profdant139 wrote:
Mex, somewhere north of Mammoth and south of Tahoe -- we will be moving around, looking for high altitude boondocking to escape the heat. And someplace we can camp in the shade but then put my new panel in the sun. And then I will proceed to bore my poor wife to tears while taking readings off the panels and the batteries while experimentally moving the panel around to find the best angle.
You need to know that the higher the state of charge of your battery, the more resistance to recharging it will experience. Pulling 18 amp /hrs off the top of a group 31 in a day is still 80 to 85% state of charge. If you start charging first thing in the morning when the sun comes up, of course the panel won't put out max amps, meanwhile it begins to refill the battery, maybe at 4 amp/hr rate or a little better. By the time the sun is good and high in the sky, say 10 or 11 am, you may very well be close to topping off the charge in your battery, again amp flow will be lower.
Now, then, if you decide to hook up your solar panel at 11 AM in the morning, after a full 24 hours of usage, then with proper aiming, you should see the full 6.6 or perhaps even more amps per flowing in to the battery from your 120 wart portable folding solar panel.
Keep the dust and junk off the panel for maximum power generation, wipe it down with a wet paper towel every now and then... idiots racing on dirt roads at over 5mph are the worst culprits in dusting up your solar panel.
We hope you bring pencil and paper and keep log sheets of your results. You'll find if you have an amp meter, going 2 days and then recharging will yield a higher amp recharge rate mid day than recharging every single day, for experimental purposes.
You may even find that now you only need one battery. I am not kidding you when I say this, solar power and daily recharging restructures what your battery needs may be when you can replenish the charge regularly.
With a worn out T-1275 originally rated at 150 AH, I am probably lucky to actually get 120 to 125AH out of it currently, half of that in reality, to keep it charged at at least 50%soc. I go through about 35- 40 amps a day, this time of year. My 150w solar panel has no problems so far, most any day, keeping up and topping off that battery. I get by easily with just one panel. I should add, I don't have a wife running the shower the full 6 gallons of hot water, or wanting the heater turned on if it gets below 60f outside either. Water pumps and stock heaters and electric fans are the big power eaters, if you already have LED lights everywhere in your TT.
When you want to give your battery an Equalize charging (fully supervised of course, you need to change wiring when the V at the battery terminals reaches 16.0V, with regular frequent babysitting/monitoring) just bypass the charge controller wiring, maybe make yourself a couple of really short jumper wires with alligator clips out of 16 gauge wire to do it. You basically want to run the V off the panel at 17.0V straight to the battery, and monitor either V rise to 16.0V then stop, or monitor Specific gravity at each cell, to 1.275 or better. Always a good idea to do this every 7 to 10 days while camping, and always do it once you get home back from camping before putting the trailer in storage. Also a good idea to do it shortly before you leave on a trip in the unit has been unused for a month or more since last out camping or fully recharging it.
Some things you may consider further down the road.
A. heavier gauge wire from charge controller to battery to minimize voltage loss as length increases.
B. a shorter run from charge controller to battery with heavier gauge wire.
C. An adjustable voltage charge controller so you can control or charge at a higher voltage, be it 14.8, 15.0 or 15.3V, depending on what the battery manufacturer gives or recommends for top charge voltage needed to completely charge your batteries to 100% SOC, not 95, 96 or 97%
