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Unread 02-04-2016, 12:50
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GeeTwo GeeTwo is offline
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AKA: Gus Michel II
FRC #3946 (Tiger Robotics)
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Re: Multiple batteries?

Quote:
Originally Posted by GreyingJay View Post
The amperage rating of a power supply tells you how much current it is capable of supplying. You can can safely replace any DC power supply with another one that has the same voltage rating and equal or higher current rating.
Provided that you use the same size (or smaller) main breaker (and robustly insulate against any shorts before the main breaker). If you use a larger main breaker, you will need larger main supply wires, and probably a different fuse/breaker panel.

Quote:
Originally Posted by GreyingJay View Post
FRC batteries are 12 volts and rated for about 18 amp-hours. A battery capable of 12 volts at 36 amp-hours, for example, will power your robot for twice as long.
At least twice as long, probably a bit longer, as the ratings are based on fairly slow steady discharge, and our use in FRC is much faster, resulting in fewer net amp-hours. For example, one of the AM batteries is rated:
Quote:
Originally Posted by ES17-2 Spec Sheet
Nominal Capacity
  • 20 hour rate ( 0.9A to 10.50V ) 18Ah
  • 10 hour rate ( 1.71A to 10.50V ) 17.1Ah
  • 5 hour rate ( 3.06A to 10.20V ) 15.3Ah
  • 1C ( 18A to 9.60V ) 9.6Ah
  • 3C ( 54A to 9.60V ) 6.3Ah
In typical FRC usage of 54A, the battery can only provide 1/3 as many amp hours as it can at around 1A. In a pushing contest, that number probably drops by about another factor of three.
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