Custom Chargers for backup battery

[Tristan Lall]

Originally Posted by Al Skierkiewicz

Larry,
No other charging circuits were allowed under the robot rules this year. Although I didn't like the IFI design, teams who wanted the charger feature on the robot for the backup battery had to use the IFI circuit. I recommend purchasing an additional backup battery and a valid charger for off robot charging.

You know, I'm still of two minds regarding this rule. And not just because I see it as being of limited utility.

Where it says "[w]hen off the robot, the battery is to be charged with the provided 7.2V backup battery charger", it specifies that if off-robot, a certain charger is the only one permitted. But when it says "[w]hen mounted on the robot, the backup battery may be charged from the EX18-12 primary battery by using the custom charging circuit available from Innovation First Inc.", it specifies that when on-robot, the battery may be charged by that method, but doesn't specifically preclude another charger, as it would have if "may only" were substituted for "may" in that sentence. The implication is that this does not specify the IFI charger to the exclusion of all else, but rather that you may choose between the IFI charger or an unidentified alternative. (Steve and I argued about this during the season, and I believe that we agreed to disagree....) That would mean, that as long as the battery is "on" the robot (secured with Velcro, perhaps), it could be charged in any manner (including, obviously, the IFI charger). Maybe (indeed, probably) they meant something else, but that's not what was written, and I don't remember a Q&A response clarifying that intention.

As for the usefulness of the rule, it's not as if we're charging potentially-explosive lithium-ion batteries here; the Ni-Cd battery is a robust and relatively safe type. I'm not sure we need this rule, as written. Maybe it would be enough to require any COTS charger rated for use with the appropriate battery type and voltage.

[Al Skierkiewicz]

Tris,
I believe the "may" in the language is meant that you may or may not charge the battery in the robot. If you choose to charge in the robot then the IFI charger is to be used. The issue I have with the on robot charger is that a charger with no designed in safeguards will alllow the full charge of the main battery to be dumped into the backup battery. This is a dangerous condition as all additional current will be turned into heat at the backup battery. The other problem (the one that is more likely) is that the charger will allow a sneak path for the main battery to keep circuits on the robot energized at the full potential and current of the main battery or by the backup battery alone. In either case, it gives the team a false sense of security thinking that both batteries are fully charged when they are not.

[greencactus3]

i cannot seem to find this whitepaper or w/e on ifirobotics.com.
can anyone give me a direct link?
this is about the backup battery chargeing while on the robot.
thanks

[Joe Ross]

Originally Posted by greencactus3

i cannot seem to find this whitepaper or w/e on ifirobotics.com.
can anyone give me a direct link?
this is about the backup battery chargeing while on the robot.
thanks

It's on the main page of ifirobotics.com under the "news or announcements" section and links to: http://www.ifirobotics.com/docs/firs...up-charger.pdf