Boats With Electric Propulsion: (This page is still being edited.)
Boats propelled solely by electric motors are becoming more and more common. There have been significant developments in electric propulsion and battery technology which has allowed going all electric to be more affordable and more practical. It has become common enough that ABYC has developed standards for Lithium Batteries and electric propulsion systems.
For more Information Contact ABYC at abycinc.org and purchase a copy of E-13 Lithium Batteries and E-30 Electric Propulsion Systems. In addition to the ABYC E-13 and E-30 Standards there are Underwriters Laboratories (UL) Standards, IEC Standards and SAE standards for Lithium batteries and installations. All of these are referenced in the ABYC standard.
The U.S. Coast Guard has published a policy letter regarding standards for Flotation, Safe Loading and Maximum Horsepower ratings on boats with electric propulsion. Essentially the policy letter says that manufacturers of electric propulsion recreational boats should comply with the same standards for Safe Loading, Flotation, and Safe horsepower as gasoline powered recreational boats and refers to ABYC Standard E-30 for Boats with Electric Propulsion. The policy letter can be seen at the Coast Guard's website at https://safeafloat.com/wp-content/uploads/2022/08/BSX-23-Electric-Propulsion-Policy-FINAL.pdf
There are electric outboards on the market ranging from trolling motors which are less than 1 horsepower, to much more powerful outboards such as Axopar 25 with the Evoy Storm Electric outboard, rated 300 Horsepower. 11,000 Watts is about 15 horsepower. 300 HP is in the range of 220KW. So it takes a lot of watts to generate horsepower. Electric drives have also entered the sailing world. Yanmar has a drop-in saildrive rated at 15KW, replacement for their engines.
As with gasoline powered engines, how your engine performs is dependent on the size and weight of the boat, and the type of boat. Here is a link to a converter from Watts to horsepower. https://www.unitconverters.net/power/watts-to-hp.htm
The more powerful the motor is, the more batteries you need to power it. The other consideration is weight. If you use 12V marine lead acid batteries, which can weigh up to fifty pounds (22.7 KG), the weight can be considerable. If you use 12V lithium batteries, which weigh about half as much, the weight is reduced considerably. But lithium electrical systems are more complex than lead acid systems. See Batteries.
There are two categories to consider: inboard electric motors and electric outboards,.
Inboard Electric propulsion:
Electric propulsion boats have been around a long time. ELCO has been in business for 130 years (https://www.elcomotoryachts.com/) so inboard electric propulsion is nothing new. Even large commercial and naval vessels have used electric propulsion. It was called diesel electric. That is, generators were driven by diesel engines. The resulting electricity was used to drive large electric motors which drove the propellers. Probably the most common use of this was submarines. Today we call this a hybrid system. But electric recreational boats have almost always used batteries. Until the advent of lithium batteries, this has almost always been lead acid batteries. This required long charging hours and added a lot of weight to the boat. This resulted in restricted use of the boat, and slow speeds. The features of lithium batteries, light weight and longer amp-hours, along with better design of small electric motors, has made it possible to power boats for much longer times and achieve much higher speeds.
Outboard Electric propulsion:
Electric outboards have also been around for many years in the form of trolling motors. They were invented in 1934. See https://en.wikipedia.org/wiki/Trolling_motor Trolling motors are battery powered low horsepower electric motors. Typically they are used on small rowboats, dinghies, canoes, and inflatables. However in the last twenty years or so the boating market has seen higher power outboards being introduced, such as Torqeedo and lately the Evoy Spirit, featured by Axopar. This has resulted in planing boats being able to achieve speeds comparable to gas outboards.
Power Sources: (battery banks) This gets into battery banks, multiple batteries hooked up together in series and parallel to provide the voltage and watts, and the amp-hours to power the motor. Battery banks are two or more batteries connected in series or parallel, to increase the amount of power available, or make it last longer. See https://newboatbuilders.com/pages/electricity3.html and https://newboatbuilders.com/pages/electricity4.html to explain battery types and series/parallel circuits.
When planning for electric propulsion you need to determine the size of your battery bank, and how long power will last. So first I need to define some terms.
Volts and Voltage. Voltage is a measure of potential energy
contained in the battery and is measured in volts.
The symbol for volts is V.
Voltage is what drives current flow. The amount of current is measured in Amperes, often shortened to Amps, or milliamperes. The symbol for Amperes is A, or milliamperes mA.
