Hidden around the galaxy, you will find four yellow chests that contain Stim Canisters.
These canisters a vital for those playing on the harder difficulties, as the upgrade allows BD-1 to increase his stim holding capacity from 2 up to six.
Stim Canister 1
Found in the Subterranean area on Bogano, simply head left of the landing pad and jump across to the far left corner of the map. Once you reach the big dome, look for the large hole in the middle of the area. Jump down this hole and you will find the yellow chest sitting on the ledge.
Stim Canister 2
Located directly beneath the landing pad – in the same as the the Bogling Companion – you will find a stim canister that is locked behind a large metal fence. In order to obtain this stim canister though, you will need to have unlocked the Force Push ability.
This particular one is a bit tricky and will take you several attempts before you manage to successfully get the ball in the hole. To do so, you will need to use a mixture of the Force Push and Force Slow abilities to maneuver the ball onto the ramp and into the hole.
Stim Canister 3
The third stim canister can be found on Zeffo near the Derelict Hangar location. In order to find this canister, follow the main path passed the two Skazz that are attacking the dead Storm Trooper. Once you reach the fork in the road, head right and jump across to the small cave.
Once you are inside the cave, using your lightsaber as a light source, turn left and walk across the pipe until you reach the platform. It is here, at the top of the metal platform, that you will find the yellow chest.
Stim Canister 4
The fourth Stim canister can be found on Zeffo, in the Venator Wreckage area. Unfortunately, this stim is only available once you have obtained the Force Pull, Force Push, and the Double-Jump ability from Kashyyyk.
The yellow chest can be sitting on top of a ledge, as soon as you come out of the large tunnel that is full of droids.
Stim Canister 5
Found within the Ice Caves on Zeffo, this Stim Canister requires the use of Force Push, Force Pull, Powered Zipline, and Overcharge in order to get to.
While the chest may be located in the Ice Caves, the only way to access it is by going through the very end of the Imperial Dig Site. Using the vine at the back of the Dig Site, swing on it and use it to propel you onto the zipline. BD-1 will then kick in and power you up the line. Once you reach the ledge, follow the path until you come across the bright yellow chest that sits along the wall.