One of our club members had an unfortunate experience with a brand new
ElectriFly 1250 LiPo pack purchased through a local hobby shop. He charged
it through the charge connector and all was well. Then he put it in his
plane, a small 4 motored B-17 from a Gillow kit . . . smoke city! 4 motors
came on full force in reverse, 20 Amp speed controller toast.

The discharged connectors were wired in reverse at the pack terminals. Deans
Ultra that came on pack OK, red to --, black to | so he didn't suspect
anything.

Note the difference in the wires on a good pack (foreground) vs. the reversed wired pack.


Probably an isolated instance but check those new packs with your voltmeter
as soon as you get them.