Need Help for a Hydrogen-Powered electric boat

[Modphase]

Hello everyone. My name is Matt. I'm a senior mechanical engineering student at California State University, Fullerton. Me and 8 other team members are working on a project to design a hydrogen-powered RC Boat. Going into this project, none of us knew anything about building RC boats. After some searching, we were very fortunate to come into contact with Steve Lopez of Insaneboats.com. He's local, so we were able to meet up with him and he gave us some very useful pointers on how to go about constructing our project, and that's when he referred us to this forum. It's great to meet you all.

Our project consists of an otherwise fairly standard electric motor-driven RC boat. The big difference is that the battery and some of the other components are hooked up to a hydrogen fuel cell that takes hydrogen stored in small capsules and converts it to electricity. The specific fuel cell our team purchased is called the H-Cell 2.0 from Horizon Educational: https://www.horizoneducational.com/h...cell-2-0/p1233 . It has a downloadable user manual. In the manual it gives a recommended parts list for an RC car. Unfortunately, even to purchase these parts to test it would be impossible because almost all of them are discontinued:
Screenshot 2024-02-04 190833.jpg

I'm wondering, based on the given parts list, what some alternatives could be that would be specific to boating. I noticed that it also specified a 7.4V battery. I want to make sure before we go out and purchase, because I don't want us to use something wrong and fry this expensive piece of equipment. Also, here are what the connectors look like:
20240202_170827.jpg 20240202_170916.jpg20240202_170932.jpg

And like I said, the use manual is in the link I sent up above. Any help would be greatly appreciated. Steve is very enthusiastic about our project, so I hope some of ya'll share his sentiment.

[tbonemcniel]

Looking over it briefly. First off, just like full size equipment, the power requirements of a boat are much more than a car. Much more.

So the claims of that fuel cell is that it will run the RC car for 4x longer than on battery alone. So if that claim is made based on the 2800 mAh 2S battery, then best case that fuel cell can put out 80 watt hours of power total (battery holding about 20 watt hours). If we figure the car will run for 10 minutes on it's own, than those 80 watt hours must be generated within 40 minutes, and the fuel cell can output at a rate of 120 watts, or 16.2 amps at 7.4v nominal. That's the claim anyway, that I'm trying to back out of the documentation since it doesn't actually say how much power it can generate. Seems high to me. But let's go with it for now. 120 watts. That's not a lot of power. My racing boats start at like 3000 watts. So things need to be waayy slower. And here's the thing, it looks like to me that this fuel cell control box wires in-line between the battery and the ESC, such that all current must pass through the fuel cell control box with its small Tamiya connectors. That's a real power limiter right there. Those connectors are only good for 8-10 amps.

So small and low power demands. But still needs to be big enough to house the fuel cell.

I'm thinking, a small cat, with a small outboard (will turn much better at very low speeds than a racing style inboard and rudder) as well as take up less space inside the hull, leaving room for the fuel cell. But, I still think this combo will pull way more amps than those Tamiya connectors will handle. You'd either want to wire that fuel cell controller in parallel so the majority of the current could bypass the controller, or get a lower kv rated motor that would bolt up to the outboard unit.

https://www.offshoreelectrics.com/proddetail.php?prod=df-Cat-29

https://www.offshoreelectrics.com/proddetail.php?prod=ose-80980

https://www.offshoreelectrics.com/proddetail.php?prod=ker-seaking-30a-v3

Just my thoughts.

[lohring]

It's very hard to find the data on the fuel cell. As far as I can tell, this fuel cell is rated at 30 watts. That's 8.4 volts with 6.4 amps. Most fast RC boats run power in the kilowatt range with currents over 100 amps. Even the off the shelf boats draw over 40 amps. Cars have a lot less resistance and a lot lower current draw. Even the least expensive lithium polymer battery can produce currents 10 times its rated capacity without breaking a sweat. We can run 40 times the rated capacity when racing.

Propeller diameter and rpm are critical in determining current draw. A guide to get you started is at https://www.radiocontrolinfo.com/rci-fe-boat-calc/ However, it assumes lithium polymer battery power. I think that battery type is a lot more powerful than your fuel cell.

Lohring Miller

[tbonemcniel]

It's very hard to find the data on the fuel cell. As far as I can tell, this fuel cell is rated at 30 watts. That's 8.4 volts with 6.4 amps. Most fast RC boats run power in the kilowatt range with currents over 100 amps. Even the off the shelf boats draw over 40 amps. Cars have a lot less resistance and a lot lower current draw. Even the least expensive lithium polymer battery can produce currents 10 times its rated capacity without breaking a sweat. We can run 40 times the rated capacity when racing.

Propeller diameter and rpm are critical in determining current draw. A guide to get you started is at https://www.radiocontrolinfo.com/rci-fe-boat-calc/ However, it assumes lithium polymer battery power. I think that battery type is a lot more powerful than your fuel cell.

Lohring Miller

I forgot about that tool. I tried it several years ago. Well, punching up as close as I can to what I recommended, I get 17A at 24.8 mph. I would wire the fuel cell controller in parallel between the battery and ESC, so that all the current isn't forced through the Tamiya connectors, but they can still read and supply some charge current to the battery.

