D batteries are fine, but C batteries are not common here. We have 2 cat feeders that use 4 C batteries. If they are empty I need to order new ones on the interwebs, they just don't have them in stores here. We now have same spare of course. But pretty annoying the first time.
But maybe if they are just in more stuff I can buy them in a store here.
I have a flashlight that uses 4 C batteries and just purchased a rechargeable ones, could that be an option?
I don't know if this is global phenomenon or just US, but 25 years ago when I lived in Europe C and D batteries were as popular as AA. But yeah, I don't see much of C and D in local US stores.
Not really. Things don't magically get better just because time has passed. Efficiency reaches a plateau, and the laws of thermodynamics prevent any further improvements.
Since it's a battery operated device, they're almost certainly using brushed motors. Those are less efficient than brushless, but brushed DC motors are cheap and easy to run from a DC source. The complex electronics to run brushless motors only got cheap in the last decade or so, and there's still plenty of sex toy vibrators that use brushed because it's easy and doesn't take much space in the device.
The difference isn't even that big. About 75-80% efficient for brushed, and 85-90% efficient for brushless. The extra complication of electronics isn't always worthwhile even today. The basic mechanics of this stuff was invented over a century ago and was all but perfected decades before OP's advertisement ever existed. It can't be better than 100% efficiency, and it's already pretty close to that. Unless someone comes up with a really clever design that gets brushless efficiency with little to no additional electronics, there's not much improvement to be seen.
Batteries, OTOH, have improved by leaps since then.
Interesting information, ty - my electrical knowledge is pretty minimal, basic, and spotty AF since it's almost entirely self-taught. Only slightly more than those who know nothing, I guess.
Would increase current increase the motors intensity? I guess the motor speed wouldn't increase, but when you start using the motor, the current would help sustain the speed.
To increase current, you have to either increase voltage or decrease the overall resistance of a circuit. For changing resistance of motors, that usually means changing the windings. Meaning it's a matter of part selection during design.
What that means is that when they chose a motor, they needed to take into account the C rating of typical batteries available at the time.