horton333 wrote:
Hi:
My normal 2 weeks per year of dry camping will be more like 2 months this year I expect so I am investing in a better 'off grid' setup and the single output voltage converter has to go. For reference 220 AHs of AGM will be the battery. Hence two, one rather detailed, questions.
Questions 1:
Researching converters there seem to be several good multi-stage models on the market, but there is one thing that is bugging the EE in me. There seem to be two major classes. One class have an internal transfer relay, and when on AC the battery is charged by a separate circuit board thru an isolated circuit. The issue is these all seem to be far low amperage for my setup as I really want no more than say 2 hours per day charging (75 AHs is what I guess I need per average day).
The models that have the 75-100 Amps I want all seem to have a single 12 volt output and this is shown in the manuals as going to both battery and the 12 volt accessories, so this leads to question 1. With some of the load being the battery and some being lights or whatever (and variable) how does the charger know when to scale back the voltage when fully charged? If it just guesses on current draw I can see it never coming off 14.4 volts. Is there something I missed that allows them to accurately know where the battery charge level is at to lower the voltage when charged or _______? If the AGMs can handle sustained 14.4 volts, my motorcycle which puts out 16 volts leads me to believe they may be able to but the manufacturers seem to say no, then maybe I would get almost the same result (its only 55 amps, a waste with all that battery capacity and a 2.2 kw generator)by just cranking the voltage on the existing converter?
Question 2)
I have not seen any units that have remote voltage sensing, only temperature. Do you know of any out there that sense the voltage at the battery?
John
Battery chemistry limits amperage and charge rate. The closer to topped off charged you are, the less chemicals in the form of sulfur on the plates there are to go back into the AGM solution, there is just less ions of sulfur to react and take from the plates and get back into the Glass Mats. This creates more internal resistance to charging... which is what the charge controller senses and measures.
If you stick with AGM batteries, something like a Progressive Dynamics 9245 or 9255 with charge wizard pendants, that limits bulk voltage to 14.4V is ideal. If you were running typical Lead Acid with vent cap batteries like deep cycle golf cart batteries, then something that you can set up like an Iota that generates 14.8V is more desireable for NON AGM batteries.
If you have AGMS, look at the spec sheet of the manufacturer of the batteries and see what Vabs is rated at. If it's 14.4V like most AGMS, you know which model charge controller to get.