[NativePaul]

While it takes a lot less energy to keep a boat on the plane than it does to get it up on the plane, I don't beleive that 30W is enough to keep any boat capable of carrying that amount of ballast on the plane so you should be looking at displacement hulls, not planing hulls.
If you are interested in speed at all longer and thinner hulls are more efficient for displacement boats so look at frigate warships, or a canoes.

I don't know where you will be using it, but given the high cost of the setup if it will be open or flowing water, I'd advise using a name brand radio with an RF protocol that covers all of the band and has great interference suppression like Futaba or Jetti, if its near the university buildings it may even be worth staying away from the 2.4ghz band to avoid the pollution from thousands of wifi devices. Or maybe you have a rowing lake at university, and a runaway doesn't matter at all in which case something like a flysky gt3 may be worth a punt as it is massively cheaper and they do well if the environment isn't too noisy.

The Futaba BLS551 servo is good but totally unnecessary expense for your project, id go to your local hobby shop and but the cheapest standard size digital servo they have from a name brand like Hitec, Futaba, Multiplex, Savox or Spektrum, if you don't mind spending a little more, an upgrade to a waterproof servo like the Hitec D646WP would offer piece of mind in case of any disasters, but with 2K of electrics inside it, a servo will be the least of your worries, and waterproofing the whole boat would be my priority over the servo.

For the ESC if you use a surface radio I'd go with a car ESC for forward and reverse which not all boat ESCs have, the Tamiya 3.5t brushless motor is capable of pulling a fair amount of current at very high revs though, and for a boat and especially a displacement boat you will want a lot less RPM than that,
I'm not too familiar with displacement boats and props so surely others will offer better advice here, but I'd guess you want 2000KV or lower, maybe a Hobbywing Axe 1400kv combo.
It may be worth noting that while the suggested components list you showed list a brushless motor and ESC, all the photos in the manual are of a brushed motor and ESC, not the ones listed.

The battery suggestion seems reasonable, the photo in the manual is of a 2s hardcase LiPo pack which ties in with the 7.4v suggestion.

The 2 pin connectors you show are Tamiya ones, you may be able to find some 2s batterys with these on as they were the standard many years ago and i would guess that some still use them, but they are not very good and the industry has thankfully moved away from them, so buying adapters or replacing them with your choice of connectors may be easier. Deans plugs, and 4mm gold bullets are common for RC car batteries these days, the big multipin one looks like a similar format to Tamiya Mini connectors but with way more pins, its not something I've seen before, but as it only has 30W going through it I expect that its fine.

Chassis, tyres, tube and hubcaps are not applicable to boats

[Modphase]

I appreciate everyone's help so far. I want to specify that we're not really looking for speed with this thing. We just want it to run. My big concern is purchasing the wrong parts and then frying this $2,000 piece of equipment that we have. In addition, it seems like the Tamiya connectors are definitely a bottleneck. Does there happen to be any RC boat companies that happen to use Tamiya connectors? Or some kind of adapter wires?

[NativePaul]

I think most model shops and airsoft shops will sell adapter wires, but that doesn't remove the bottleneck, if you don't have anyone in the group with soldering skills take it into your LHS and the will usually change connectors for a small fee, or often for free if you buy the battery and ESC from them

[Modphase]

Got it. Appreciate the information.

[Modphase]

I'm compiling an order form to be sent to the school, with the following parts, just to hook them up to the fuel cell to see if it works. Hopefully these will be suitable replacements for the discontinued items.

Battery: https://www.amazon.com/Zeee-3600mAh-...33&sr=8-3&th=1

Motor: https://www.amazon.com/Tamiya-RS540-...s%2C151&sr=1-2

Speed controller: https://www.amazon.com/TAMIYA-300045...0-4513d670b6bc

Radio: https://www.amazon.com/Futaba-3PRKA-...05EFZBB4&psc=1

Servo: https://www.amazon.com/Torque-Motors...42&sr=8-1&th=1

[tbonemcniel]

I appreciate everyone's help so far. I want to specify that we're not really looking for speed with this thing. We just want it to run. My big concern is purchasing the wrong parts and then frying this $2,000 piece of equipment that we have. In addition, it seems like the Tamiya connectors are definitely a bottleneck. Does there happen to be any RC boat companies that happen to use Tamiya connectors? Or some kind of adapter wires?

My concern, is that the control box for the fuel cell that has the two Tamiya connectors on it, is clearly meant for all the current between the battery and the ESC to pass through it. I'm concerned with it's ability to handle the amps drawn by the motor. But I don't see why it would NEED the current to pass through it, it just needs to be able to add some current to the ESC's demand from the battery. Hence why I'm thinking the fuel cell control box should just be added in parallel to our normal battery to ESC connection. Like connect the battery to ESC using an XT60, then parallel the wires off the fuel cell control box into the that circuit. That way, if they ESC demands 40A from the battery while accelerating, the current SHOULD go through the path of least resistance from the battery to the ESC (the XT60) and not through the fuel cell control box with it's little Tamiya connectors and unknown internal configuration.