Yeah I'm sure most explorers have that experience!Of course, an explorer doesn't need a lot of shields, but just when you've been lulled into a false sense of security, a planet with high gravity appears in front of your nose. After you have hopefully survived the lithobraking, the shields can recharge on the surface.
Happily I found out without actually losing my ship that a 3D shield gen with no boosters (171 MJ!) wasn't really appropriate for my Exploraconda. It now has a 6D (ELP, Hi-cap) and 3 0E boosters (HD/SC) for a grand total of 1155 MJ, or nearly 7 times as much. (I also added a HRP while I was at it, for a 50% boost to hull points.)