Backup Battery

[PhilBot]

Team 1629 designed and built an on-board charger circuit for 2007. It was based on the "Improved" charger design that was released late in the build season (the one that showed the extra battery terminal that was required).

The schematic and PCB were designed with the free software from ExpressPCB.com.

The board is larger than it needs to be (2.5x3.8) but this is their economic "Mini-pcb" size. By keeping to this size you can get 3 pcb's made in 3 days for less than $60. Build one for real, one for a spare and give one away

I've attached a zip to this message. It includes a pdf of the schematic and PCB as well as the actual ExpressPCB files. So you can go to ExpressPCB.com, download the software, open the PCB design file and then "Order Online".

It was great not having to remember to remove the battery to keep it charged.

This circuit also has pads for including a blocking diode so that the backup battery cannot back-power the RC. This was not included in the "official" schematic" so if you want to play by the letter of the law, just insert a wire in place of D3.

Also note that R1 and R4 dissipate power (get hot), so make sure you use at least 2W resistors.

Phil.