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View Full Version : Is 2nd battery a must when running 2+ amplifiers



cab13367
04-10-2008, 03:51 PM
Another newbie question - what is the reasoning behind having a second battery when having a stereo system with multiple amps? Is it because the amps will run the battery down when listening to the stereo with the engine not running, and thus, the 2nd battery is insurance that you can get the boat started? If this is the case, is a battery minder an acceptable alternate (shuts the power off when the battery gets below a certain voltage, allowing enough juice to start the engine) along with a portable battery pack?

Or is it because the amps draw so much juice that one battery is not enough to supply the juice needed by the amps and the engine and accessories?

I don't have a problem adding a second battery other than the space it takes up so I want to make sure I understand it's purpose.

Thanks in advance to the stereo experts out there.

Al

zabooda
04-10-2008, 04:34 PM
I only have one battery and I have a stereo and a seperate amp for the subwoofer. Nothing really big. I carry jumper cables and I rely on administrative controls over engineered controls. I take the boat out at least every 1.5 hours of stereo operation and charge the batteries while pulling someone. You need to get a feel for what works for you. I'm a skier also so added weight is not good.

qb12
04-10-2008, 04:51 PM
I only have one battery and I have a stereo and a seperate amp for the subwoofer. Nothing really big. I carry jumper cables and I rely on administrative controls over engineered controls. I take the boat out at least every 1.5 hours of stereo operation and charge the batteries while pulling someone. You need to get a feel for what works for you. I'm a skier also so added weight is not good.

in my old supra i had two amps, 14 inch sub and 4 tower speakers and used only 1 battery. as with booda, i carried along a jumper box and never drained my battery.

tlatoani
04-10-2008, 05:00 PM
I think a jumper box is a good solution, but I'm a bit anal so I just added a second battery. I was also afraid that I would forget the jumper box the one time I needed it. It is pretty cheap to add a battery. (I got an optima bluetop for 155 at Sams, plus ~50 for a relay, and maybe 20 for cables and stuff).

On a side note-I saw a neat jump box with a usb power socket. Pretty cool.

byronkoz
04-10-2008, 08:15 PM
A second battery is not only just in case one goes dead, its also to give you more power to your stereo. Its a good idea when running multiple amps and espesially when running a sub, to have more than one battery. Running multiple batteries parralell you'll have a better chance of maintaining a voltage over 11.5 for a much longer period of time, anything under that you take the risk of damaging your amp(s) or if there decent amps then thell probley go into protection mode and shut off. Its really best to have an acc battery and starting battery with a switch/isolator or better yet 2 acc batteries and a starting battery depending on the size of your system.

bamaspiveys
04-10-2008, 09:08 PM
so to tag a question on to this I see the perko battery switches, and think I understand howe they work but several people have mentioned a "relay" what is the realy for and where do you get one?

tlatoani
04-10-2008, 10:33 PM
so to tag a question on to this I see the perko battery switches, and think I understand howe they work but several people have mentioned a "relay" what is the realy for and where do you get one?

http://www.tmcowners.com/teamtalk/showthread.php?t=3557&highlight=dual+battery

Some great info in there. I ended up just buying a stinger relay from ebay-same thing as the one mentioned in the link. Install was easy-the purple wire on my ignition was the switched one just like the mc's.

byronkoz
04-10-2008, 11:42 PM
Im pretty sure skiers choice puts a relay+perko style switch in alot of there boats?? This would be the best way to run multiple batteries. Heres a thread I just found on WW that has some good info.

http://www.wakeworld.com/MB/Discus/messages/3183/566726.html?1207863641

zabooda
04-10-2008, 11:59 PM
bama,
A motorhome isolation relay would work and is about $15. You need to have it in a ventilated area as when the contacts close they do spark even though the relay is enclosed it could spell trouble around gas fumes. You could goop it up real well and fix that. The attached website has a good explanation.

http://www.neon-john.com/RV/Electrical/rv_battery_isolation_relays.htm

tlatoani
04-11-2008, 12:11 AM
I avoided a switch just because I have kids. If they flip it off while the boat is running it can do some damage. Not likely but you never know...

moomba_armada
04-11-2008, 09:38 AM
This is the way to go:
http://www.bepautomotive.com/showproduct.cfm?productid=1023

And this is the way SC connects it and the way I followed:
http://thumb14.webshots.net/t/55/455/7/37/67/2615737670101539954RpFmGh_th.jpg (http://good-times.webshots.com/photo/2615737670101539954RpFmGh)

Digger
04-11-2008, 11:41 AM
I believe that a second battery is crucial when running a larger stereo than stock. Another thing that has not been mentioned is that you want both batteries to be the same. They should have the same cranking amps and the same reserve capacity. This makes it a lot easier on your system and long term will keep your batteries in better condition. You will also want to make sure that you do the necessary maintenance to help prolong the batteries life and avoid problems on the water. As for the switch that sparks.... sounds a little dangerous. Something to think about is putting a little vasoline on exposed switches and also battery connections. This avoids sparks and helps prevent corrosion. It will not affect the contact if you apply it after you have made the connections. Good luck.