minionhunter wrote: ↑Thu Mar 19, 2020 1:35 pm
The motors arrived but I have no idea what/if they are what I ordered. There are no markings. Is it safe to use the 9v battery trick to test them (just to see if they work)?
Absolutely safe. 9v will not kill the motors, especially with no load. Also a 9v battery probably has quite high internal resistance (so it is "kinder" to to the motors than a lipo).
It is super difficult to judge the speed by looking. You could try attaching a piece of tape to the shaft, clamping the motor in a vise or something, then videoing it on your phone running (off a known voltage) to compare the different motors.
Usually they have no markings but subtle differences exist which are visible.
Any suggestions on buying batteries (I'll get lipo bags to store them) if you would buy domestic to save hassle or ordered form China to get cheap prices?
Lipo cannot be shipped internationally in general. Get the lipo from Hobbyking, their prices are excellent and I've not had a bad batch.
Like LH said - the latest 180mah 2S packs from Hobbyking have a super tiny (JST-PH) balance plug which is not compatible with the majority of chargers. The obvious workarounds are
a) Replace it with a standard balance plug - requires crimping tool, crimps, or splicing (be super careful with splicing lipo wires, short circuits are a Bad Idea) - I've spliced one pack.
b) Make up an adapter cable - I've done this. This is ideal because you'll then get a pack with a slightly smaller, lighter balance plug in your robot.
c) Charge it through the discharge plug - not recommended as it won't balance the cells - probably if you need to do this, stop lower than 8.4v so you don't overcook it
Exercise caution when modifying battery packs, it's a useful thing to do though.