The charging parameters of AGM batteries are critical to the life of the batteries. 14.2-14.4 for the bulk/absorption stages, and then 13.2-13.4 for the float.
Three Stage Charging is different for regular lead acis batteries and AGM batteries, but for AGM batteries, in the Bulk Stage current (amps) is sent to batteries at the maximum safe rate they will accept until voltage rises to a pre-set limit, in this case 14.2-14.4 volts, which is near (80-90%) full charge. With Lifelines, the max current is up to 500% of the battery's amp hour rating, so they'll take anything you can give them.
In the Absorption Stage, the batteries are continues to be charged at the constant voltage rate of 14.2-14.4 until the current drops to less than 0.5% of the battery's amp hour capacity (.5 amps for a 100AH battery, or 1.5 amps for a 300 AH battery). At that point the battery is fully charged.
The Float Stage (also known as trickle charge, or maintenance charge) is where the voltage is reduced to a level that minimizes overcharge while maintaining the battery at a 100% state of charge. For AGM's, that's 13.2-13.4. More than that and you're overcharging, less than that and the batteries will not maintain a full charge.
These numbers are for 77° F (25° C) and the voltages will have to go up or down depending on temperature. Temperature compensated charging is crucial to the proper charging of the batteries. At 90° F, instead of 14.2-14.4 volts, you need 14.05-14.25 volts for the Absorption, and 13.03-13.23 volts for the Float. If you set the voltage to 14.2-14.4 and the charge controller will automatically compensate for the monitored temperature, you're good to go.
The other critical component to proper care and long life is the Depth of Discharge (DoD), which should be as little as possible, but not more than 50% on a routine basis. So, for a 300 amp hour battery bank, never discharge more than 150 amps without fully recharging them. Far as I know, the Xantrex Charge Controllers will only remain at the Absorption Stage for 1 hour, and then will move to the Float Stage, and how long it stays at the Bulk Stage depends on the internal voltage of the batteries. These controllers are designed for PV applications and can sometimes be a problem when charging from an alternator (if that's how you have it hooked up). So it's something to keep an eye on. Also, make sure the Low Voltage Disconnect is set to somewhere around the 12.0-12.2 volt range. If you let it get down below 12.0 volts, you are well under the 50% DoD mark.
Lastly, be careful of the Automatic Equalization mode of the Controller. Concord batteries require some specific charging requirements for equalizing (actually, Conditioning with AGM batteries) and it is different from how the Xantrex Controller performs the task. You charge the battery fully, and the Xantrex will raise the charge voltage to one volt above the normal bulk charge (in this case it would be 15.3 volts), but it will only run it at that voltage for one hour. But Concord Lifelines (and SunXtenders) require 15.6 volts for 8 hours. Also, the Xantrex will perform an equalization once a month if set to Auto, but Concord recommend conditioning the battery only when it begins to lose capacity. If you Condition them too often you will dramatically reduce the life of the battery. I'm pretty sure that the Xantrex defaults to Manual Equalization instead of Auto, though. Just something to be aware of. When performing a Manual Equalization, the voltage will remain at the elevated level for 2 hours, so when you do this you'll want to perform 4 cycles one right after the other to get the 8 hours in. Instead of once a month, more than likely once every 6 months will be fine, especially if you never discharge more than 50%. If your loads are low amp draws and you rarely go down below 80% or so, then you might not even need it as often as every 6 months. Concords that have not been boost-charged (Bulk) for several months, or have been operated in a partially charged or low state of charge for 90 days or more will probably need to be conditioned, but if you fully recharge the batteries on a regular basis, no need to condition them until you actually see a reduced capacity (which might be a year or two depending on your amp requirements).
So, basically, you're good to go with the setting you have, just keep a close eye on the DoD and make sure they are regularly recharged fully.
