Installing our Balmar alternator

Although we decided that our main engine will not be used to charge our batteries, as per Calder’s and other diesel gurus advice that running your diesel to charge your battery takes a lot of life out of it, we still wanted a spare alternator and we wanted a better performance alternator than the stock alternator.
Livia did a lot of research and concluded that the most used one, although a lot more expensive, was the Balmar. Since customer service was important to us we realized from SSCA and other forums that people had complaints against Balmar for customer service and also we realized that as per our research people burn through their alternator from using them at full power for too long. With that in mind we decided to go with West Marine to alleviate customer service issues knowing that West Marine will back up their product while we are in N America. Waited for a good West Marine sale and purchased the alternator 6 series for the Volvo, the 621, 100 Amp alternator which is the max that our engine can take without any modification to it. Also, knowing that an alternator takes horse power away from your engine, already limited in engine power we didn’t want to affect the main reason of having an engine, to take you places.
Installation-wise, instructions provided by Balmar were very weak because I believe that they don’t want people to install it themselves. They want a certified electrician to do it. Many hours were spent researching on the net and books like Casey and Calder and also with our Volvo engine manual to figure out who is who in the zoo. By the way, we like Calder's book but Don Casey’s book “Sailboat Electrics Simplified” was better at explaining the terminal designation part of the installation than Calder’s. Once everything was figured out, taking the old alternator off was a piece of cake and putting the new one in was straightforward but with one time consuming hang up. The original bolt from the stock alternator was too big for the spacer provided by Balmar to fit the Volvo Penta saddle. Good enough, we are walking distance from a boat store so it did not cause too much delay.
Because we are going AGM batteries an external regulator was necessary to provide the right charging pattern. We bought the ARS-5 from Balmar. One good recommendation from Balmar was to install a three way switch for an emergency switch to switch from external regulator to internal regulator in case of failure of the external regulator which have a tendency to fail as per forums after our research.
It worked right away. We obviously see an improvement in the charging. We reduced the capacity of the alternator with the regulator because we currently have a small battery bank and don’t want to run the alternator too hot because the alternator runs hot when it runs full power compared to the stock one.
Now we are going to clean the old stock one, seal it up into a bag, and have it as a spare alternator which we would not feel comfortable to go without.
My first post!
- Carol


  1. This is great info Carol, definitely worthy of a post.

  2. Hi Carol -

    I don't know how yours does it, but some diesel engines use the pulse rate of the alternator to drive the tachometer. If the number of poles or the pulley diameter on the new alternator do not match that of the old one, you may need to recalibrate your tach.

    s/v Eolian

  3. Carol,

    Kathleen was reading your blog and left it up on the laptop, so I read your most recent entry... not that I have any time! I highly recommend the $30-$40 alternator temp sensor. It will automatically reduce the output of the alternator by 50% when it gets super hot from high charging output, something that doesn't do electronics any good. It's an easy, one-wire install between the alternator and the regulator.

    Also, West Marine will match prices. I always research for the cheapest price of an item online and print it out! Has saved us thousands!

    Estrellita is coming along,

    s/v Vicarious

  4. @Bob - I read about this in the Balmar manual and Calder's book. The pulleys are the same, but was unable to confirm the number of poles in the stocK alternator. Balmar 621 has 12. So, I was hoping for the best when I first started the engine after the install. RPMs were similar then before, so I am assuming that everything is good.

    @Spencer - Done! I am a big fan of temp sensors and both sensors came with the kit. Thanks for the info on WM. This may come handy soon, since we are looking to buy a water maker at some point.



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