Freewing Cougar F9F-8 Second Flight with Battery Issues

The second flight was with the afterburner connected. The power for the afterburner is taken from the balance lead on the lipo. From power up to take off it felt like I was using a 5 cell lipo not 6S. After one circuit at full power I landed as it was clear things were not right. When I landed the ESC was beeping as though the thermal cut off had kicked in.
The lipo used for this flight has had 100 cycles, the internal resistance is 28 across 6 cells but cell 5 had an internal resistance of 15. I am not sure if this was the issue or it is to do with the afterburner unit but it was safer to land than carry on at full throttle just above stall speed.
Please leave comments as to your thoughts on the issue.

[@shozzy69]

Glad you got it back ok

[@All_things_RC.]

I thought the safe option was the best which was the right decision because the bec cut the power to 20% and started beeping as I taxed back. I will have to do more testing to see if it was the lipo at fault or the afterburner. This has been the only flight I have used the after burner which uses the balance plug for the power.