PDA

View Full Version : I've gone and confused myself about adding a 2nd battery...



beedish
04-19-2011, 10:34 AM
So here's what I'm planning on doing:

I've added an amp for my in-boat speakers that is currently being powered by my #1, and only, battery.

I am adding tower speakers and an additional amp and will be installing a #2 battery. I intend to power the new amp and move the amp for the in-boat's to this new battery.

I have purchased a Perko 2 battery switch. I plan on following their installation setup for the 'Single Engine, 2 Batteries."

Now my question/confusion. My H/U is still being powered from battery #1; and my in-boats and tower's will be powered from battery #2. Will I run into any problems leaving this setup how it is, or is it worth the time to get the power to the H/U coming from battery #2 as well?

I intend to leave the Perko in the "ALL" position while at rest listening to music.

I hate being blonde...

-Blake

mmandley
04-19-2011, 12:18 PM
Blake

Lets assume you leave everything the way it is.

Problem you might see is Noise in your stereo when the boat runs.

After you listen for a few hours at the party cove the boat wont crank and you have defeated the purpose of a second battery.

This is what i would change if my thinking if i was you.

1 No problem with Deck staying on battery 1 as its wired threw the main boat harness to the fuse panel and thats a good thing. What you need to change is just the ground line off the deck. Find the black ground wire and extend it and connect it directly to the Negative terminal of battery 2.

2 Never run both battery in the All position if you are going to have the engine off for any extended time. In effect what you have is a huge 12v single battery when its in the ALL position. This is when you switch the selector to 2. 2 is where all the stereo Amps are plugged into. This is the stereo or Aux battery. This way when you are party coving and listening to music you are only draining the Aux battery. Now if you kill the battery then you switch the selector to 1 and crank the boat up. Once the boat is running for a minute or two or you are driving it then set the selector to All to charge both batteries.

Never Never put the selector to All if you think 1 battey is dead as this Equalized both batteries and you may have 2 dead batteries now. Also try to refrain from the temptation to start the boat and then switch to 2 and send all your alternator charging to your dead battery as this can over load the alternator and in time burn it out as well. The dead battery will be like a starving child screaming for voltage and the alternator will act like a man just rolling out of bed before coffee.

I run a 3 battery setup currently and when the boat is cruising we always have it in All.

When we stop we change it to 2

When we start going again we change it to 1 to start it, then All while driving.

When i get home i check all the batteries with a charger.

This also brings up the question how do you home charge it? Put the selector in All or Both and connect the charger to any battery you like as it will see it as 1 big 12v battery and charge them both at the same time.

Razzman
04-19-2011, 12:24 PM
Ditto what Mike said, never ever park and listen to tunes in the "all" position or you may end up stranded one day! I had a Perko on mine when I bought it and for the record I hate Perkos! I switched over to an ACR so I don't have to make switch changes, it's all automatic.

beedish
04-19-2011, 12:49 PM
So if the positive of the H/U is on batt #1 an it is grounded through batt #2 then I'll still have radio functionality when perko is on batt #2 only?

mmandley
04-19-2011, 01:25 PM
Yes you will. The deck Positive should be looped threw the boats accessory cable. Its generally a 8 gauge line that goes to the drivers side and plugs into the Fuse box over there.

Having the Stereo Negative cable on battery 2 wont batter at all. It will help stop any noise from getting into your stereo. The noise comes from all the accessories on the boat and it travels threw the ground buss bar the boat uses. This is why when you ground just the stereo to the Battery 2 you help eliminate boat noise in the stereo.

beedish
04-19-2011, 02:30 PM
Excellent! Thanks for the help! I'm a little more clear now. We'll see how I do this weekend!

EarmarkMarine
04-19-2011, 03:16 PM
beedish,
You never want your source unit to access power from a different battery than the amplifiers. The same current flow created by voltage potential attempting to circumvent the dual battery isolation and equalize, that causes the noise, can indeed harm the fragile IC OP amps that are the preamp output of your source unit. It is precisely the ground shield on the RCAs that pass the voltage even though they may terminate into 10kOhms. I'm sorry for getting technical but I've got to give you what is really taking place and the risk involved.
If you properly wire the Perko switch so that all the stereo equipment including amplification, the helm buss and the starter/alternator cable is connected to the Perko common post and nothing else is wired directly to the batteries except the Perko switch #1 and 2 posts, then you will never have to worry about the above noise or possible equipment failure.
Moving the source unit ground and/or supply off the factory harness is always a good idea, especially as your system gets more sophisticated. Connecting them to the primary terminals of your largest amplifier satisfies the need to reference the lowest potential difference at the most critical relationship.
ACR/VSRs can, not always, but can get more complex. Many totally isolate all stereo equipment on one battery while combining the house bank/helm buss and alternator feed/starter on the other bank...especially when using a really large stereo. However, some models of boats will dictate other schemes. But since you are not looking at that option right now I'll let it pass.

