If you are worried about the cost of changing over a couple of fixtures to LED's, then go to this website, and search for 24 LED 5050 panel. THen click on "Lowest price" at the top. Most of the first page will be 1000 minimum quanity, but by page 2 you will see 10 each for about $1.95 each.
AliExpress.comWhat I did was cut off the wires going to the old lamp, and use little blue wire nuts to connect two adapters to each old fixture. Then I can install 1 or 2 of the light panels, depending on how much light I want. In my bathroom, I have 2 panels in each side of my old fixture, or 4 total, 96 LED's all for about 0.4 amps.
Others have removed all the light bulbs and ballast from a florescent light fixture, then glue in 4-8 of these panels, and wire them up for much more light with less power.
There are a couple of LED light fixture posts. You can search for them.
To really extend the power of your battery you can install a Olympic Catalytic safety heater, it will not use any 12 volt power, and can put out up to 6,000 Btu's of heat.
and install a couple of 100 - 120 watt solar panels, nominal cost right now of around $100. Get a $18 solar controller (they have 20 amp PWM solar controllers for $18 with free shipping. These will recharge the battery each day - if you are camping or not.
Fred.