Marine Hybrid Drives for Boats
by Walter Schulz
The following is my “stock” response to people who contact me concerning hybrid drives for boats.

Yes, I have some “experience” with hybrid drive boats. Two years ago, I went through a very extensive exercise with hybrids on a 52 Shannon motorsailer for Bob “Bitchin” editor and publisher of “Latitudes and Attitudes” boating magazine.

We were working with Glacier Bay, Solomon Technology, Siemens Industries and others. I have been talking to Solomon about electric drive and hybrids for well over fifteen years and I firmly believe that someday electric drive is the future for certain types of boats. Unfortunately, electric can only be stored for future use using DC (direct current). AC (alternating current) must be used as it is generated. Elco was successfully running battery-type electric launches at the 1893 Chicago Exposition so we’re not talking about breakthrough electrical technology. The short version of a very long story is very little has happened with DC batteries since 1893. We are still using the same “chunk of lead” battery science that was developed in the late 1700’s. Even with some advances in lithium ion and other exotic compounds the batteries are very expensive. I just read that a 130 amp lithium battery costs around $2500! If a boat has four 130 amp batteries that’s a $10k expenditure. A high quality 130 amp AGM battery costs about $200, so a lithium battery will have to be willed to grandchildren to justify the initial cost.

The great thing about an electric motor either AC or DC is the fact that you obtain 100% torque 100% of the time which is incredibly efficient (a combustion engine needs to spool up to a certain RPM to obtain any reasonable torque or power). If a boat or a car had a 200 mile long extension cord plugged into the National Grid then electric drive would be great. However, once you introduce batteries for power/range being charged and supplemented by a combustion engine everything gets complicated, expensive and much less efficient. Added to the problem is the amperage draw on a Drive motor is large, meaning that high DC voltage and batteries need to get up into the 400 amp plus category to push a boat. Wiring a 400 amp DC motor hybrid electric system is no small job. You will need several banks of big amperage, heavy duty batteries just to run the boat a couple of hours. Once you introduce a combustion engine to extend range and charge the batteries the whole issue of fuel economy becomes very small. For instance, a Prius hybrid auto gets about 40 miles a gallon on the highway and a diesel powered VW Golf gets about the same mileage without the expensive complications and battery issues. Other than being politically and environmentally correct I don’t see any real gain in hybrid boats at this time. Also, no one wants to talk about the environmental problems of what we are going to do with all the hybrid auto batteries in the next five years when those batteries drop dead. Plugging the boat (or car) into a shore power cord that is powered by a generating plant that is burning coal negates much of the pollution abatement advantage.

Personally, I am waiting for a real, not hype, battery technology breakthrough before I put hybrid drive in any Shannon. I vetoed the hybrid drive on Bob’s boat because we need much better electric storage devices (batteries) to make it really work on boats. “Practical Sailor” newsletter did an article on hybrid drives a few years ago that is an excellent discourse on marine hybrid drives. I’m sure you can get the article on line to help you make a decision.