Originally Posted by LakeSuperiorGeezer
This would be correct if you have an alternator or a really large charger in the 30 amp range or more, but with the 5 to 10 amp chargers I use, there is not enough current to push the voltage to the absorption level until near the end of the obsorption stage.
Absorption does not start until you hit the absorption voltage set point of the regulator or charger. If you are not at the "limiting voltage" or absorption voltage then you are still technically in bulk charge. The smaller the charger the longer the bulk phase. Bulk ends when the voltage has risen to the absorption voltage which is nothing more than a pre-set voltage limit...
What Bill said is spot on and short of owning a Midtronics, Argus or other expensive analyzer the best test is to do a 20 hour load test for Ah capacity. Volts tell you nothing about the ability to support a load and for how long.
If your batts are 115 Ah then you'll want to apply a 5.75 amp load and monitor when the voltage drops to 10.5 volts using a DVM connected to the pos & neg posts while doing the capacity test. New 115 Ah batteries should go 20 hours before hitting 10.5 volts. When you get out to 16 or so hours begin checking the voltage unless it is dropping off far faster than it should and in that case the batteries are likely toast.
You can use a dimmer switch and some light bulbs to get your 5.75 a load dialed in. Test each battery separately.
Like Bill said you can also throw them on an analyzer which will measure CA and voltage and can give an approx "condition" assessment but nothing beats a true 20 hour capacity test.
Everstart batteries are normally Wal*Marts starting batteries and the Everstart MAXX brand are their marine deep cycling batts. Be sure that you are looking at an amp hour rating not a reserve minutes rating and chec to see if you have the MAXX series which are deep cycle/trolling or the regular Everstarts, which would not hold up for long in a cycling application..