I’ve owned cordless tools of various kinds since I was a teenager and they were always marketed by voltage. In the nineties, 9.6 volt was the big thing. Then in the 00s it was twelve volt, and eventually 24. Now it seems like the larger tools are all 40 volt and above, but not all; my chainsaw is 24 volt and cuts down small trees just fine, and my string trimmer is 40 volt and doesn’t seem to be any more powerful than the chainsaw but the battery lasts longer.
What I don’t understand is why these things seem to be growing in voltage rather than amperage, and in marketing it seems like the voltage is supposed to be a proxy for how powerful it is. I understand the larger tool needs more power but why are the cells wired in serial rather than parallel?
In: 9
The power of an electric motor is voltage * power. So you can either increase voltage or current to have a more powerful motor.
Let’s say we like to increase the power by just changing the voltage or current and keep the other constant.
The current tough a the motor is current = voltage /resistance. I skip the Counter-electromotive force that results in a low effective voltage over the engine. The current is not limited by the batteries or at least that is not the case with the Li-ion cells we used today, it is the motor resistance that limits it.
To increase voltage you just need to have an external voltage source with a higher voltage. The current will also increase because it depends on the voltage and the motor’s resistance. To keep the current the same we can increase the resistance, this can mean thinner wires in the motor so the motor size can shrink. So if we increase voltage we can higher power even if the motor strings in the sizer.
If we on the other hand like to keep the voltage constant and increase the current we need to decrease the resistance. The mean thicker wire so a large had heavier motor.
So for an electric motor of the same size, you can get out more power if the voltage is higher. In hand tools, large motors are quite impractical so the best option to get out more power is to increase the voltage
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