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In a LiPo battery, we find the "C rating" to be the maximum discharge rate (current draw) in terms of C (the capacity of the battery divided by one hour). But, what determines this value? Does it have something to do with its inside chemistry? Is it only limited by the protection circuit that comes with it? Is it just roughly calculated by testing which current it blows up at?

Iaka Noe
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  • "C" ratings are determined by marketting, Engineers would use ESR, Watts, Joules and 'C rise/Watt new and end of life with aging rates vs temp rise. – Tony Stewart EE75 Jun 03 '19 at 20:37

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If I'm not mistaken, it's just the internal resistance relative to the battery's amp-hour capacity. Less internal resistance for a given amp-hour capacity means that the battery can deliver proportionally more current for its capacity before heating up to damaging levels.

DKNguyen
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  • That actually makes sense and I can't believe it hasn't come across my head... But so, what is the internal resistance of a battery determined by? – Iaka Noe Jun 03 '19 at 00:03
  • Thanks! I'll mark yours as correct (at least until you're corrected lol) and ask a new question about the internal resistance. – Iaka Noe Jun 03 '19 at 00:11
  • I couldn't tell you exactly, but I heard on the grapevine that batteries of unusually high C-ratings have fewer charge cycles in them due to using thinner films (or something like that) in construction of the battery. I'm sure chemistry also plays a role as easily observed by comparing batteries of different chemistry types. But I don't know whether chemistry differences plays a significant role in differentiating between C-rating amongst different LiPo batteries. – DKNguyen Jun 03 '19 at 00:16
  • What is the internal resistance of a LiPo battery determined by? – Iaka Noe Jun 03 '19 at 17:43