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Unread 24-03-2016, 14:33
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juchong juchong is offline
Electrical Engineer
AKA: Juan Chong
FRC #2655 (Flying Platypi)
Team Role: Engineer
 
Join Date: Aug 2008
Rookie Year: 2008
Location: Greensboro, NC
Posts: 104
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Re: Batteries on AndyMark

Quote:
Originally Posted by engunneer View Post
please define "performs better". More Amp hours? more recharge cycles? Lasts 10 minutes instead of 9?
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!
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What I do: Analog Devices iSensor Product Engineer