I'm capacity testing a Headway LiFePO4 38120 cell - charging puts 8300 mAh in, but capacity testing/discharging it only gives me6400 mAh (cut off is 2.5 volts). I've ran this test multiple times and get essentially the same resulting mAh's even after tryingdifferent charging current (12 A, 6 A, 1 A and trickling in 100 mA), different discharging current (800 mA and400 mA) and even discharging immediately after charging. Any idea why I'm not getting 1900 mAh more when discharging?