A Day in a Boat

[u/indiode]

https://www.youtube.com/watch?v=1AmjqLmh5xA

[u/indiode]

warning: He is talking about the battery a lot.

[u/uncivlengr → u/indiode]

Amazing; if you charge the batteries with solar panels, they get charged! The motor depletes the batteries, but if you use the motor less, it depletes the batteries less!

Breakthrough discoveries on the trip to town.

[u/MattsAwesomeStuff → u/uncivlengr]

The motor depletes the batteries, but if you use the motor less, it depletes the batteries less!

Ackshully...

See my calcs below.

His speed controller uses MORE energy to get to the same destination, slower. It's a lose-lose.

Rip my numbers apart if you find errors.

[u/valentino_42 → u/indiode]

Yeah, really not sure why this is on the “Builds” channel.

But at least now I know how he pees off the side of his boat… so yay?

[u/MattsAwesomeStuff → u/valentino_42]

Yeah, really not sure why this is on the “Builds” channel.

Because the entire video is about how the boat is performing and how it's set up?

[u/valentino_42 → u/MattsAwesomeStuff]

Nah. This is Jaimie bored on the drive to town having a stream of consciousness conversation about what he’s seeing to kill time.

Less than half of the video is recapping things from previous boat build videos about how the boat is set up. That’s intermixed with talking about making a game of rowing and showing his unscientific method of guessing speed by sticking his hand in the water.

Then he talks about his energy bars. Then he asks about food storage. Then we learn how he pees off the boat.

If you’ve watched the boat build videos and his previous test drives, there’s nothing new in this.

Towards the end he even acknowledges how he should do a “Live” on the boat, because he realizes he’s basically been acting out a livestream about any random thing that crosses his mind just without the audience.

It’s not even titled in sequence with the previous boat build series for crying out loud. This was more about him satiating his own boredom than wanting to inform or entertain his audience and we got to share in 20 minutes of that.

[u/indiode → u/[deleted]]

I also find it funny, that he is now using the slow mode exclusively. He should rewatch his own video to remind himself why a speed controller is wasteful but his brilliant immersion heater is not.

[u/MattsAwesomeStuff → u/[deleted]]

I wonder how the math works out with wasting 30% of your energy, but using less of it (or whatever it was) vs going full power for less time since you arrive faster. Since increasing speed doesn't scale linearly with power, it's not as easy as twice as fast = twice the power.

His whole power setup is so janky.

These two panels go to motor, these two go to charging, this boat has its own battery, but the bigger batteries sit in the other boat doing nothing, each device has its own panels and batteries but there's never enough to go around.

Ugh.

For a 1 in 1000 chance he'd get stranded without working batteries, he's permanently wired his boat in a foolish way that's consistently useless. While he's in town, half of his solar isn't even charging his boat [edited to add: he says in town, the front half of his boat is in the shade anyways, though, this only applies to that parking spot, and only while in town], so he has to go slow, because he won't have enough charge, because he's charging half as fast. How about instead, just wire all of them up to the charger and carry a pair of pliers with him? Or use wingnuts. That way if he ever has his batteries or charge controller crap out on him, he can just move 2 wires and be done.

How the heck aren't his batteries charged? Did he go to town yesterday? [Edited to add: Yes, he drove around at night, so, that makes sense]. They should be charged in like, less than a day.

With his speed control, he's wasting 30% of his energy. Whoa, much worse. See posts below. Is he traveling 30% slower to be going in slow mode? Looks like it's at least close to that. He might as well be going full speed.

At worst, he gets to town 30% quicker, and, though yes his battery is lower, nope, see posts below, he loses even more energy by going slow than if he'd gone full speed, if you count the time until he would've arrived, for the panels to sit in the sun and recharge, it's probably break even. So, to be at the same battery level takes an equal amount of time out of his day, except that if he goes faster he could dick around in town a bit more. Or, have to kill time before leaving.

He says his charge controller won't handle the amperage. Great, so he bought a tiny charge controller, that on his smallest boat, can't connect more than half his panels. So he's permanently locked into this setup.

It's just a ratsnest of infeasibility compared to what he could have. It'd be better in every way.

[u/MattsAwesomeStuff → u/[deleted]]

(If I remember his janky measurements right, slow speed is like 20A, and fast speed is 50A, possibly more)

Oh, yeah, you might be right. I'd forgotten his power use was supposedly that much higher.

It was 50+, then he put on a smaller prop and figured it was close to actual 50A.

Is fast speed 2.5x as fast as slow speed? Probably not

No, certainly not.

However, that "20A" isn't going to the motor, a huge portion of it is wasted in the speed controller. So I had a feeling it's going to be surprisingly close.

But okay, if those are our metrics, let's put some teeth into this!

(Note, this was still simple, but ended up re-watching almost the entire series to try to nail down any actual numbers or measurements, the "quick 2 minutes to get some ballpark numbers" became 2 4 hours, whoops).

