Battery Charging Box

[Al Skierkiewicz]

Originally Posted by MikeDubreuil

People had been creating battery charging devices long before FIRST made the ruling last year prohobiting them last year. Many teams have them, and I have yet to see a fire or explosion. Anyone want to share some schematics?

I planned on hooking the 7.2V battery in parallel with the 12V Exide to keep it highly charged

DON'T DO THIS! If you do it, please be far away from me in the pits. I hate the smell of burning electrolyte and have never very much cared for shrapnel. As a few informed people have said on these fori in the past, FIRST means just what the rules state. Charge a single battery with a single charger at no more than 6 amps or the battery will be damaged and people might get hurt. Think about the consequences of connecting the 7.2 volt battery in parallel with the 12 volt battery. Even if the 7.2 volt battery was charged the potential difference is 12-7.2=4.8 volts. This voltage will drop across the internal resistance of each of the batteries and assuming that the NiCad resistance is very small then 4.8v/.011 ohms=436 amps Is that enough to scare you? If the gods are smilling on you, the NiCad will short and the wires feeding it will go incandescent for a few seconds before they burn open, showering the pit with burning copper and vinyl insulation.
As Ken has stated above, under no circumstance charge multiple batteries in parallel unless the charging system was intentionally designed for that duty. Chargers of that type are usually prohibitively expensive for teams to own.