High capacity alternators
Jack & Fernando – much thanks for your thoughtful and very helpful responses to my post.
Jack, I am very much aware of the position the alternator plays in the electrical system as one of multiple integrated components and agree with your, “forest for the trees” caution. In fact, this project could easily spread to other components and I’m not sure that is worth it to me. You offer some very interesting alternatives to the obvious “bolt on a Balmar” approach that I had not thought of. I will explore them – thanks!
Fernando, you touch on at least one point for my hesitancy about the move to a high capacity alternator. Frankly, keeping a stock of 10 spare belts on board and replacing them frequently may be more annoyance than running the engine longer or more frequently to my style of sailing (enjoyment - I’m not a live aboard). Also, I was interested in your assumption that my auxiliary must be in the 100 HP range, given my interest in 100 to 150 A alternator. Mine is a 55 HP Volvo. I expect a 150A alternator to draw slightly less than 4 HP to run at its peak output. The stock alternator is drawing approximately 1.8 HP (calculated). Accepting those estimates (for the sake of discussion) the difference is an additional 2 HP load on the diesel. I would have expected this to be only marginally noticeable, if at all.
Another concern (paranoia?) is the increased side loading on the various shafts. Mine is a single belt installation. All the additional belt tension required to transfer those 4 HP from drive shaft to alternator will be shared by each shaft on the belt. Over time, that will take its toll on the water pump – first seals, then bearings. Any experience with how long that inevitable bit of “erosion” will take? A dual belt solution is certainly possible, but not inexpensive!
I’m not trying to talk myself out of the upgrade – there’s just enough engineer in me to be suspicious of the “something for nothing” that, “bolt on a Balmar” assumes.