Re: Backup onboard charger not correct
 

Hooked up the IFI charger circuit tonight and took some measurements.

First with a fully charged 12V battery, no connection to RC, and no backup battery connected:
Vin @ J1 - 13.2v Vcharge @ J2 - 8.7v Vout @ J3 - 8.6v
Circuit draws 102mA from 12v battery

Then I connected a discharged (7.7v, would no longer power camera) back-up battery. Backup battery was charging at 130mA, charging circuit was drawing 140mA from 12v battery.

Re: Backup onboard charger not correct
 

Bud, these circuit improvements that you've made are fantastic. I would recommend presenting your design to IFI, because as it stands you won't be allowed to use it in competition. My guess is that they won't update it again this season, but considering the work that you have obviously put into it, it's worth a try.

Re: Backup onboard charger not correct
 

That sounds pretty high for a 700maHr battery. Did it fall after a few minutes or stay at 130 ma? If it didn't I think you need to change the series resistor and bring it down into the 70-80 ma range.

Re: Backup onboard charger not correct
 

Do we have to built this circuit or can we do it the old way?

Re: (Earlier version of) Backup onboard charger not correct
 

Julie,
You can use the supplied charger. If you want to charge while the battery is on the robot, you must use the IFI charger as drawn on their website.