solar panel/battery question

[jen_in_southtexas]

I was just wondering how many watts does a solar panel have to have to be able to charge a 12V 75ah deep cycle marine,RV battery effectively? My current set up is the HF panels with a 12v deep cycle 75ah battery?
I already know that these two can be joined in parallel but i was just curious as to how big(wattage wise)a solar panel it takes to charge ONE of these batteries.

Thx.
-Jen ;)

[12vman]

45 watts.. 3.75 amps in full sunlight..

Prime charge "Window".. 10 am to 2 pm.. 4 hours.. (with a fixed array..)

4 hrs. x 3.75 amps = 15 amps or 15 aHr..

The above is what your Harbor 45 watt system can provide you on a good day..

To be safe, your panels should provide at least half of the aHr rating of the battery in a day. For a 75 aHr. battery, you should have around 38 aHr. of charge. This figures out to around 115 watts of panel. You must only pull the battery down to 25% of it's aHr rating in a 24 hr. period. This allows you to work with around 19 aHr. of usage in a day. Staying within these parameters will assure that the battery obtains a full daily and no damage will come to it.. (from being under charged)

The Harbor Freight system will charge the 75 aHr. battery BUT the amount of energy that you can use is less than the 25% *of the battery. Instead of 19 aHr., you should only use 15 aHr. max.. You must replace what you use to assure that the battery can get fully charged again..