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Old 15-05-2015, 16:43   #1
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12volt TV broken after starting boat motor

Hi all

Purchased a 2nd hand 12v LED TV to leave on the boat instead of lugging one of our home TV's to the boat every time the family was staying overnight.

The TV worked fine for 2-3 days on the mooring but the first time I started the boat motor with the TV plugged into the 12V system via a cigarette lighter connection and turned on the TV blank screened with a blown inverter.

Is this fairly a common experience or was I just unlucky with the make/model/age of the 2nd hand TV, is there anything I can put inline with the TV power cable that would prevent the engine start power fluctuation from damaging the TV.

Thanks in advance

Jim
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Old 15-05-2015, 17:07   #2
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Re: 12volt TV broken after starting boat motor

Blown inverter ? thought it was a 12v TV Or are you referring to the power supply of the TV ?. Get a multimeter and find out what your alternator output voltage is when the engine is running. Shouldn't be a problem for most 12v TV's had one on an old boat for years.
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Old 15-05-2015, 17:09   #3
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Re: 12volt TV broken after starting boat motor

It's an omen, TV's don't belong on boats.
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Old 15-05-2015, 17:10   #4
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Re: 12volt TV broken after starting boat motor

Possibly the design of the TV. We've got a 12 vdc LG that hasn't had any problems and I've got it hard wired to the switch panel. Having said that, it sounds like perhaps a voltage drop has killed it so maybe the supply wiring/socket is an issue.

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Old 15-05-2015, 17:48   #5
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Re: 12volt TV broken after starting boat motor

Quote:
Originally Posted by Emmalina View Post
Blown inverter ? thought it was a 12v TV Or are you referring to the power supply of the TV ?. Get a multimeter and find out what your alternator output voltage is when the engine is running. Shouldn't be a problem for most 12v TV's had one on an old boat for years.
Yes sorry, should have been more specific, its the inverter board internal to the TV set which drives the display which has blown, ie I get sound but no picture and when I shine a torch into the screen in a blacken room I can see a faint picture image, a replacement inverter board for this TV is about $30 but I don't won't to do this each time I start the boat motor.

Jim
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Old 15-05-2015, 17:50   #6
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Re: 12volt TV broken after starting boat motor

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It's an omen, TV's don't belong on boats.
If you hate that, you're going to hate my pop corn maker.
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Old 15-05-2015, 18:03   #7
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Re: 12volt TV broken after starting boat motor

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Originally Posted by Reefmagnet View Post
Possibly the design of the TV. We've got a 12 vdc LG that hasn't had any problems and I've got it hard wired to the switch panel. Having said that, it sounds like perhaps a voltage drop has killed it so maybe the supply wiring/socket is an issue.

Sent from my SGP521 using Cruisers Sailing Forum mobile app
Thanks for that, the battery voltage does drop a lot on starting as measured by my solar panel management system which displays min and max voltages over a set period, its recorded minimum voltage spikes as low as 10.5 volts when cranking the big ford lehman from a 12 month old truck size crank battery,

I do tend to start the boat with both the crank and house batteries banks combined together by selecting the "All" position on the battery selector switch, but this is because I'm worried about switching the battery selector from "crank" to "all" once the engine is started and the alternator is charging.

Sounds like I just got a TV which doesn't suffer voltage fluctuation well.

Jim
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Old 15-05-2015, 18:09   #8
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Re: 12volt TV broken after starting boat motor

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Originally Posted by Jimd1971 View Post
Yes sorry, should have been more specific, its the inverter board internal to the TV set which drives the display which has blown, ie I get sound but no picture and when I shine a torch into the screen in a blacken room I can see a faint picture image, a replacement inverter board for this TV is about $30 but I don't won't to do this each time I start the boat motor.

Jim
I should note that the LG I have is a LED TV. Not sure if the LED backlights need an inverter board? My somewhat limited knowledge of flouro backlit flat screens is that the board that powers the backlighting is a component with a relatively high failure rate.
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Old 15-05-2015, 18:30   #9
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Re: 12volt TV broken after starting boat motor

Not a good idea to crank a big motor from the house batteries, since you not only draw down voltage but you can induce much more harmful voltage spikes into sensitive instruments and electronic appliances.

