Thanks for your reply.
I'm using East-Penn VRLA 8A31DTM AGM batteries. I've read the comments from many manufacturer and vendor sites regarding AGMs, and they are generally consistent. Some say that AGMs require no special charging considerations. East-Penn, the manufacturer of my batteries states in their VRLA technical manual (available at: http://www.eastpenn-deka.com/products/pdfs/0139.pdf
, page 9) about charging their AGMs:
"Automatic temperature sensing, voltage-regulated chargers must
"Charge voltage must be limited (14.4 to 14.6 volts maximum at 68°F)"
(their emphasis on must, not mine.)
Where I work we have alot of experience with them and prefer to use specialized chargers to assure availability and long life. These AGMs with Analytic System chargers have worked well for our shipboard UPS and navigation systems with many installation-years of operation.
1. The Xantrex PROSine 2.0 does have a generic AGM setting, but also allows the user to set customizable charging algorithms for nearly all charging parameters. I'm using the optional temperature sensor attached to a negative terminal on the batteries to monitor battery temperature for charge compensation.
Differences in the PROSine charge profiles for AGM vs other batteries include:
a) If the user has configured the PROSine 2.0 battery algorithm for AGMs, there will be no "overcharge" charge stage.
b) No "equalization" charge stage is available if AGM is selected.
c) Temperature compensation coefficient is different (-27mV/°C for flooded cell vs -21mV/°C for AGM) along with different absorption stage voltage limits. The correct settings depend on the battery manufacturer's recommendations.
I've tested both Concorde PVC-12100 and the East-Penn 8A31DTM with the PROSine 2.0 and their charge behavior is slightly different, but since I cannot rigorously test them I can't say if it is due to age (Concordes are about a year old with more cycles on them, East-Penns are new) or due to fabrication and chemistry differences. Both seem to be suitable batteries for my application.
2. The reason I'm installing a DC/DC charge controller from the tow vehicle is to provide for controlled 2-stage charging to the endpoint voltage of the AGMs regardless of the tow-vehicle source voltage. The BCD-605-12-12 provides a voltage regulated (within 50mV of the setpoint) charge at currents up to 42A with inputs from 10.5 to 14V from the tow vehicle. It can boost or reduce the input voltage as necessary to maintain user-selected charge voltage and should prevent overcharging.