Low Battery Voltage

CCA is not a very valid test for our use of a battery. That is a rating for how big a burst of power a battery can put out in a very short time (like for turning over an engine). Slightly more meaningful, but not much, is how many times the battery can pass the test without recharging. I've seen many that can pass the test once, but have no lifespan at all for longer term lower draws. Other than putting a know load on it, and periodically monitoring the voltage over time, there isn't any quick way to test for it's ability to deliver rated amp hour capacity.
If you have the meter, and time, you may want to swap with a vehicle battery and see how that does over time. But periodically monitor, so you don't over discharge your test battery and ruin that too....