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Catalina/Capri 25/250 Sailor's Forums

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Portable Speaker Power

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rsdavis
Deckhand

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7 Posts

Initially Posted - 06/20/2014 : 14:03:45

Hello all,

Recently bought a Catalina 25 with no audio system. I would like to simply buy one of those portable speaker systems, but want to make sure I can power it. They all come with AC adapters and charge from 12V DC. I am wondering if I can just cut off the AC adapter part, strip some of the wire back, and connect directly to my battery bank (switch panel). Will this work? Is this a common thing to do? Any comments on using portable speakers rather than installing traditional speakers and cd player?

Any feedback is appreciated, thanks.

Here are some speakers I am looking at:

http://tinyurl.com/oowg2a6
http://tinyurl.com/mzfsur6

Edited by - on

jduck00
Captain

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USA
313 Posts

Response Posted - 06/20/2014 : 17:04:27

Rather than destroying the AC adapter, you could get the DC jack from radio shack and wire up a pigtail to your switch block or your battery. If you straight to the battery, put an inline fuse on it.

Can't comment on the advantage of one over the other. I went ahead and put some decent speakers in mine and love them. The portable would definitely be easier. My vote would be go for whatever gets you the most time on the water and save the hard work for winter.

Edited by - on

Chief RA
Chief Technical Advisor

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USA
191 Posts

Response Posted - 06/20/2014 : 18:18:50

Measure the DC output from the AC to DC adapter and make sure it is close to 12v DC. If it is just tie you a DC connector on the DC wires and not cut off the adapter. That way you can use it from AC or DC. If AC is not important just cut it off and do the DC. There are some transponders on the market for about $20 bucks each that stick to the back side of your fiberglass panels and speaker style transmit through. Supposedly work great and no holes!
If you guys need me on this electronic stuff just ask, I have such a background if I told you, you would want to throw up! ha
Chief, EE,IE,ET,FCC lic#1890

Edited by - Chief RA on 06/20/2014 18:21:03

Voyager
Master Marine Consultant

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USA
5353 Posts

Response Posted - 06/22/2014 : 11:26:27

Rather than hardwire to the battery, why not purchase 2-3 12VDC cigarette lighter receptacles and install one near the galley, one near the port bulkhead and another near the starboard settee.

You can install them permanently by drilling a hole and running the wire behind.
Or you can run some 12-2 cables along the hull deck joint and lay the outlet on a shelf or secure it with a tie wrap.

There's a switch on my electrical panel marked "deck light". If yours has a spare circuit, connect the 12VDC outlets to it.
If not, you may want to connect it directly to the main DC house power switch.

I connected my Sony FM/CD/USB receiver and speakers to the deck light circuit and added a few 12VDC receptacles.

I recommend 12-2 cable since you can pull a lot of current through a cigarette plug. Put a 10A fuse on each circuit and you'll be safe. 15A fuse might result in too much power draw. My audio unit takes 1A idling and ~4-5A at max volume.

Having the lighter plugs gives you a lot of options. Recharge a cell phone, a wifi modem, LED lamp, or handheld VHF.

Edited by - on

pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 06/23/2014 : 05:31:01

Speaking of installing a 12 volt power port AKA cigarette lighter socket...
In the early 80's I wanted to use my 9" B&W TV on my Spirit 23 so I installed a cigarette lighter. I however was completely ignorant of the bastardization of physics known as "Negative Ground". Electrons flow from Negative to Positive, everyone knows that. SO I installed my cigarette lighter accordingly and promptly blew the TV. I had to be told that Detroit had done things differently by a friend. So, make sure you ignore any Physics or Electronics circuit design you know and install that 12 volt port the "Detroit way".

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 06/23/2014 : 06:16:53

If you want to wire directly to the battery, I highly recommend these. Replaceable fuse is built-in, small quick-disconnect plug runs easily through tight spaces, etc. I used it to run a 12v through my steering pedestal and out the unused hole for a trottle lever. The only negative is that I suspect it's not marine grade, so keep an eye on corrosion over time:

http://www.amazon.com/Battery-Tender-081-0069-6-Terminal-Disconnect/dp/B000NCOKZQ/

http://www.amazon.com/dp/B0041CDPQO/

Edited by - on

Voyager
Master Marine Consultant

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USA
5353 Posts

Response Posted - 06/23/2014 : 10:31:31

Rick, I have some of these for my solar panel (it came with them).
They work great and are small and inconspicuous BUT polarity can be ambiguous (per Frank's observations about lighter plugs!).The red positive battery side is recessed (receptacle) and the black negative battery side (plug) is the standard hookup configuration. But it's too easy to swap a battery side connector with an appliance side connector, so you could easily blow your TV, radio, USB, etc.
This should not be possible with a cig plug. The standard hookup should be center conductor = red+, side conductor = black-. But remember the rules of "idiot proofing", nature is infinitely resourceful.

