Champion capsule drop rates

Is there some info somewhere on champ capsule drop rates? I've opened 8 in a row, got 600BE in the first 7 and only finally got a champ shard in the last one. Other friends tell me getting BE for them is fairly rare, but happens from time to time. And my room mate who already owns every champ mostly paid for with real world money said he's never got BE in capsules and just has stacks of the same champ shards saved up because he gets so many. Am I just super unlucky? or is it something to do with levels? Should I be holding onto the capsules and opening them when my account is a higher level?
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