Yachts, displacement boats, multi hulls, kayaks, dinghies and tenders are all perfectly suited for electric motors.
- A. History of Electric Boating
- Β. What types of boats are suitable for electrification?
- C. What types of boats are NOT suited for electric?
- D. Are electric motors and boats expensive?
- E. What are the benefits of electric power boat?
- F. How efficient are electric motors?
- G. What size motor do I need?
- H. How many batteries do I need?
- I. What are the PROS and CONS of lead acid batteries?
- J. What are the PROS and CONS of lithium batteries?
- K. Lead Acid batteries Vs lithium batteries
- L. What are the options to recharge my electric motor batteries?
The first revival of electric boating took place in 1970’s due to the global energy crisis. As a result there was a resurrection of recreational electric boats.
Today’s drive for electric boating has come from an added focus on sustainability helped by the broader success and interest around electric cars with Tesla leading the way.
Europe and USA are leading the march in electric boating spurred on by government legislation that has banned powered boats along a large number of internal waterways.
As a result of this global demand for cleaner and more sustainable energy the technology behind electric boating has significantly advanced. The demand also means that going electric is now not only an option for corporate companies or wealthy indivduals. With electric motors now starting from as little as €2,000 its an attractive option for the many, not just the few.
Any speed boat plus displacement boats that need more than 8 hours of motoring.
- Prices have dropped significantly in recent years due to a dramatic increase in global demand and advancement in technology.
Converting an existing boat to electric, buying a new electric motor or purchasing an electric boat is now a viable option for many people.
There are many!
- – Enviromentally friendly
- – Sustainble with no reliance on damaging fossil fuels (you can even recharge your electric motor via wind and solar energy)
- – Whisper quiet – no more loud motor noises
- – No smelly fuel smells (ideal for those who suffer from sea sickness)
- – No leaking of fuels inside the boat or into the water
- – Extremely relable with no/little maintenance required due to the small number of moving parts
- – Highly economical with no fuel to buy and very little maintenance
- – Most electric motors have more than 90% effenciency making them significantly more efficient than combustion motors.
- – Electric motors have >90% efficiency: much more efficient than combustion motors
- – For displacement boats, highest overall efficiency is achieved by large propeller with a high pitch, that turns relatively slowly through the water
- – This ensures as little energy as possible is wasted. Some modern electric drive systems have an overall efficiency of up to 50%, whereas in comparison a petrol motor has an overall efficiency of 10% or less
- – Combustion engines need reduction gear. Because of the loss associated with gearing, many electric drives eliminate it by using low RPM, high-torque motors
- – On top of this, generating electricity at a large PowerStation is much more effIcient than burning fossil fuels in a small motor onboard
- – Research by the Greek Govt has shown that a small 2 stroke outboard can be as polluting as 50 cars covering the same distance!
First step is to think how you wish to use your boat, what the conditions of local waterway and what is the range and speed you are looking for. Generally speaking ;
1 kilo Watt (kW) = 1.35 Horse Power (HP)
However, in real life on a displacement style craft:
1kW replaces 3HP!
- – Max torque at any rpm
- – Minimal heat/friction losses (alternator, water pump, flywheel, etc)
- – Electric motor can be overloaded where a diesel motor will stall
If current diesel performance is adequate: replace with 1/3 in kW
If diesel power is unknown use the follow empiric rule:
*Motor size rule: kW rating of motor needed = displacement x 2
Size of motor depends on:
- – performance requirements of boats owner
- – area of usage (open or enclosed, currents)
- – corrections for hull shape and water line length (eg multihull or heavy monohull)
Most recreational electric boats operate at 24 / 36 / 48V
Minimum battery requirements:
2-3 hours boating (auxiliary drive on yachts): motor kW x 1.5 = battery capacity in kWh
6-7 hours boating (motor boats): motor kW x 2.5 = battery capacity in kWh
19’ couta boat with 3.6kW inboard (sailing boat)
3.6 x 1.5 = 5.4kW battery bank (36V / 150Ah) à total weight approx 135kg
20’ classic launch with 4.2kW Pod motor (motor boat)
4.2 x 2.5 = 10.5kW battery bank (48V / 225Ah) à total weight approx 260kg
- – For longer running times/higher speeds, more batteries are needed
- – When choosing Lithium batteries you will get more capacity in a smaller pack
High quality lead acids such as sealed AGM deep cycle batteries are most cost effective for most displacement boat applications.
Approx 500 cycles over 10 year period.
- – Weight can be used as ballast
- – Relatively inexpensive
- – Big & heavy
- – Lose their charge over time
- – Can only be charged slowly
- – Should not be discharged too deep
In some instances Lithium batteries are desirable for their benefits over lead acid
Approx 2000 cycles over 10 year period.
- – Lighter & smaller
- – Deep discharge possible
- – Fast charging possible
- – Require sophisticated battery management system (BMS)
- – Expensive
Lead-Acid and Lithium both have a life expectancy of approx 10 years max
In these 10 years a Lead Acid battery will give up to 500 discharge cycles
on the other hand in these 10 years a Lithium battery will give up to 3000 discharge cycles
Lithium is 3 times more expensive than Lead Acid
If you use the boat a lot (more than 150 times per year) Lithium works out cheaper
As this is often not the case with recreational boats, the remaining benefits of Lithium are:
- – higher energy density (smaller & lighter battery)
- – very deep discharge with no harm to the battery
- – quick recharging
- – ideal for solar charging as Lithium batteries don’t mind sitting empty as much
If you have a displacement boat which needs weight: use lead acid
If you have a racing yacht and a big budget: use lithium
AT THE MARINA = plug in to shore power 240V
ON A TRAILER = plug into the mains at home 240V
ON A SWING MOORING = use solar panels / (wind)generator
ON BOARD = HYBRID VERSION = engines recharge batteries