Why would batteries run down to zero power but still show 66% capacity

[trexamanic]

I got 4 batteries included in a purchase off here recently.
What is happening is that i charge them put them in the 130 x and round about 50 seconds the power just drops away until the heli lands.
they are connected via a red 2 pin connector that prev owner soldered onto main board.
I checked the capacity of the first one when it did this and it was 66%
i put the next one on and it was doing the same but if i landed when powere dropped i could restart for another 30 seconds or so it was 23%
voltages are over 3.3 each cell

Are these just duff well used batteries?

i have used my own lipos in the same heli and no issues at all

[3dx]

Sounds like the lipo's are heading for the salt water bath, you've basically answered your own question,they may read as charged but are failing under load,.

[cjcj1949]

Lipos work better when warm.

[trexamanic]

Sounds like the lipo's are heading for the salt water bath, you've basically answered your own question,they may read as charged but are failing under load,.

Great....

all that glitters........