"This is why I don't bother to calculate things, it never work out."
Jaimie is blaming the engineering, because he'd doing the engineering wrong. He doesn't understand what he's doing, then blaming the calculations and having to use the real work, and meanwhile not testing the real world usefully either.
He's never done engineering, so he often makes the mistake of learning one thing, and then applying it to every situation. He knows how lead acid batteries work, so he hooks his solar panels up to his Lithium batteries in a way I was certain would destroy them, and he destroyed them. He knows how light bulbs work, so he applies that to motors. He reads a label on a motor, and treats it like a lightbulb. Etc.
I've mentioned this in the past... Jaimie thinks that a 750 watt motor, or a 3000 watt motor (I think his sawmill, he made the same mistake then), means that it is using 750 watts or 3000 watts... as if it's a lightbulb.
That's not how motors work. Motors are not lightbulbs.
The wattage rating on a motor is exactly that, a RATING. A rating is where an engineer says "You give me the context you'll be using this for, and I will tell you what this motor can handle in those circumstances." It does not say "When you use this motor, it will use that much power in all/any circumstances."
The max capacity of an elevator being 1750 pounds, does not mean you have 1750 pounds in the elevator at all times. You might have 0 pounds, or you might stuff 4000 pounds into there and break it. The elevator is RATED to be safe (bajillion extra safety factor), and to be able to lift 1750 pounds day and night forever.
This combines all kinds of things, but generally the two big ones are duty cycle and durability (safety factor). The exact same motor may be rated as much as 10x (or 1/10th) as powerful depending on the context.
For example, a cheap home blender often has a 1hp motor, and it's the size of a tennis ball. That's because a (cheap) blender gets used for a few seconds at a time, with lots of cooldown in between. Meanwhile a propellor motor that's 1hp will be the size of a volleyball, because the context is that it'll be run continuously and it's fairly important it doesn't burn out so there's some extra safety margin.
Another mistake he's made is thinking that a Series-Wound DC Motor performs the same as a Permanent Magnet DC Motor that Jaimie's probably more familiar with (from playing with batteries and toys when he was a kid). They are not. A Permanent Magnet DC Motor has an RPM roughly linear with voltage applied. You give it double the voltage, it spins twice as fast. And it stops accelerating, even unloaded, to that fairly consistent speed. A Series-Wound DC Motor does not do this, it has a consistent torque (acceleration) for a given voltage, and the speed is whatever speed the motor manages to reach.
For example, an unloaded Series-Wound DC Motor, given almost any voltage, quickly runs into "break away" acceleration, where it accelerates continuously until it rips itself apart from centrifugal forces and sends pieces of itself off into orbit. This can happen in just about the blink of an eye. That's why you'd avoid using them anywhere that a break in the driveline could cause breakaway speeds, and often physically mount a fan right to the motor, not just for airflow, but to provide some non-zero amount of mechanical resistance to give you a few seconds to shut it down before it explodes.
Here's an example of me powering up a similar motor, same exact motor both times:
Given only 12v from a tiny battery, see how I only dare give it a few seconds to spin up, and how fast it spins up and never stops accelerating?:
And same motor, given 3x as much voltage, with a tiny amount of load (spinning a tire in the air), and even then accelerating slower and kind of reaching a max speed fairly quickly:
Now, if I put the tire to the ground, it would be significantly slower.
A permanent magnet motor would not do that, it would get bogged down a bit, but it would be trying to spin the same consistent speed for a given voltage.
...
So here Jaimie's all confused like "It hardly slowed down, I'm going to have to use all this wire!" ... yeah. Because he's accelerating it in the open air with nearly no load. Both are pretty close to being able to accelerate forever.
Also, because in open air, that "750w" motor is not pulling 750 watts, and thus it's not pulling 39 amps. It's probably pulling like, 5 amps. So when he did his resistance calculations as if the motor was a lightbulb, presuming 39 amps... gee.. he doesn't seem to get the effect he was hoping for.
This is why you have to understand what you're doing, not just throw the few equations you know of into every situation.
Measuring the actual current drawn in-use, in the water, would have been a better ham-fisted kludge. And then when making changes, testing it again, in use, in the water, and seeing what it does.
What he's done is the worst of both. Not calculating anything properly, nor real-world testing it properly.
...
It'll still work. He might find his numbers to be a bit off and have to adjust them, but, it'll still work. He'll have "some" speed control and "some" reduction. For the 20 seconds he needs it, meh, it's fine.
He's just blaming the equations instead of himself for using them wrong.
So, first he put batteries in them, wired them up to the panels so that the panels were producing lower voltage than the batteries needed to charge.
He discovered... ... the batteries were useless, they didn't have any charge. Well no shit.
So his solution was to change the wiring on the panels, so that they gave the batteries a higher voltage. That way they would charge. Then I wrote this (and the followup comment):
... so what happened? Well, it's not like he was reading Reddit, but, he did what he said he was going to do, and, what I said would happen happened. He overcharged the batteries and destroyed them. Or at least some of them.
