I need your help with the project of an autonomous watercraft that sails on the water.

We will use 3 T200 pushers, 2 of which are in the back and 1 in the middle, and when we think that the weight of the vehicle can reach up to 64 kilograms, which battery can offer us 100 minutes of use?

Hi @Aliars, welcome to the forum

This depends on how you plan to use the thrusters - there’s a significant difference between sustained full throttle for 100 minutes vs sustained low throttle or occasional throttle.

As a rough indication, our lithium-ion battery is expected to run our 6-thruster BlueROV2 for ~2 hours with “normal use”, and ~4 hours with “light use”.

From the “maximums” side of things, a T200 will draw 24A at full throttle, assuming a nominal supply voltage of 16V. Our lithium-ion battery (nominally 14.8V) can handle a sustained current of 60A (so a bit under full throttle for three thrusters simultaneously), but that’s reliant on keeping it cool (see the Learn tab). A 15.6Ah battery has enough energy to supply 15.6A for 1 hour, but that same energy at 60A runs out after \frac{15.6 A\cdot hr}{60 A} = 0.26\text{ hrs} = 15.6\text{ minutes.} To run three T200s at full throttle for 100 minutes with a 16V battery would require a capacity of 1.\dot{6}\text{ hrs}\times 24A = 40A\cdot hr.

The main things to consider are:

- the maximum thrust you require

→ determines the voltage and accordingly the max current → battery discharge capacity - how hard you expect to drive the thrusters (on average) throughout your 100 minute duration

→ determines the required energy capacity

Technical information and performance across a range of voltages and commanded inputs can be found in our T200 technical details

hello Eliot

Actually, I have examined the Engine data you shared before, but what I am not sure about is that we assume that our autonomous vessel will go on the water and will not dive, we assume that it will be 60 kg at most, and these 3 T200 engines, which will be 2 m long, can carry this load easily if we use a 12V battery? And what kind of battery should we integrate a 12V or 14.8V battery in a boat with this information for 100 minutes operational time? What is your opinion? Would a 12V 60Ah lithium battery be sufficient? Also we do not always plan to go full throttle as driving, of course, it will be on the normal test track, sometimes we will flow on the water without pressing the gas at all, and sometimes we will maneuver on the pontoons.

I appreciate your answer, but these are stuck in my head.

Finally, if I cannot find a lithium battery due to the conditions and cost of the country I am in, would you recommend a 12V 60Ah dry(lead-acid) battery for this situation?

thanks for everything @EliotBR

I can’t meaningfully provide advice on how well T200s will carry a load without knowing the drag properties of it or the speed it needs to travel at. There are some rough example calculations here for using T200s to propel a diver in the water - I would assume a surface vessel should have quite a bit less drag, and 60kg is likely lighter than the assumptions made by diving companies for “the average diver”, so for both those reasons your vessel should be able to go faster (or go for longer, if driven slower) than the results determined there.

It’s also worth noting that a vessel with a sail can gets some velocity from the wind, whereas the calculations I linked to are for only the propulsion provided by the thrusters.

Assuming the energy capacity is enough for your desired combination of speed and runtime, my main concern with a lead-acid battery would be the extended discharge current capacity. You would need to make sure to get a “leisure” battery (for extended current supply) rather than a “starter” one (only for brief bursts of current), and you would also need to make sure the battery can supply the high levels of current needed to run thrusters for the time-periods you’re expecting.