Did I make a mistake?

[Brian66D]

Re: Did I make a mistake?

Lol.. just stick with that 105A DB Electrical model.. it will do you just fine. It handled things great up until around the 4th amplifier mark. Make sure to upgrade the wiring though along with it.. 6AWG with nice set screw type ring terminals on all ends. You'll need to get a slightly longer screw for the ground post on the alternator since the ring terminal is thicker than normal.

How often do you get re-inspected during the summer? Not that I would ever suggest putting in the 24 just for inspection and then swapping it out after for the 29s after you're through. *cough*



Confused by this. If you can fit one, why can't you fit the other? If you're planning on battery longevity why wouldn't you use both at the same time?

..and the biggest question: What's so hard about just firing the motor every couple of hours for a few minutes to charge it up? I say if you really can't fit the bigger batteries, then go with dual 24 series MDCs and be done with it. Run both at the same time or just one until you get a feel for how much power you'll really be using for how loud and long you're playing and gain the confidence to just run both.

I will buy all the cables and terminals online soon.
You only get inspected once at the beginning of the summer, so switching it out wouldn't be a problem...however I would think there would be fines if lake patrol were to board your boat upon stopping you (which happens more than you would think).

I'm not 100% sure that I could even fit one of them with the 24 in there vs 2x 24s. The space in the battery compartment runs right up to the back of the boat, where the fiberglass goes up to the top of the seat, then drops down low for the step off the back of the boat so clearance on the inside is an issue and the 24 is a SQUEEZE in there...might be easier if i can find a double battery box or make one...

Only running a head unit, one amp, and one bazooka tube I feel in comparison to your system that I should be fine for what I'm trying to gain. I also don't have a problem getting up in the boat and letting it run to charge for a few minutes...but sometimes sitting down in the water with a cooler full of beer you don't realize how much time has passed.

 

[bruceb58]

Re: Did I make a mistake?

2 deep cycles are fine. That is what I use for my boat and they start a 7.4L engine fine.

You also don't need to upgrade your alternator. See what your battery voltage goes to after you have been running your stereo. 12.0V is around 50% discharged and is as far as you really want to discharge if you want the battery to last very long at all.

You will be surprised how little this stereo will actually draw unless you have it turned up so loud that the entire lake can hear. Bottom line, you could have a 10,000W stereo and it won't draw that much more current than a 40W stereo if played at the same sound level.

I laugh at the notion that you could start your engine for a few minutes to recharge a heavily discharged battery. Even if a 100A alternator actually puts out 100A, which it won't, 5 minutes running the motor at a very fast idle, 2000RPM or more is going to put at most 8AH back in.

 

[fishrdan]

Re: Did I make a mistake?

FYI a 105A marine alternator is only $70 from DB Electrical and they work great. My 200A bad boy was $170 from PowerMax USA.

If you are hitting a discharged battery with that much current you need to check the electrolyte level in the batteries often as the high charge current will boil the electrolyte. I charge a pair of group 29's (trolling motor) off the 105 amp alt mark suggested and have to add water a couple times a year. And, I'm not charging the batts at high RPM, 700-900RPM while trolling off the main engine, so they are only getting about 65 amps between the pair, alt is spec'ed at 65amps at idle. (Every once in a while I'll hit the discharged batts with the full output of the alt if I'm running a couple miles and forget to flip the batt switch, though I try not to if they are deeply discharged.)

 

[mark1905]

Re: Did I make a mistake?

You will be surprised how little this stereo will actually draw unless you have it turned up so loud that the entire lake can hear. Bottom line, you could have a 10,000W stereo and it won't draw that much more current than a 40W stereo if played at the same sound level.

This is true and was stated previously.. but when multiple amplifiers are added you would have to keep turning down the volume as more are added to achieve that "same sound level". Moot point.

I laugh at the notion that you could start your engine for a few minutes to recharge a heavily discharged battery. Even if a 100A alternator actually puts out 100A, which it won't, 5 minutes running the motor at a very fast idle, 2000RPM or more is going to put at most 8AH back in.