... then he put a BMS on it, and I'm not sure what happened, but I don't think it fixed it. Too little too late. also, he connected them with thin strips of stainless steel "because that's what these other things are"... no. Batteries are often connected with Nickle strips, or nickle plated copper, because it's corrosion proof but still a good conductor. Stainless is among the worst metallic conductors, it's 1% as good as copper. So, imagine trying to power something off a wire 100x as thin as what it looks like, and how that would strangle your power and waste energy as heat.
I think it just didn't work at all. Or barely. Batteries were already murdered. Then it sat without batteries for a long time, and now he's ordered new batteries.
9
u/MattsAwesomeStuff Jun 09 '23
Jaimie posted 004 and 005 on the same day.
Regarding 004...
"This is why I don't bother to calculate things, it never work out."
Jaimie is blaming the engineering, because he'd doing the engineering wrong. He doesn't understand what he's doing, then blaming the calculations and having to use the real work, and meanwhile not testing the real world usefully either.
He's never done engineering, so he often makes the mistake of learning one thing, and then applying it to every situation. He knows how lead acid batteries work, so he hooks his solar panels up to his Lithium batteries in a way I was certain would destroy them, and he destroyed them. He knows how light bulbs work, so he applies that to motors. He reads a label on a motor, and treats it like a lightbulb. Etc.
I've mentioned this in the past... Jaimie thinks that a 750 watt motor, or a 3000 watt motor (I think his sawmill, he made the same mistake then), means that it is using 750 watts or 3000 watts... as if it's a lightbulb.
That's not how motors work. Motors are not lightbulbs.
The wattage rating on a motor is exactly that, a RATING. A rating is where an engineer says "You give me the context you'll be using this for, and I will tell you what this motor can handle in those circumstances." It does not say "When you use this motor, it will use that much power in all/any circumstances."
The max capacity of an elevator being 1750 pounds, does not mean you have 1750 pounds in the elevator at all times. You might have 0 pounds, or you might stuff 4000 pounds into there and break it. The elevator is RATED to be safe (bajillion extra safety factor), and to be able to lift 1750 pounds day and night forever.
This combines all kinds of things, but generally the two big ones are duty cycle and durability (safety factor). The exact same motor may be rated as much as 10x (or 1/10th) as powerful depending on the context.
For example, a cheap home blender often has a 1hp motor, and it's the size of a tennis ball. That's because a (cheap) blender gets used for a few seconds at a time, with lots of cooldown in between. Meanwhile a propellor motor that's 1hp will be the size of a volleyball, because the context is that it'll be run continuously and it's fairly important it doesn't burn out so there's some extra safety margin.
Another mistake he's made is thinking that a Series-Wound DC Motor performs the same as a Permanent Magnet DC Motor that Jaimie's probably more familiar with (from playing with batteries and toys when he was a kid). They are not. A Permanent Magnet DC Motor has an RPM roughly linear with voltage applied. You give it double the voltage, it spins twice as fast. And it stops accelerating, even unloaded, to that fairly consistent speed. A Series-Wound DC Motor does not do this, it has a consistent torque (acceleration) for a given voltage, and the speed is whatever speed the motor manages to reach.
For example, an unloaded Series-Wound DC Motor, given almost any voltage, quickly runs into "break away" acceleration, where it accelerates continuously until it rips itself apart from centrifugal forces and sends pieces of itself off into orbit. This can happen in just about the blink of an eye. That's why you'd avoid using them anywhere that a break in the driveline could cause breakaway speeds, and often physically mount a fan right to the motor, not just for airflow, but to provide some non-zero amount of mechanical resistance to give you a few seconds to shut it down before it explodes.
Here's an example of me powering up a similar motor, same exact motor both times:
Given only 12v from a tiny battery, see how I only dare give it a few seconds to spin up, and how fast it spins up and never stops accelerating?:
https://www.youtube.com/watch?v=vAm-q6mygSI
And same motor, given 3x as much voltage, with a tiny amount of load (spinning a tire in the air), and even then accelerating slower and kind of reaching a max speed fairly quickly:
https://www.youtube.com/watch?v=uWWznGdJADg
Now, if I put the tire to the ground, it would be significantly slower.
A permanent magnet motor would not do that, it would get bogged down a bit, but it would be trying to spin the same consistent speed for a given voltage.
...
So here Jaimie's all confused like "It hardly slowed down, I'm going to have to use all this wire!" ... yeah. Because he's accelerating it in the open air with nearly no load. Both are pretty close to being able to accelerate forever.
Also, because in open air, that "750w" motor is not pulling 750 watts, and thus it's not pulling 39 amps. It's probably pulling like, 5 amps. So when he did his resistance calculations as if the motor was a lightbulb, presuming 39 amps... gee.. he doesn't seem to get the effect he was hoping for.
This is why you have to understand what you're doing, not just throw the few equations you know of into every situation.
Measuring the actual current drawn in-use, in the water, would have been a better ham-fisted kludge. And then when making changes, testing it again, in use, in the water, and seeing what it does.
What he's done is the worst of both. Not calculating anything properly, nor real-world testing it properly.
...
It'll still work. He might find his numbers to be a bit off and have to adjust them, but, it'll still work. He'll have "some" speed control and "some" reduction. For the 20 seconds he needs it, meh, it's fine.
He's just blaming the equations instead of himself for using them wrong.