Help me build a battery charge controller please

I am new to electronics, so please help me develop my project, here is what I am trying to do:

I have a device that requires 12V at 1.5 A to run. If power is disconnected I will still needed to run it for certain time before the power is back again.... I will be using a 12 V rechargeable battery 5AH that will be inside the device. Please help me build a controller that will be charging the battery (the input power to the device is 12VDC 3A Adapter)
When the battery voltage is at 11.5V it should start charging, if it reaches 12.2V it should stop from charging.

Any help is appreciated it

What type of battery is it?

it's a Werker battery 12V 2.3 Ah sealed non spillable like this one
http://ecx.images-amazon.com/images/I/31hlBD3fqjL.SL500_AA300.jpg

If your input is 12V how would the battery ever reach 12.2V?

Also, the proper float voltage for an SLA battery is ~13.5V. For your 2.3Ah the recommended charge rate would be 230ma for the longest lifetime of the battery and no more than ~700ma.

Thanks for your quick reply. I am looking for a circuit that will handle all of this! My device requires 12 VDC and about 1.25 Ah to run from an adapter. What I am trying to do is when I unplug the adapter or the power goes off is to have a backup/rechargeable battery take over. The battery has an output of 12.69 VDC at 2.5 Ah. The power input from the adapter is 12.20 VDC 2 A.

I am looking for a circuit that will be able to charge my battery while device is powered by the adapter and who will not over charge the battery when the battery is fully charged and also provide power to my device in case of a power outage.

Thank you in advance

I saw this video on youtube How To Make Your Own Battery Backup Circuit! Extremely Easy & Inexpensive! - YouTube it is good to get the battery take over when the input power is out, but it's not complete to charge the battery when needed without over charging it!

shansb:
it's a Werker battery 12V 2.3 Ah sealed non spillable like this one
http://ecx.images-amazon.com/images/I/31hlBD3fqjL.SL500_AA300.jpg

I don't mean what brand, I mean what chemistry. Is it lead/acid, NiMh, LiPo, or what?

plomb Acide Etanche (Lead/Acid)

10 seconds with Mr. Google revealed these hits on the 1st page, among several million others:
http://www.circuitdiagram.org/lead-acid-battery-charger-circuit.html
http://discovercircuits.com/B/batt-chrg2.htm

Thank you very much, I guess i was searching for an answer on google by typing the wrong keywords...Now in this circuit where do I need to connect my device that i need to run so when is connected to the power it will run and when the power goes off it will run on the battery. What I am trying to do is just like a UPS backup but the input power will be only 12V and the output in case of a power failure is 12V

Use two diodes, each capable of conducting 2 amperes or more. Google "diode battery isolator" to see how to connect them. If the circuit misbehaves after making this modification, you can try adding an extra, fairly large capacitor (for example, 1000 uF) across the power leads of the circuit.