Installing a High Powered Alternator

What is a High powered Alternator?

First, lets start with ‘what is an alternator’? An alternator is a mechanical device fitted to an internal combustion engine which takes power from a belt and translates that into electrical energy production. Then, a regulator regulates all those electrons into a charging source for the electrical system and battery storage.

A ‘High Powered’ Alternator is one which makes substantially more power than a typical OEM fitted alternator. For instance, Volvo uses a pretty standard 60 amp internally regulated alternator for charging service. Our ‘High Powered’ alternator is 250 amps and externally regulated (more on that latter).

How good is a balmar alternator?

Really good! We have now installed two on various sailboats and loved each one. The quality is top-notch, and honestly, its a shame it’s not on display because its a work of art! Balmar alternator’s are rated for marine use, which means they are properly coated, or use materials which will endure a little longer in the marine environment.

Balmar 250XT is the star of the show! (Belt tension is not yet set here)

Details of our Balmar installation:

Diesel Engine - Volvo Penta D2-55F, built circa 2015.

Balmar Alternator - 250XT-DF4-250-K6-KIT -> Translates to: 250amp XT model, double foot mount, K6 pully, with regulator kit.

Mount - Volvo’s ‘extra’ alternator mount kit: #21384685. This is a Volvo part number for mounting a second alternator in this configuration pictured.

Installation Issues

I would have to say we had very little issues installing with very standard parts. The quality and accuracy of the Volvo mount kit was superb, though you do pay a pretty penny. However, a custom mount would probably net you the same costs if your hiring out the engineering and manufacturing work.

We did encounter one issue where the positive stud on the Balmar 250XT interferes with the fuel injector lines. The Balmar is designed to have a terminal mounted on the stud which exits radially from the alternator, but that just won’t work. In this case, I did have to make a sort of custom stud, and used a lot of insulation around the closest fuel line to mitigate any potential grounding.

Interference with fuel pump output lines. A longer stud was added for the positive cable to exit vertically.

power output of our balmar 250xt

This thing is a BEAST! It has exceeded our expectations for continuous power production. I’ll get to some numbers, but let me first explain a few things:

First, we are charging a lithium bank, in which the capacity greatly exceeds the production ability for these alternators. So, when charging, the lithium bank will accept all charge, and if not properly regulated, will BURN OUT an alternator from heat. The Balmar has a temperature sensor in which reaching 92C (200F), the regulator will lower the field voltage and thus reduce output current, and waste heat.

Now keeping this in mind, we have two limitations: Our BMS (battery management system) has a combined limit of 200amp input. We also have solar at maybe 25amp max, so we have to limit our alternator to ~170amp maximum output. The second limitation is this temperature. After about 15-20 minutes from cold, the alternator will cycle due to it’s temperature limitation. Thus, we do not operate for maximum peak production, but rather the long production game.

Monitoring charge via our Victron Energy SmartBMV monitor.

The Balmar MC-618 regulator has a belt limiter function, which we set to F-3 to limit our output on both these parameters. Thus, on a typical charge, we will get about 170 amps maximum, then limited to an AVERAGE of 130amps as it cycles between 140-100 amps. Colder climates this average is a little higher due to the increased ability to shed all that waste heat.

Why upgrade to a second high performance alternator?

Motoring Time! If you are living aboard, passage making, or simply love running an ice machine 24/7, you will adore the power this produces. We all hate the noise, vibration, and smell of our diesel engines, so why not limit how much time they have to run? For us, getting a high powered alternator reduces our ‘charge time’ by a good 80% from just the stock OEM alternator.

We have modest house loads on our Neel 45 trimaran, about 130ah per day (or ~1,500 watts), running a fridge, freezer, fans, and stereo. Coupled with our 400ah lithium battery bank, we start our engine to charge once every three days, of which we can get mostly what we need in 2 hours or so. We do have a small solar array, but that only nets maybe 200-500 watts per day.

Why Balmar?

Because they are AWESOME! I’m serious. We don’t have any affiliation, we simply love their products. I swear we get more compliments in the engine room on our alternator. It’s the star of the show! And, not only are their alternators great, but their externally regulated controller, the MC-618 is quality at it’s best. I even see IMOCA and other classes of racing boats use them because they are very reliable. Not to mention their customer service, ordering, and dealer network are fantastic.

I hope you enjoyed this little tech piece! If you have questions or comments, write below, or send me an email!

Darren Seltzer