Need some input on deep cycle batteries

We are very new to rving this year.  We purchased a used by nice 1972 Shasta travel trailer.  We got a great deal on it but we are starting to outgrow it already.  My question is regarding deep cycle batteries.  Usually when we go camping it is to the Yogi bear campground and we have a water and electric site.  Well next weekend they are all full and we could only get a rustic site.  That normally would not be a big deal but I love to watch tv and use a fan during camping.  (Tv helps  the little ones fall asleep) 

From what I understand about batteries is that a deep cycle battery would only work on my inside trailer lights.  For the fan and tv, I would need to use an inverter (which I do have).  My question is that could I use a golf cart battery (6 volts) to power the inside lights and then use a 12 volt battery with the inverter to power the rest?  We will be gone for three days and I am just not sure if it would make it?  The reason for doing it this way is that there is not very much room to put the batteries.  The trailer has an outside connectors (where I would put the smaller batteries for the lights) then I would thinking about mounting the inverter into the bottom side bunk (where the holding tank sits) and put the battery it in one of those plastic battery boxes (the bigger deep cell battery). 

What is everyones thoughts on this?  The tv is only about 13 inches and the dvd player is real small.  I was trying to figure out the amp load and etc but I am lost on it.  The battery that I looked at, at Wallyworld was 115 amp load for $55.  Live in a small town and resources are limited.

From what I understand about batteries is that a deep cycle battery would only work on my inside trailer lights.  For

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Your fridge, water pump and furnace draw on 12VDC as well as your lights.  There are 12VDC TVs like the one HERE.  There are cheaper CRT TVs on the same site.

Adding batteries can be done by having a frame welded in adjacent to your exisiting battery -- if there is space.  Use 2 6-volt units hitched in series or 2 12V units in parallel.    Your lighting is most likely 12V, as all the other items I mentioned.  6 volts would not work.  At least work well.  Dim lights at best.

My question is that could I use a golf cart battery (6 volts) to power the inside lights and then use a 12 volt battery with the inverter to power the rest?

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6 volt golf cart batteries are always used in pairs - two six volt batteries in series produce 12 volts.  If you tried to use a single 6 volt battery your 12 volt interior lights would be very dim.

I'd try adding a second 12 volt battery to the one you have and see if that gives you enough juice to last 3 days.  You could even do something like charge it at home using a plug-in charger then when you get to the campsite place it on the ground next to your existing battery and use a set of automotive jumper cables to tie them together.

Another advantage to having a portable battery and charger - if you ran the battery down I'll bet you could find a kind fellow camper (or even the office) who'd let you plug in for a recharge.

To figure out how many amps the TV and DVD player will draw, look on their nameplates.  The power consumption will be listed in Watts.  Or you might see Amps @ 120 volts.

Watts = Amps x Volts.

If the power is listed in Watts, divide by 12 to get the 12 volt amperage.  If the power consumption is given as Amps @ 120 volts, multiply the amps by 10 to get the 12 volt draw.  As an example, 2 amps times 120 volts = 240 watts.  Divide 240 watts by 12 and you'll draw 20 amps from the batteries.

I was out looking at my battery connectors and one is blue and the other is white.  It doesn't say positive or neg. on either one?  Which would be which or is there a way to test so I do not connect them wrong?

A single 6V battery won't work - got to have 12V.

I would recommend a second 12V battery and some jumper cables, as Lou suggests. It's easy to add on when needed and easy to recharge.

You will need to figure out if your inverter is large enough for the fan and/or tv and how long you can expect the bateries to last.  When te inverted increases the voltage from 12VDC to 120VAC (a tenfold increase), it also also increases the power draw on the battery tenfold.  That means that a little 1 or 2 amp load on the inverter becomes a 10 or 20 amp load on the battery.  A small tv probably draws about 60 watts or about 0.5 amps a 120 VAC, which translates to 5 amps per hour on the battery.  A typical Size 24 12V battery has a max capacity of about 85 amp-hours and a practical limit of only 50-60% of that, so you can't expect to draw 10 amps for more than a few hours without recharging.

garypely said:

I was out looking at my battery connectors and one is blue and the other is white. It doesn't say positive or neg. on either one? Which would be which or is there a way to test so I do not connect them wrong?

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Trace out the cable paths.  One of them will end at a connector to the trailer frame.  That is the negative connection.

If you can't easily trace the wires, do this: Take an ordinary 12 volt automotive bulb like a 1004, and wrap the stripped end of a length of copper wire around the base and tape in place. Don't cover the small solder blob on the bottom of the bulb. Next, clean a spot on the frame near the battery so it will make a good electrical connection. Touch the solder blob to the clean area while touching the other end of the wire to one of the battery posts. If it lights, you've found the positive (+) side of the battery. If not, that's the negative side. Try both battery posts to make sure the spot on the frame you cleaned is truly a ground. If neither battery post lights the light, find a different spot on the frame to use.