Interesting problem

[eddieperkins]

Now here's one to confuse and confound. I have a 12v colour TV rated at 3 amps, but when it is plugged in via a cigar lighter type socket in the helm switch board it pull my batteries down from 12.68 volts to around 11.9 volts. after around 30 minutes of this the TV gives up the ghost due to low voltage. I have 3 domestic batteries giving 390 amp hours total and they have been checked out ok on a 'battery computer' I have had the TV checked and it worked fine pulling 2amps and not effecting the supply voltage so I guess I have a wiring problem however I have a fridge pulling 5 amps coming off the same switch board that only drops the voltage by around .2 volts. I would have thought to drop the voltage by .8 of a volt would cause melt down in the wiring - or would it. Can any one out there cast any light on what the problem might be.
Regards,
Eddie

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[Born_Free]

Not sure of the answer to this one, but I used to have exactly the same problem with a miniature 12v Casio T.V. that I used to use in my car, it could flatten the battery in about 20 mins, so I had to stop using it.

<hr width=100% size=1>I have nothing to declare, except my genius
(Sorry Oscar)

 

[duncan]

you say it pulls the batteries down to .......do you mean by this that the voltage actually measured accross the batteries when the TV is on is pulled down or that it is only capable of getting that voltage from the socket?
I ask because I experienced a problem with a VHF - it switched on OK but wouldn't transmit. Wiring delivered 12v (13.4) when checked but when I took it back it worked fine. Told to check voltage at unit under load. Sure enough the voltage at the unit feed dropped when the unit was switched on and this turned out to be a bit of corrosion in the wireing for that unit. COuldn't really see it, joint felt fine and voltage OK unit a load applied.
May be nothing to do with your problem - may help.
Good luck

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[longjohnsilver]

3 amps sounds pretty low for a colour tv, suspect it's quite a bit more than that. But not enough for the problems you seem to have.

Could be a cell is down on the battery?

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[Mike21]

Check connections to helm position, could be a bad connection causing excess current to be drawn, or could be as pointed out corrosion on socket.

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[Nick_Fairfax]

Where are you measuring the voltage - at the TV or at the battery ?
If you are measuring the voltage at the TV, then it is voltage drop due to too thin a diameter wiring. Even a 2 amp current through a reasonably long piece of fairly small diameter wire will create a large voltage drop. Your fridge will probably only intermittently draw up to 5 amps and is less sensitive to low voltage, whereas your TV will continuously draw 2 amps and probably a lot more at power up. Try temporarily connecting the TV as close to the battery as possible, if this works then you will have to replace the wiring to your helm position with a thicker piece of cable. If you are measuring the voltage at the battery, then I would agree with Long John that your battery may have a bad cell.

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[oldgit]

Hmm sounds like joint somewhere.Ok when cold but high resistance when warm ie.joint is getting hot.Have you tried runing hand over that bit of wiring to see if warm.do not forget earth return may also be fused with rubbishy old type fuses.My fridge stopped working cos fuse red hot after running for bit.
Of course after long and extensive strip down was last thing checked as did not realise any fuse in return circuit.That TV may want 3amp on 240V but loads more amps on 12V.ie er 15 amps?

<hr width=100% size=1>If it aint broke fix it till it is.

 

[Dave1258]

LJS has it right ..a small t.v 10" will use 45A ..a small t.v. 14" uses 65A
(been down this road before with motorhome issues)!

3 A is the fuse rating surely?

<hr width=100% size=1> A man should have two things in life, a boat and a wife willing to let him have one.

 

[GARYOFFSHORE]

I recently fitted a TV to a Swordsman 40ft and the tv supplied was a 12v unit with a 240v to 12v convertor. The tv was designed to operate within a certain range of voltage ie. 11.8v to 12.8v. The tv convertor will provide this because it's output is constant. On your boat the variable voltage is liable to damage the tv and invalidate any warraranties. I suggest that you should invest in a convertor of correct wattage along with the correct cabling.

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[andyball]

How much !

We had a 12V only 10" colur tv with the boat.....& it certainly doesn't take 45Amps.

3 Amps does sound optimistic, & would be quite impressive for a non-lcd tv.

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[MainlySteam]

<<<a small t.v 10" will use 45A ..a small t.v. 14" uses 65A>>>

You are very much mistaken I am afraid - they may be 45 or 65 watts, but not 600 odd watts (say 50A x 12v) as your figures indicate.

John

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[eddieperkins]

Interesting train of thought!. I have been measuring the voltage from the tv end, I have a cigar type plug with a 3 way splitter with tv and ariel booster plugged in, I measured the voltage at the spare socket on the splitter, so it could just be a dry joint or corrosion. I will check voltage at the batteries and see shat I have got, if they are ok it must be wiring/joints/corrosion.
Many thanks
Eddie

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[eddieperkins]

Hi, batteries tested out ok, all cells are good, and the tv consumption was by bench test at an electronics workshop so I guess it is accurate. May increase with the volume up though!.
Regards,
Eddie

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[eddieperkins]

Mike,
I think you may be dead right, will check this out.
Regards,
Eddie

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[eddieperkins]

Nick,
Thanks for that, I will check the size of wiring, in fact I think I will replace wire and socket just to be on the safe side. Will check voltage at battery first also.
Regards,
Eddie

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[eddieperkins]

Thanks for the reply, I think I am going to rewire and fit new socket 'cause all postings point towards wiring/corrosion/bad connections issues.
Regards,
Eddie

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[duncan]

let us know how it turns out please

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[chrisarvor]

first thing to check is the plug on the cigarette light, is it a pointed pin on the end of the plug if so file it flat to get a better connection.
also check the socket on the light itself some have a small disc in the base which makes abad connection

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[eddieperkins]

Got it sorted! It was a combination of things, firstly the battery I was given to replace the one that had a dud cell turned out to have a problem. Secondly the socket on the dash is not allowing the full current to pass through. Thirdly the three way socket I was using also was not allowing the full current to pass through. TV is fine, and does draw 2 amp at 12 volts. I have now got it plugged into a newly fitted socket and all is well. Many thanks to all who helped.
Eddie

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