Need help with build a custom circuit for the backup battery

we are looking to build a backup battery circuit on the robot and was wondering if anyone who build one last yr. could send us a pic. or step by step on how to build one. we would like to use our camera this yr. but are backup battery dies to fast to use it no matter how much we charge them.


  1. I don’t know about this year’s rules as we have not seen them yet. Last year, you had to build **exactly **the circuit FIRST dictated. Most of us did not as we had technical concerns on that circuit’s design.

  2. You can not build **anything **for this year’s robot until after 1/5/2008.

  3. (according to last year’s rules) You can use any 7.2V NiCAD battery pack for your robot. if it is discharging too fast, get a bigger capacity battery (amp-hour rating).

  4. The 7.2V battery in the KOP last year would run a robot through at least one full day of competition (including pit operations). We would charge the battery overnight for the next day. Also (during build development), camera operation for 1-2 hours continuous is usually seen before you have to switch the battery. You have something seriously wrong if you can’t last 2 minutes…



Did you use the backup battery charger provided in the kit last year? As I recall, it was actually a power supply, not a charger. I know we killed our backup battery charging on that charger and had to purchase a replacement. Hopefully, next year FIRST will correct this mistake and backup batteries dying will no longer be an issue.

Has anyone found a link to IFI’s 2008 onboard backup battery charging circuit diagram, as mentioned in <R49>?

Since this year’s rules allow the use of any equivalent circuit, maybe the question is moot. But it would still be nice to know if a diagram is being provided for reference.

Here is the latest schematic for the backup battery charging circuit.

As I understood the rules, you could either build this already configured circuit, or you could make your own that served as the same purpose. As we may use a camera this year, it would be great if my interpretation is correct and I could just swing by RadioShack, pick up a Variable Voltage Regulator, a potentiometer, some diodes, some resistors, and put it all together myself with my own wiring method.

That is the same design as last year as you can tell by the date on the page. Whats annoying is that I still have a good 25-30 of the boards for the circuit of that design sitting around that we can’t use or give away due to the must be made after 1/5/08 requirement. I’ll have the electronics kids look into designing a new board and have them link it up on here when they finish.

Where in the rules does it say you must use the 2008 IFI charger design, or you cannot use the 2007 IFI charger design?

And if it does say you must use the 2008 design… it is 2008, and the charger is on the IFI website, so technically, it is the 2008 version even though it was upadated 1/25/07. Think of it like cars… you can get a 2009 car this summer.

It’s not the design he’s talking about being unable to use. It’s the actual fabricated circuit boards.