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  Wiring a 12V radio in a 24V series battery setup

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Author Topic:   Wiring a 12V radio in a 24V series battery setup
mutschle posted 05-01-2010 04:24 PM ET (US)   Profile for mutschle   Send Email to mutschle  
Hi, new member and hoping someone can help me out!

I am trying to install a radio in my River Rave 175VS. I have a 12V battery connected to the motor, which I found out today also has the bilge and other electronics on it.

I am trying to connect a radio to the trolling motor system which has two 12V batteries connected serially for 24V and am having some pretty good problems. I've fried 2 radios so far and am not sure what to do. Here's my problem (I hope I explain it right)...

I'll use the following abbreviations to lessen the length of the post.

Radio Positive wire = RP
Radio Negative wire = RN

Battery A Positive = AP
Battery A Negative = AN

Battery B Positive = BP
Battery B Negative = BN

Here goes!!!

I connected RP to AP & RN to AN and no power to the radio.
I connected RP to BP & RN to BN and no power to the radio.
I connected RP to AP & RN to BN and no power to the radio.
I connected RP to BP & RN to AN and got power to the radio but it immediately shut down.

(Any reason why the 1st three didn't work at all?)

I disconnected the trolling motor from the batteries and made battery A a stand alone battery. I then connected RP to AP & RN to AN and no power to the radio.

I put the battery back in series and connected everything back up normal, but could only get power when in the one config above.

I then had the bright idea that maybe I needed to use the yellow radio wire which is the continuous power. I tied RP and the yellow wire together to BP & RN to AN and viola, everything worked!!! Success? Not so fast!

15 seconds later, I turn up the volume to about 30 and hear a sizzle, see a flash on the inside, and see & smell smoke in the radio. FRIED!!!

I don't want to run the radio off the starting battery, so I would like any help I can get on how to run it off the 24V system. I've done this to 2 radios so far and would like to only buy one more and call it done.

If I hook RP and the yellow wire to AP * RN to AN, will that give me the power I need without frying anything? If that's what I have to do, how do I keep that from draining the battery during the week when it is stored? Or am I stuck wiring to the starting battery and hoping that I don't use all the battery power jamming tunes on the water?

The radio in question is a Pyle PLMR18.

Sorry for the long winded post. Hope someone can help me out! Let me know if you need more info!

Thanks in advance,

Matt

jimh posted 05-01-2010 04:41 PM ET (US)     Profile for jimh  Send Email to jimh     
Make a schematic diagram. It is impossible to describe electrical circuits in a narrative.
contender posted 05-01-2010 08:02 PM ET (US)     Profile for contender  Send Email to contender     
Jim is correct: However, Make it simple and connect your radio to the battery with the bilge pump. The way I read your thread is that you have 3 batteries 2 for the trolling motor and one for your outboard/engine. I would also use a small in line fuse on the power side of the radio (protect yourself, or your radio). A radio does not use all that much power and your engine should charge that battery...good luck
Chuck Tribolet posted 05-02-2010 08:55 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I connected RP to AP & RN to AN and no power to the radio.
This should have worked.

I connected RP to BP & RN to BN and no power to the radio.
This should have worked.

That happens with the later two is a function of how the
batteries are connected together, that is whether AP is connected to BN (based on symptoms, this is the case), or
BP to AN.

I connected RP to AP & RN to BN and no power to the radio.
If AP to BN, you should have no power to the radio.
If AN to BP, you just put 24 volts across the radio.

I connected RP to BP & RN to AN and got power to the radio but it immediately shut down.
If AP to BN, you just put 24 volts across the radio.
If AN to BP, you should have no power to radio.


I googled up the manual on your stereo.

RP (red) and yellow go to a source of +12V. The RP SHOULD go
to an accessory switch but the radio will work even if it
doesn't. Yellow should go to a source that's always on. RN
(black) go to -12V ON THE SAME Battery. It doesn't matter
WHICH battery.

