 I've been talking about making this resistive speed control for one of my boats and it's basically a thing where you got the batteries and the motor and wires connect them and then you just put different size resistors in the way to slow down the electricity to the motor and that's how you do your speed control and some of the energy gets wasted and people are pointing this out to me a lot that it's wasting so much energy but it's not as bad as you think and I'm going to show you some math in a second first I'm going to show you my resistive speed control isn't that awesome that's it that's the whole speed control it replaces so much stuff like this is I think this piece of wire this is a nichrome wire cost like I think it was like around ten dollars it replaces like a five or six six hundred dollar other thing anyway let me show you why it's not as bad as you think say you've got a battery here right and then you've got a motor here and let's say it's a hundred watt motor and when you connect the battery directly to the motor it runs at 100 watts now say if I want to run the motor at 50 watts I stick a big fat resistor in here to slow down the electricity a lot of people are under the impression that 50 watts are being thrown away wasted on the resistor so you're only getting half the energy and you're wasting the other half however let's let's just check the math on that all right we've got our battery here now let's make the numbers really simple so this is easy to do let's make this a 10 volt battery and over here we've got a motor that's 100 watts so you connect it direct there will be 10 amps going through here because 10 volts times 10 amps equals 100 watts which makes the resistance on this motor one ohm and that one ohm is going to make the math really easy for this and the reason the way you know this is one ohm is because let's see voltage equals current times resistance so the resistance equals let's throw that down there equals voltage over current so the voltage 10 divided by 10 equals one so the resistance on this motor is one so let's say we want to run the motor at not 50 watts our battery is still 10 volts now somehow we have to figure out how to slow down the electricity so only half as much is going in here now let's connect our one wire that's going to be the same and this wire we're going to throw a resistor in here that's going to slow down the electricity and it slows down the electricity by throwing away part of the voltage and to get 50 watts we know the voltage and the current is going to be the same because the current is one i mean the resistance is one so i'm not going to be able to get exact but like seven times seven equals 49 that's close enough to 50 so let's go with seven volts seven amps okay so we need seven amps running through this whole circuit and we want seven volts to be hitting the motor that means we have to waste three volts over here so we make this resistor three sevenths of what this resistance is so since this is one this ends up being three sevenths of an element which is not important at the moment but whatever okay so how much energy is actually being wasted by this resistor well let's see how much oh wait we know 50 is going into the motor right let's see how much is coming out of the battery we know that the voltage is still 10 10 volts and the amperage is seven times seven amps equals 70 watts so only 70 watts are coming out of the motor and uh 50 are making it to the motor that means we're wasting 20 watts we're not wasting 50 watts we're only wasting 20 lines of being like 21 or whatever but this is just rough numbers to give a give you a rough idea so technically this would be 49 watts and you'd be wasting 21 from right uh let's let's do another one so this is a lot better than than wasting 50 watts all right let's do another one here uh let's say we've got our 10 volt battery still and we still got our 100 watt motor that we want to run at 80 watts okay i'm picking 80 because nine times nine equals 81 which is close enough so we're just going to call that heat so technically this is 81 whatever so we connect that and then we connect this through a resistor that's going to waste one volt so that nine volts make it to the motor nine volts um since the resistance on this motor is still one nine volts is going to have nine amps going through and so 10 volts oh let's just check what's coming out of the battery 10 volts times nine amps is 90 watts coming out of the battery and 80 well technically 81 are making it to the motor so we're not wasting 20 all right let me just make this actually 81 okay we're not wasting 19 we're wasting nine so so we're wasting nine nine watts to get the 80 watt speed control so uh yeah you're not actually when you when you use a resistive speed control to reduce your 100 watts to these others you're not actually wasting 50 50 watts to get down to 50 watts you're only wasting 20 21 to get to 49 whatever and you know to get down to 80 you're not wasting 20 you're only wasting nine okay so there is another reason i really like this speed resist this resistive speed control actually two other reasons one i i kind of already mentioned that it's this costs ten dollars and it replaces like a six hundred dollar thing it's also super simple and uh here's the thing it replaces this complicated piece of electronic stuff and it's got like a solenoid you have to have with it and it's just all this extra crap you have to have it's got a that doesn't matter this is like a pretty expensive speed control so it's expensive it's uh you know hard to repair if it if it breaks like basically can't repair okay so that's this that's the second reason i like this resistive thing the third reason has to do with overall efficiency now this bit of reasoning is a vehicle specific thing this is the boat that i'm using it with and this boat only goes like 10 miles an hour top speed so almost always i'm going to be driving full speed so the only the only two circumstances i can really think that i'll use the slower speed controls or the slower speeds is when i'm starting the motor so instead of just jamming it into full speed i'll go uh first speed second speed go full speed so it's like a second right the other time is maybe if i'm parking at a dock and i need to come in slow so for a few seconds i'll run the motor slow other than that if i'm driving i'm just going full speed so like 99 percent of the time i'll be driving full speed now this fancy speed control thing is a very nice speed controller it works great and everything it boasts something like 98 percent efficiency or or something i don't remember what the efficiency is but it's it's pretty high high efficiency that means if i want to run the motor at 50 watts i'm only going to be wasting a couple watts not 20 right so the the lower speeds on the other speed controller are definitely more efficient however if i'm running full speed that other speed controller is still going to be using some energy it's going to be wasting some energy however with with the resistive speed control i just bypass the resistor completely connect direct this is more efficient than the fancy six hundred dollar super electronic mega speed control and if i'm going to be running full speed 99 percent of the time the resistive speed control is going to be more efficient overall it's going to be more efficient more robust cheaper everything about it is great and you know after i start using it i may eat my words but on paper it's all looking great and the funny thing is i originally wanted to do this because it was cheap and simple but then once i started doing the math on it i realized how good this actually is it is really really good particularly if you're driving full speed most of the time and with any luck three months from now i will not be making a video saying oh i was wrong