[ratdude747]

Originally Posted by juchong

I don't have any documented evidence on discharge rates, instantaneous current draw, internal resistance, etc. This is all purely empirical, but I have noticed that the MK batteries perform better than the Genesis and PowerPatrol batteries.

The MK batteries seem to handle high current draw better. By this I mean that the internal resistance of the MK batteries does not increase as fast as the other two brands under heavy current draw, or equivalently as the internal temperature of the battery increases.

Our robot drive train this year uses a 2-cim gearbox and 3 x driven 8" pneumatic wheels per side. We noticed that the Genesis/PowerPatrol batteries' ability to provide instantaneous current to the robot decreases to the point of being unable to drive over defenses at about 2 minutes into a match. The MK batteries seem to provide about 5 minutes of power before failing. In both cases, once the battery is allowed to cool, they are both able to provide another 2 minutes of drive time before requiring a recharge.

I hope to build an active load after this season to properly characterize the batteries over time, but for now that is what we have observed this season.

Hope this helps!

In regards to brand differences, I've heard similar things in the past. Sounds like a materials/construction difference. These batteries, as I remember being taught when I was a student years ago, aren't meant for the abuse use demanded by FRC. Thus, the specs may all be the same on paper, but that's only good for typical batteries in typical use. Our use isn't typical, so brand differences are, theoretically, plausible.