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Replacement alternator for Yanmar 1GM diesel?
Elias Aarnio wrote in news:48333bfb$0$2669$9b536df3
@news.fv.fi: kirjoitti: To be exact a higher amp one does not take more engine power unless it is called on to deliver more current. I'm assuming the op has a reason he wants more current like a multiple battery installation. If not then there is no reason to go to a larger amp one. Bingo. I forgot to say that I have a 60 Ah battery for cranking the diesel and 2 x 80Ah for other use. A 35A alternator is not really sufficient for this much batteries to be charged. The cranking battery recharges in just a few minutes as you never discharge it unless there's something wrong with the diesel, so it's not part of the problem..... 160 AH house batteries should be charged at 25% of their amp-hour rating or 40 Amps to start the recharging cycle from 50% discharge. This current soon drops off as battery voltage comes up on the regulator setting. Recharging these house batteries at more than 40A will overheat them and warp the plates, especially if you have them in the usual boater's pretty box which acts as an insulator so the poor batteries can't cool themselves by natural convection, or have them stored in the hot engine room at 180F next to the dieselbeast. Charging current must be severely reduced as battery temperature increases due to poor cooling or operation in a hot environment to prevent soft lead plates from warping, possibly leading to a cell explosion if those plates touch! If you ever get a chance to look into a boat where a battery has exploded, do so and you'll want to get rid of this stupid idea that you're going to recharge the house batteries in 30 minutes at 500 amps.....a really dumb idea that just permeates every marina you come to. I think your problem is not how much current the alternator is capable of producing, I think your problem is light duty alternator overheating if the discharged house batteries are going to pull 40A out of it for 5-6 hours before the charge starts tapering off allowing the poor alternator trying to cool itself in that HOT engineroom all sealed up, COOKING IT. 60A would be a great size, if we need to add a 20A underway power load to the charging house batteries....60A continuous duty, not a $69 cheap car/boat alternator. 60A dual rectifier alternator is around $400US, here in the states. Go to a Finnish alternator shop where you are and talk to the experts. Tell them what your constant electrical load is from all the lights and electronics pulling on the house batteries, a sort of worst case scenario, out there in the dark on a stormy night with nearly dead house batteries from leaving the engine off way too long. They'll know how much alternator you need that will survive this awful loading..... |
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