I look at many LiPo packs during a month's time, generally because the racer has experienced a performance problem or a mechanical problem on the pack. In all cases, we are attempting to isolate the cause: is the pack is at fault?
In order, these are the typical recurring issues I see with racing LiPo packs and their cause:
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Pack Swelling - Discharging pack below 6.3v (2S pack). The closer you get to 6v, the greater the swelling will be. May not happen immediately, but within a few days. As a rule of thumb, when you check pack voltage after a run (you should do this after every run), and you find voltage less than 7.0v (2S pack), you may be less than 6.3v when racing (especially with heavy cars such as SC Mod oval) caused by the load when you accelerate.
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Higher than normal pack temperature - Several potential reasons: a) Loose connection on the pack generates resistance and local high temperatures b) Gearing motor too high which results in high discharge rates 3) High Charge rates eventually changes the internal makeup of the cells, resulting in accelerating internal resistance increases, and high pack temp.
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Mechanical Pack Damage such as loose pack terminals or case being melted (see above) - a) Loose connection at the bullet connector is the number one cause. Change your bullet connector frequently to keep these connections tight. b) See Item 2 above.