Updated on January 11, 2016
Electricity Part 4 – Three ways to fill a battery (mostly alternator)
Persistence. Whether repeating the same tired joke for the thousandth time, or not giving up on a difficult IV start, or relentlessly describing the DC systems on a cruising boat, persistence is a quality that has served me well. I know you guys are eager to move on from the Electricity series to something a little more exciting. “I hear he is an ER nurse, must be some good stories there.” (Yeah, lots of them. Too bad.)
Sticking with electricity.
On Milou we currently have two ways to charge the batteries, and we will have a third installed before we set sail.
Method 1: Plug the boat in and turn on the battery charger.
One of the few items that works and did not need to be repaired or replaced is our trusty Xantrex 40-amp dual bank battery charger. This works well as long as someone else makes the electricity and we have an extension cord long enough to reach an electrical outlet on shore. Obviously, of zero use while not at a fancy dock.
Method 2: Run a motor.
A lot of cruising boats have a diesel generator; Milou does not. Even if someone gave us a generator, I have no idea where I would put it. There is not a lot of extra space aboard. Our motor is a Perkins 4108 marine diesel. It is old. It is ugly. It is a huge hunk of iron. And it is nearly bombproof.
The 4108 puts out 50 hp, but is governed to 40 hp. It makes electricity the same way your car does, by using a belt to spin an alternator. Milou came to us with a 55-amp alternator, which makes enough electricity to charge our house battery bank from empty to full in about four hours of the engine running at top speed, maybe eight hours at idle. Not good enough. I wanted to be able to get more electricity out of the motor, to make it act more like a generator.
I was thinking around 150 amps to triple the speed at which we can charge the batteries. Balmar makes nice marine alternator, a set-up like that from Defender.com runs around $1500, including a fancy regulator. After hundreds of hours of research, and measuring the available space 10 or 12 times I settled on an industrial Leece Neville alternator. I went with the BLD2333GH. It is 185 amps, but it is the same size as the 160-amp version; also, I stumbled across a new one on Ebay for $230. Of course it was not a simple part trade-out to gain all of that charging capacity. First, the distance between the mounting feet was wider, at 4 inches, and the mounting bolts were bigger 1/2-inch bolts. I spent about $50 at a local welding shop to modify the alternator mount.
The next issue was that the torque required to turn the 185 amp alternator is a little more then three times the required torque to turn the old 55 amp. The new alternator needs about 12 hp to turn at full output. The single V belt that turned the original alternator wouldn’t have enough contact area to spin the new larger alternator without slipping. I would have to upgrade to a flat, multi-groove serpentine-style belt. I rang up Trans Atlantic Diesels and ordered a serpentine belt kit (along with the parts to convert the diesel from raw water-cooled to closed-cooling–a different story).
I paid about $570 for the serpentine belt kit, which came with a belt, alternator pulley, crankshaft pulley and a new water pump. The alternator pulley did not fit the alternator shaft and the belt ended up being too long, so I spent another $70 for the right belt and pulley. After spending half a day relocating the fuel filter, I finally had the thing bolted in place.
Then I realized that once the new pipe for the coolant circuit was installed, the alternator–which hinges up and down to allow for belt tightening–only had room to be at “all the way out”.
So, I cut the pipe and soldered in a couple of elbows to bend it around and under the motor attachment and foot (yeah, not perfect the first time: coolant leak). The last thing I needed for the physical install was a way to tighten the belt.
The conventional way to do this is to loosen a bolt; use a bar to pry the alternator away from the motor; then, while holding the correct pressure on the pry bar, use the other hand to tighten the bolt and hope it does not slip. This is a total pain in the butt. Also, with my decreased room in which to maneuver, almost impossible.
I went and bought a $12 turnbuckle from the lawn and garden section of Ace Hardware. After epoxying some 1/2-inch interior diameter sleeves in the ends of the turnbuckle and modifying one hole on an engine mounting plate, I now have a simple way to dial in the exact correct belt tension.
Now I could fire up the motor and the alternator, securely in place with proper belt tension, would spin around. The BLD2333GH has its own internal regulator-rectifier, which means I did not need an external regulator to change the varying alternating current output of the alternator to rock-steady 12 volts DC. But I did want a way to specify the exact voltage at which the batteries charged, and I also wanted to keep the starting circuit isolated from the house battery. After another 100 or so hours of research I settled on Sterling Power: Alternator to Battery Charger for $330 (I see the price has gone up). This unit tricks the alternator to get the output it needs and charges the starting and house batteries independently at whatever voltage I specify.
If you followed the hyperlink about the alternator and read the brochure on the BLD2333GH you already know that the new alternator is “self exciting”. At this point in the game I did not know a whole lot about alternators. I knew that you spin them and they make electricity. I ran electrical cable from the alternator to the charge unit and from the charge unit to the batteries, then I started the motor… and nothing. No charge. No electricity coming from the alternator to the charge unit. Maybe that $230 eBay alternator was not such a good deal after all.
I removed the alternator for the 12th time (did mention the thing is heavy?) and took it to an alternator shop 30 minutes south of Oconto in Green Bay. The guy at the shop put it on his test bench and, for no charge, assured me the alternator was operating perfectly. It only needed 12 volts for an initial exciting of the field coil.
Me: It's self exciting.
Alternator Guy: Not really, it still needs 12 volts at this terminal. *points at one of many bolts sticking out of the back of the alternator.*
Alternator Guy: What's it on?
Me: A 30-year-old English diesel motor inside of a 30-year-old French sail boat.
Alternator Guy *gets a look on his face like he really has to poop*
Older Guy sticks his head out from around the corner and they both whistle at the same time. I explain about my trick new alternator-to-battery charger and he is unimpressed. He says there must be some diodes in the charge unit which keep the starting battery isolated from the house battery. The diodes are keeping the alternator from getting the initial 12 volts it needs. Alternator Guy says that I could run a wire from the crank position of my ignition switch to the bolt on the back of the alternator. That way, the alternator gets a little bit of juice while you are starting the engine and is then able to make electricity.
Older Guy, in a quite-non-confrontational-in-the-background way, mentions that on a set up like mine, where Who Knows How Things Have Been Wired, he might use a momentary “on” switch. After the engine is started and the alternator is spinning, you can push a button and give the alternator 12 volts for a second to get it going.
At this point, Milou had been at the dock for the first week of our three-week summer vacation, with my family waiting as I farted around with the alternator. I had a long piece of wire and I ran it from the ignition switch to the alternator. And… the charge system worked! It worked beautifully. This thing really makes some electrons. It took us from 90% to 100% charged after 12 minutes of idling.
Little did I know that my last-minute ignition wire fix had caused some other problems (Rule #1 Always listen to Old Guy). Problems that would delay our vacation for another week and eventually lead to the creation of… The Frankenstarter! But you’ll have to wait for that tragic tale, because remember, people–we’re in electricity here.
Method 3: Solar (you almost forgot about the third, not-yet-installed system!).
These babies will be installed up high on the new radar arch. In full sunlight, 380 watts divided by 12 volts is about 30 amps of charging capacity. I expect these to put out more like 20 amps in real-world conditions. The solar should pretty much keep up with our energy needs; I’ll let you know how it goes once we are actually using it.
After $1300 spent on an alternator and the parts to get it to turn, we have an engine that is a pretty good generator. Add another $1200, and we will soon have enough solar so that we won’t have to use it.
The Electricity Series is a pretty good overview of the DC electrical system aboard Milou. Up next: the much-anticipated Engine series.