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 main reason: Because the litium-ion battery technology allows us to have compact, yet powerful, batteries with higher voltages.
Back in the days, the 7.2 and 9.6 volt batteries were with 6 and 8 cells, respectively.
Now, we have 24 volts with 6 litium-ion cells. This higer voltage allows much higher power at the same current (and the current is limited by wire cross-section, mostly in the motor).
In addition to higher voltages, modern batteries also store much more energy (for better runtimes). They also do not suffer (as much) from cold than some older batteries (which could only deliver full power when they were warm directly from the charging).
The bigger voltage does not guarantee higher power. The manufacturer can of course just reduce the amount of copper (read: put a much smaller motor in). But, especially the good modern tools with brushless motors (another new thing from this millenia) are way more powerful than their 90s counterparts (and run for far longer).
The 40 volts will likely remain the new maximum for a long while. Now, the limit is about safety (to keep the tools “low-voltage” battery operated, as opposed to corded tools, so, below about 50 volts depending on local regulations).
But, a good 9.6 V, not to mention ~20 V, tool, will likely outperform a cheap 40 V tool. Higher voltage is not magic that guarantees performance.
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