If your start battery can't start the engine easily, there's something wrong:

- it's too small
- it's capacity has been eroded thru sulfation or other
- you have loose or corroded cables or bad cable terminations
- your wiring is too small in the start circuit

Leave the 1-2-BOTH switch with the engine and house batteries separated, and find out what's wrong with the starting circuit.

If you absolutely must start the engine when in the "BOTH" position, then unplug or turn off sensitive equipment first.

Bill
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Old 15-05-2015, 19:41   #10
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Re: 12volt TV broken after starting boat motor

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Not a good idea to crank a big motor from the house batteries, since you not only draw down voltage but you can induce much more harmful voltage spikes into sensitive instruments and electronic appliances.

If your start battery can't start the engine easily, there's something wrong:

- it's too small
- it's capacity has been eroded thru sulfation or other
- you have loose or corroded cables or bad cable terminations
- your wiring is too small in the start circuit

Leave the 1-2-BOTH switch with the engine and house batteries separated, and find out what's wrong with the starting circuit.

If you absolutely must start the engine when in the "BOTH" position, then unplug or turn off sensitive equipment first.

Bill
Agree, not a good idea to crank from the house batteries, but I'm more worried about switching the battery banks once the alternator is pumping charge as I tried it once and it produced a pretty blue arc flash when it went from "crank" to "all". Since then I've left it in "all" for starting (as per the original owners advice) as this also links both battery banks for charging

I can start the motor off the "crank" and "all" position and it certainly cranks off the "house" when I forget to change it over, but I mentally kick myself when I do, so there is no problem with the battery output. I just don't like changing between banks once the engine is running.

Jim
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Old 15-05-2015, 20:10   #11
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Re: 12volt TV broken after starting boat motor

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Originally Posted by Jimd1971 View Post
Agree, not a good idea to crank from the house batteries, but I'm more worried about switching the battery banks once the alternator is pumping charge as I tried it once and it produced a pretty blue arc flash when it went from "crank" to "all". Since then I've left it in "all" for starting (as per the original owners advice) as this also links both battery banks for charging

I can start the motor off the "crank" and "all" position and it certainly cranks off the "house" when I forget to change it over, but I mentally kick myself when I do, so there is no problem with the battery output. I just don't like changing between banks once the engine is running.

Jim
Well, Jim, yes switching when the motor is running even with a "make-before-break switch" isn't a good idea.

However, you missed the main point: if the house banks are in the starting circuit -- as they most certainly are when in the "Both" switch position -- then high voltage spikes from the starter motor (not the alternator) when the solenoid releases can damage sensitive electronics.

Keep 'em separate, and use an ACR or voltage follower device to link both battery banks for charging.

Bill
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Old 15-05-2015, 20:30   #12
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Re: 12volt TV broken after starting boat motor

I have a NEXA 12 volt TV aboard. I've not had this issue. I also run it on both 12 volt, and off of the inverter when I want. No issues. BTW, the nexa is cheap. 22 " was $200.00 or so online shipped to St. Thomas.
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Old 16-05-2015, 09:39   #13
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Re: 12volt TV broken after starting boat motor

It 's my understanding that switching from one battery to another with the engine at idle and low/no load on the alternator won't harm the diodes. May be wrong but have done it forever without a problem. Pretty sure the battery switches in my early days were not 'make before break' types. Do they even make marine battery switches that are not 'make before break'.
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Old 16-05-2015, 10:56   #14
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Re: 12volt TV broken after starting boat motor

Peter,

Yeah, lots of folks have got away with this, even before the make-before-break switches became commonplace.

HOWEVER, I REPEAT, SWITCHING WHILE THE ENGINE RUNNING IS DANGEROUS...EVEN WITH A M-B-B SWITCH.

Why?

Don't forget about the OFF position. If you hit that (and maybe linger awhile -- a guest? a distraction?? You can certainly blow the diodes in the alternator.

Why risk this at all, when there are much better ways to avoid the possibility?

Bill
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Old 16-05-2015, 13:03   #15
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Re: 12volt TV broken after starting boat motor

Hi All,
The Majestic folks have a line of TVs that are designed to work from 9V through to 27V DC. Have a look at their U.S.A. distributers web site for the 15" model;
CWR Electronics.com: Product Detail or the 32" model;
CWR Electronics.com: Product Detail or those in between. My site focuses on my Marine-PCs, but I'll be glad to arrange for one of these units to be dropped shipped to a CF member with a 10% discount from the retail price shown.
Cheers,
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