Extra battery question

Adding a few blue tops and have a wiring issue. I have a two position perko witch. I'll run the red power to the strating and the acc. battery. Can I connect the grounds of the battery, or do I have to run both grounds to the grounding block? This would save about 12 feet of 1/0 wire. Can I do this, or there is an issue I'm missing?

First off 1/0 wire is overkill from an electrical standpoint, although it looks great so why not? Since you have about 3 times the capacity that the battery could ever deliver with the 1/0 wire go ahead and connect the grounds together.

That's what the manufacture wired the alt and battery with, so I figure I'd stick with that.

I wouldnt say its overkill.
I used the 1/0 wire too. It all depends on length. 3-6 ft #2, 6- 8 ft #1 , 7-12 ft. 1/0. This is from my factory manual.

The steady state current delivery capacity of 1/0 wire is 195 amps at 60 degrees celsius. Running individual wires from the batteries would provide 390 amps of steady state delivery capacity, that's definately overkill. Steady state delivery is also very different from what our stereo's demand.

This is an interesting subject that I have discussed offline with several individuals and I still have the opinion that 1/0 is overkill. I have access to some electrical measuring equipment including capability to measure 100amps DC with a clamp on meter. I think some real world measurements would be very enlightening to all of us (myself included). With the help of Grant and a few others I hope to take some measurements and draw some conclusions. Most likely it will be October 15th or so before I will have the time. Jeff, if you would like to be included keep in touch with me. We'll probably go out to ski beach or the BWSC beach where we can run our systems without disturbing anybody.

Mike (my e-mail address is in my profile)

mikeski:

There are two issues regarding the proper wire size:

First, and most importantant, is the ability of the wire to carry the current without overheating. This calculation does not consider the overall length of the wire.

Second consideration is the voltage drop. If your battery was mounted in the bow then you could easily have a 15 foot run of wire to get to the starter, giving you a round trip distance of 30 feet. 30 feet of 1/0 wire, while carrying 195 amps, will drop 1.4 volts. That can make a big difference to the starter!

Good question as my new soundstream keeps popping my 100 amp circuit breaker and the gain is only set at about 6/10th's or so and im not turning the volume all the way up. It is no doubt very loud though before it decides to let go. Amp says you can run up to a 140 amp fuse but im trying to protect my speakers as others occasionally touch my controls.

Mike count me in. I live a mile from Orwoods, and have a HUGE garage. If you need anywhere to do some land based prep before heading out, let me know. It might be interesting to get a few boats together, with diffrent wiring set ups and do some tests to post here. I'll help out in anyway I can. I have a lot to learn, and sure some of you can help me with that.

Rod makes a good point, I didn't want to bring in the voltage drop variable since because it varies with temperature. The key in his statement is "while carrying 195 amps". Like I often tell my work collegues, let's just measure it and see what's going on in the real world.

The testing is pretty easy with the clamp on meter so no prep is necessary.

How about mounting the batteries close to the amp since the alternator will most likely put out less current then the batteries will be delivering to the amps. Use smaller gauge wire for the longer distance = cheaper