No one is claiming that anyone is fully re-charging a battery.. just topping off to keep a safe amount of juice for engine starting. By your own admission of figures, 10 min = 16AH.. and if the stereo which is at half volume is drawing about 15A.. which is even on the high side and more like 10A.. how much more time did we just buy ourselves? Exxxxxxactly.. and this why yes, an upgraded alternator for the price is not absolutely "needed" but very desired. The stereo itself isn't "needed".. but it's damn nice to have just like that upgraded alternator

 

[bruceb58]

Re: Did I make a mistake?

If you are drawing 10A I would be very surprised. Probably less than half of that for what most people listen to stereos at. My point is there is no need to be upgrading an alternator for a stereo. If he was running a refrigerator or had an overnight cabin cruiser, that would be different.

 

[mark1905]

Re: Did I make a mistake?

[..] for what most people listen to stereos at. [..]

Exactly.. again. "For what most people listen to stereos at"

He's not "most people"


:facepalm:

 

[bruceb58]

Re: Did I make a mistake?

He's not "most people"

LOL...ok....whatever!

 

[bruceb58]

Re: Did I make a mistake?

pure deep cycle batteries have thinner plates (and more of them)

Actually, its the other way around. Deep cycle batteries have thicker plates. Starter batteries use thinner plates and more of them to increase the surface area to deliver more current.

Here is an excellent write up on batteries. It includes a chart of voltage vs state of charge.
http://www.windsun.com/Batteries/Battery_FAQ.htm#Major Battery Types

Also read about charging currents. Using a 200A or 100A alternator will cause the early death to your batteries if you are using the smaller size batteries that we have in our boats like group 24 or 27. Bigger alternators are used if you are using large banks of Trojan 6Vs for example. The article reccomends no more than 1/8 charge current of the capacity of your battery. The OP's stock alternator should be the one he sticks with.

 

[Brian66D]

Re: Did I make a mistake?

AHHHH so many opinons.

So do I get the alternator? Probably will....can't really hurt. IF i have to add water every once in a while thats no biggie, that being said i'm stressing the "IF" part.

I am also talking about playing the stereo at a fairly loud volume. A small cove with 30+ people sometimes many more, sometimes less....can really get rockin' lol

I don't plan on vibrating the fish death as I said before, but having it nice and loud for all to hear while enjoying some adult beverages is an ideal day on the water for me....which is why I'm coming to you all with questions

 

[Brian66D]

Re: Did I make a mistake?

Probably less than half of that for what most people listen to stereos at.

I do fall victim of cranking it a few db too loud...I'm in the "other people" category I think

 

[bruceb58]

Re: Did I make a mistake?

So do I get the alternator? Probably will....can't really hurt.

Only your batteries but you can always buy new ones more often. There is a drawback with the bigger alternator.

My suggestion is try without changing it and see how it goes. You can also measure your current with a meter and see how much you are really drawing from the battery and calculate what your needs will be.

 

[mark1905]

Re: Did I make a mistake?

I ran a 105A DB Electrical alternator for about 6 years with zero problems frying batteries.

Remember too that stereo amplifiers need power to make sound.. and crave it. The more constant, high power you can give them the better. Your music will simply sound better while running with a new, higher output alternator.. point blank. Add that to nice, reliable, efficient charging.. and it's a no-brainer.

..but hey.. do what ya like. I think we've covered enough bases here..





I'm still waiting to hear one of these old-timers start talking about vacuum tube stereo amplifiers..

 

[bruceb58]

Re: Did I make a mistake?

Remember too that stereo amplifiers need power to make sound.. and crave it. The more constant, high power you can give them the better. Your music will simply sound better while running with a new, higher output alternator.. point blank. Add that to nice, reliable, efficient charging.. and it's a no-brainer.

Hate to tell you this but the alternator only charges with the engine running. First time I have ever heard of an alternator making a stereo sound better. The stereo won't care how much output the alternator puts out unless you are pulling more current than the battery can provide which isn't happening.

 

[fishrdan]

Re: Did I make a mistake?

I ran a 105A DB Electrical alternator for about 6 years with zero problems frying batteries.

Yes, but how many batteries were you charging up and were the batteries severely depleted when charging them, or just a little run down? Just because you got away with it, doesn't mean everyone will.

I agree with Bruce on sticking with the stock 55-65 amp alternator, it has plenty of output for recharging 1 deep cycle battery. The DB 105 amp alternator would have WAY too much output for a single, severely depleted battery. I'm even leery of it's output at idle or above idle as I can tell it's kicking out a bunch of current, and I'm charging 2 depleted group 29's...

