Alternator Question

[HPBoats83]

Ok so I went to what I thought was a pretty reliable battery and alternator shop in Havasu yesterday and was talking to him about building my alternator bigger to like 130 amps. He said "An alternator doesn't charge a battery, it just maintain's it!" Is this true because I thought an alternator charged the batteries. I want a bigger alternator because I have (4) blue top optimas and I don't think my little 65amp is cutting it. Please advise.

[GunninGopher]

Based on my experience talking to them, most mechanics will say that you should charge a battery that is heavily discharged with a charger, not the alternator. I don't think there is much that we boaters can do about our situation, however.
He should have asked you what you load was. My understanding is that you get an alternator to cover your load + a little more.
He should be reminded that you often use your power (presumably you have all of those batteries because you have a big stereo) when the engine is off. I'm not sure, but I think the ideal situation is to have a generator for battery regeneration. I suppose it could be engine driven?

[AZKC]

He's pretty much telling the truth. But you do need more than a 65 amp alternator.
I think there are a few guys run small aux generators to run their systems and recharge batteries.

[HPBoats83]

I have a decent stereo in there with a shore power charger; however, if I don't pull my boat off the water (leave it in the slip) then it makes me worry and I was hoping that with the bigger alternator it could charge it a little (I know it won't charge as good as my shorepower charger) but can get me by for a day or two.

[GunninGopher]

Tell him what you have and how you use it and ask what the options are. Obviously we can't just have our boats idling for hours just to run the stereo, so we need the reserve power and a way to regenerate it. He may realize that a big alternator is your only option, or have a better idea, like an engine mounted generator for your auxiliary batteries.