You have had your batteries in your TT for 3, 4, 5 years. You do a voltage check and it shows 12.6Volts (full charge) looks good to me, but what about the Amp Hours of the battery? New it was rated at 84Ah, it is now 4 years old, so how many Ah's does the OLD battery really have?
My first test was performed on an old interstate battery to see what the CURRENT Ah would be. The battery is an Interstate 84Ah battery. It still takes a full charge and sits for months at 12.8VDC, without any charger on it. So to the average camper it looks like a good battery. Why did I do this test? So, I can eventually test my Trojan T-145 batteries, but decided to do a test on my original Interstate that came with the TT.
Battery information: Interstate SRM-24 84Ah (4 years old)
(Mostly used with my office UPS system and electronics projects)
Wind Turbine dump load resistor (15Amp load)
After an 8 Hour rest, Battery Voltage 12.98,
Connected battery to the dump load resistor
Voltage start 12.98VDC, Voltage End 10.5VDC
165 minutes / 60 minutes = 2.75 hours
2.75 hours * 15 amps = 41.25Amp Hours (current Ah available at full charge)
Useable Ah = 20.5Ah (not very much when you turn on a heating system or Tv…)
So, now you are curious as to what your current old batteries Ah's really are.
I also posted the test results on the RVing with SOLAR
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package
Our Solar Album http://www.jaycoowners.com/album.php?albumid=329