Also, the wiring for the alternator needs to be looked at to make sure it can handle the extra current, darn near double the current of the stock alternator. I upgraded the alt to starter wire to 6ga, since I had some extra...

 

[Brian66D]

Re: Did I make a mistake?

since I'm staying with the same size batteries....is it going to hurt IF need be I drive around the lake with the switch on "BOTH"?

 

[hrdwrkingacguy]

Re: Did I make a mistake?

There are a lot of posts here and I might have missed it already stated, but I would wire everything to the common terminal of the battery selector switch so you can just switch to the other battery and alternate which one is the stereo battery...That factoid is something silvertip usually mentions in posts like this one...The other is "Don't bring that loud stereo to my lake"

 

[bruceb58]

Re: Did I make a mistake?

since I'm staying with the same size batteries....is it going to hurt IF need be I drive around the lake with the switch on "BOTH"?

Not at all. Another thing you can also do is hook up an ACR. What it does is detect when either battery is charging and hooks them together so they both charge and then disconnects them when you turn off the boat.

This is the one I use:

http://bluesea.com/category/78/79/productline/overview/387

 

[mark1905]

Re: Did I make a mistake?

First time I have ever heard of an alternator making a stereo sound better.

From watching your ill-informed commentary, I can fully believe this statement.

The stereo won't care how much output the alternator puts out unless you are pulling more current than the battery can provide which isn't happening.

Lol.. ok.. listen. :facepalm:

Amplifiers need power to work.. that is how they amplify things. The more power that an amplifier has, the more clean power that it puts out. Amplifiers like 14.5v. Batteries put out around 12.5v. Bass notes typically use more power to reproduce and will instantly drain the electrical system if you're not feeding the electrical system with sufficient current. If you are using an underpowered alternator, then when the bass notes hit and/or you have the system turned up loud, then you are not able to constantly feed the amplifier the 14.5v on a steady basis that it's craving.

Hence.. the music and/or bass will not sound as good as if you are feeding it that nice, steady, clean, powerful source of 14.5v.

Which.. an upgraded alternator will give you when you have an electrical system that is a high drain system.

Not only will it physically sound better to your ears, but it will sound better to your speakers. If you do not feed your amplifiers sufficient voltage and you starve them, then they will send out a distorted sound signal to the speakers and can possibly fry them or blow the crossover capacitors in the case of coaxial speakers. These days with higher quality speakers, it's more common to blow your speakers from actually under-powering them than over powering them due to trying to turn things up too much with an under-fed or under-powered amplifier and distorting.

..and when I say "blow the crossover capacitors" I mean physically like *BANG* and they turn into what looks like a popped piece of popcorn. I've seen it happen in many, many clients boats when they bring them to me after a home or shoddy install that went wrong.. You know.. the ones that I've been professionally installing sound systems in for over 20 years now. Those ones.


No, you will have no problems keeping the batteries in the "BOTH" position either when the engine is on or off and especially if they are the exact, identical batteries and of similar age.

 

[bruceb58]

Re: Did I make a mistake?

So...I am still curious. If the OP wants to sit in a cove drinking beer and listening to his stereo, why does he need a 100A alternator when his engine is off? And lets say for some reason he wants his engine on while doing this, why does he need a 100A alternator when his stereo is probably drawing current in the single digits?

 

[hrdwrkingacguy]

Re: Did I make a mistake?

It depends on the system...A single head unit wired to four speakers isn't going to draw anything...The system in my truck(1800watts, 2 kicker CVR 12's and full boston acoustic pro front and rear speakers) will run for about 5 minutes at mild volume before the lights start to flicker...After 20 minutes my truck won't start...I have a 235amp alternator and a 2 farad stiffening cap and at idle there isn't any flickering with the volume turned up to ridiculous levels...The battery starts the truck but the system runs off the alternator at idle...

A boat is the same thing, you have finite amount of time you can run off a battery and a much better experience off a decent alternator...As for the stereo sounding better, it won't clip as bad and you have enough current to push subs properly with the engine on...But other then that you can't tell a sound quality difference on or off...

So you need a proper charging system for the application...You aren't going to run a 1200watt stereo off one battery for very long, but you can run a 100 watt stereo for a lot longer...