Charging away from the dock

This is the third in a series of posts on my power system upgrade which will cover design, install, and specific implementation challenges.

One of the biggest challenges with my old DC power system was apparent when away from the dock. Grace has a Yanmar engine with a factory alternator, which on a good day output 30 amps into the battery bank. Not only was this not enough for the new bank, but the regulator was not programmable and would damage my new Firefly batteries. After a bunch of research, I chose Balmar as a complete system.

The new system was composed of:

Old alternator on engine

Old alternator on engine

One of the constraints in replacing the alternator was the belt setup and draw it would put on the engine. I wanted to keep a single belt solution due to simplicity. That limited my choices to a max of a 100 amp alternator.

There were other options including replacing pulleys and adding more belts which could have produced more amperage, but I was concerned about the complexity this would add, along with the load on the engine.

Old alternator

Old alternator

The old alternator was pretty easy to get off.  It had been repainted at some point, making many of the labels unreadable.

Old alternator connections

Old alternator connections

I took a lot of photographs of the wiring for reference and ensured all of my battery bank and DC supply was completely isolated while removing. The existing positive wire can be seen uncovered in the middle of the picture. It seems undersized to me – I wonder if that is why I never saw more than 25-30 amps of current from the alternator.

Old and new alternators

Old and new alternators

The original alternator was a saddle mount, or dual foot setup. It was easy to use Balmar’s web page configurator to figure out what model of alternator I needed to purchase, but I would recommend confirming by examining your existing one.

New alternator

New alternator

The mounting on the new one looked like it would fit perfectly.

New alternator back

New alternator back

I read and re-read the wiring instructions before reconnecting everything. Many of the concepts behind an alternator and the way things are wired are a bit different than your average battery setup. It is important that you wire things exactly as required.

One of the biggest changes to this setup I covered in the arteries and veins of your electrical system. This included replacing all of the wiring going to and from the alternator with new and much larger wire. This was critical to ensure that the power generated by the alternator makes it to the battery bank as efficiently and safely as possible.

Mounting bracket

Mounting bracket

Here is the dual foot mounting necessary for my engine.

One thing that was very helpful was Balmar’s extremely detailed installation instructions for both the alternator and regulator. Lots of pictures, lots of good diagrams, and a step by step for most scenarios that has clear explanations of why you’re doing something. I wish other manufacturers spent the time to produce such quality install and troubleshooting documentation, and include a printed copy with something like this – I know I referred to them at least a bazillion times while double and triple checking my wiring.

New alternator installed

New alternator installed

Installing the new alternator was very easy compared to most boat-related projects. I did have to acquire a new, longer bolt from my local supply store as the new foot was a bit thicker on the rear of the unit.

Once installed, I tensioned the belt per the manufacturers instructions, reconnected all the wiring, and was ready to install the regulator.

Regulator installed

Regulator installed

The regulator was a bit more complicated to install, mainly because of the amount of connections. Besides the standard connections, I also added battery and alternator temperature sensors. I felt this was necessary to make the system as safe and thorough as possible.  The battery temp sensor ensures that the system isn’t overcharging the batteries or charging them too fast, and the alternator temp sensor ensures the alternator isn’t working too hard. Given how hot the engine room can get, both of these will help in preventing damage.

When it came to programming the regulator, I chose to create a custom profile that matches the Firefly batteries requirements.  I also setup a delayed startup time of 60 seconds for the alternator – allowing the engine to start and warm up a bit before the alternator starts charging heavily.  I may increase this to prevent such a big load from occurring so quickly after starting.  I forgot to document all of the bits and pieces to the exact program but will do so in a future post.

Amps flowing in from the alternator

Amps flowing in from the alternator

I did a lot of testing to ensure there were no wiring issues or problems – metering out various spots and ensuring the connections behaved the exact way the instructions indicated.  Then I tested charging with the battery bank at mostly full capacity and was happy with the measured voltages at the right places.

After discharging the battery bank for a few hours, a load test showed over 90 amps of continuous power being generated by the alternator into the bank.  Note that in the pic above, the shunt was configured backwards, showing a negative value.  In addition, there was about 6 amps of load on the system.

In continued testing and usage for the last few months, I’ve seen consistent charging voltages and really good amperage amounts that make a huge difference in topping off the battery bank while away from the dock. I’ve noticed a moderate amount of dusting from the belt, and believe this is because of tensioning, but will continue to monitor.

Some might consider this part of the power project to be optional, at least the alternator. For sure you will need a better regulator if you choose to use Firefly batteries, or you will damage them / reduce their life.  I consider the alternator just as important so that I can charge the bank back up as fast as possible while away from the dock, and ultimately spend more time out on the water!

About Steve Mitchell

I live in Seattle, WA and love sailing, technology, & playing and composing music. I started playing the piano when I was 3, and ended up figuring out many other instruments along the way. I’m an avid sailor and have a 2000 Beneteau 311 named Grace, and sail it whenever and wherever I can.

  • Saffy The Pook

    Steve, it looks like there’s enough room in the engine compartment to fit a longer belt and swing the alternator outboard a bit on its mount. The power you can transfer by belt follows the capstan equation (https://en.wikipedia.org/wiki/Capstan_equation), which is linear in tension but exponential in wrap angle. Increasing tension may help the dusting issue but at the expense of every bearing in the loop. Increasing the wrap angle has no downside.

    • Saffy,
      Good point, I hadn’t even thought of that. Definitely do not want to increase the tension more than is recommended for the very reason you cite! I will have to add this to my list of projects to look into, thanks for the suggestion!

  • steveallwine

    First question: is that a Yanmar 2GM engine?

    I have similar charging issues with my 32′ Hunter, although I’ve been going at the problem from the opposite end. I went the route of installing a flexible thin-film soliban solar panel on top of the Bimini to handle the topping off of my house bank, and letting my anemic stock alternator take care of the bulk charging.

    This route has worked pretty well for me over the past few years, with one exception. Whenever I use my 2,000 watt inverter for the microwave, while underway, I can see that the little alternator tries its best to handle the ~90 amp load for about 10 seconds before overheating and shutting down. It’ll cool down for about 10 seconds before trying again. It’s pretty obvious, as I can hear the 2GM20F engine slow down slightly while under extra load, then let off.

    I worry that this will put excess strain on the system, and have been contemplating going the Balmar route. I’ve heard great things about them, and I’d love to hear your ongoing opinion of the new alternator.

    • Hi steveallwine,

      It is a 2GM engine, 2GM20F to be exact – sounds like the same as you. I love the engine, easy to get to all of the parts, the only thing that irritates is the leaky fuel filter copper washer that many people have had issues with. Sometimes I can get it to stop leaking, but mostly not.

      What alternator do you have on your engine? For Beneteau they had two different options for alternators, and I believe I got the “big” one, which was a ~55 amp model that once I got her, never really put that out.

      I definitely think you should look at upgrading the alternator if yours is shutting down after short periods of inverter time. That’s quite a decent size load to be running with a small alternator. If you can’t replace it right away, you might want to consider setting up some way to disable the alternator while you’re running big inverter loads so that it doesn’t kill itself, and then re-enable it once things have settled down.

      I have several other friends that have gone the Balmar route and absolutely stand by their decisions – that’s one of the reasons I chose it as well. For sure if you do it, make sure to get the regulator (they sell the whole thing as a bundle in many places) so it can be controlled the most efficient way!

      I’ll post any updates I have on the longevity.

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