I just put a new stereo in my boat and added a second battery with a stinger 200 amp relay. The set up is with the head unit off the main ignition battery as it was set up stock, while the second battery is powering an Infinity 4x111 Watts at 4ohm, an Alpine 1x600 at 2ohm class D sub, and an Orion 2x100 at 4ohm, the system plays well of the battery (only issue is battery life) but once we have sat and ran off the battery for a while and start the boat, the system skips on and off. We swapped the alternator from a 55amp stock to a 110amp alternator, do we need to go bigger yet to prevent the system from skipping? or would adding a capacitor help with this? I don't really like caps but if it will solve the problem then I'm all for it. Thanks for the help
Mat - you're going to have the guy spending $300 he doesn't need to spend. Unless full volume test tones are his favorite music type the current draw will never even approach 170A, or even half that, probably not 1/3.
No on the cap.
How long does the skipping last once you restart the engine?
Are you using an isolator between the two batteries?
Your alt is probably doing OK. There isn't much demand from a boat's electrical system except the ignition system - that's why they come with such small alternators. Sounds to me like you're just draining the amp battery low enough that after starting the engine there's not enough voltage to keep the amps turned on. They typically don't like anything much under 12v.
Once the alt catches back up things should run ok.
hahahahahahaha matt HE DOES NOT NEED 170 AMPS! youre pulling about 120 amps and thats only if its full volume like optidriven said. so you need like a 200 amp alt and even a 180amp alt would work.....
Sorry for the long time between replies. Its more or less that the head unit shuts off what seems like randomly when the boat is running. Normally running at 3000rpm so the alt is putting out its rated. The head unit shuts and then turns back on. What I don't get is why the system doesn't then just pull off the battery right away. When the boat is off the systems runs great, but when running it becomes an issue. Is it that the alternator is too small?
that's just plain weird. I'm running ABOUT the same size system in my car - two under-rated amps - one at 700 rms, one at 360 rms - add to that the hvac system, electric fan motors, other creature comforts that most cars have but few boats do, and I have no charging problems whatsoever (110A alt).
If I were you I'd be wondering if there's not just a glitch with your HU that only shows up when you're moving.