geoff57 said:
The number of shunts is determined by the board type not the power rating; ....
The number of shunts is determined by how much current the board is designed to source, i.e. the power rating.
The reason they add shunts in parallel on the larger boards is to handle the additional current.
3.8mOhms is way too high of a shunt resistance for a +50A board. 1mOhm or less would be more appropriate.
The 6 fet boards can get away with 1 shunt since they are running 30A or less.
geoff57 said:
What site did you get those details from?
I calculated them with Ohms law: V = I * R
R = shunt resistance = 3.8mOhms
I = rated current of the controller, i.e. 30A
Power = I^2 * R = rated current squared * shunt resistance
The power across the shunt must be minimized while taking care to still develop enough voltage across the shunt to provide good resolution to the A/D's in the uC.
This is how you tell if your shunt is big enough.
This is how they decided to parallel up the shunts on the 12 fet and 18 fet boards.
I was just pointing out that if someone uses the firmware to up the current on a 6 fet board they need to solder the shunt to handle the additional current.
(well, they dont have to, but it would be advisable)
-methods