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)
Test Equipment:
Wind Turbine dump load resistor (15Amp load)
Test Information:
After an 8 Hour rest, Battery Voltage 12.98,
Test Results:
Voltage start 12.98VDC, Voltage End 10.5VDC
Test Time:
165 minutes
Calculations:
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…)