T-Pain Is On A Boat: [Electric Boats] Abusive and dangerous Re-Epower technical specification

Monday, July 27, 2009

[Electric Boats] Abusive and dangerous Re-Epower technical specification

Present time I prefer to pass more time to build my Tiki46 than going to the forums but I can't keep the silence concerning the abusive adverts of Re-Epower.
From its website I copied the technical specifications of the E-pod 3000 system :

Technical Specifications of the E-POD 3000 System
Operates on 36-48 volts DC (48 volts recommended)
AMPERAGE: Peak 200
Max continuous 100
Recommended Cruise......
40-60 amps @ 48 volts
(Performance = to 20 hp outboard / 25 hp inboard)

In reading that I can't know what is the max continuous power at the shaft. I have to estimate it : absorbed power 48Vx100A=4800W - a minimum of 15% of losses in the engines and its controller = 4080W or 5,5Hp. So by which miracle a 5,5Hp electric engine can do the job of 25 hp inboard!!!!!!

I know the advantages of an electric engine are to deliver a good torque at low rpm and to have a quick reply when you request the full power and can even during a very short time deliver a peak power as example to stop the boat (if the controller accept that). So it's easier to handle the boat with precision when docking. To have a good reply with a such little engine on heavy boats you need a large propeller with a little pitch.
All that seems marvelous only if you have good conditions with no wind and or no current.
As soon as you have to motor against the waves and the wind, the torque at low rpm and the quick reply don't change anything and you'll never get the push of a 25 hp inboard engine with a 5.5hp electric engine.
If you try to reach a shelter in a gale against the wind and waves in a long rocky entrance, you'll push the throttle at the maximum to get the maximum continuous power of 5,5hp at the shaft (in fact the propeller has an efficiency of 50% and the useful power to push the boat is only of 2,25hp). As you draw a high amperage, the real capacity of your battery bank will be lower than if you draw a little amperage. Your speed is very low, so you have no hull speed inertia and each gust or wave will stop the boat. As the speed is very low, the angle of attack of the propeller blades increases, so the propeller stalls reducing its efficiency. The engine and controller warm more and more and so the useful power is going down.........
The boat don't progress and in less of a half hour (if you have a good battery bank) you loose the control of the boat due to lack of electric energy ( if the controller or engine don't shut down before). The boat wrecks on the rocks in hoping you don't loose your life!!!!!

So I can say IT'S CRIMINAL to affirm to the customers that an electric engine of 5.5hp can does the job of a 25hp inboard engine!!!!!!!

An hp is an hp, there is no difference if the power is produced by electricity, or by humans, or by animals or by petrol or by nuclear, so and so. Behind the power delivers on the shaft the difference depends of the efficiency of the propeller and if the propeller is well adapted with the hull. This kind of comparison is only available about facilities to handle a boat in an harbour but it's not possible at full throttle. With the same propeller efficiency, with the same boats, the bigger power engine will produce the bigger propulsion power.

Bertrand