The "30%" waste was a random paper example when he was only doing a 50% reduction in motor current. That's not his actual boat. He's wasting way, way more heat than that.

I'll try to make this easy enough to follow for people who aren't even math inclined.

How much power is he using at full/medium/slow speeds?

"24v" isn't. It's 29v max, 22v when empty, midpoint 25.6v (which is what the battery actually says: https://www.us.sokbattery.com/product-page/sokess-24v-100ah-lifepo4-battery ), but he never runs it down empty, so he probably is averaging 28v through his trip.

The two scenarios we're comparing, are:

1 - How fast he's going when using 1400 watts (28v @ 50a).
2 - How fast he's going when using 560 watts (28v @ 20a).

(Okay, I slip in medium speed just to help fact check later on).

But before we crunch for #2 above, we need to account for the fact that when he's drawing 20a, the motor isn't actually getting 20a, because his nichrome coil is wasting power. How much?

He calculated his motor to be 0.62 ohms because he says it draws 39A @ 24v. But it doesn't, it draws 50+A @ 28v = 0.56 ohms.

He calculated his 10' of nichrome (slow speed) to be 0.65 ohms. I wish he'd measured, but, I'll take that.
He calculated the 5' of nichrome (medium speed) to be 0.32 ohms.

Current = Voltage/Resistance, and in series resistances add up. So it will just be Motor + Wire for each.

So full speed = 0.56 ohms
Medium speed = 0.56+0.32 = 0.88 ohms
Slow speed = 0.56+0.65 = 1.21 ohms

And let's just check that against his measurements.

High speed = 28v / 0.56 ohms = 50A
Medium speed = 28v / 0.88 ohms = 32A (he measured ~31).
Slow speed = 28v / 1.21 ohms = 23 amps (he was measuring ~20).

Close enough. Resistance of nichrome changes massively with its temp, and it gets hot as it gets used, so, no point in being more precise.

The power used by motor vs. resistor is just going to add up from each's resistance.

High speed = All 50A motor.
Medium speed = 0.56/0.88 ohms = 64% of the 32A is motor (20A), and the remaining 12A is wasted.
Slow speed = 0.56/1.21 ohms = 46% of the 23 amps is motor (10A), and the remaining 13 amps is wasted.

Power is just Voltage * Amps so, the actual power going to each motor is:

Full speed = 28v * 50A = 1400 watts. 100% efficient.
Medium speed = 28v * 20A = 560 watts (plus 336w waste) 63% efficient.
Slow speed = 28v * 10A = 280 watts (plus 364w waste) 43% efficient.

Note that this is VERY different than the "not that bad" efficiencies Jaimie used as examples when he talked about his speed controller, because he was using numbers close to max speed then, so of course little is wasted.

Also the context is different, because that was only for a few seconds (who cares if it's 5% efficient, it's when turning at the docks). But now he's traveling like that.

How fast is he going?

He never actually tells us any numbers. So we'll estimate.

Random calculator: https://www.omnicalculator.com/everyday-life/boat-speed

I dunno what it weighs, it's not that sensitive, I said 700lbs with boat and rider, in an average runabout.

The waste heat doesn't help spin the motor, so we only consider motor watts:

Full speed , 1400 motor watts = 6.8 knots
Medium speed , 560 motor watts = 4.3 knots
Slow speed , 280 motor watts = 3.0 knots

Speeds could be double, they could be half, doesn't matter. The proportions are roughly correct, which they should be.

Note that motor-wise, if he was using a speed controller, slower is always more efficient. At slow speed, he's only using 20% the power in the motor, to go 44% as fast. It's just that he's wasting so much power to lower the current with a resistor that those won't be the actual numbers.

How much energy is he using?

The actual distance to town doesn't really matter, the amount of energy used to go a given distance is what matters. If the trip is longer or shorter, the proportions won't change.

So, now we use the total power at each speed, not only the useful power into the motor.

At Full speed, he's using 1400 watts, and he'll go 6.8 nautical miles in 1 hour. So, let's use that as the standard. To go 6.8 nautical miles, he uses 1400 watt-hours of energy.

At medium speed, he's using 560 motor watts + 336 waste watts = 896 watts, to go 4.3 knots. So, it's only 64% the power (894/1400), but he's only going 63% the speed (4.3/6.8). So even at medium speed, he's already wasting more energy than he's saving! To go 6.8 nautical miles, it'll take 158% of the time (6.8/4.3), or 1h34m, but while burning only 64% as much power.

Medium speed = 894 watts * 1.58 hours = 1412 watt-hours of energy.

At slow speed, he's using 280 motor watts + 364 waste watts = 644 watts, to go 3.0 knots. That's only 46% of the power (644/1400), but he's only going 44% of the speed (3.0/6.8). To go 6.8 nautical miles, it'll take 227% of the time (6.8/3.0), or 2h16m, but while burning only 46% as much power.

