Here is what I use and it works good. With the help of a DC Engener friend of mine. I run a 12V 150 ah. bat, with a 20a 13.8vdc p/s, and a 1500W converter. I run the feeds off of the P/S in PARALLEL with the BAT. To a Fused power distribution unit, and the inverter fed off of that. The bat Stays charged by the P/S and stays condidtioned from use by the radios and equipment. and when there is a brown out or a outage the equipment dosent even flinch. as recomended I fuse both leads coming from the P/S and to the PDU, one not form normal reasons just incase the leads ever shorted together to keep the bat. from blowing up! I run HEAVY insulated 6 ga. wire for all the main leads with 6 ga. crimed lugs. This sounds weird but it is the same way we run our communication sites and is the way most telco companys run there sites. With it in this configuration "apparantly" all the equipment is run off the battery, and the battery is suposed to act like a line conditioner. Here is a link the the bat i have and dont know how much the curent cost is new, but they are suposed to last around 10yrs if taken care of. http://www.cdpowercom.com/cd/products/batteries/sealed/fa12_383.htm
Just rember if you have a long period with no power your P/S will be working over time to charge the bat up if your talking on the radios and using the laptop.
I have ran for many hours this way during black outs, and have not have any problems. My system is fused with 100 amp circuit brakers so i can disconect the P/S if the power has been off for a while and i still need to talk, and just turn them back on when im done and dont plan on being on for a while.
Hope this helps.