sciolyqa wrote:SPP SciO,
Thanks for sharing your experience. The students had terrible experience with 9V batteries in another project and completely avoided them. The lead team member wants to use LiPo2s 7.4 v 1000mAh (or 3000mAh if necessary). For performance, I agree with his thoughts, but not without concerns.
The rules were modified once to allow using brushless motors in DC proportion devices most of which are 12 V DC fans. Although the kids understand probably all SO contestants face the same 9 V battery /12 V DC fan issue, they wish the rules would be modified again to allow 12 V power supply, unless they can miraculously find 9 V DC fans for optimization. - A Parent Mentor
I would recommend the 3000mah batteries. I use 2700 mAh and they work fine. As mentioned above, some 12v batteries can do significant harm, and while batteries under 9v can two, the risk is compounded by no voltage regulator circuits and moving parts. Ultimately it comes down to the fact that the objective is to optimize the device under the rules, not the componentry in the device(s). While it would make it easier to be able to use 12v power supplies, the point of SO is not to be easy. My 12v, brushless fan lifts up to 3.3 kg operating at 7.4 volts. My brushed, DC motor rated for 18v will move 2kg with a 7.4 volt battery. I don't think a change is necessary.
The last thing I'd throw out is that optimization is finding the arguments (inputs) that yield the minimum or maximum result (output) given the parameters of the situation. This event is a beautiful example of having to do that. It's hard, but with research, trial, error, and a little ingenuity, it's very achievable. Sorry if I went ranty... I would love to help; I just see little utility in appealing for a parameter change rather than seeking a solution.
Good luck, and more than willing to answer questions