After proofreading this, I realized it has somewhat of a 'psychic fortuneteller' feel to it, in the sense that it doesn't directly answer your question, but here it is anyway...
12.71 is not exactly full (unless thats your standing voltage after several hours), but without an accurate SOC measurement, its difficult to tell. If you get decent wind at night, let it charge then. The closer to ~70 F the better, but everything isn't always ideal.
Wattage is subjective at this point, and without knowing the capacity of your bank, thats a difficult call to make. IMO however, you're probably just fine, based on the picture. 6-20W is probably safe for anything larger than 25AH at just about any temp. Even if every watt is converted to heat (such as is approached in overcharge), you'd be pressed to be able to detect the difference in the case temp. The idea behind not charging/discharging at elevated temps is to avoid as much damage as possible by not compounding the temp issue with internal power dissipation.
Honestly, it could be debated all the way from "dont move a single electron at that temp", to "don't worry about it". For example, Car batteries charge under some rough conditions, temp being one of them. Under the hood of a car is not exactly the coolest place in the vehicle, yet if charging is controlled properly, they can still last for years.
Nobody will ever debate that temp definitely affects lifespan, charge acceptance, self discharge rate, and power delivery capability. It's just a matter of trade off.
I remember reading something on here somewhere that said something to the effect of "the best way to treat a battery is to charge it occasionally just enough to ward off self discharge and prevent sulfation, and never discharge it."
It went on to say, "But what's the point?"
Know what I mean?
Steve
