thats fairly easy only need a small backup battery like a computer desktop has maybe 100 ma battery at 7.4 volts with a diode for protection,when charging your battery your EZB stays on kinda hard to charge a battery hook up to a load ,it wont really charge it right ,because it charges by current at contant voltage battery can be smaller or as low as 6 volts,other problem you will need a relay and delay circuit to switch the main battery for charging and backup battery for charging ,delay circuit using 555 timer is for to keep on battery always connect while switch batteries also without timer and relays is use 3 diodes and current set resistor i dont have a drawing software to draw it it easy,can find ond for you and send link fairly simple circuit one diode is connected to input of regulator, cathode to input pin and anode to main battery ,then another diode anode to postive of back up battery and cathode to regulator input pin,3 diode is for keeping the backup battery charged,anode to main battery cathode to current set resistor about 680 ohms then other end goes to backup battery battery that would work is like a telephone battery or cell phone battery,may need two to get 6 volts to 7.4 volts i design and build backup battery circuits and in-house testers for test equipment at a company i work for

@Robotmaker, Wow! thanks! I actually was speaking with an electrical engineer at the company i work for and he said the same thing... however im mechanical and not electrical and for some reason cannot grasp what he said and what you said above...:( (i need visual aids). A diagram would help significantly. However, one thing i was told was to test the load of the board and motors when the robot is at stand still and see if the load is below or above 70ma. I was told that if the load is below 70ma then i do not need to impliment a switch and relay into the schematic and i can just attach everything together... to my understanding i think the reasoning is my charger will be charging at a rate of 1A+ and 70ma is nothing compared to 1A so therefore my battery will have no issue being charged. What are you thoughts about this?

-Garrett

i dont know what type of battery you have to be charged

back up circuit you dont need the regulator circuit the link,where is connects to 5 volt regulator that is where your battery connects too and charger connects ,where the switch in the circuit you connect to the power supply of the EZB BOARD it w ill be well be above 70 ma depending on sensors charging the battery will not charge right thats in most light systems burglar alarms and more use this type of circuit will need a few sensors on to tell when battery is charged,plus need a disconnect relay to remove charger from charger and connect,and you using charging plates like used on the roomba

@robotmaker the battery i was thinking of using is this one at Fry's Electronics: http://www.frys.com/product/6468002?site=sr:SEARCH:MAIN_RSLT_PG

It comes with a charger too which is definately a plus since the circuitry is inside that already.

The circuit that you provided looks really complicated to me and hard for me to grasp, tomorrow i will have a circuit i can post that i had some help with from the engineer at my work. It most likely is going to be similar to the circuit you posted.

-Garrett

dont forget you only need the diode circuit only and where the regulator is you connect the battery and charger where switch is goes to input of the EZB

battery from tenergy look good ,but doesnt say the size so found at battery site ,where sometimes i get batteries it is 5.39 inches long,with that fit inside your robot tenergy 7.2 volt battery

@robotmaker

The battery size is not an issue. However, is there a more simpler circuit for my application? I look at the circuit you provided and i have not a clue to what components i need to purchase, what will be included in my actual charger and how to connect these components. I mean, do i need to have a PCB made for this application? To me it looks like i do...

-Garrett

only need the 3 diodes and one resistor

Here is a schematic that i put together. My questions are:

1. Does only positive (+) from the charger and battery connect together at C ?

2. Does only positive (+) go from B to A (+) ?

3. Does ground (-) at A tie into the battery ground?

4. What happens at D?

Attached below is the image:

Thanks,

Garrett