Prepare Me For Battle--HAVE to 2nd Battery

[bschmaus]

Speaking of amps--does anyone have issues with their amps overheating in the front compartment under the stereo head? I had mine get really hot. I punched holes in the air intake tube that runs through the compartment and boy did that help. Just wondering?

[Domsz06]

yes my ppi amp overheats if I don't either leave the seats open. I put a squirll cage fan on it and that helped out a lot, but would still over heat on hot days. I now just make sure I have the compartments open until I set up my cooling system for the whole compartment.

[chpthril]

ok, bringing this topic back from the dead. IS there anything wrong with me adding a third or fourth battery to my boat? Right now I have a switch, has 1, 2 or both. I thought I could run it to my second one, put one or two more batteries there, run them in series, and then I could start from #1 and when I stop and just want music for a few hours go to #2, which would have 2 or 3 batteries.

First, add up the AMP/HR usage of your accessories and see if you will need 2 or 3 deepcycle batts for a day on the water.

An Isolator, in addition to the switch, is the best way to go. The Iso will allow you to run your system w/eng off for as long as you want (with accessories wired to the deepcycles) while the starting battery sits untouched. With the engine running, the alt will be charging both banks without having to switch anything.

The switch will allow you to switch over to the deeps for starting in an emergency such as a dead or failed starting batt. Otherwise, you can just leave it in the #1 position.

If you are using 12V marine deepcycles, wire them paralell so you stay at 12V: + to +, - to -.

Speaking of amps--does anyone have issues with their amps overheating in the front compartment under the stereo head? I had mine get really hot. I punched holes in the air intake tube that runs through the compartment and boy did that help. Just wondering?

Good point, I've got 2 kickers in the port console, have not noticed them getting hot in there, I will be keeping an eye on that this summer.

[Domsz06]

by amp/hr what exactly do you mean? As in for example, I have three amps, one is a 200x4 watt, 300x4watt, and a 1200x2? Is this what you mean, then figure an 8 hr day? Or is it something like I go look in the manual and pull the amps useage from there?



Thanks.

[spharis]

What is the total wattage per channel on your amps the way you are running them? Is the 1200x2 mono, at what load? If you can answer that, I can tell you your total amperage draw.

[chpthril]

Basicly, you take your system usage and devide it into your battery(s) AH rating and that will tell you how long it will run at that given load.

[spharis]

Yes the basic math to find your total stereo draw is by using Ohm's law. Keep in mind this is not entirely accurate as your amp will no doubt step up or down its power draw using Mosfets, and transistor rails, but this is pretty close. Music is rarely constant, so the amperage draw varies greatly with the frequencies. An amp rating is an average, and does not take into account peaks.....similar to an RMS and Peak on a driver.
Not knowing how your amps are run, I am going to take a guess.

Current (A) = Square Root of (wattage(P) / resistance in Ohms(R))
200x4 draws ~ 7A
300x4 draws ~ 9A
1200x2 draws (wired mono) ~ 25A

so your total stereo draw is the sum of those ~ 40-45A

An amp hour is the amperage available discharged over a 20 hour period. Irrelevant to your figuring, but that's how they get them. So in their math, a 100AH battery was able to supply 5A for 20hours above 10.5V........This is why certain batteries may not ouput advertised rating for short periods of time. A small drain for a long time is going to be easier than a high drain for a short time. The 20 hour method makes it look better on paper.

OK back to your scenario:
Determining your reserve is a simple multiply or divide. In your case, you need 45A for 8 hours, so just multiply them. 360A would run you for 8 hours before the voltage was decreased to 10.5 volts. Then take 40% of that because you are not going to be jamming at 100% all day, and you also should run an alt occasionally.

45*8*.4 = 144

So pick up 2 100AH batts and you'll be set for a long day on the lake with tunes.

[Domsz06]

ok, I got it. I'll pull the specs on the amps tonight, if I still have the paperwork, and go from there. I'll do the math, have you check the numbers and we will come up with some info.

Thanks

[TigeDuner]

spharis, are these batteries to be deep cycle marine for the sound system and are they in addition to the starting battery? Usually the starting battery is not a deep cycle type. I have one 640 watt amp that is connected to a deep cycle marine through a two battery perko switch. The other battery on the switch is a non deep cycle battery for starting the boat. When we are out on the water with the engine on, the switch is in the "all" position to charge both batteries. When we stop for an extended period of time, we put the switch to "batt 2" for the sounds. The starting battery is then isolated and in reserve. I beleive this is about as generic as it gets and we have not been left stranded yet....
What about fusing? Not much mention about protection of systems. I chose a fuse before the amp rather than circuit breakers all through the system. Any thoughts?????

[chpthril]

Duner, Nothing wrong w/what you got IMO, this is what I had on my last boat. fuse works just as good as a C/B, just have to replace if one blows.

Always a good idea to have some sort of circuit protection between the source and the load and as close to the power source as possible.

[TigeDuner]

chpthril, I believe I have a high amp fuse in the line from the battery to the amp and it is located just before the amp. The deck is fused with what came with it. So far, so good, but I have several spare fuses in the glove box..

[chpthril]

A 'short to ground' is not as common on boats as it is in cars, but the thought behind protection close to the batt is that if the short is between the fuse and amp (or other componant) the fuse blows, no harm, no foul. If the short is between the batt and fuse, the wire is still 'hot' til it burns in half. So, if the fuse is as close to the battery as possible, you only have a small amount of damaged harness.

[xpjim1]

I read this post over and over and still do not have a clue. Glad my boat came with 2 batteries. If I ever upgrade to a better sound system you guys will be getting pm'd

[chpthril]

I read this post over and over and still do not have a clue. Glad my boat came with 2 batteries. If I ever upgrade to a better sound system you guys will be getting pm'd

I work for food, i'll come out and help

[spharis]

spharis, are these batteries to be deep cycle marine for the sound system and are they in addition to the starting battery? Usually the starting battery is not a deep cycle type. I have one 640 watt amp that is connected to a deep cycle marine through a two battery perko switch. The other battery on the switch is a non deep cycle battery for starting the boat. When we are out on the water with the engine on, the switch is in the "all" position to charge both batteries. When we stop for an extended period of time, we put the switch to "batt 2" for the sounds. The starting battery is then isolated and in reserve. I beleive this is about as generic as it gets and we have not been left stranded yet....
What about fusing? Not much mention about protection of systems. I chose a fuse before the amp rather than circuit breakers all through the system. Any thoughts?????

Obviously the best batteries are a dual purpose type (which most marine deep/starters are) and yes you are correct. I go back to the analogy of water with electrical. If you think of batteries as a huge tank of water......a starting battery has a huge hose....lots of water but it doesn't last long, a deep cycle is a huge tank with a little hose....nice stream of steady water for a long time. You can read the top of the batteries in the store to get the totals. A starter is usually rated in CCA (cold cranking amps...or the number of amps that can be output for 30 seconds @ 0 degrees) and a regular or deep cycle is going to have total amp hours listed somewhere. Starter batteries also will not take recharging and depletion as well as deep cycle.