Parallax Converter

BFL13 wrote:
Phil, based on your postings of this over the years I recently grabbed a 7445 (deck mount version of a 7345) at a garage sale to run my new AGM in the truck camper.

I'm curious ... is your particular AGM battery type specified to be floated at around 13.5-13.8 volts (at 77 degrees F)? I believe that some AGM batteries specify the normal liquid acid float voltage of 13.2 volts and I would hesitate to expose them to a 73XX converter for long periods as they might "dry out" (i.e. heat up enough internally to periodically release small amounts of their water in vapor form out of their one-way relief valve).

Probably Mex would disagree with me, but when an AGM battery is specified for a float range of 13.5-13.8 volts instead of the usual lead-acid value of 13.2 volts I take it to mean that the AGM battery is designed slightly different mechanically or electro-chemically such that the higher float voltage will not dry it out. However, maybe all AGM batteries can be floated anywhere from 13.2 volts to 13.8 volts due to their intrinsic lower internal resistance giving rise to lower internal heating at any applied voltage. :h

(A Concord rep told me that Lifeline AGM batteries should not be floated at normal fixed voltage converter output voltages, so I passed on using Lifeline AGM's at our last battery change. I chose a set of AGM batteries with a higher specified float voltage.)

By the way ... the Parallax converter I would REALLY LIKE to use to take care of my particular AGM batteries is one of their discontinued 73XX "T" models. These models had an internal timer circuit such that every time you powered them up they supplied 14.4 volts for four hours then dropped back to 13.6 volts for the rest of the time you had the converter powered up.

That (four hours at 14.4 volts then the rest of the time at 13.6 volts) would be perfect for AGM batteries with the specified higher float voltage: Whenever one's AGM battery bank was low, just fire up the generator for a fast charge due to four hours at 14.4 volts and whatever hours needed after that at ~13.6 volts ... all automatically. In essence, the perfect set-it-and-forget-it two-stage converter/charger for use on AGM batteries with a higher specified float voltage.