Second Battery or Capacitor?

[alanholt]

We're running an amp, sub and pair of tower speakers off the standard Alternator and battery in our '01 Air Nautique. When the tunes are cranked we get the Tacho and volts gauge dancing along! trying to decide if we need to run another battery or if a cap will do? any advice?

[Hollywood]

RE: Second Battery or Capacitor?

If you're running low on power while the engine is running, a capacitor is your answer. If you're running out of power while the boat is off, get another battery.

[alanholt]

RE: Second Battery or Capacitor?

cheers Hollywood, we try to not run the stereo if the boats not running. A couple of times last year the amp popped the charge trip fuse while we were running and we didn't notice which killed the battery PDQ! but my main concern is the amp sucking the volts at idle rpm and the tacho needle swinging all over the place. I guess a Capacitor will stop that, how are they rated? how big will i need?

[Flux]

Sounds like you could have some improper wiring in there as well. We had a similar problem with a head unit sucking all the power from the dash, as well as some loose wiring on the temp gauge. I would definately check to see where all the equipment is drawing power from. The head unit and/or amp might be sucking everything out of your dash.

From what i have read and what I understand about these things, you may want to consider getting a second battery to protect your system as a whole. A second deep cycle battery isolated from your starting battery will protect the operation of the boat from you cranking up the stereo. Personally, I also like the idea of having all the stereo and auxiliary loads working off of a different battery than the starter. It's way easier to troubleshoot as well.

We also had trouble with the alternator and may have ruined the voltage regulator on the alternator with a short from the stereo, our gauges were all over the place. The previous owner had wired it funny, we rewired it into an empty breaker switch on the dash (92' sport) and replaced the alternator and all was fine. We had no amps though, just a head unit.

Your gauges going nuts is alot like what happened to us and I would suggest checking over the system as a whole just to be safe. Our problems ruined a nice weekend, but we learned alot about the boat by tracing the wiring and fixing the problem. You could search these forums for battery isolators, lot's of folks who run amps and such get a second isolated battery and maybe even a High Output alternator to handle the increased demand. Don't want to scare you or anything, but electrical problems caused by a stereo can cause your boat to go down, and nobody really wants that to happen.

Good luck.

[Grant_West]

Alot of dissussion has been done over the choice between Caps' and Extra battery's, IMO you cant beeat a 2 or 3rd or 4th battery.

I think of it this way a cap is about $150 and a Blue Top Marine Battery is about $150. So bang for buck. How long will your system run off a cap alone, (not Long) How long will your system run off a extra battery? (quite a bit) So if you already have extra batterys and your system is still making your voltage jump up and down while your boat is running Yes a cap might help. But extra batterys IMO will always win the war.

You should always have a second battery that runs all your accessories Lights Stereo ect. Make it so your styem pulls from that power source alone, and leaves your starting battery alone and fully charged. A stock alternator has enought juce to push 2 batterys

[Hollywood]

A second battery is definitely worth the money, cap or no cap. They are rated by Farads, I would suggest a 5 farad if you go that route. I'm using a 15 for 1850 watts in my car.

[clubmyke]

agree with grant....would suggest another battery ( gel top optima's) and perko switch....

if it still persists, would sugest checking the ouput of your alternator and going 100-150 amp upgrade...

[Timber]

I would get a couple extra batteries and upgrade the stock ALT to a 130.

[alanholt]

Thanks Guys! I wired the Head unit into some existing wiring where the previous owner had removed his unit prior to sale, definately got to check that out, sounds like its taking its feed from the instrument supply. From your input I think I will install a second Battery anyway. I agree, peace of mind that its not affecting other circuits is a good thing! Also once its in place future upgrades and accessories will be way easier. As for a Cap, sounds like that route will cure the symptoms but not the cause. Sorry to ask another question but I guess I'll need a split charge relay for the second battery, where is best to take a live ignition feed from to energise the relay? I'm thinking somewhere that is only live when the motor is running.
Cheers! Alan.

[clubmyke]

just as a heads up if you install a perko switch with a second battery...

the batteries should be identical...

[EchoLodge]

It maybe the old school way but.... I use a continuous duty solenoid rather then a perko switch or battery isolator to join my two batteries. Perko requires you to remember to switch it and isolators cause 1 volt power drops. When boat is off, all my gear is running off the acc battery. Turn the key to start and the batteries are in parallel and both charging.

[alanholt]

Cheers Echo Lodge,
I think this is the way I Shall go I'm pretty old skool too, Perko requires too much manual intervention. Kids jump in the boat at the dock crank up the Stereo forget to switch the Perko..... two dead batteries! I'm going to take an ignition feed off the lanyard/Ign cutout switch to energise the relay so when the engine is dead all accesories run from battery two and are completely isolated from the starting battery.

[jwhposon]

Alanholt, echolodge,

You guys give great information but for a rookie who is has an 04 SAN and am trying to put a five channel amp, and extra battery can you guys give a simple diagram? I am nervous messing around with the existing switch for battery operation and appreciate what you guys have said about having a starting battery and accessory battery. I currently have perko from my old boat but would like to move towards what you folks are going with. Do both batteries have to be the same as mentioned above? Can you show a diagram for a rookie ? When you say accessories, does that also include the bilge pump? Because I thought that was a benefit to have a manual switch, if the builge was somehow left on overnight and drained the battery, how do you get the boat started in your scenario?