Electric RIB overpowered?

[alan craig]

This might be best in the Powerboat forum, not sure.
I found a Youtube video of an EVOY electric RIB which appears to be in a Scandinavian country judging by the delightful scenery, and took a picture showing power consumption at 42Kt of 380kW which seems extraordinarily high. The boat is taking about six passengers on a high speed pleasure trip and the RIB seems to be about 30ft. long. I know nothing about big planing boats so my question is, does this power level seem normal? Also the remaining duration and battery capacity shown on the display don't seem to correlate. If you search youtube "evoy electric" would probably find it.

 

[bajansailor]

I had not heard about Evoy O/B motors - thank you for the heads up about them.

I could not find your specific video, but I found this one with a large RIB - is this the RIB that you saw?

Here is another interesting video - not as fast as the one mentioned in your original post above, but still pretty impressive.

 

[comfisherman]

We have a few locally that are about 30 ft one's powered by twin 300 horsepower Suzuki is the other by twin 325 horsepower Cummins. 42kn is near the max operating speed, doing the quick brain estimation of hp to kw those numbers sound about right.

 

[fallguy]

It seems high for consumption, but 520 hp consumption is not what is being delivered at the prop iirc. How much less is unknown.

The issue is power of 380.4kw can only run for 78.7/380.4 or for 0.2 hours.

At 0.2 hours, 42.1kts is 8.4 kts; not sure why the estimated range is a bit more.

Conversation starter for wiser electrical fellows, but things seem correct, albeit ugly.

 

[BlueBell]

I've many hours on commercial and rescue RIB's.
I would expect more like 52-knots from ~500HP on a 30 ft even with six people on board.

 

[fallguy]

I've many hours on commercial and rescue RIB's.
I would expect more like 52-knots from ~500HP on a 30 ft even with six people on board.

Do you think yield at the prop is that much bb? Or too speculative?

 

[BlueBell]

Do you think yield at the prop is that much bb? Or too speculative?

Too speculative for me.
There are a lot of unknown variables here.
Seeing the video might help...

 

[alan craig]

Found the original video, boat appears to be same as one in the middle of video linked by bajansailor:

So far concensus is that power is either fairly normal or too high. And the company is in Norway, where they have ample hydroelectric power.

 

[BlueBell]

~45 knots at ~371 kw (~490HP) is the initial image on the video.
Taking losses into account this doesn't seem unreasonable to me.
I'd be more interested to see what it consumes at 30 knots.

 

[SolGato]

Regarding the range prediction, that’s exactly what it is and it takes a number of variables into account and often depends on how the battery monitor software was programmed and if it learns over time or has to be re-synced manually.

For example new batteries can exceed their rated capacity when first installed later settling into their factory ratings, and then the discharge rate can also affect performance and usable capacity.

But in this case, it looks like it might simply be a reflection of the measured average kW consumed per mile at 7.4kW which would predict a remaining range of closer to the 10.2 miles displayed based on 74% capacity remaining and the consumption behavior logged up until the point where we see the dashboard.

What’s really impressive is the discharge rate as it looks as though the capacity of the battery system is around 100kW and they are pulling almost 4X that at speed, plus they are operating in a cold environment, although they likely have built in heating for the bank in order to achieve optimal performance.

Either way dumping that much power quickly and reliably is no easy task.

On a related note, we have a number of similar sizes hard bottom ribs here running tourists up and down the Napali Coast and a few of them have recently switched to the BMW based OXE Diesel outboards (300HP x 2) in an effort to reduce operating costs, increase profit margin and reduce maintenance.

And for a point of reference here is my favorite high power electric propulsion technology.

It’s pushing a boat that weighs a ton and a half, and the motor has been limited to 250HP.

If you watch until the end you will see it is able to achieve 30 Knots at a consumption of 140kW with two passengers on board. It was throttled up to over 40 knots at one point but consumption at that speed wasn’t mentioned by the reviewer.

What I like most about it is that it is a small package that is scalable and applicable across a variety of hull designs, that it has fewer moving parts, and that it has the potential to be more efficient at speed than conventional “outboard” style designs.

 

[alan craig]

Re. duration figure - I'm now thinking that figure displayed is duration of voyage so far and not duration remaining at this power.