David
Earmark Marine

cab13367
04-19-2011, 03:34 PM
You never want your source unit to access power from a different battery than the amplifiers.

David,

My head unit is grounded directly to the same battery as my amp (battery 2), but I left the power wire in stock configuration, which I assume runs from the head unit to the stereo switch on the dash to the buss bar under the dash, which means it's being fed by the starting battery. I've had it in this configuration for a while now and I have not seen any problems. Have I just been lucky? Am I in danger of frying my head unit?

Al

EarmarkMarine
04-19-2011, 04:06 PM
Al,
I know I get a little technical sometimes but I try to introduce the readers to different concepts rather than the same old same old, plus I want to provide the real reasons why.
The affects can be variable. If the charge level between the batteries are minimal than there is less voltage differential that is trying to equalize. As the charge level is quite a bit different due to a larger system, larger battery reserves and longer playtime at rest, the difference can be more profound and the risk can be greater.
If its not too much trouble I would recommend making the change.

David
Earmark Marine

beedish
04-19-2011, 04:19 PM
David; to paraphrase, you're concerned that the system trying to equalize the voltages between the H/U and the amps would introduce 'noise' into the output?

If that's the case, it shouldn't be a problem to change the power source over to the new battery for the H/U. My only question is that I have a red (power), black (ground) and yellow (constant power) to the H/U. All else is through RCA's. I assume red to positive terminal and black to negative terminal of battery #2; but will the yellow go to the positive terminal of battery #2 as well, or can i leave it connected to battery #1? Or is it one of those cases where 'you're already moving the others, just move one more...' ????

Edit: Is it a smart decision to re-route with shielded wire to avoid any possible interference?

Edit #2: Just realized the radio is switched; so would the red accessory wire to the back of the H/U stay in place and it would be necessary for me to find the hot lead into the switch and re-route that to battery #2??

EarmarkMarine
04-19-2011, 05:04 PM
beedish,
Seldomly are the proximity of the RCAs to the power wire a real source of noise unless you run them parallel over a long distance. Its more of an accumulative issue with cheaper RCAs, lose RCAs or overgained amplifier inputs. So just avoid long side by side stretches and you should be fine. We've never had to actually move RCAs in a boat. Its a bit different in a car if you run both down the same side under tight rocker panels over a 15 foot span.
Yes, even though the memory circuits don't usually have any relationship to the signal path, while you are at it go ahead and move the memory too. Some people run the memory battery direct so they don't lose programming over short durations but they add a switch for long term storage as to avoid the drain which can empty a battery in 3 to 4 weeks. It depends on the particular radio defaults and your particular usage as to whether or not this is worthwhile.
If you want isolation from the helm buss but you still want the switched function a basic interrupt relay (horn relay from any auto parts store or stereo shop that does alarms) will do the trick. Its very easy surgery.

David
Earmark Marine

cab13367
04-19-2011, 05:06 PM
Al,
I know I get a little technical sometimes but I try to introduce the readers to different concepts rather than the same old same old, plus I want to provide the real reasons why.
The affects can be variable. If the charge level between the batteries are minimal than there is less voltage differential that is trying to equalize. As the charge level is quite a bit different due to a larger system, larger battery reserves and longer playtime at rest, the difference can be more profound and the risk can be greater.
If its not too much trouble I would recommend making the change.

David
Earmark Marine

David,

Thanks for the response, I understand the concern now. I will go ahead and make the change, but want to keep the functionality of the stereo ON/OFF switch on the dash, so I will re-route the power from the switch back to the port side where the stereo batt is. I don't know how many wires I have running through my ski locker now but looks like I need to add another!

Thanks again.

Al

beedish
04-19-2011, 05:10 PM
Yeah, I'll just pull my switch panel off and run a new power wire from the switch to the new battery. I'll just wire-nut up and tie the old power wire that was running to the switch.

Thanks for the help!