IF you remember to turn the stereo off, it won't run the
battery down. The yellow wire is for the internal memory
of the stereo and draws a minute amount of current. An
accessory switch is a good idea, esp. one with a pilot
light. I've been putting the boat and trailer back in the
garage on several occasions when I noticed that the pilot
light on the acc switch was on.

I'd also recommend a basic electricity course. The above is all
stuff I learned in a 9-week electricity shop class in the
ninth grade.


Chuck

mutschle posted 05-03-2010 02:59 PM ET (US)     Profile for mutschle  Send Email to mutschle     
Thanks for the info / advice. I didn't get a chance to draw up a schematic and post it here, but based on the responses so far, I think I'm going to 1) connect the radio to the other single battery and 2) see if I can learn a little more about electricity so I don't electrocute myself!

Thanks again!

Matt

Jerry Townsend posted 05-03-2010 04:25 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Matt - your solution is simple - just connect your 12V radio to any ONE of your batteries - yes, even one of the two 12V batteries connected in series. --- Jerry/Idaho
Chuck Tribolet posted 05-03-2010 07:24 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
You aren't going to electrocute yourself with 12V, but you
are going to fry stuff if you hook it up to 24V.


Chuck

mutschle posted 05-04-2010 09:39 AM ET (US)     Profile for mutschle  Send Email to mutschle     
@ Jerry - Yeah, I thought it was that simple too, but it didn't work like I thought it should. I was only able to get power to the radio in one config. I think I'll hook the red power wire to the accessory switch and run the ground to the battery.

@ Chuck - Yeah, I found out the 24v stuff the hard way (twice) The first I accidentally dropped the radio on the batter post and fried it that way!

Again, thanks for the advice.

Matt

Jerry Townsend posted 05-04-2010 11:38 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Matt - It is that simple - you must have hooked up something wrong.

But aside from that - be careful -or you will see a bit of smoke. That is, say with two batteries A & B in series. Now, if your red lead is coming from the positive post of battery B - and you hook your ground to the negative post of battery A - you will have 24 volts. Make SURE that you are powering the radio from ONLY one battery. ---- Jerry/Idaho

mutschle posted 05-04-2010 03:24 PM ET (US)     Profile for mutschle  Send Email to mutschle     
Jerry,

That's pretty much what I figured, and it is entirely possible that I fried the radio right away and couldn't get it working like it should have later on.

It is connected positive on Battery A to Negative on Battery B, so it is 24v. I did try as you said earlier (connecting radio positive to battery A positive and radio negative to battery A negative) with no luck, so hard telling what I did.

I am definitely going to be more careful and make a few calls before I attempt the third one!

I do appreciate the advice and will let you know how it turns out this weekend, hopefully. (Ordered radio #3, so we'll see when it gets here)

Matt

Chuck Tribolet posted 05-04-2010 03:47 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
If you are going to use one of the trolling motor batteries,
use A because it's negative will be at about the same level
(if not exactly the same level) has the starting battery.
If you use B, the case of the radio will be at +12V relative
to all the grounds in the boat, and someday you will get
sparks.


Chuck

mutschle posted 05-04-2010 04:16 PM ET (US)     Profile for mutschle  Send Email to mutschle     
Chuck,

I've decided to hook the positive up to an existing, but unused toggle / accessory switch, and the negative up to the starting battery. Not going to take my chances with doubling up the juice to the radio anymore on the 24v setup!

I should have done this in the first place, but the radio was about 6 inches from the trolling motor batteries and figured I would have it up and working in 10 - 15 minutes.

Matt

whale posted 05-04-2010 07:00 PM ET (US)     Profile for whale  Send Email to whale     
make sure you use a fuse in the line. if you had one in, it shouldnt fried it.
mutschle posted 05-05-2010 08:08 AM ET (US)     Profile for mutschle  Send Email to mutschle     
Whale,

No, this particular radio had the fuse tied into the back of the radio next to where the power connected in, not inline.

Matt

Jerry Townsend posted 05-05-2010 11:46 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Hey guys - remember that fuses are blown by high current - not high voltage - as having been mentioned so many times on this site that I hesitate to mention it again. --- Jerry/Idaho

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