More About the Motor: Wiring and Batteries

Our batteries are the fuel that make our motor go. Richard did a lot of research, we thought about safety, efficiency and cost. In the end we decided on premium AGM (Absorbed Glass Mat) batteries, an affordable compromise between flooded lead acid batteries (which would need to be vented outside the boat and require maintenance) and lithium (light, but expensive).

Our motor runs on 48 volts. We decided that two banks of batteries wired into 48 volt packs would allow us to find the best balance of space and weight. This meant that we had eight batteries to distribute in the way we thought would benefit us most. And that would be to keep them low and close to or in the middle of the boat.



We distributed them as follows:

• Two batteries in the compartment below the floor boards that is closest to the motor.
• Two batteries in the compartment forward of that (which leaves half of that compartment for other storage).
• Two in the bottom of the old icebox (Richard cut away part of the old icebox floor and part of the wall so that the batteries would sit close to the center of the boat and low down).
• One under the sink (Richard cut part of the liner so that it would be as low as possible, close to the center of the boat).
• One in the 'wet locker' by the galley.
  

This did mean giving up some storage space, and having to divide the large compartment below the floorboards into two. In the old icebox and the wet locker the batteries will be covered to create a shelf in one and a new bottom in the other.

For our charging system we chose to use four 24 volt Guest chargers. They charge each battery individually. They keep the batteries in balance by making sure that each one is charged as much as it needs, and using them avoids the distortions that can happen in charging each battery that happen when they are charged as a string.

We chose Guest because they are completely waterproof and available at a reasonable price. And in the electric boat forum Richard belongs to those that have them were pleased with and recommended them. The chargers can be hooked up to either shore power or to a generator.

The rest of our charging system uses solar panels, or the regeneration that is built in to the motor, and these are what we expect to rely on most of the time.

One of our friends, Uli Rentsch, is an electrical engineer. He helped us to develop our wiring diagram.
For the wiring we used the type of wire used in battery cables (#2). Richard worked out the wiring size using a chart that shows the voltage loss for different sizes of wire. This size wire means that losses would be minimal with the current we're going to run.

We used lugs to connect the wires to the battery terminals, and protected all the connections with marine grade heat shrink which has a sealant in it that is activated by heat.

One very important thing we learned: as we wired the two 48 volt packs we needed to make sure that the lengths of the wires between corresponding pairs of batteries in each bank were the same. That is, the length of the wire between batteries 1 and 2 in the first bank had to be the same as the length of the wire between batteries 1 and 2 in the second bank, and so on. Each bank has its own switch, so that we can operate either on one or the other, or on both when both switches are turned on.

Setting the switches up this way means that if necessary (if, say, there is a problem with one battery in one bank) we can isolate the banks from each other and still have 48 volts of power to run on.

Using both banks at the same time has the advantage of reducing the Peukert effect. This can be described this way: The more current you draw from a battery the less capacity it has, so that it provides power for a shorter time than it would if you drew less current from it. You could think of it this way: the greater draw actually reduces the real capacity of the battery - a 10 amp draw from a 100 amp battery allows the battery to operate as if it had 100 amps, but a 50 amp draw on the same battery would make it operate as an 80 amp battery.


Although the wiring diagram does not show it, there is main fuse that acts for both banks when both are switched on and providing power as one.


Rather than have a separate battery, we decided to run house loads through a converter which steps the 48 volt current down to 12 volts. Partly this means not having to carry and find space for one more battery - but it also means that our batteries will be used rather than sit idle, and this is better for them.

The actual weight of the electric motor plus batteries, wiring and chargers, etc, is about the same as the weight of an Atomic 4 engine and a full tank of gas.

Goodbye Diesel, Hello Electric

So - Why Electric?

Everyone has their own reason for choosing what kind of motor they want as the auxiliary in their sailboat. When we bought Into The Blue we were very happy to have a diesel engine, preferring to have diesel rather than gas on board.

Then, as happens, our old diesel began to feel and show its age. When it finally and indisputably declared its reluctance to continue to operate without expensive repairs (assuming we could find the parts), and emphasized that reluctance by filling the boat with diesel fumes, we decided it was time to investigate what kind of motor to replace it with. We had learned that while sailing without an engine is certainly possible it can also be uncomfortable, and we appreciate comfort. So - time to make a decision.

Richard undertook the research. We were interested in electric motors for a number of reasons. One was that we would no longer have to listen to the thump of a diesel motor, or smell the aroma of diesel fumes. Another was the hope that with solar power to replenish the batteries, and careful use of the motor, we would largely be free of the need to buy fuel. We do foresee buying a generator, but experience on the water this summer has been reassuring. Regeneration while sailing works well, and should work better in the future. We should not have to use a generator too much - so some fuel on board, but much less.

So far we are very happy with our motor, which we bought from Electric Yacht. And very happy with Electric Yacht, who answered all our questions (and still do). Other things that are really nice: the motor is very quiet, and super simple to drive.

Installing the New Motor

Of course, before we could put our new motor in we had to remove the diesel. The engine was small, which helped simplify the process. And then we made it smaller by removing it in bits and pieces. First Richard took all the accessories off (like the alternator and water pump). Then he took other bits off, such as the head and cylinder and the front crank pulley, taking the bits off the boat as he went along. After that he separated what was left of the engine from the transmission, and took them off the boat separately.

That left us with a diesel-stained engine compartment, so the first order of business was to clean the compartment up. Richard cleaned and sanded, then painted the compartment with gelcoat (tougher than paint). The difference was very pleasant to see.

Once the compartment was clean Richard decided to take advantage of the space and ease of access to the area behind the engine to do a few other jobs. He replaced the hose on the stuffing box, the cutless bearing and the stuffing box packing, and put new hoses on the cockpit drains.

And now that we did not need them any more he removed the old coolant hose and its through-hull and filled the hull where the through-hull had been. One less hole below the waterline.

Then it was time to put in new motor mounts. The mounts on the engine would fall between the original motor mounts, so Richard put 1/4 inch thick stainless steel bar across between and bolted them into those original motor mounts.

After careful measuring, he drilled the stainless steel to take the mounts that came with the new engine and bolted them into place.


The next step was exciting - actually putting the motor in place. The mounts that come with the motor can be put together in a variety of ways, which means that there is a lot of adjustment possible when you are putting the motor in. It took a little experimenting to decide which combination seemed best. Then it was time to hook it up to the shaft.

The motor comes with a special shaft coupling that helps align motor and shaft properly. Richard loosened all the bolts fastening the motor to its mounts. Loosening the bolts allows the motor a certain amount of adjustment as the shaft coupling does its work - the mounts on the motor are slotted to allow it to move backward and forward as you align it. The number of slots allow you to choose which height works best in your boat.


With everything in place, Richard tightened the shaft coupling, then tightened the mounting bolts on the engine in their slots. Then he used what we had to check that the shaft was straight: He bolted a coat hanger in place with the tip just touching the shaft, then rotated the shaft slowly while watching to see whether it moved toward or away from the coat hanger tip. All was as it should be. As the supplier had told us it would, the coupling aligned shaft and motor without problem.

The controls and instrumentation for the electric motor is considerably simpler than for the diesel. So we removed the old levers and instrumentation, and changed the areas where they had been.
The single lever for the electric motor we decided to install where the compass was (replacing the compass with one we can see from inside or outside). Changing the compass area and installing the batteries and wiring for the motor are processes we'll cover in subsequent posts.