Modifying a Belkin battery backup system for "off-grid" lighting application.

[cyf]

I recently pulled a Belkin Residential Gateway (RG) Battery Backup system (BU3DC001-12V) out of my garage, which was used for our AT&T U-Verse box at our old place.  The device provides back-up battery power in case the power goes out so one can make emergency calls.  Is has a CSB GP 1272 F2 sealed lead acid battery (Capacity 7.2 Ah @ 20hr-rate to 1.75V per cell @ 25°C (77°F)).

The nice thing about the device is that it can charge the battery AND provide a 12V-2A supply (supposedly I saw it could go higher) simultaneously.  I would like to modify it so I can use it as a "off-the-grid" power solution for some LED lights where:

STATE 1) From time A --> time B and time C --> time A, it will be plugged in and charging the battery (and maybe supply power to the LED lights part of this time); and
STATE 2) From time B --> time C, it will operate on battery mode only to supply power to the LED lights.

Assume that times A, B, and C are fixed--I wondered if anyone had any thoughts as to how I can:

1.  Switch the device from STATE 1 to STATE 2 at time B and switch from STATE 2 to STATE 1 at time C even if the battery is not fully charged--i.e., only provide 120V power to the device from time-B  --> time-C . Because effectively STATE 2 just means the device is off grid I can probably get one of those timed wall switches (the kind that people use to turn on lights when they are on vacation to make burglars think they are at home ), but I would like to be able to add more "ON" periods and not stack too many of those wall timer switches  .

2.  Assuming that typically the device will be in STATE 2 proportionally much longer than in STATE 1, and generally, except on rare occasions, there will be a net surplus of power going to the device such that there will always be time for the battery to charge to an amount greater than what was consumed during a previous off-grid cycle, would anyone see any problems with replacing the battery with a MUCH larger capacity battery such as a car battery?  This is so in those "rare occasions" the device will supply power for extended periods of time until the battery discharges (almost completely)--hence question 1.

3.  I don't know how much electricity is consumed by the device if it's not powering anything AND when the battery is fully charged, but I would like to also automatically disconnect the device when the battery is charged.  There is a 833H-1C-F-C-12VDC relay controlled by an "ON/OFF" switch, but it seems to only control output to the load (i.e., the plug that goes into the U-Verse device) because there is always at least a ~13V+ output at the terminals that connect to the battery even if I remove the battery AND turn the Power Switch to "OFF".

I'm open to buying (or putting together) a controller--my preference is not to just throw an Arduino at it (which also would seem like overkill from a power and $$$ perspective).

[Seekonk]

An arduino always seems like overkill.  So much capacity for applications that only need 20 lines of code.  Slowly I am getting used to it the way I kissed analog goodby.  With controllers only $6 shipped I can't see how you could call that expensive compared to a wall of timers.

[cyf]

An arduino always seems like overkill.  So much capacity for applications that only need 20 lines of code.  Slowly I am getting used to it the way I kissed analog goodby.  With controllers only $6 shipped I can't see how you could call that expensive compared to a wall of timers.

I just did a search after reading your reply--I hadn't realized they came down so much in price!!!  I guess it is getting to the point where we can take these things for granted--I barely use 2-3GB of my HTC One, even with all my documents loaded.

I haven't used Arduinos before, but I guess it would be time, especially if I can deploy a few of them around the house.  Do you have a link?  Are you talking about something like this?

http://www.aliexpress.com/store/812021

from this link:

http://www.instructables.com/id/The-RRRRRRRRRRBA-or-What-They-Dont-Teach-You-in-/?ALLSTEPS

I would get a few at that price because I have many applications I want to use them for, including teaching my kids to program, solder, etc.

[Seekonk]

That second doc is nice item I can pass out to people.  I keep making so many changes that I always need to have a USB port.  I bought one clone on ebay from China.  It was the ugliest looking picture of a board I had seen.  Figured I would use it in something I would bury away.  What came was a board That was identical to an actual Italian one.  I went over that board was with a magnifying glass, no cosmetic difference.  Think these were the result of some copyright infringement and they had to sell them as an ugly clone.  Anyway I keep a half dozen on hand for some kind of conversion.   I animated this plane with one, sound, motion, lights.