supply very high current peaks for short periods as needed with such tools.

AC power supplies will shut down almost instantly with a current overload, so must be rated for the highest current the tool can use, even it if it only takes that for a fraction of a second at a time.
(Or you need a massive capacitor bank to smooth out the peaks, and a slightly less massive PSU).

 

[Diver300]

I was just about to say the same as rjenkinsgb.

I measured the peak current on a large 240 V power tool. It took around 40 A peak, so the power was around 10 kW for a moment. Even a small power tool might peak at 1 kW when starting. A 18 V Li-Ion battery would have no problem producing 50 A for a very short time to start a small power tool, but an 18 V power supply that can generate 50 A is physically quite large.

 

[Reloadron]

Why can't they bypass directly to source the mains 110/220V AC either with or without adapter ?

I have a few older corded electric drills in 3/8 and 1/2 inch drive. Problem is while they work fine I don't always have 120 VAC available easily. I always reach for my cordless tools. My neighbor let me use his 1/2" impact drive to change lug nuts on my wife's truck. Quick and done. The instant tightening and breakaway torque numbers are incredible. No cord and no problem. Use it anywhere. Cordless sells and sells well. Anything new I buy now is battery powered cordless.

A 18 V Li-Ion battery would have no problem producing 50 A for a very short time to start a small power tool, but an 18 V power supply that can generate 50 A is physically quite large.

Absolutely!

Ron