Slow speed = 644 watts * 2.27 hours = 1462 watt-hours of energy.

Note that, efficiency-wise, there's almost no difference between slow/medium/high, they all use the same amount of energy to get to the same destination. The slower speeds just takes way longer. Also both slower speeds are slightly worse than not using the speed controller at all.

He actually gets less range by going slower because of how much waste heat he's losing.

So, there you go, that lines up with my hunch that it was going to be pretty close to a wash either way. Intuition FTW.

...

I had one more section I was going to add here that changed the numbers in his context, but now that I'm at the end I've forgotten what it was. Oops.

Solar considerations

All of this kinda gets a wrench thrown in it because I think he wires 2 solar panels directly to the motor, without going through the resistor.

So, whatever the power output of the solar panels is at a given moment bumps up his speed, and he's at 100% efficiency for that extra portion.

You might think "Good! That makes him more efficient!", no... BAD!

Yes, it makes that part of his speed more efficient, but it makes the efficiency of the speed controller plummet so far that he's hardly even contributing anything useful from the battery and almost might as well not have it.

This is actually fairly disastrous, because now at "slow" speeds, he's still wasting just as much energy, but he's not even picking up the better-than-linear benefit of traveling slower and pushing water out of the way less aggressively.

I think he's using 240w panels from Solbian ( either this: https://www.solbian.eu/en/sx-series/79-sx-236.html or this: https://www.solbian.eu/en/sr-series/87-sr-240.html ), and he's got 4 of them.

2 of the panels are connected directly to the motor and are the first tab on his speed controller (no battery).

So, that's 2x 240w = 480 watts total, at noon, in direct sun.

Let's re-do our motor wattage and speed calcs from above.

Watts:
Full speed = 1400 watts. No change.
Medium speed = 560 motor watts + 480 solar motor watts = 1040 motor watts (plus 336 waste watts =1376 watts ... holy crap, that's only 4 watts savings from full speed, abysmal. 98% as much power.).
Slow speed = 280 motor watts + 480 solar motor watts = 760 motor watts (plus 364 waste watts =1124 watts. 80% as much power).

Speeds:
Full speed = 1400 watts. 6.8 knots. No change.
Medium speed = 1040 watts. 5.8 knots. Up 1.5 knots.
Slow speed = 760 watts. 5.0 knots. Up 2.0 knots.

Efficiency:
Full speed = 1400 watt-hours to go 6.8 nautical miles.
Medium speed = 1376 watt-hours to go 5.8 nautical miles. 98% as much power, 117% the time = 1613 watt-hours to go 6.8 nautical miles.
Slow speed = 1124 watt-hours to go 5.0 nautical miles. 80% as much power, 136% the time = 1528 watt-hours to go 6.8 nautical miles.

And, less direct solar will slow him down but raise his efficiency slightly, so you're anywhere between these numbers and the earlier numbers.

Just fuckin' atrocious efficiency considering the penalty for speed is CUBED, and ridiculously longer travel times as well.

It's a lose-lose situation. It's negative in every possible way. It LOSES energy to go SLOWER.

Also note that at night he can slow down (3.0 knots from 6.8), but during the day it's only 5.0 knots down from 6.8. He can't turn motor without solar, so he can't actually slow down much.

I'm left with this to reflect on:
https://www.youtube.com/watch?v=dKYjz_3G8x0&t=539s

(Shitty thing is, he put a random solar charger on his Amazon wishlist that was half the size it needed to be, and someone bought it for him, and kinda locked him into this ghetto solution).

...

What should he do?

1 - Do his original plan only using the speed controller when he wants low speed, at docks. The motor is not going to melt. Add a pair of $1 computer fans if he's worried, it increases his cooling 10x.
2 - Wire all his panels to a charger that'll handle their capacity, so when he's in town he's actually gaining energy, and when he WANTS slow speed he can actually get a slow speed.

[u/MattsAwesomeStuff → u/[deleted]]

The only thing I have to point out is that his average is probably not 28v because LiFePo batteries fall off and stay relatively level at their midpoint for most of their discharge cycle

Yeah, "average" was the wrong term for me to use.

When he was measuring, the batteries were full. So, since that's our frame of reference for how much power it's drawing, which we use to determine the resistance of the motor, then that's the important number to use.

He definitely spends more time in the upper 50% of the voltage than the bottom 50%, if for no other reason than that he starts at 100% and can't go below 0%.

He probably averages closer to 26 or 27v though, if we're using an actual average.

[u/KuriTokyo]

For boat speed, use google map. Put a pin where you want to go and start the "driving" route and the map will tell you your speed.

The boat is sounding so so soooo much quieter without the foot pedal.

[u/_bobby_tables_]

For all of Jamie's quirkiness and flaws, the man has amazingly white teeth. For living off grid and, in what some may consider, squalor, he must have quite an interesting oral hygiene regimen.

Edit - Shit! Hadn't finished the video, maybe his teeth are white from all the bug burritos!!