Topic: Car battery question

[daveeb]

Howdy y'all, any car battery experts out there  

I have a portable lcd tv that i want to take camping.  it uses 10 AA batteries so instead i want to run it via its car cigarette lighter connector.  Problem is you cant run electricals from our car cig output if the engine is off (well you can but it stops the central locking from working  :roll: ).  What i want to do is buy a spare car battery and run the tv from that.  My rational head tells me the tv will draw the current it needs and will run fine, my paranoid head tells me the tv will be instantly vapourised by 100 Amps .  Anyone thoughts, especially anyone who has installed a cigerette socket in a car, is there any additional circuitry/resistance between the battery and the power socket

[Sandra]

Your rational head wins out over your paranoid one Dave  

The TV will only draw what it needs.

In the old days when I knew about such things, the cigar lighter was always connected via a 35 or 50 amp fuse directly into the permanently live circuit, the same as the lights etc and were independant of the ignition circuit.
Later on they were routed from the auxillary circuit via a relay so that the ignition key had to be in the first position, the same as for accessories such as the radio.

[daveeb]

Cheers Sandra you are a pc and automotive guru  

Is there any type of battery i should go for bearing in mind it wont be charging as it would in normal car use, i'll charge it with a mains charger when its nearly flat.

[gmax]

you need a "a deep cycle battery"

     * A car's battery is designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs, so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity. Used in this way, a car battery can last a number of years. To achieve a large amount of current, a car battery uses thin plates in order to increase its surface area.

    * A deep cycle battery is designed to provide a steady amount of current over a long period of time. A deep cycle battery can provide a surge when needed, but nothing like the surge a car battery can. A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates.  

[daveeb]

Thanks gmax, sounds like good advice. Would something like a golf cart battery be more suitable for my needs then i.e. all i want is a steady supply of 12 Volts  

[gmax]

a golf cart battery would be ok, but don't leave the battery flat for too long.