Batteries are also rated by amp-hours. 1 amp for 1 hour is 1 amp-hr. Shown as 1 Ah.
The amount of power is measured in Watts. Watts are calculated by multiplying Voltage times Amps.
V x A = W
1000 Watts is a Kilowatt written as kW.
When
designing battery banks, the most important factors are watts and watt hours.
Watt hours is defined as the measure of how many watts can be used for how
long. 1 watt for one hour is one watt hour. But since we are dealing
mainly with KiloWatts, (kW), we are mainly interested in Kilo watt hours.
Kwh = Volts x Amp-Hours. Kwh = V X Ah.
12V X 1 Ah = 1Wh.
12v x 1000 Ah = 1000Wh which equals 1 Kwh.
A Watt Hour is how much work 1 watt per second can do in 1 hour (3,600 seconds). See A Tutorial on Electric Propulsion For Boats. https://boattest.com/article/tutorial-electrical-propulsion-boats. But we are dealing with a thousand Watts, that is, 1 KiloWatt (1kW). This is a measure of how many Kilowatts you can use per hour. This depends on the Voltage, amperes, amp hours, and the Watts. It also depends on the type of drive system you have, the boats weight, size and type.
Sizing the battery bank is basically the same as sizing a battery bank for running all the electrical equipment and appliances on your boat. You first need to determine the amount of power you need to run everything. The supplier of the propulsion system should give you instructions on how to size the battery bank for their system. Often they sell the batteries. For instance the ePropulsion sells a 1276 Wh battery for the Spirit 1.0 EVO. For the Evoy 25 you need two 63Kwh Evoy batteries. That's 126 Kwh (126,000 watt hours)
Critical Decisions to be made in selecting how to power your boats:
Safety: Safety is paramount. Having a safe electrical system and batteries is all important. This involves selecting the right type of batteries and selecting a low voltage system. Currently, 48 Volts appears to be the system of choice. The voltage is low enough to reduce the danger of shock and fires, but high enough to deliver the performance and reliability needed. There a many types of Lithium batteries but at the time of this writing LiFePO4 are the batteries of choice for boats as they present the least danger of thermal runaway, yet are reliable and able to deliver the needed perfomance. The Battery Management System is very critical to the battery's performance. You can chose an internal BMS built into the battery, or an external BMS. Both can do the job.
When I speak of performance I am not talking about speed alone. Reliability, longer Watt Hours, as well as speed are important. As I have said before, this is not a time to cut corners. Spending more will result in a longer lasting, safer, and better performing system.
Charging Stations: There are no current specific standards for Marine Charging Stations, plugs, sockets, cords, and adapters. Currently available charging stations are all designed for shoreside use. What is available are listed below.
Level 1 is the standard 120V outlet that boats use for charging batteries and running AC equipment on board the boat.
Level 2 is a Standard SAE J1772 outlet used for EVs. It is 240V and 12KW, 50 amps. It is medium speed and universally compatible with EVs but not specifically designed for use with boats.
Level 3 is not yet recognized by SAE. It would be anywhere from 480 to 1000V, 50 KW and 500 amps. It would be a very fast charging system and would charge your battery bank up to 80% charge.
The boat builder needs to concern themselves with the connections on the boat and the connections to the charging station. CCS (Combined Charging Systems) is now the default marine connection and is in NFPA 70, ISO standards 13297 ISO part 3.
How to install galvanic isolation of charging systems has not yet been determined.
Other things to look for:
IP rating. The IP Code or Ingress Protection Code rates how well the battery is protected against water and dust.
Battery Cases: How protective is the battery cases
Other Standards: Standards for Electric Propulsion boats, for Flotation, Safe Loading and Maximum Horsepower Ratings.
Links to Other Pages having information for Electric Propulsion Boat Manufacturers
Other standards that may be applicable to bolts with electric propulsion.
References:
Lithium Ion Batteries on Wikipedia. https://en.wikipedia.org/wiki/Lithium-ion_battery
List of Battery Types; Containing a list of Lithium Battery Types. https://en.wikipedia.org/wiki/List_of_battery_types
Battery University; List of Lithium Battery Types and their uses. https://batteryuniversity.com/article/bu-205-types-of-lithium-ion
© newboatbuilders.com 2024 All rights reserved Revised 11/22/2024
Index to all Basic Electricty Pages.
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