Here is an informative site:
What You Should Know About Batteries
I love the opening quote "few batteries die a natural death, most are murdered".
This article talks mostly of charge voltages, not amperage, so may not be as useful in this case.
One thing I got out of this article is that you CAN accurately determine the charge state of a
battery using a Digital Volt Meter....but only if you let the battery "rest", neither charging nor discharging. They have a useful chart to refer to. It all even shows up well on my iPhone, where I have it bookmarked as a useful reference.
The part about most "trickle chargers" supplying 13.8 volts, not enough to fully charge but enough to cause sulfate deposit and off gassing, and eventual ruin of the battery, was also an eye-opener. My old 1980's "10 amp" charger is now under my scrutiny....as I presently am using it in an attempt to revive a weak battery on an old truck. I've learned I have to monitor it closely. Might be time (for me) to step into this century and get a decent charger, maybe even one with the fancy "reconditioning charge", using variable frequency pulse charging.