Yes to upgrade it you need to run into people and kill them with it. I hated upgrading it.
I upgraded mine at the first planet. Oozla I think. It has those weird snail guys and they
take like 3 hits. There might not be very many vendors but it gets you some exp for the
weapon.

I worked out ho to kill enemies fast with it, if you jump on top of the enemy it does more
damage than running in to them. you should go to oozla because them snail things are quick
to kill and give of quite a bit of exp.

It took forever for my Shield Charger to upgrade into the Tesla Barrier. The main idea is
to let the weaker enemies run right into you, but sometimes the strong ones if you're
brave enough.

this is what i do you don't have to do it ok youlet the enemies shoot you than you ran
into them