http://www.mpja.com/2-Ohm-120W-Power-Resistor/productinfo/17786%20RSI have one of these with test leads attached, to test my inverter batteries at work. I clamp my Fluke 187 leads onto the lugs. A charged battery should still be above 12V with the 6 Amp load imposed. I'm referring to 7.5AHr & up batteries. It's not good to discharge your VRLA batteries below 1.75 Volts Per Cell(VPC). It's normal to see 14 or more volts across bad batteries on charge, and 10V or less when you disable the charger. With your FACP, it's supposed to run for 24 hours on standby and then 5 minutes in alarm. You should definitely swap them out together or you won't likely make the requirement. Remember that brand new batteries will self-discharge and die on the shelf, so you should float charge them or top them off at least every 6 months.
Joe
