Advice on Lipo cells, have I killed them?

[mattym0310]

I came to charging my saddle pack lipos, and somehow they are completely flat. They have no charge in them at all. I think it is because I left the car plugged into them since last use, although it was left switched off Because they are flat, none of my chargers will charge the battery, so Is there anything I can do to start them up again to use this weekend?

thanks a lot