WWAN Internet Disconnecting when on Battery Power X301

[u751920]

Hi All,
I use a SE F3507g wwan card very occasionally and have noticed that when I am using battery power only the connection is dropped after about 30 secs. If I turn the WWAN card off then back on I get another 30secs. When I am plugged in to an A/C connection this problem does not happen. So I assume it's some kind of power management issue, or BIOS setting. Can somebody point me in the right direction? I don't have Access Connections or Lenovo Power Manager.
Thanks
In my Lenovo x301.