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 06/23/2014 : 20:39:44

quote:
Originally posted by Voyager

Rick, I have some of these for my solar panel (it came with them).
They work great and are small and inconspicuous BUT polarity can be ambiguous (per Frank's observations about lighter plugs!).The red positive battery side is recessed (receptacle) and the black negative battery side (plug) is the standard hookup configuration. But it's too easy to swap a battery side connector with an appliance side connector, so you could easily blow your TV, radio, USB, etc.
This should not be possible with a cig plug. The standard hookup should be center conductor = red+, side conductor = black-. But remember the rules of "idiot proofing", nature is infinitely resourceful.

None of my Battery Tender cables have an appliance side connector - they all have +12v leads recessed. And that is as it should be, since the "hot" (high potential) wire is always recessed by convention of all electrical standards. So anytime you connect the harness to the battery or other source of energy, the + lead will be recessed in the plug for safety reasons.

Where I have run into problems is when looking to connect two hot sources together, such as connecting two identical batteries together to form a bank. (Your solar panel/battery combo is another example of connecting two hot sources, so actually analogous.) I actually connected two identical batteries this weekend to prepare for a cruise next week. For ease of access, I wanted to locate the second battery under the companionway steps, about 7' away from the first one, and have the ability to make a quick disconnect in case I want to put the battery into the dinghy with a trolling motor, so I used the battery tender system to connect the two batteries. For a few minutes it was tempting to connect one harness backwards to get positive to positive between the two batteries, but that could be VERY DANGEROUS if I left the backwards harness on the battery and then went to use it for something else. So instead I used a cable like this:
<center>

</center>
So now each battery has the harness on the correct way, and a 12v socket connected to that. To join the batteries, I connect the two 12v sockets using the dual-male cable like shown above. Having the harnesses on the batteries the correct way will ensure that if I ever use the harnesses for something else I won't fry whatever I connect to it - or fry my whole electrical system.

I do need to be careful that the current between the two batteries never exceeds 7.5A, but if it does it will just blow a fuse harmlessly. This will be especially important if I discharge one battery with the trolling motor - I need to charge it separately before joining it with the other battery, otherwise the flow from one battery to the other could exceed 7.5A.

I don't really understand why 12v electric is so confusing to some. I'm not aware of any unusual Detroit hanky-panky on the electrical standard. Everything I've always seen agrees with what I learned in Physics and Electrochemistry. First of all, the negative terminal on a 12v system is NOT ground. And many references will warn you not to connect a boat's 12v system to ground. "Current" is defined as flowing in the direction of positive cations, and electroneutrality dictates that negative anions and electrons will flow in the opposite direction from the "current." While it may be confusing since only electrons flow through copper wire, anyone who has ever measured conductivity of liquid electrolytes, done electroplating, or worked with a wet cell battery recognizes that cations have a contribution to the flow of current in those cases. The key is to realize that "current" and "electrons" are totally separate things, and flow in opposite directions by definition.

It's important to recognize the property of electrical potential, which is maximum at the battery's (+) terminal, and minimum (but not necessarily zero) at the battery's (-) terminal. As current flows through devices on the circuit from + to -, the potential drops. None of this requires a ground.

I'm open-minded to any arguments that you want to make that this conflicts with Physics. But as far as I can remember, it's in total agreement with Physics 102 when I learned it.

Edited by - TakeFive on 06/24/2014 05:45:27

Voyager
Master Marine Consultant

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USA
5353 Posts

Response Posted - 06/25/2014 : 21:19:10

I think we're in violent agreement on this. I like your dual ended connector, since it follows the rules of receptacles and shielding the positive terminal. I also agree that nobody needs to confuse the (+) and (-) terminals accidentally, so that's why I am skittish about using potentially "reversible" connectors for power sources and appliances, and prefer cigarette lighter type connectors.
The saving grace for my solar panel connector is that the solar panel does not connect directly to a hot battery, instead it connects to a voltage regulator that cannot source battery current accidentally. That, by the way is why I did not automatically eliminate it from the boat - it has a very specific purpose and no other power sources or appliances can use this connector on my boat.
All other connectors on board use cigarette lighter types so everything interconnects:
my handhelf VHF, my portable FM radio, my Coleman LED lantern, my Coleman fluorescent lantern, my bilge pump, the LED spotlight and my USB power adapters.

Edited by - on

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